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Biology STEMscopes Georgia Student Notebook

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a part of STEMscopes NGSS

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Biology

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developed by Accelerate Learning, Inc. & Rice University

Notebook

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GEORGIA Student Notebook – Biology ISBN: 978-1-946725-80-6

Published by Accelerate Learning Inc., 5177 Richmond Ave, Suite 800, Houston, TX 77056. Copyright © 2017, by Accelerate Learning Inc. All rights reserved. No part of this publication may be reproduced or distributed in any form or by any means, or stored in a database or retrieval system, without prior written consent of Accelerate Learning Inc., including, but not limited to, in any network or other electronic storage or transmission, or broadcast for distance learning. To learn more, visit us at www.acceleratelearning.com

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GEORGIA

This Student Notebook is designed to be used as a companion piece to our online curriculum. The pages of this book are organized and follow the 5E model.

Student Handout

ENGAGE

A short activity to grab students’ interest

Student Journal

EXPLORE

A hands-on activity in which students get expereince with the concept being taught

STEMscopedia

EXPLAIN

A reference material that includes parent connections, technology, and science news

Reading Science A reading passage about the concept that includes comprehension questions

ELABORATE Math Connection

A set of grade-level appropriate math problems that address the concept

Writing Science

EVALUATE

A writing prompt based on the concept studied in which the students can demonstrate what they have learned

Only student pages are included in this book and directions on how to use these pages are found in our online curriculum. Use the URL address and password provided to you by your district to access our full curriculum.

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Biology Student Notebook Table of Contents

Lesson B1A

B1B

B1C

B1D

B1E

105

B2AB

131

B2C

159

B3A

179

B3B

197

Cell Structures and Homeostasis

Cellular Reproduction

Macromolecules

Cellular Transport and Homeostasis

Photosynthesis and Respiration in the Cell

DNA and RNA

Biotechnology

Mendel's Laws

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Page

iii

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Biology Student Notebook Table of Contents

Lesson

Page

B3C

227

Advantages and Disadvantages of Sexual and Asexual Reproduction B4A

Structure, Function, and Classification

249

B4B

275

B4C

299

B5A

327

B5B

349

Relationships Among Groups of Organisms

Viruses

Biodiversity and Populations in Ecosystems

Photosynthesis and Respiration in Ecosystems B5CD

Changes in Ecosystems and Environments

377

B6A

407

B6B

429

Our Evolving Understanding of Biology

Speciation

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Biology Student Notebook Table of Contents

Lesson

Page

B6C

445

Common Descent B6D

Natural Selection and Genetic Drift

465

B6E

489

Biological Resistance

Appendix Glossary

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High School Biology

B1A

Cell Structures and Homeostasis

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B1A Cell Structures and Homeostasis

Student Handout Name:

Date:

Directions: Complete the chart during the activity.

Cell Phone Part

Organelle

Function of Organelle

Analogy

Phone Charger

Core Processor

Motherboard

Screen Lock

Case

Camera

Recycle Bin

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Student Journal Name:

B1A Cell Structures and Homeostasis

Date:

Group:

Part I: Cell Organelles 1.

Fill in the chart below. Location

Function Within School

Organelle

1 2 3 4 5 6 7 8 9 10 11 2.

How would the school work differently if any of the above locations were missing?

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B1A Cell Structures and Homeostasis

Student Journal Part II: Maintaining Homeostasis 1.

Correctly match the disease with the malfunctioning organelle.

Disease/Disorder

Organelle

How do specific cell structures and organelles contribute to maintaining homeostasis in the cell?

Is maintaining homeostasis only important for multicellular organisms? Why?

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B1A Cell Structures and Homeostasis

Student Journal Part III: Argument for Organelles 1.

Scenario _________________

Write a scientific explanation agreeing or disagreeing with the opinion of the person in your chosen scenario. Was the organelle not important enough to include in the homework assignment? Make sure to provide evidence in your opinion.

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B1A Cell Structures and Homeostasis

Student Journal Reflections and Conclusions 1.

How do cell structures and organelles interact as a system to maintain homeostasis?

What are the two main differences between plant and animal cells?

Using all of the following terms, develop a graphic organizer. Use another sheet of paper, if needed.

Terms: cell, prokaryotic, eukaryotic, cytoplasm, membrane-bound, nucleus, DNA, organelle, cell size, eukaryote, prokaryote, chloroplast, cell wall, ribosome, vacuole, lysosome, mitochondria, Golgi body, endoplasmic reticulum, cell membrane, plant, animal

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STEMscopedia: CELL STRUCTURES AND

HOMEOSTASIS

Reflect

B1A

Have you wondered why you shiver in the cold? Or maybe why your stomach gets upset after eating something bad? These and many other reactions are ways your body is responding to a change in its internal environment. Different responses and processes will occur in your body to help it reach a state known as homeostasis. When an external change occurs, such as a decrease in the outside temperature, our body has to compensate for what effect this decreased temperature will have on us. The internal body will pick up on signals and tell it how to respond to ensure the body stays at its optimal internal temperature. For this particular example, shivering increases body temperature to compensate for the cooler temperatures on the outside. How COOL is that? But HOW does the body adjust to these changes? The body counts on cells, and the parts that make up a cell, to carry out their normal functions, allowing the body to change and adapt. Cells are the smallest unit of life, meaning that within each cell there are “parts” that allow these microscopic living beings to grow, change, protect the cell, reproduce, obtain nutrients, and discard waste. These “parts” are called organelles, or small organs. Each organelle has a function, or role, to play to maintain the cells balance.

Look Out Think for a moment about all the living things on Earth. There is great diversity among organisms, from microscopic bacteria to massive whales, the largest animals on the planet. Despite the tremendous variety of life, all organisms have something in common—they are all made of cells. Some organisms are unicellular, composed of just a single cell. Other organisms are multicellular, composed of more than one cell. In fact, the human body is made of about 100 trillion cells! The two categories of cells are prokaryotic cells and eukaryotic cells. A prokaryotic cell is a simple cell that does not contain a nucleus or other membrane-bound organelles. In contrast to prokaryotic cells, eukaryotic cells are more complex. They contain a nucleus and other membrane-bound organelles that perform specific functions that contribute to the overall metabolism and growth of the cell. Eukaryotic cells are found in multicellular organisms including plants, animals, fungi, and protists. They can also be unicellular protists.

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STEMscopedia: CELL STRUCTURES AND

HOMEOSTASIS

Prokaryotic Chart capsule cell wall plasma membrane

cytoplasm DNA

nucleoid plasmids

The capsule is the thin, outermost layer of the cell that provides protection. The cell wall surrounds the cell and maintains the cell’s shape. Individual membranes do not surround internal structures. However, a single plasma membrane surrounds the entire cell. The membrane helps move materials into and out of the cell. Prokaryotic cells contain a gel-like fluid called cytoplasm. Cytoplasm takes up most of the space inside the cell. DNA within a prokaryotic cell is a single, circular molecule that is not enclosed in a membrane-bound compartment. DNA carries the instructions and genetic code for the cell. Although DNA is not enclosed in a nucleus, it is generally confined to a central region called the nucleoid. Circular structures called plasmids are found inside prokaryotic cells. Plasmids are a genetic element of the cell but are not part of the main DNA strand. They are involved in cell activities, such as growth and metabolism.

ribosomes

Prokaryotic cells contain ribosomes that play roles in manufacturing proteins.

pili

Hollow, hairlike structures called pili surround prokaryotic cells. Pili enable prokaryotic cells to attach to other cells. Long, whip-like structures called flagella (singular: flagellum) help prokaryotic cells move. A cell may have one flagellum, or it may have several flagella.

flagella

In addition to the structures shown, prokaryotic cells contain a central area around the DNA called the nucleoid.

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STEMscopedia: CELL STRUCTURES AND Eukaryotic Chart

HOMEOSTASIS

cell wall

The cell wall surrounds the cell and maintains the cell’s shape.

plasma membrane

Individual membranes do not surround internal structures. However, a single plasma membrane surrounds the entire cell. The membrane helps move materials into and out of the cell. Prokaryotic cells contain a gel-like fluid called cytoplasm. Cytoplasm takes up most of the space inside the cell. The nucleus is the central organelle that holds DNA.

cytoplasm nucleus DNA

mitochondria

endoplasmic reticulum (ER) Golgi body ribosomes

lysosomes chloroplast

central vacuole

DNA within a prokaryotic cell is a single, circular molecule that is not enclosed in a membrane-bound compartment. DNA carries the instructions and genetic code for the cell. The mitochondria play major roles in transforming the energy in food into a usable form of energy called ATP. The cell then uses ATP to carry out activities such as reproduction and growth. The endoplasmic reticulum, or ER, transports proteins and helps produce lipids. The Golgi body helps package and distribute proteins and lipids within the cell. Like prokaryotic cells, eukaryotic cells contain ribosomes that play roles in manufacturing proteins. However, the ribosomes in eukaryotic cells are larger and more complex. Lysosomes contain enzymes that help break down food or break down the cell when it dies. Plant cells and some protists contain chloroplasts. These structures contain the green pigment chlorophyll, which captures the energy of sunlight for use in photosynthesis. Many plant cells contain a large central vacuole, which stores water, food, and waste. Animal cells contain vacuoles, but they are much smaller than the central vacuole found in plant cells.

In addition to the structures shown in this animal cell, plant cells contain a cell wall, a central vacuole, and chloroplasts.

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STEMscopedia: CELL STRUCTURES AND

HOMEOSTASIS

What Do You Think? Take a look at the following images of cells. Based on organelle complexity, can you determine which one is eukaryotic and which one is prokaryotic?

Discover Science: The Cell Theory Before the 1600s, people did not know that cells existed at all. This may be hard to believe, considering how much we now know about cells. But until scientists were able to fully observe cells and their functions, people believed life arose spontaneously. Thanks to the work of Robert Hooke, Antonie van Leeuwenhoek, Matthias Jakob Schleiden, Theodor Schwann, Rudolf Virchow, and other scientists, the cell theory was developed. British scientist Robert Hooke was the first person to observe matter that made up what he called cells. In the 1660s, Hooke used a microscope to look at cork from the bark of an oak tree. He noted the cork looked like it was made of small compartments that reminded him of the rooms, or cells, in which monks lived. For this reason, Hooke named the structures he observed cells. Hooke was unknowingly observing nonliving cell walls. The next major development came in the later part of the 1600s when Antonie van Leeuwenhoek observed living cells under a microscope. He examined what he called animalcules, what we now call microorganisms. Based on his notes, scientists today think that van Leeuwenhoek was observing algae and bacteria. Matthias Jakob Schleiden, Theodor Schwann, and Rudolf Virchow are the three scientists who are typically given credit for the development of the cell theory. Schleiden studied plants and discovered they were made of cells. At the same time, Schwann discovered animals were made of cells. In 1838, Schleiden and Schwann proposed the first two parts of the current cell theory. The theory states that all living things are made of cells and that cells are the basic units of structure and function in living things. Virchow developed the third part of the cell theory, which states that all cells arise from pre-existing cells. This magnified image of cork tissue is from Robert Hooke’s book Micrographia.

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STEMscopedia: CELL STRUCTURES AND

HOMEOSTASIS

Try Now Each organelle plays a role in how a cell maintains balance, or homeostasis, within the body. Take a look at the following images and predict what organelles are active in helping to maintain balance for each individual.

Connecting With Your Child To help your child learn more about how organelles help maintain homeostasis, have them draw or create a three-dimensional model of a eukaryotic cell. Ask them to choose either a plant cell or an animal cell. If drawing their models, have them use colored pencils to sketch the cells and their structures. They should include labels and list the functions of each structure. If creating threedimensional models, help them brainstorm ideas of materials they can use such as pipe cleaners, wax craft sticks, pompoms, and string. Three-dimensional models should also include labels. Next, have your child use toothpicks, tape, and small pieces of paper to create numbered labels. Then he or she can create a written numbered key on a sheet of paper. For example, a toothpick taped with the number 1 can be placed on the nucleus. The written key would indicate that number 1 is a nucleus and is the centrally located organelle that contains DNA. Here are some questions to discuss with your child: • What type of cell did you create? • Do you think you would be able to see all of the structures under a microscope? Explain. • Can you give some examples of how these organelles are maintaining balance within the cell?

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B1A Cell Structures and Homeostasis

Reading Science Name:

Date:

Group:

Prokaryotic and Eukaryotic Cells 1

The cell, the basic unit of life, is found in every living organism on Earth. Each individual cell is a complex system that performs specific functions and roles. Some organisms are unicellular, made of a single cell. Other organisms are multicellular, made of many different types of cells. It is important to note that whether the cell comes from a unicellular or multicellular organism, all living biological cells share certain characteristics. All cells are bound by a plasma membrane. Within that membrane, all cells contain a cytoplasmic solution known as cytosol. Cytosol is semifluid and is where organelles are found. Finally, all cells contain ribosomes, which are responsible for building proteins. However, there are also major differences between cells. There are two major categories of cell types: prokaryotic and eukaryotic cells.

Prokaryotic cells are found in the domains Eubacteria and Archaea. They have a very simple structure with no membrane-bound organelles. The genetic material in prokaryotic cells, the DNA, is found in a single, unbound chromosome in a region called the nucleoid within the cytosol. There is no membrane acting as a boundary between the DNA and the rest of the cytosol. Prokaryotic cells are surrounded by a cell wall. These cell types usually reproduce asexually. Most prokaryotic organisms are unicellular.

Eukaryotic cells are found in the domain Eukaryote. They are usually much more complex than prokaryotic cells. These cells usually have many membrane-bound organelles, each with its own specific structure and function. The genetic material in eukaryotic cells can be found on chromosomes within a true nucleus. Thus, a boundary is formed by a membrane that separates the DNA from the rest of the cell. Some eukaryotic cells, such as those found in plants, fungi, and some protists, have cell walls outside their plasma membranes. These cell types usually reproduce through the processes of meiosis and mitosis. Most eukaryotic organisms are multicellular.

One of the most obvious differences between prokaryotic and eukaryotic cells is their size. Eukaryotic cells are much larger than prokaryotic cells, with some eukaryotic cells even being visible to the naked eye. How large is this difference? On average, eukaryotic cells are 10 times larger than prokaryotic cells. Here is a way to picture the relative size difference. If an average prokaryotic cell were the size of a pea, then an average eukaryotic cell would be about the size of a medium grapefruit. In this case, a pea would be roughly 1 cm in diameter. A grapefruit would be roughly 10 cm in diameter.

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B1A Cell Structures and Homeostasis

Reading Science 5

Because of this great difference in size, prokaryotic and eukaryotic cells have different ways of carrying on life processes, such as moving materials through the cell. Materials inside prokaryotic cells move mainly by diffusion. This random movement is fast enough to spread chemicals over short distances. Enzymes that help prokaryotes carry on chemical processes can be attached to the inside of the cell membrane.

In larger eukaryotic cells, diffusion alone cannot move materials around the cell fast enough. A eukaryotic cell that is 10 times bigger than a prokaryote has up to 1,000 times the volume of cytosol. This bigger volume requires much more organization. Specific membrane-bound organelles do separate, specialized jobs. A eukaryotic cell employs a multipart system to move materials across the cell. Materials are made inside the endoplasmic reticulum, are processed in the Golgi body, or can come from outside the cell. When they move within the cell, they are encased in membrane packages called vesicles for transport. With the aid of various motor proteins and the microtubules of the cytoskeleton, the vesicles are moved through the cell. The following analogy illustrates the difference between using diffusion and the vesicle transport mechanisms of eukaryotic cells. Diffusion is like using bicycles or cars to move people around a small town. In comparison, eukaryotic methods are like using mass transit in a large metropolitan area like Houston or Austin.

Other life functions in eukaryotic cells take place inside of other membrane-bound organelles as well. Mitochondria, Golgi bodies, vacuoles, lysosomes, and chloroplasts can be found in eukaryotic cells. Their details may not be visible with a light microscope, but you can see them in a stained cell.

Biological cells cannot usually be seen without magnification. So, how are cell types identified and measured? To determine whether a cell is prokaryotic or eukaryotic, the sample is placed on a microscope slide. The cell is examined through the microscope lens on medium power of 100x. If any details of the sample can be observed at medium power, it is most likely a eukaryotic cell. Most prokaryotic cells cannot be seen without the high-powered lens due to their incredibly small size. The next time you observe cells, see how easily you are able to distinguish between prokaryotic and eukaryotic cells based solely on size.

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B1A Cell Structures and Homeostasis

Reading Science 1

Which of the following can best explain why eukaryotic cells must use mechanisms other than diffusion to transport materials around the cell? A

In eukaryotic cells, materials can flow through microtubules.

Enzymes cannot attach to eukaryotic membranes.

Random movement of molecules is not fast enough to disperse through the larger eukaryotic cell volume.

In eukaryotic cells, internal membranes get in the way and block diffusion.

What cell type has no membrane-bound organelles, has a single unbound chromosome, and is very small? A

Eukaryotic cell

Prokaryotic cell

Animal cell

Plant cell

You are looking through a light microscope with a eyepiece trying to determine what type of cells you are seeing. You can only see individual cells with 100x total magnification. What type of cell is it, and how much detail would you expect to see? A

Prokaryotic cell, very little detail

Prokaryotic cell, much detail

Eukaryotic cell, very little detail

Eukaryotic cell, much detail

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B1A Cell Structures and Homeostasis

Reading Science 4

You are looking through a microscope at stained cells that appear to have a stiff outer edge and smaller structures inside, including a large rounded object near the center. What type of cell would you expect these cells to be, and why? A

Prokaryotic, because only prokaryotic cells have cell walls.

Prokaryotic, because prokaryotic cells have ribosomes inside.

Eukaryotic, because only eukaryotic cells have cell walls.

Eukaryotic, because only eukaryotic cells have a nucleus and organelles.

Which structure would not be found in both prokaryotic and eukaryotic cells? A

Cytosol

Mitochondria

Ribosomes

Plasma membrane

Prokaryotic and eukaryotic cells have several differences. Which statement below is not one of those differences? A

Prokaryotic cells are found in the domains Eubacteria and Archaea.

Eukaryotic cells have organelles for processes like respiration or photosynthesis.

Prokaryotic cells cannot make their own proteins.

Eukaryotic cells are generally 10 times larger than prokaryotic cells.

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B1A Cell Structures and Homeostasis

Math Connections Name:

Date:

Group:

Eukaryotic Cells A Microscopic View of Eukaryotic Cells The following table lists the number of structures or organelles in a mixture containing prokaryotic and eukaryotic cells that can be seen in the view screen of an electron microscope at certain magnification settings. Using your knowledge of cells and exponential functions [f(x) = abx], answer questions 1–5. 1.

Fill in the table by figuring out the pattern each column is being divided by.

Organelles Mitochondria Nuclei Lysosome Chloroplast Cilia Vacuoles 2.

Zoom 0 40,000 10,000 20,000 1,000,000 30,000

200 500 10,000

3,000

Zoom 3 40 10

Max Zoom

50 1,000 30

5 100 3

f(x)=10•ax

f(x)=a•x10

f(x)=10bx

What is the magnification power at the max zoom setting of this particular microscope? (Hint: compare the max zoom to zero zoom.) 2 times

Zoom 2 400

Which function below can be used to show the number of organelles at any zoom x? (Hint: use the table to function rule feature on the graphing calculator. Column 1 will be the zoom number (0,1,2,3,4) and column 2 will be the value from column zoom 0.) f(x)=a•(0.1)x

Zoom 1 4,000 1,000 2,000 5,000

5 times

10 times

100 times

1,000 times

10,000 times

For chloroplast, the function f(3) = 50,000 x (0.1)3 shows the number of chloroplasts seen in the view screen at the zoom 3 setting. Using your answer from question 3, and the notation form f(x) = abx, what does a represent?

What does b represent?

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B1A Cell Structures and Homeostasis

Math Connections 5.

The number of organelles per cell varies depending on the type of cell (prokaryotic versus eukaryotic cell) and the species. A lab technician analyzing the above sample found only one species of eukaryotic cell with cilia. If that species has 2,000 cilia per cell, how many cells are seen in the zoom 2 setting?

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B1A Cell Structures and Homeostasis

Writing Science Name:

Date:

Group:

LOOK

THINK The woman in the picture is running a fever and has sought medical attention. When a person feels sick enough to seek medical attention, they usually go to their primary doctor first. Then, depending on the tests needed or the diagnosis, a patient may be admitted to a hospital. Just as there is a procedure for diagnosing and curing a patient at the doctor’s office, there is also a system used by the hospital. In some cases, a team of specialists work together to make sure their patient is healed from their ailment or injury. When we are healing, our bodies also work hard to maintain or restore homeostasis systematically. WRITE Describe how cell structures and organelles interact systematically to maintain or restore homeostasis in the body. Be sure to • clearly state your central idea; • organize your thoughts; • develop your essay in detail; • choose your words carefully; and • use correct spelling, capitalization, punctuation, and grammar.

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B1A Cell Structures and Homeostasis

Writing Science

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High School Biology

B1B

Cellular Reproduction

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B1B Cellular Reproduction

Student Handout Name:

Obtain a square from your teacher. Use that square to fill area A below.

Date:

Now fill in area B below. See your teacher for any resources you may need.

Now fill in area C below. You may need to join with a classmate to complete this task.

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B1B Cellular Reproduction

Student Handout Post-Activity Questions: 1.

If areas A, B, and C represent the body of an organism, what do the individual squares represent?

As the area “grew,” what did you have to do?

Give an example of when an organism might go from area A to area B. What life process is this modeling?

When your teacher came around and removed one of your squares, what did you have to do?

Give an example of when an organism might need to replace a cell that has been removed.

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B1B Cellular Reproduction

Student Journal Name:

Date:

Group:

Part I: The Cell Cycle After you have completed the card sort, draw a picture and explain the cell activities in each of the stages below. The cell cycle stages are in order and already named for you. Cell Cycle Stage

Picture

Cell Activities

1. Interphase

2. Prophase

3. Metaphase

4. Anaphase

5. Telophase

6. Cytokinesis

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B1B Cellular Reproduction

Student Journal Part I: The Cell Cycle, continued 1.

Explain how you determined how to place the cards in order.

Which cell cycle stage(s) do you think the cell is actively dividing in?

Some organisms use the cell cycle for reproduction. What type of reproduction? How do you know what type it is?

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Student Journal

B1B Cellular Reproduction

Part II: The Cell Cycle Stages Examine the microscope slides and complete table below. Slide

Cell Cycle Stage

Sketch and Magnification

Clues

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B1B Cellular Reproduction

Student Journal Part II: The Cell Cycle Stages, continued 1. Explain what must happen before a cell is ready to begin the process of mitosis.

What is the function of centromeres? How are they important in nuclear division?

At what phase of the cell cycle are chromatids considered complete chromosomes? Why is this important?

During telophase, describe what distinguishes the process of cytokinesis. Why is this important?

Are parent cells and daugther cells involved in mitosis considered haploid or diploid? What does this mean?

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Student Journal

B1B Cellular Reproduction

Part III: Introduction to Meiosis 1.

How many cell divisions take place during meiosis?

What differences do you notice between the parent cell and the daughter cells?

Based on the reading, explain what ploidy is and how it is represented throughout the process of meiosis.

Which type of cells does meiosis take place in?

Part IV: Genetic Continuity 1.

How does each process pictured in the Student Guide maintain genetic continuity?

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B1B Cellular Reproduction

Student Journal Reflections and Conclusions 1.

Why is it important for the DNA in a cell to be completely replicated prior to cell division? How does this help the cell cycle maintain chromosomal numbers?

How do mitosis and meiosis differ?

Why is it important for cells to maintain genetic continuity?

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STEMscopedia: CELLULAR REPRODUCTION B1B

Reflect Over the past several years, a debate has been brewing over the use of stem cells. Stem cells can be used to treat certain diseases and conditions such as spinal cord injuries, diabetes, arthritis, and heart disease. The sources of stem cells include umbilical blood, bone marrow, specially treated peripheral blood, and embryos. The use of embryos as a source of stem cells has stirred controversies over the past several years. Interestingly, stem cells are unique because, while not specialized, they have the embryo: an early stage of potential to specialize into a variety of cell types. Since stem cells development in organisms are undifferentiated, meaning they have not yet developed speciﬁc structures or functions, they can be used to replace unhealthy cells. As cells grow in an embryo, they differentiate and become a distinct type of cell. For example, muscle cells and nerve cells in animals, and root cells and leaf cells in plants are differentiated. Cell differentiation allows each type of cell to perform its necessary function. To better understand what makes cells special, we will explore the answers to these questions: How do cells divide and grow? How do they become differentiated? What factors affect cell differentiation? What happens if cell differentiation is disrupted? The Cell Cycle Eukaryotic cells grow and divide through a series of events called the cell cycle. The cell cycle consists of two main stages: interphase and mitosis. During the cell cycle, a cell grows, prepares to divide, and then divides into two daughter cells. A cell spends 90 percent of its life in interphase, which includes G1, synthesis, and G2. These are growth and development stages.

eukaryotic: having a membrane-bound nucleus and other organelles

G1: This phase is characterized by cell growth. In G1, which stands for “Gap 1,” the cell grows larger, makes new proteins, and develops organelles. Synthesis: From G1, cells move into the S phase, or synthesis. This phase is characterized by the replication of the genetic material held within a cell, DNA (deoxyribonucleic acid). DNA replication makes an exact copy of the genetic material, which will be passed on to each daughter cell during mitosis. DNA replication begins when enzymes unzip the DNA molecule and form two strands. Then nucleotides are added to each of the strands following the rules of base pairing. There are four nucleotides in DNA: adenine (A), thymine (T), guanine (G), and cytosine (C). Adenine always pairs with thymine, and guanine always pairs with cytosine. For example, a section of the template DNA strand reading TGATC would be paired with the nucleotides ACTAG. At the end of the S phase, the cell contains double its original amount of DNA.

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STEMscopedia: CELLULAR REPRODUCTION G2: This is the last phase before the cell enters mitosis. During G2, the cell continues to grow and prepares for mitosis by producing the structures needed for the upcoming division. Mitosis: Although it is the shortest phase of the cell cycle, mitosis is a time of great activity. Mitosis divides the nucleus, distributing DNA to each daughter cell. It is completed by cytokinesis, which divides the cytoplasm and separates the cell into two individual cells. Mitosis is divided into four phases, To start DNA replication, which are described in the table on the following page. the molecule unzips along the base pairs, creating two single strands.

What Do You Think? Why do you think the strict rules of base pairing are important to DNA replication?

Look Out prokaryotic: lacking a membrane-bound nucleus and other organelles

Only eukaryotic cells go through the stages of the cell cycle, including mitosis. Prokaryotic cells undergo a simpler form of cell division called binary ﬁssion. It is a form of asexual reproduction that results in two identical cells. It begins when a prokaryote replicates its DNA and attaches the copy to one part of the cell membrane and the original DNA to another. The cell pulls apart, separating the copy of DNA from the original genetic material and forming two identical cells.

Try Now If you were to examine a plant or animal cell under a microscope, what phase of the cell cycle would you most likely see? Explain your reasoning.

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STEMscopedia: CELLULAR REPRODUCTION Prophase

•

DNA condenses into chromosomes made up of two sister chromatids connected at the centromere. The spindle ﬁber forms, radiating from the centrioles. The centrioles move toward opposite ends of the cell. The nuclear envelope breaks down.

•

The centromeres attach to the spindle fibers.

•

Chromosomes are lined up at the center of the cell.

•

Sister chromatids separate at the centromere and are now called chromosomes. The chromosomes move to opposite ends of the cell along the spindle ﬁbers. The cell begins to elongate at the ends.

• • Metaphase

Anaphase

• •

Telophase

• • •

Cytokinesis

• • •

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Chromosomes uncoil. The mass of the uncoiled chromosomes is called chromatin. Nuclear envelopes form around each cluster of chromosomes. The spindle ﬁber breaks down and disappears. The cytoplasm divides in two. In animals, the cytoplasm is drawn in until it is pinched in two, creating two new daughter cells. In plants, a cell plate forms between the daughter cells. It gradually forms a membrane and cell wall, separating the two cells.

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STEMscopedia: CELLULAR REPRODUCTION Meiosis: Sexual Reproduction Another important way that some cells divide is by meiosis. There are a few main differences between meiosis and mitosis, including the type of cell that is dividing. Sex cells, also known as gametes, require a second set of a division process to cut the number of chromosomes in half. The original sperm or egg contains two sets of chromosomes. When the cell is ready to reproduce, that number must be divided in half. Two sets of chromosomes are known as a diploid cell, and one set of chromosomes is known as a haploid cell. This extra division is divided into two stages, meiosis 1 and meiosis 2. In addition to the new haploid cell, there are also now four new cells created from the parent cell. All of which are different and have a unique set of genetic variability.

What Do You Think? Take a look at each of the following characteristics and decide if it describes mitosis, meiosis, or binary fission by circling the correct division process. Hint: Some may have more than one answer! Produces four daughter cells.

mitosis

meiosis

binary fission

Produces two daughter cells.

mitosis

meiosis

binary fission

Prokaryotic division.

mitosis

meiosis

binary fission

Cytoplasm divides.

mitosis

meiosis

binary fission

Chromosome number remains the same after division. Chromosome number is cut in half after division.

mitosis

meiosis

binary fission

mitosis

meiosis

binary fission

Division for sperm and egg.

mitosis

meiosis

binary fission

Division for growth and repair of a cell.

mitosis

meiosis

binary fission

Contains prophase, metaphase, anaphase, and telophase. Asexual reproduction.

mitosis

meiosis

binary fission

mitosis

meiosis

binary fission

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STEMscopedia: CELLULAR REPRODUCTION Look Out External factors in the environment can affect cellular differentiation by disrupting gene expression. Certain genes may become activated or inactivated in response to such triggers as temperature changes, injuries, exposure to chemicals, and lack of nutrients. For example, when the body is infected with a disease, white blood cells of the immune system will express genes that produce antibodies. Injuries, such as cuts and wounds, will initiate the expression of genes in the cells of the injured tissues for clotting factors. Temperature even determines male or female differentiation in some organisms. In certain species of alligators, eggs incubated at temperatures below 30 degrees Celsius will typically develop into females, while eggs incubated above 34 degrees Celsius will typically develop into males.

What Do You Think? Use what you have learned to label the diagram of the cell cycle below. Begin by labeling the stages. Write your answers inside the sections of the circle. Then, on the outside of the circle, write the main processes that occur in each stage.

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STEMscopedia: CELLULAR REPRODUCTION Connecting With Your Child To help your child learn more about cell reproduction, have your child research ways that cells divide and create a PowerPoint presentation or poster that highlights the findings. Encourage your child to compare cellular reproduction in prokaryotes (bacteria) and eukaryotes. You may have your child design his or her own chart comparing and contrasting the two types of cells. If possible, have your child observe different types of cells under a microscope (prepared slides can be obtained from science supply companies) or find images of each cell type on the Internet. Have your child include stem cells in the research to learn more about cell differentiation. You may also have them look up the diseases that can be treated with stem cells and why only undifferentiated cells work in this type of therapy. Encourage your child to read about the controversy surrounding stem cells and explain the arguments for each side. Here are some questions to discuss with your child: 1. What are the differences between cellular division among prokaryotes and eukaryotes? 2. What are the stages of the cell cycle? Why are these stages necessary for organisms to grow and develop? 3. What are the consequences of disruptions to the cell cycle and differentiation? How can some of these disruptions be avoided? 4. Do you think cell differentiation is a trait that has evolved over time? Why is cell differentiation beneficial to organisms?

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B1B Cellular Reproduction

Reading Science Name:

Date:

Group:

Genetic Continuity 1

Every time a cell divides, its genetic material has to be copied or replicated. However, to maintain genetic continuity, replication has to produce a copy of the original with the least number of errors possible. In humans, it is estimated that the error rate is less than one mutation per cell division over the whole genome of six billion nucleotides!

Bacteria frequently reproduce using binary fission. The single circular chromosome is copied, and one copy is given to each of the resulting cells. Bacterial chromosomes contain relatively few genes. If one of the resulting bacteria did not end up with all of the genes, it will likely not survive.

Mitosis maintains genetic continuity across generations of cells. Each cell ends up with exactly the same amount of DNA and the same genes. The importance of genetic continuity is especially apparent during development. Mature tissues are made up of different cell types, all arising from stem cells present in the embryo. Each stem cell must have the same genes so it can develop into the necessary specialized cell. Genetic discontinuity in mitosis frequently results in cancer. Cancer can be either a loss or a gain of genetic material in the affected generation of cells.

On the other hand, during meiosis, each daughter cell receives only 23 chromosomes. This maintains genetic continuity by ensuring that when an egg and sperm fuse, the resulting organism ends up with the same amount of DNA and the same number of genes as each parent. Therefore, each offspring will have all the genes it needs to survive and will be able to mate with other organisms of the same species.

Genetic discontinuity during meiosis often has major consequences for offspring. For example, about one in 1,000 babies are born with Down’s syndrome. They have extra genetic material from chromosome 21 in each cell’s nucleus. People with Down’s syndrome have a variety of physical differences and intellectual disabilities. With good health, care, and support, people with Down’s syndrome can live fulfilling and productive lives.

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B1B Cellular Reproduction

Reading Science 1

Which of the following statements best describes the bacterial genome? A

It consists of two to three linear chromosomes with many genes.

It consists of one circular chromosome with many genes.

It consists of two to three linear chromosomes with few genes.

It consists of one circular chromosome with few genes.

Which statement best describes the relationship between stem cells and mature tissue? A

Mature tissue produces large numbers of stem cells.

Stem cells give rise to all the cell types in mature tissue.

Mature tissue cells have fewer genes than stem cells.

Stem cells have to fuse with each other to produce tissue cells.

What is one consequence of genetic discontinuity during mitosis? A

Cancer

Allergies

Larger cells

Fewer offspring

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B1B Cellular Reproduction

Reading Science 4

Genetic continuity during meiosis allows offspring to ____________. A

have more mutations than the parents

mate with other offspring

survive in a changing environment

become larger than the parents

People with trisomy 13 have extra genetic material of chromosome 13. This syndrome most likely results ____________. A

in physical and intellectual disabilities

in cells that cannot undergo mitosis

from genetic discontinuity during binary fission

from genetic discontinuity during mitosis

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B1B Cell Reproduction

Math Connections Name:

Date:

Group:

Part I: Calculating Total Magnification This microscope has 3 objective magnifications: scanning, low, and high. Each objective has a certain magnification: 4, 10, and 40. In addition, the ocular lens has a magnification of 10. 1.

Total magnification=objective magnification×ocular magnification Fill in the table below with the ocular magnification and total magnification of each type of power: Objective magnification Scanning power

Low power

10x

High power

40x

Ocular magnification

Total magnification

Part II: Exponential Growth Viruses can grow exponentially. The formula for exponential growth is: a (1+r )x, where a is the initial amount, r is the growth rate (usually in decimal form), and x is the number of intervals passed. Use this formula to answer the following question: 1. E. Coli has been growing at an exponential rate in a piece of meat you were about to eat. Initially, 5,000 E. coli bacteria were found, and after 20 minutes, 10,000 bacteria were in that piece of meat. How many bacteria would there be after two hours?

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B1B Cell Reproduction

Math Connections Part III: Graphing Bacteria Population Growth 1.

A certain bacterium cell divides to form two new cells every 30 minutes. If a culture starts out with 100 bacterial cells, how many bacteria will be present after three hours?

Fill in the table below, and graph the population growth in the grid below the table. Time (minutes)

Number of bacteria

100

30 60 90 120 150 180 Graph the exponential growth of this bacteria population.

Time (minutes) What are the parameters of the graph of this function?

Use the formula in question 2 to verify your answer in question 3.

Number of bacteria

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B1B Cellular Reproduction

Writing Science Name:

Date:

Group:

LOOK

THINK Cellular reproduction involves several processes, including meiosis, mitosis, and binary fission, in order to maintain genetic continuity. Genetic continuity is important as it ensures that two organisms can create offspring with the correct number and type of genes. It also accounts for daughter cells having the same number of cells as the original cell during division. These processes are important for ensuring that future generations are born without disease or defect. WRITE Describe a model useful for explaining the importance and the role of cellular reproduction, including meiosis, mitosis, and binary fission, to maintain genetic continuity. Be sure to • clearly state your central idea; • organize your thoughts; • develop your essay in detail; • choose your words carefully; and • use correct spelling, capitalization, punctuation, and grammar.

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B1B Cellular Reproduction

Writing Science

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High School Biology

B1C

Macromolecules

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B1C Macromolecules

Student Handout Name:

Date:

You Are What You Eat 1.

What is a biomolecule (macromolecule)? What are the main components that make up a biomolecule?

What are the four biomolecules? (Hint: You have already learned three.) __________________________

__________________________

You consume biomolecules every day. Use the nutritional labels provided by your teacher to record the following information below. Food Source

Net Weight (grams)

# of Calories (per seving)

Carbohydrates (grams)

Protein (grams)

Lipids (grams)

#1 #2 #3

List as many functions as you can for carbohydrates, proteins, and lipids.

Use the recorded data above, as well as your previous knowledge of the biomolecule functions, to analyze how the body may respond to each type of food source.

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B1C Macromolecules

Student Journal Name:

Date:

Group:

Part I: Biomolecule Interview Interview Questions 1.

What is your name (e.g., Emmy the Enzyme or Robbie Ribosome)?

Describe your appearance and what you are made of. (Include the monomer and elements you are composed of as well as the structure of your biomolecule.)

A drawing of your biomolecule’s basic structure:

Give me two interesting facts about yourself.

What can you offer us that the other applicants cannot?

What job would be affected if we did not hire you?

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B1C Macromolecules

Student Journal

Biomolecule

Monomer

Structure

Elements in Biomolecule

Function

Part I: Biomolecule Interview, continued Interview Chart

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B1C Macromolecules

Student Journal Part II: Biomolecule Structure 1.

What are the four major biomolecules. Give an example of each biomolecule’s monomer.

Draw a picture of your completed models below, including a key for what each molecule represents.

Biomolecule #1: _________________________

Biomolecule #2: __________________________

Biomolecule #3: __________________________

Biomolecule #4: __________________________

Key

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B1C Macromolecules

Student Journal Part III: Enzyme Puzzles Carbohydrate Puzzle

Before Carbohydrate and Enzyme Reaction

During Carbohydrate and Enzyme Reaction

After Carbohydrate and Enzyme Reaction

During Lipid and Enzyme Reaction

After Lipid and Enzyme Reaction

Lipid Puzzle

Before Lipid and Enzyme Reaction 54

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B1C Macromolecules

Student Journal Protein Puzzle

Before Protein and Enzyme Reaction

During Protein and Enzyme Reaction

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After Protein and Enzyme Reaction

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B1C Macromolecules

Student Journal Discussion Questions 1. Why did we color the last pieces in the puzzle?

2. By looking at the completed puzzles, how can you tell a chemical reaction has taken place, instead of a physical reaction?

3. How do the puzzles model the idea that matter is conserved during a chemical reaction?

4. Why is it important that the digestive system break our food into smaller molecules?

5. Why is it important that our bodies have enzymes to aid in the digestive process?

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B1C Macromolecules

Student Journal Reflections and Conclusions 1.

What is the difference between a monomer and a polymer?

What are some similarities between the structures of the four classes of biomolecules?

What makes nucleic acids different from the other biomolecules?

You are going to the gym to work out. Which biomolecule would be best for you to consume before your workout and why?

Explain an instance when two of these biomolecules interact to perform a cellular process.

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STEMscopedia: MACROMOLECULES B1C

Reflect A child’s building blocks are relatively simple structures. When they come together, however, they can form magnificent structures. The elaborate city scene to the right is made of small, simple building blocks. Organisms are built in much the same way. Despite their complexity, organisms are made of relatively simple building blocks. How are these building blocks assembled into complex organisms? What role does each main type of molecule play? Types of Biomolecules Biomolecules are molecules that are made by organisms and are essential for performing life functions. They range in size and perform specific functions in and among cells. Their function is often determined by their structure. If the structure is disrupted, the biomolecule can no longer function properly. Biomolecules are made of building-block monomers. A monomer is a small molecule that can be combined chemically with other monomers to form larger molecules. Monomers are made up of relatively simple elements. The most abundant elements in biological monomers are carbon, hydrogen, and oxygen. A polymer is a group of monomers linked to form a much larger molecule. “Mono-” means “one,” and “poly-” means many. Think of monomers as the building blocks and polymers as the final product. The process of making a polymer is called polymerization.

Glucose

Lactose

The linking of monosaccharide monomers to form lactose is an example of polymerization.

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STEMscopedia: MACROMOLECULES When a biomolecule is built, monomers link together via strong covalent bonds. Each time two monomers are linked a water molecule is released. This process is called dehydration synthesis. When a water molecule is added to a polymer, it breaks apart the polymer during a process called hydrolysis.

Sucrose is made of the monomers glucose and fructose. Water breaks apart sucrose into these two monomers through a hydrolysis reaction.

There are four main types of large biomolecules (called macromolecules): carbohydrates, lipids, proteins, and nucleic acids. As shown in the chart below, they are composed of different types of monomers that link together to form polymers.* Type of Biomolecule

Monomer

Carbohydrate Lipid

Monosaccharide Fatty acid

Protein Nucleic acid

Amino acid Nucleotide

Polymer or LinkedMonomer Compound Polysaccharide Diglyceride, triglyceride, phospholipid* Polypeptide, protein DNA, RNA

*Lipids are not composed of true polymers because they are smaller, and the monomers are not repeating. Carbohydrates Carbohydrates are made of carbon, oxygen, and hydrogen. Carbohydrates usually have a hydrogen:oxygen ratio of 2:1. This, combined with the presence of carbon in the molecule, gives carbohydrates their name. Another name for a carbohydrate biomolecule is saccharide. Carbohydrate monomers are called monosaccharides. Monosaccharides include glucose, fructose, and galactose.

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Pasta is made of carbohydrates.

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STEMscopedia: MACROMOLECULES Polysaccharides are polymers of monosaccharides linked together by dehydration synthesis reactions. Carbohydrate polysaccharides can be made from the same type of monomers, or from different monosaccharides linked together. Look at the example of sucrose in the diagram on the previous page. Sucrose is a polysaccharide, made up of two different monosaccharides, glucose and fructose. Carbohydrates are important energy storage molecules in cells. In the human diet, carbohydrates are found in flour, sugar, pasta, potatoes, and other “starchy” foods. Carbohydrates also play a number of important structural and signaling roles in all living cells. They form part of the molecular backbone of nucleic acids, and they are critical for maintaining life. Animals store sugars such as glycogen, made of glucose molecules linked together. Plants store sugars as starch. Lipids Lipids are a diverse group of hydrophobic biomolecules. Fats, a common type of lipid, are combinations of fatty acids and glycerol. Fatty acids are long chains of carbon and hydrogen linked together into a hydrocarbon chain. Some chains are straight, while others bend wherever there is an unsaturated carbon in the hydrocarbon chain. A double bond will form Fatty acids are the building blocks of fats. between two adjacent unsaturated carbons. The Fats are found in many dietary sources, carbons on either side of the double bond have including fish, eggs, and oil. one less hydrogen (they are not saturated with hydrogen) than other carbons in the chain. The term unsaturated is used to describe this type of fatty acid. Fatty Unsaturated: having at acids are used to store energy. These monomers are linked least one double or triple together with glycerol to form diglycerides (two monomers) or bond between carbon atoms triglycerides (three monomers). Lipids are the main structural component of the cell membranes of all organisms. Similar to carbohydrates, lipids are used for long-term energy storage. They are nonpolar, which makes them hydrophobic, or water-repelling. They do not dissolve in water. Plant lipids are usually liquids, such as olive oil, while animal lipids are usually solids, like the fat in beef.

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STEMscopedia: MACROMOLECULES

Proteins Amino acids are the building blocks of proteins. There are hundreds of types of amino acids, but just twenty of these make up our proteins. Each amino acid has a common core of a central carbon, an amine group containing nitrogen, a carboxyl group made of carbon and oxygen, and a side chain (labeled R on amino acid diagrams). The side chain is different for each of the twenty amino acids. Some side chains are hydrophobic, while others are hydrophilic, or watersoluble. Some side chains are charged, while others are neutral. The different properties of the side chains give each amino acid different properties. Amino acids are linked together by covalent bonds called peptide bonds. This type of bond only forms between amino acids. The reaction to form a peptide bond is a dehydration synthesis reaction. One hydrogen atom and one hydroxyl group (–OH) are removed from the amino acids to form one water molecule for each peptide bond that is formed.

Amino acids are linked together by strong peptide bonds.

Amino acids are linked together to form a polypeptide chain. Inside the cell, an organelle called the ribosome is responsible for linking together amino acids to form the polypeptide chain. When a chain contains more than about 50 amino acids arranged in a biologically functional way, it is called a protein.

Amine: a functional group with the general formula R—NH2

Proteins are essential biomolecules in all cells. They give a cell structure, communicate information, synthesize molecules, transport molecules, and make up enzymes, molecules that speed up chemical reactions necessary for life.

Carboxyl: a functional group with the general formula R—COOH

What Do You Think? Some weight loss diets focus on eliminating specific foods from the diet, such as fats or carbohydrates. They can be effective for weight loss. However, they deprive the body of essential biomolecules that support life. Do you think this type of dieting is healthy? Why or why not?

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STEMscopedia: MACROMOLECULES Nucleic Acids Nucleotides are small molecules made of a sugar (monosaccharide), one or more phosphate groups, and a nitrogenous base. The nucleotides ATP (adenosine triphosphate) and GTP (guanosine triphosphate) are important for energy transport within cells. The nitrogenous base of ATP is adenosine, and the phosphate group is a triphosphate (three phosphates linked together). GTP is similar to ATP, with guanosine replacing adenosine as the nitrogenous base. Other nucleotides are enzyme cofactors and signalling molecules. Nucleic acids have three Nucleotides are the shared components: a building blocks of nucleic phosphate group, a sugar, acids, including DNA and a nitrogenous base. (deoxyribonucleic acid) and RNA (ribonucleic acid). DNA includes four nucleotides—guanine, adenine, thymine, and cytosine. In RNA, uracil replaces thymine as a nucleotide. DNA and RNA are essential for storing and utilizing genetic information. DNA and RNA work together to create proteins. As you can see in the diagram on the left, alternating bonds between sugar and phosphate molecules of adjacent nucleotides link the nucleotides that make up DNA. This forms the sugar-phosphate backbone of a strand of DNA. Two DNA strands typically join together via weak hydrogen bonds between nitrogenous bases. The DNA strands twist around further to form the familiar double-helix configuration. In contrast, RNA is typically single-stranded and does not form a double-helix. How does DNA encode protein? The arrangement of nucleotides in DNA stores the code for which amino acids should be brought together in the protein. RNA helps by transferring amino acids to ribosomes for protein creation and by helping to build new proteins.

Look Out Be careful not to confuse the function of DNA with its structure. A DNA molecule provides information about which amino acids are needed to produce certain proteins. Amino acids are not, however, part of a DNA molecule.

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STEMscopedia: MACROMOLECULES Formation of Biomolecules Scientists have several hypotheses about the origin of biomolecules. They have focused on figuring out how biomolecules that self-replicate could have come into existence in the primordial soup of early Earth. Scientists have performed experiments that support each of these hypotheses. It is difficult to know which hypothesis is correct, given the limited amount of available information from the early Earth. The true answer could be a combination of the existing hypotheses. It could also be a completely different alternative that is yet to be discovered. The Oparin-Haldane hypothesis was proposed in the 1920s. According to this hypothesis, the atmosphere of the early Earth was rich in methane, ammonia, and water. When water and ammonia combine in the presence of an energy source (such as lightning or ultraviolet light from the Sun), inorganic molecules react to form organic molecules, such as amino acids.

Combining ammonia, water, and energy creates organic molecules in the lab. This observation led to the Oparin-Haldane hypothesis.

A competing theory is the RNA-world hypothesis. This hypothesis states that RNA developed first. It may have self-replicated and also served as a template for making DNA. Today, RNA serves as the intermediate between DNA and proteins. If this hypothesis is true, DNA took over the role of RNA as the hereditary molecule at some point. A third competing hypothesis is the iron-sulfur world hypothesis proposed in the late 1980s. Under this theory, biomolecules first formed around deep-sea thermal vents. These vents are openings in the ocean floor that emit mineral-rich water that has been superheated by magma. These areas are rich in iron sulfide minerals that can act as catalysts for chemical reactions, especially in the presence of heat. Scientists believe these conditions may have favored the formation of biomolecules.

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STEMscopedia: MACROMOLECULES Getting Technical: Synthetic Biomolecules Organisms usually make biomolecules. However, biomolecules can also be made synthetically in the lab. Biopharmaceutical companies specialize in creating synthetic biomolecules that are used to treat diseases. For example, in 1922, doctors discovered that injections of the polypeptide insulin could treat diabetes. Insulin was harvested from animals, mainly pigs, to be given to humans. In the late 1970s, scientists figured out how to insert the human insulin gene into bacteria, creating bacterial “factories” for producing human insulin. The ability to use a non-animal source for human insulin was a major step forward in treating diabetes. What Do You Know? The box below lists some of the characteristics of the four main types of large biomolecules. • Made of nucleotides

• Made of monosaccharaides

• Make up oils and fats

• Make up enzymes

• Made of amino acids

• Main component of bread and pasta

• Store and utilize genetic information

• Made of fatty acids linked with glycerol

• Main structural component of cell membranes

• Stored in plants as starch

The table on the next page lists the four main types of large biomolecules. Match each characteristic in the box to the correct biomolecule in the table. Write your answers in the right column of the table.

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STEMscopedia: MACROMOLECULES Biomolecule

Characteristics

Carbohydrate

Lipid

Protein

Nucleic acids

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STEMscopedia: MACROMOLECULES Connecting With Your Child Identifying Biomolecules in Foods Biomolecules are the building blocks of life. Not surprisingly, biomolecules are found in foods that humans consume on a daily basis. Carbohydrates, fats (lipids), and proteins are listed on food labels to educate consumers about nutritional content. While nucleic acids are often not listed on labels, most relatively unprocessed foods derived from organisms contain nucleic acids. Food scientists have numerous tests to determine the biomolecules contained in food. One of the simpler tests can be performed at home. Be sure to wear gloves and safety glasses when handling iodine, and place newspaper under the experiment area to prevent staining. To perform this simple experiment to identify starch in foods, gather these materials: • a small bottle of iodine • a small cube from a potato, mashed • a tablespoon of butter • a tablespoon of olive or other vegetable-based oil • a tablespoon of applesauce • a tablespoon of water • five small clear plastic cups Place the test items (potato, butter, oil, applesauce, and water) into individual cups. Add 1–2 drops of iodine to each cup, and carefully swirl to mix. If starch is present, the food will turn blue-black. If no starch is present, the mixture will remain brown. The potato and applesauce should be positive (blue-black), while the butter, oil, and water should be negative (brown). As you progress through the experiment, ask: Why did the iodine not change color when added to water, butter, and oil? (No starch was present.) Why did the applesauce turn blue-black in the iodine experiment? (Starch was present.) What other foods would you expect to contain starch? (Possible correct answers: rice, banana, cashews, oats) Here are some other questions to discuss with students: • What are the general structures of the four biomolecules? • How are proteins and DNA related? • What are some ideas about how the original biomolecules formed?

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B1C Macromolecules

Reading Science Name:

Date:

Group:

RNA World 1

Which came first, the chicken or the egg? This is difficult to answer. You cannot have a hen without her first hatching from an egg, but you cannot have an egg without the hen. There is a similar dilemma with DNA and proteins. In the modern world, they both need each other to replicate. So, which came first, DNA or protein? The “code” embedded within the DNA molecules is needed to create proteins. The dilemma, however, is that there are proteins required to read the DNA code. The answer could lie in the RNA molecule found in all living organisms. RNA also contains genetic information. It is the intermediate messenger in the DNA RNA Protein path. It may be that RNA actually predates both proteins and DNA. Let us look at this in a little more detail.

DNA, or deoxyribonucleic acid, is a self-replicating molecule that stores all of an organism’s genetic material. It is the basis of every organism’s heredity, or the process by which genetic information is passed from one generation to the next. Genes are specific coding segments of the DNA. Genes hold the information required for creating the proteins. Some of these proteins—enzymes—make all biological functions possible. In the modern world, the information held within the DNA molecule is first transcribed to an RNA (ribonucleic acid) molecule. The information contained within that RNA molecule is then translated to manufacture specific proteins. All of the proteins found within organisms, including enzymes, are created in this way.

Therefore, genes (segments of DNA) are required to create proteins; however, certain enzymes are required to “read” the information on the DNA. Remember that enzymes are proteins. A growing number of scientific researchers have a hypothesis about the early history of Earth. They propose that RNA may not only have been the first hereditary material, but may also have served as the first enzyme. RNA may have been all that was needed to hold and transfer genetic materials from one organism to the next generation. They are calling this period RNA World. There must be evidence to support why scientific researchers have come to this conclusion.

In 1986, Nobel Prize-winning scientist Walter Gilbert was the first scientist to use the term RNA World. He suggested that if RNA had the ability to self-replicate and act as its own catalyst (enzyme), then neither DNA nor proteins would be required for the transfer of genetic information. In that case, in the primitive world RNA could potentially serve as the storage molecule for all genetic information and also serve as the catalyst for primitive self-replicating mechanisms.

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B1C Macromolecules

Reading Science 5

Scientists have proposed the following hypothesis. In the early conditions of Earth, the RNA monomers, called nucleotides, could have somehow replicated on their own. Experiments were designed to test this hypothesis to see if RNA could, in fact, self-replicate. In the experiments, short segments of RNA were added to a solution containing the required nucleotides. The results? Short sequences of RNA were created from the original RNA segment without the use of enzymes. This was a positive step toward supporting the RNA World hypothesis.

This initial laboratory test was then expanded upon. In the 1980s, a scientist named Thomas Cech found that an enzyme called a ribozyme aids in the creation of new RNA molecules. Specifically, a ribozyme helps create rRNA, tRNA, and mRNA, which are all vital to the production of proteins. This modern finding showed that RNA does, in fact, have the ability to replicate itself. This was further evidence to support the RNA World hypothesis. How? RNA currently has a catalyst that can help in the replication process. Therefore, it is very likely that RNA in the primitive world would also have had this self-replicating ability.

Extreme conditions of early Earth may not have supported the chemical reactions required for this self-replicating process. Life emerged about 3.5 billion years ago. It is possible that for the first (approximately) half a billion years, RNA World may have existed. As you can see from this, further studies will be required before this hypothesis is fully supported by science.

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B1C Macromolecules

Reading Science 1

In the modern world, what is the path for the transfer of genetic material? A

RNA

DNA

Protein

DNA

RNA

Protein

RNA

DNA

RNA

Protein

DNA

Which of the following statements about DNA is true? A

The information in DNA code is the basis of every organism’s inheritance.

The information held within the DNA molecule is first transcribed to an RNA molecule.

Segments of DNA, called genes, hold information required for creating the proteins that make all biological functions possible.

All of the above.

What does the RNA World hypothesis suggest? A

DNA is required to create proteins for all living organisms.

RNA can self-replicate and act as its own catalyst.

RNA is not needed to create proteins.

Both A and C

Which of the items below is not evidence that supports the RNA World hypothesis? A

The DNA-protein system is too complex to have developed on its own without a more simple initial method.

The RNA molecule is a storage unit for genetic information.

RNA monomers were able to create short segments from an RNA strand in solution.

The discovery of ribozymes showed that RNA had the ability to self-replicate.

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B1C Macromolecules

Reading Science 5

Nucleotides are the monomers, or building blocks, of which polymers or molecules? A

DNA and proteins

RNA and proteins

DNA only

DNA and RNA

Experiments have been conducted to test if the RNA World hypothesis could be true. What are these experiments trying to determine? A

If it is possible for RNA to self-replicate

If RNA carries genetic information

If it is possible that RNA is not needed to make proteins

If RNA is all that is needed to create life

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B1C Macromolecules

Math Connections Name:

Date:

Group:

Exploring Biomolecules Answer the multiple-choice questions below to find a simplified radical. Match this simplified radical with its unsimplified form at the end of the multiple-choice questions to determine the answer to the riddle on page 85. 1. I n the picture of the nucleic acid, which arrow points to a sugar-phosphate backbone? −8x√2

10√5x

−40x√5

16x√2

4 and 5

36x

1 and 3

2. Which of the following is a monomer of a carbohydrate? −49√x

Fatty acid

−28x

Amino acid

−60x

Nucleotide

36√2x

Monosaccharide

6√70x

Protein

3. What is the function of a lipid? 36x√2

Stored energy, structural part of cell membranes

56x√7

Provide energy for living things

−48√2x

Molecules of genetic code

−3√30x

“

Necessary for growth and repair of tissues, found in cell membranes, enzymes, and other important functions

80x√2

Protein

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B1C Macromolecules

Math Connections 4. Which is not true of amino acids? −21√7x

Proteins are made up of amino acids.

−30x√2

Amino acids are small molecules composed of a nitrogen group, a carbon and oxygen group, and a side chain.

−49√2x

Cells can break down amino acids for use as an energy source.

−35x√5

Most amino acids are structurally the same, except for their side chains.

3x√5

Most organisms use 32 standard amino acids to make all of their proteins.

5. Which amino acid does the picture at right represent? −7√105x

Glutamine

−28x√6x

Glycine

49x√6

Proline

16x√2

Threonine

4√5x

Alanine

6. C arbohydrates are compounds that consist of hydrogen, carbon, and which other element in a 1:2:1 ratio? −25√3x

Nitrogen

−35√3x

Phosphorus

−32√3x

Oxygen

−10x√5

Sulfur

24x√3

Helium

7. Which is not a function of a lipid? −32√2x

Provides structure of all biological membranes

32√2x

Used as signaling molecules, carrying signals across membranes

80x

Used by cells to store energy

−4x√2

Used to make other, more complex lipids

6√6x

Used as pathway to convert cellulose back into glucose

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B1C Macromolecules

Math Connections 8. Which of these statements is true about triglycerides? 4x√5x

Triglycerides are composed of glycerol and three fatty acids that can be packed tightly as saturated fat.

56x√3

Triglycerides have a carbon backbone that consists of four fused ring-like structures.

7√70x

Triglycerides are composed of two fatty acids, a glycerol unit, a phosphate group, and a polar molecule.

32√2x

When placed in water, triglycerides will orient themselves into a bilayer.

28x

Triglycerides are found on the leaves of Brazilian palm trees and used for car waxes.

9. The structure to the right is what type of steroid? 16x

Cholesterol

−70

Testosterone

−64x√6

Progesterone

−30√6x

Estrone

−24√6x

Cortisone

10. Which of the following statements are true about steroids? 40√3x

They have a backbone of carbon.

−15√3x

They include cholesterol, sex hormones, and cortisone.

−24x√3

They are a type of lipid.

5√5x

All of the above.

48√2x

None of the above.

11. What type of biomolecule is pictured to the right? 4x√30

Carbohydrate

49√2x

Lipid

10√5x

Nucleotide

−4x

Protein

24x√2

Steroid

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B1C Macromolecules

Math Connections 12. DNA and RNA are what type of biomolecule? 6x√6

Nucleic acid

Lipid

−64√2x

Protein

−28x√2

Carbohydrate

−56√3x

Starch

13. What is a molecule that can bind to other molecules to make a polymer? −24x√5

Protein

RNA

16x√2x

Monomer

−20x√7x

Carboxyl

4√5x

Cellulose

14. The function of DNA is to…

3x√42x

…carry information from RNA to ribosomes.

10x√x

…store genetic information.

5√70x

…carry amino acids to the ribosomes.

6x√70

…match specific amino acids with specific nucleotide sequences in mRNAs.

−12x√3x

…bind to smRNAs to regulate gene function.

15. Proteins are made up of amino acids joined in a chain. 12x√6

Monosaccharide

28√5x

Triglyceride

8x√105x

Carbohydrate

−6x√2x

Nucleotide

−16x√6x

Polypeptide

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B1C Macromolecules

Math Connections Riddle: Why did the microbiology students keep uploading videos to the internet? √100x3

√125x

√216x

√216x4

−8√24x3

√45x2

√512x2

−6√150x

2√125x

−4√192x

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√216x

√80x3

6√72x

7√96x3

√100x3

√216x4

√512x3

6√72x2

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B1C Macromolecules

Writing Science Name:

Date:

Group:

LOOK

THINK about organic molecules and how they form from simple molecules into complex molecules. Four groups of complex organic compounds are found in living organisms: carbohydrates, lipids, proteins, and nucleic acids. These compounds store and use the energy cells need to perform the function of life. What are some ways these more complex organic molecules could have formed? In the 1920s, two scientists, Oparin and Haldane, independently hypothesized that the elements found in the early atmosphere may have encouraged the joining of simple molecules to form more complex ones, potentially forming the first organic molecules. Because the early atmosphere had little oxygen, oxidation would not potentially destroy the chemical bonding process of the molecules. They further hypothesized that with the right energy source, such as lightning, organic molecules, the building blocks of life, could be formed. This became the Oparin-Haldane hypothesis. Two other scientists, Miller and Urey, tested the Oparin-Haldane hypothesis in the 1950s. In a laboratory, they simulated the conditions of the early atmosphere and the warm seas that existed when Earth was first formed. By using a spark to simulate lightning, their model produced a variety of amino acids, the simple molecules that make up proteins. WRITE the evidence that was used to form the conclusions from the observational testing of the Oparin-Haldane hypothesis. Be sure to • clearly state your central idea; • organize your thoughts; • develop your essay in detail; • choose your words carefully; and • use correct spelling, capitalization, punctuation, and grammar.

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B1C Macromolecules

Writing Science

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High School Biology

B1D

Cellular Transport and Homeostasis

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B1D Cellular Transport and Homeostasis

Student Handout Name:

Date:

Movement of Molecules 1.

Obtain a plastic drinking bottle, balloon, plastic wrap, vanilla, and a rubber band.

Place a few drops of vanilla in the bottle and quickly replace the cap on the bottle.

Smell the bottle. Can you smell the vanilla in the bottle? _________

Remove the bottlecap and quickly place some plastic wrap over the bottle opening and secure the wrap with a rubber band. Can you smell the vanilla in the bottle? ______________ Blow up the balloon, remove the plastic wrap, and place the opening of the balloon around the opening of the bottle. Can you smell the vanilla through the balloon? ___________

Reflection Questions: 1.

Could you smell the vanilla best through the plastic wrap or the balloon? Why do you think this happened?

List other examples of molecules passing through substances in everyday life.

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B1D Cellular Transport and Homeostasis

Student Journal Name:

Date:

Group:

Part I: Cell Membrane and Transport Station A: Egg Mass 1.

Molecules move according to the type of solution and concentration gradient. Hypothesize what you would expect to happen to the mass of an egg in a hypotonic, isotonic, and hypertonic solution

Data Table Mass Before

Mass After

Mass Difference

Egg #1 Egg #2 Egg #3 2.

Use the data to predict in which type of solution—hypotonic, isotonic, or hypertonic—each of the eggs was soaking. Record below and explain how you know.

Explain a major function of a cellular membrane and what is meant by semi-permeable. How does the egg represent a cell with a semi-permeable membrane?

Draw a picture representing water movement in the egg for each type of environment. Hypotonic

Hypertonic

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Isotonic

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B1D Cellular Transport and Homeostasis

Student Journal Part I: Cell Membrane and Transport, continued Station B: Elodea Effects 1.

Knowing how molecules move according to the type of solution and concentration gradient, hypothesize what you would expect to happen to a plant cell when salt water is added and when distilled water is added.

Elodea Sketch Normal

Distilled Water

Salt Water

Sketch

What differences did you notice in cell shape and size when distilled water was added to the plant? Were there any other noticeable changes?

What differences did you notice in cell shape and size when salt water was added to the plant? Were there any other noticeable changes?

Which types of solutions—hypotonic, isotonic, or hypertonic—represent the normal, distilled water, and saltwater solutions in this experiment?

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B1D Cellular Transport and Homeostasis

Student Journal Part I: Cell Membrane and Transport, continued Station C: Choose Your Transport 1.

Fill in the table below. Card

Diffusion, Osmosis, or Active Transport?

One Two Three Four Five 2.

Using Card One, explain to John how he was able to smell the cologne that was in his room throughout the house. Include the term “concentration gradient” in your response.

On Card Three, how does the celery stay crisp when in water? In which direction are the water molecules moving and why?

On Card Four, how is the tea bag like a cell membrane? Explain which particles are being allowed to leave and which are not.

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B1D Cellular Transport and Homeostasis

Student Journal Part I: Cell Membrane and Transport, continued Station D: Puzzle 1. After completing the puzzle, fill in the chart below. Vocabulary Term

Definition high to low concentration diffusion of water solution causing cells to swell solution causing cells to shrink cell at homeostasis dissolved particles in a solution semi-permeable no energy required protein carrier molecule moving against concentration gradient energy

Why is it important for a cell to control what enters and leaves its structure?

What allows the cell membrane to control the substances that enter and leave the cell?

How would larger substances get into or out of the cell membrane?

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B1D Cellular Transport and Homeostasis

Student Journal Part II: Modeling Cell Transport 1.

What is the difference between osmosis and diffusion in your model?

Which type of cell transport required energy? How did you model this?

How does cell transport relate to cellular homeostasis?

Reflections and Conclusions 1.

What is one example of how understanding the transport of molecules across a cellular membrane has been useful in your own life?

What is the major difference between active and passive transport? Include the terms “energy” and “concentration gradient” in your response.

Wrinkly skin from sitting in the bathtub too long is an example of osmosis. Explain why this occurs due to the particle concentrations on the inside and outside of your skin.

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STEMscopedia: CELLULAR TRANSPORT AND HOMEOSTASIS B1D

Reflect How does the water you drink get into your cells? How about the food you eat and the oxygen you breathe? Even though you chew your food, it is still too large to get into your cells. After the food has been digested, it has been broken down into glucose molecules and placed in the bloodstream. So now you have water, food, and oxygen floating around in your blood. How do they get from the blood into the cells? nonpolar: lacking chemical polarity Cellular Transport Cellular transport is the movement of substances such as glucose, oxygen, and water across the cell membrane. Different substances are needed by the cell for life and to complete cellular processes. The cell also creates waste materials that must be removed from it. The cell membrane, sometimes called a plasma membrane, surrounds the cytoplasm of the cell and functions to protect and give shape to the cell. It also regulates what goes in and out, as well as how much of any substance goes into the cell. While some molecules can easily cross a cell membrane, the passage of many materials is tightly controlled. This variability in whether a certain substance can easily cross the membrane results from the cell membrane being selective, or semipermeable. Substances that are small and nonpolar are generally able to freely cross the cell membrane. These substances are able to squeeze through the nonpolar lipids that comprise the membrane. Examples of such substances are the gases oxygen and carbon dioxide. The cell membrane is made of phospholipids and proteins. It is arranged in what is known as a phospholipid bilayer. This bilayer allows certain small molecules to move across the membrane without expending any energy. This is called passive transport. Other larger molecules must use transport proteins, which requires energy. This is called active transport. It is the function of the phospholipid bilayer to allow only certain molecules to move across the membrane. The proteins that are embedded in the cell membrane have many functions. Some help the cell communicate with the outside environment. Others transport larger molecules across the membrane. Still, others help the cell recognize other cells of the body, such as red and white blood cells.

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STEMscopedia: CELLULAR TRANSPORT AND HOMEOSTASIS

Passive Transport When a substance can freely cross the membrane, it moves from an area of higher concentration to one of lower concentration. This type of movement is called diffusion. Like a spray of perfume spreading throughout a room, any dissolved substance will naturally diffuse in this manner. When a molecule goes freely through the lipid bilayer of the cell membrane, it is called simple diffusion. polar: having a slightly positive charge at one side of a molecule and a slightly negative charge at the other side carrier protein: a protein in the cell membrane that changes shape to allow a substance to pass through diffusion: the movement of a substance from an area of higher concentration to an area of lower concentration If a substance is too large or polar, it may require the assistance of either a carrier protein or a channel protein to diffuse across the membrane. This type of movement is called facilitated diffusion. Neither simple diffusion nor facilitated diffusion requires the input of energy. Thus, they are onsidered to be forms of passive transport across membranes.

channel protein: a protein in the cell membrane that forms a channel through which a substance can pass through

Osmosis is also considered an example of passive transport because it does not require an input of energy. It is a water-specific process. Osmosis is the movement of water across a cell membrane.

facilitated diffusion: uses a carrier protein to help a larger molecule get across the cell membrane

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STEMscopedia: CELLULAR TRANSPORT AND HOMEOSTASIS

Water (H2O) is a relatively small polar molecule. Water molecules, as with dissolved substances, must cross the plasma membrane in order to regulate the tonicity of the intracellular fluid. Tonicity refers to the relative concentration of water and solutes in a solution. A solute: a substance that hypertonic solution is one in which there is a higher solute concentration is dissolved in another compared to another solution. A hypotonic solution has a lower solute substance (called the concentration compared to another solution. Two solutions that are solvent) isotonic have the same solute concentration. There are channel proteins within cell membranes through which water molecules can pass. solution: a mixture in which the molecules of Imagine that the fluid surrounding a cell is hypertonic to the fluid inside one substance (solute) the cell. Do you think water molecules will move into or out of the cell? are dissolved in another What if the fluid outside the cell is hypotonic to the fluid inside? In each substance (solvent) of these cases, is the movement of water (osmosis) passive or active?

Hypertonic

Solution around the cell (as Solution (cytosol) in the cell compared to the cell) high (hyper) solute concentration low solute concentration low water concentration high water concentration

Hypotonic

low solute (hypo) concentration high water concentration

high solute concentration low water concentration

Isotonic

Solute and water concentration are the same as that of the cell.

Solute and water concentrations are the same as that of the solution.

Tonicity of solution around the cell

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STEMscopedia: CELLULAR TRANSPORT AND HOMEOSTASIS

Look Out Many people use the word osmosis incorrectly. They refer to anything that moves across a barrier of any type as osmosis. Osmosis is a special type of diffusion and only refers to water crossing a cell membrane. If a gas crosses a barrier, it should be called diffusion, not osmosis.

Reflect concentration gradient: a Active Transport difference in the amount of The active transport of substances, on the other hand, requires the substance on two sides of input of energy. Why would energy be required to move substances a barrier across a membrane? Substances can only move passively (diffuse) down their concentration gradient. The movement of a substance from an area of lower concentration to one of higher concentration is in a direction against, or up, its concentration gradient. Movement in this direction requires energy. The energy needed for active transport comes from ATP. ATP is produced in the cells during cellular respiration in the mitochondria. There are specialized transport proteins that recognize a substance and allow that substance to move across the membrane. Examples of these substances are glucose and calcium. Water and other substances needed by the cell must remain in balance. This is why the cell membrane regulates what goes in and what comes out of the cell. This process is called homeostasis. Homeostasis Homeostasis is the process by which systems are regulated so that internal conditions remain stable. Homeostasis happens at the cellular level and the organism level.

Active transport requires energy to move substances against their concentration gradient.

How would your body react if you stepped outside without a jacket on a cold day? Your muscles would tighten, and you would feel very uncomfortable. If you stayed outside for more than a few moments, you would likely begin to shiver. What causes the tightening of muscles and the shivering? Why does your body react this way? Does it help you get warmer? In the example on the last page, the body responded to cold air and reacted in a certain way in order to maintain homeostasis, which is the process of maintaining a constant state of balance within a normal range. The muscles tightened to conserve heat, and the body shivered to help generate heat. All of this occurred in order to help maintain a fairly constant internal body temperature.

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STEMscopedia: CELLULAR TRANSPORT AND HOMEOSTASIS

While the word itself may sound complicated, homeostasis is a fairly simple concept. Cells and organisms must exist in a state of balance. All living cells are constantly working to maintain homeostasis. Your body is even working to maintain homeostasis right now! There are three general steps in a homeostatic response. When something in the body is out of balance, it is sensed by a biological “sensor.” This sensor sends a message to the “control center,” which is usually the nervous system. The control center then sends a command to an effector—a muscle or gland—to correct the imbalance. The regulation of thirst and the regulation of body temperature are examples of homeostasis in the human body. In order to maintain proper blood volume and fluid salinity (salt concentration), an animal must continually drink and excrete an appropriate amount of water. If body fluids are high in salinity (low in water or hypertonic), specific sensor cells in the brain are triggered. These cells can send commands that trigger a thirst response. They may also send commands in the form of hormones from a gland (effector) that reduces the further elimination of fluids. With respect to temperature, the human body must be maintained close to 98.6°F (37°C). Body temperature can rise, such as during physical exertion or fever. Body temperature can also decrease, such as when you step outside on a cold day. Temperature sensors detect the imbalance, and the nervous system responds. On a warm day, a command could be sent to the sweat glands (effectors) to secrete sweat. This helps the body to cool and restore proper temperature. On a cold day, a signal might cause your muscles (effectors) to shiver, increasing your body temperature. The examples of homeostasis discussed here exist at the level of the organism. What about homeostasis at the cellular level? Individual cells must maintain their internal environment in a balanced state. This includes maintaining a constant supply of cellular energy as well as healthy cellular structures composed of biomolecules. Cells must also regulate the passage of materials across their membranes. The internal environment of a cell must maintain the proper salinity and pH. What cellular processes are important for maintaining homeostasis?

What Do You Think? The chart below lists terms associated with the cellular process in the left column. Match each term on the left with the related image or phrase on the right. Write the letter of the matching image or phrase next to the term in the left column.

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STEMscopedia: CELLULAR TRANSPORT AND HOMEOSTASIS

Concentration gradient

A. Osmosis B. A type of passive transport that uses a channel protein to move molecules across a membrane. Hypertonic solution C. Balance of conditions within a cell or organism. Active transport D. The movement of water across a cell membrane. Phospholipid bilayer E. A solution with high solute concentration. Facilitated diffusion F. Requires ATP to move substances against a concentration gradient. Hypotonic solution G. The relative concentration of water and solutes in a solution. Simple diffusion H. A solution in which the solute and water concentration are the same as that of the cell. Isotonic solution I. The structure of a cell membrane. Passive transport J. A solution with low solute concentration. Tonicity K. A difference in the amount of substance on either side of a barrier. Homeostasis L. Involves a substance moving down its concentration gradient.

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STEMscopedia: CELLULAR TRANSPORT AND HOMEOSTASIS

Connecting With Your Child Using Osmosis to Color Flowers With Dye To help your child understand the importance of water in cellular processes and how water is transported into and out of cells, allow your child to dye flowers and observe the results. First, discuss the following concepts. Water is the fundamental solvent for chemical reactions of living beings. It is the main means of substance transportation in the cell and between cells and tissues. It is responsible for the maintenance of adequate temperature for the functioning of the organism. Water is also the reagent, or the product of many biochemical reactions like photosynthesis, cellular respiration, peptide bond for protein formation, etc. Water plays a key role in organic reactions. The following two types of organic reactions incorporate or liberate water in their products and involve osmosis (diffusion of water across a membrane): 1. Photosynthesis: A biochemical process in which water is incorporated into organic molecules. In the reaction, the hydrogen atoms from water go to the produced glucose, and the oxygen atoms from water form the molecular oxygen liberated: carbon dioxide + water + light = glucose + molecular oxygen. 2. Aerobic respiration: An example of a biochemical reaction that produces water: glucose + molecular oxygen. To dye flowers, use the principle of osmosis to move the colored water in the glass up the stem into the flower petals. Cut a small piece off the stem of any white flower such as a daisy or carnation. Put five drops of red or blue food coloring in a glass of water. Place your flower into the glass for at least 12 hours. Observe the results.

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B1D Cellular Transport and Homeostasis

Reading Science Name:

Date:

Group:

Plasma Membrane and Movement of Materials 1

For a cell to stay alive, it has to cope with changes that occur inside and outside of the cell. To do this, it must sense the environment outside of its plasma membrane, bring in needed materials, and excrete wastes. The plasma membrane is said to be semipermeable because it acts as a gatekeeper for the cell: allowing only certain chemicals through. The reason only some chemicals can move through the plasma membrane is because of its chemical structure. Large molecules cannot pass through the membrane unless the cell uses energy. This includes proteins, polysaccharides, and fatty acids. The way smaller molecules can pass through depends on whether they are nonpolar or polar. Small nonpolar molecules like oxygen and carbon dioxide can diffuse into and out of the cell through the plasma membrane easily. Polar molecules, or ions such as sodium, cannot diffuse through the membrane without help.

To understand the structure of the plasma membrane, it is important to understand why chemicals are considered polar or nonpolar. A polar molecule has an uneven partial charge distribution between the atoms. Atoms of some elements have a stronger attraction for the electrons in the chemical bond than others. This can cause an uneven charge distribution between those two bonding atoms. The shape of the molecule determines whether the charge distribution over the entire structure is balanced or uneven. A water molecule is polar because it is bent. It is slightly positive on the hydrogen side and slightly negative on the oxygen side where there is a greater pull on the electrons. Polar molecules and ions are described as hydrophilic (water loving) because they are attracted to water. Nonpolar molecules like lipids have an even distribution of charge. They are described as hydrophobic (water fearing).

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B1D Cellular Transport and Homeostasis

Reading Science 3

The plasma membrane is made of several different chemicals, including phospholipids, cholesterol, and proteins. Each chemical serves a specific purpose. Phospholipids make up the bulk of the membrane structure. The lipid part of the molecule is hydrophobic and repels water and ions. The phosphate part of the molecule is made up of phosphorus and oxygen. The oxygen has a stronger pull on the electrons than the phosphorus, causing the phosphate group to be polar. This allows them to be attracted to the water molecules in the cytoplasm and the cell. They are arranged in a double layer with the phosphate groups pointing toward water inside and outside the cell. The hydrophobic lipid “tails” are attracted to each other in the inner part of the membrane. Cholesterol molecules embedded in the phospholipid bilayer help to make the membrane more firm or rigid.

Some proteins act as pumps to actively move ions and larger molecules through the membrane. Cells must use energy stored in ATP to use this active transport. Ions of potassium, sodium, and calcium cannot diffuse through the nonpolar parts of the plasma membrane because of their positive charges. Other proteins scattered through the membrane act as pores that allow small molecules to diffuse through the membrane. This passive transport does not require the cell to use ATP.

Very large molecules can be taken into the cell by the process of endocytosis. The plasma membrane moves around the molecule forming a bubble-like vacuole that completely engulfs the molecule. This is also the way that bacteria or viruses are captured by certain white blood cells of your immune system. The large molecules or bacteria can then be digested into smaller pieces.

Diffusion of water through a semipermeable membrane is called osmosis. Water passes through special pores in the membrane. Cells must keep a constant water concentration in their cytoplasm so that chemical reactions of metabolism can take place in the right environment. A hypertonic solution has a high solute concentration. If a cell is in a hypertonic solution, the water concentration outside of the cell is lower than the concentration inside the cell. Water molecules will be lost from the cell, and it will become dehydrated. If the water loss is too great, cells can die due to plasmolysis. That loss of water can be seen when sugar is put on a bowl of fresh strawberries. Since the sugar contains no water, the concentration of water outside the cells is essentially zero. The cells of the berries shrivel, and the bowl fills with juice. Fresh vegetables such as lettuce are often left in the open air of the grocery store. This is another external environment with a very low water concentration. The leaves will lose water and shrivel unless they are frequently sprayed with water.

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B1D Cellular Transport and Homeostasis

Reading Science 7

A hypotonic solution has a low solute concentration. If a cell is in a hypotonic solution, the water concentration outside of the cell is higher than the concentration inside of the cell. Water molecules will flood into the cell, and it will swell. Some organisms, such as plants, have cells with a protective outer cell wall. The influx of water makes the plasma membrane press against the inside of the wall. The cells change from limp to turgid. For cells without cell walls, if the water gain is too great, the cells can burst (lyse) and die. Single-celled organisms work to maintain homeostasis by using a special vacuole to actively pump excess water out through the plasma membrane. A multicellular animal will use tissues and organs like kidneys to maintain the body’s water concentration outside the body cells.

The best situation for a cell to live in is an isotonic solution where the water concentrations inside and outside of the cell are essentially equal. Water still continues to move through the plasma membrane. About the same number of water molecules move into the cell as move out. This allows the cell to maintain homeostasis without using a lot of energy. Saline solution for contact lenses is isotonic. It will not hurt the cells in your eyes when it is used to soak contact lenses or wash dirt from your eye. Blood plasma and the fluids surrounding your tissues are isotonic, so the body tissues do not become dehydrated. Your digestive system absorbs water, and your kidneys control water loss. These mechanisms allow your body to maintain homeostasis and allow your cells to function in the correct watery environment.

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B1D Cellular Transport and Homeostasis

Reading Science 1.

Paragraph 1 mentions the term semipermeable. What is the correct definition of semipermeable? A.

Is permeable to molecules all of the time

Moves molecules only by active transport

Allows all molecules to move through the membrane

Allows some molecules to move through the membrane

How is a polar molecule different from a nonpolar molecule? A.

Polar molecules have charges separated like poles of a magnet.

Polar molecules have charges evenly distributed across their poles.

Polar molecules are attracted to the lipids of the phospholipids of the plasma membrane.

Polar molecules are always larger than nonpolar molecules.

The plasma membrane is semipermeable because– A.

phospholipids let through both polar and nonpolar substances.

proteins in the membrane act like gates to control entrance and exit of molecules.

cholesterol makes the membrane too rigid to let small molecules through.

moving materials through the membrane always requires the use of ATP.

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Reading Science 4.

Osmosis is taking place when water molecules move in all the following situations except when – A.

water moves into the cells of limp lettuce leaves that are soaked in a bowl of water.

water moves out of strawberry cells after sugar has been sprinkled on the berries.

water moves to an area of lower concentration between sugar molecules in the bottom of a beaker.

ater moves between blood cells and blood plasma as a person’s hydration level w changes.

One way to tell the difference between hypertonic and hypotonic solutions is that – A.

cells in hypertonic solutions will shrink as water moves out.

cells in hypertonic solutions will move faster as water pushes outward.

cells in hypotonic solutions will swell as water moves into the cell.

both A and C.

People sometimes suggest putting salt on a slug to kill it. Why would the salt hurt the slug? A.

Salt soaks into the slug’s skin cells by diffusion and burns away its slimy mucus.

Salt causes the water to move out of the slug’s skin cells by osmosis and dehydrates it.

Salt soaks into the slug’s skin cells by osmosis and makes it melt.

Salt causes the slug’s skin cells to produce too much slimy mucus, and it starves.

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B1D Cellular Transport and Homeostasis

Math Connections Name:

Date:

Group:

Part A: Investigating Homeostasis Through the Diffusion of Water Osmosis is the diffusion of water across a semipermeable (selectively permeable) membrane. An isotonic solution is one where equal amounts of water are moving in and out of a cell. A hypotonic solution is where there is a higher concentration of solutes inside the cell than outside the cell. Thus, water will increase in the cell, causing the cell to swell. A hypertonic solution is one where there is a higher concentration of solute outside the cell than inside the cell. In this situation, water will leave the cell, and the cell will shrink. Fill in the missing percentages in the diagrams. Then draw an arrow to show the net directional flow of the water molecules. Label whether the external solution is isotonic, hypotonic, or hypertonic. 2.

1. Inside Cell 90% salt ___ % water

Inside Cell ___ % salt 75% water

Outside Cell 10% salt ___ % water

Outside Cell ___ % salt 66% water

The cell is in a/an:

The cell is in a/an: solution.

solution.

Part B: Lab Simulation—The Weight of Potato Slices Before and After Treatment The table shows the results of potato slices after they were sitting in sugar solutions for two hours. Calculate the mass changes and conclude what type of solutions were used in each beaker. Hypothesize what could be responsible for the weight loss or gain. Initial Potato Beaker # Weight (g) 1 2 3 4 5

4.83 4.92 4.80 4.61 5.01

% Sugar Solution 50 25 5 1 0 (distilled H2O)

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Final Potato Weight (g) 3.89 4.45 4.71 4.63 5.04

Change % Change Type of in Weight in Weight Solution (g) (g)

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Math Connections Part C: Data Analysis—Writing a Linear Function to Make Predictions +2 0 –2 –4 –6 –8 –10 –12 –14 –16 –18 –20 –22 0

3. Construct a scatterplot between the two quantitative variables, % sugar solution and % change in weight. Find the linear function that provides a reasonable fit to the data in order to make a prediction (you may use a calculator or use a ruler to draw the line).

4. Write a linear equation using the data points from beakers #3 and #5.

5. If a potato slice weighing 4.84 grams was placed into a 20% sugar solution for 2 hours, approximately what percent change of weight would you expect to occur?

6. What value on the y-axis indicates that an isotonic solution was used in the experiment? What do you think is the percent of sugar content of potato in real life? (Hint: it is the x-intercept.)

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B1D Cellular Transport and Homeostasis

Writing Science Name:

Date:

Group:

LOOK

THINK about the process of osmosis and how that process relates to cellular function. Life could not exist without water, as most living cells exist in some type of fluid environment. The health of the cells that make up all biological organisms depends on a delicate water balance, and this balance depends on both the intake and the excretion of water. For living organisms, this movement of water occurs across cell membranes. Water moves across these membranes in a process called passive diffusion, or osmosis. Most cells live in an environment where the concentrations of solutes outside the cell is not the same as is the concentration of solutes inside the cell. If the concentration of solutes outside the cell is greater than that inside the cell, the cell is said to be in a hypertonic solution. If the concentration of solutes outside the cell is less than that inside the cell, the cell is said to be in a hypotonic solution. In both cases, water will be passively transported from less concentrated solutions to more concentrated solutions. This process creates a concentration gradient that can drive many different types of cellular activities. WRITE the process of osmosis in biological cells and describe why this process is critical to both the regulation of cell structure and to cell function. Be sure to • Address the prompt, provide support, and conclude your thoughts. • Write legibly and concisely.

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B1D Cellular Transport and Homeostasis

Writing Science

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High School Biology

B1E

Photosynthesis and Respiration in the Cell

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6 CO2 + 6 H2O

light energy

Creates/Produces

C6H12O6 + 6 O2

Gives Off as Byproduct

There are several processes occurring in this illustration. Use what you already know about the process of photosynthesis to fill in the boxes. State what is being transferred to the leaf from the Sun, the air, and the soil. Use the given chemical equation for photosynthesis to help you fill in the boxes.

Photosynthesis

B1E Photosynthesis and Respiration in the Cell

Student Handout Name:

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B1E Photosynthesis and Respiration in the Cell

Student Handout 1.

In your own words, explain what is happening in the illustration on the previous page. Be as specific as you can.

What gas is used by plants during photosynthesis, where does it come from, and where does it enter the plant?

What gas is produced by plants during photosynthesis, how does it leave the plant, and where does it go?

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B1E Photosynthesis and Respiration in the Cell

Student Journal Name:

Date:

Group:

Background 1. Write the chemical reactions for photosynthesis and for cellular respiration in the space below.

Describe the relationship between the reactants and products of photosynthesis and cellular respiration.

Fill in the data chart below. Indicate if it is a reactant (needed) or product (result) in each process.

Energy

Photosynthesis

Respiration

Energy from the Sun is needed for the process to begin.

The energy molecule ATP is formed during this process.

Water Carbon dioxide Glucose Oxygen Location Organism it occurs in 4.

What is the difference between aerobic respiration and anaerobic respiration?

When and why does aerobic respiration occur during cellular respiration in plants?

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Student Journal Background, continued 5.

Match each description with the correct process.A: photosynthesis

B: cellular respiration

_____ a) Occurs only in cells containing chlorophyll. _____ f) CO2 and H2O are reactants. _____ b) Carried on by all cells. _____ g) Does not need light. _____ c) Produces energy.

_____ h) Occurs in mitochondria.

_____ d) Produces carbohydrates (sugars). _____ e) CO2, H2O, and ATP are products.

_____ i) Occurs in heterotrophs. _____ j) Breaks bonds between phosphates.

Circle the process occurring in the plant above.

cellular respiration photosynthesis

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cellular respiration photosynthesis

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B1E Photosynthesis and Respiration in the Cell

Student Journal Background, continued 6.

Where does the energy required to conduct the process of cellular respiration come from?

What are the main reactants of cellular respiration?

For each molecule of glucose broken down during glycolysis, what is produced?

Use your knowledge of the three stages of respiration and fill out the following table. Stage of Respiration

Location of Stage

Amount of ATP Produced

10. Use your knowledge of the Krebs cycle to complete the following table. The molecule

binds with…

to form...

oxaloacetic acid NAD+ FADH2

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B1E Photosynthesis and Respiration in the Cell

Student Journal Part I: Plan Your Investigation 1.

My question of inquiry:

The hypothesis

My prediction:

What is the independent variable (also known as the manipulated variable)?

What is the dependent variable (also known as the responding variable)?

Is there a control group or control variable for this investigation? Explain.

What materials, equipment, and technology will be needed for this investigation?

List all safety precautions that must be taken.

What procedures will you perform to carry out this investigation? Use additional paper, if needed.

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B1E Photosynthesis and Respiration in the Cell

Student Journal Part II: Implement Your Investigation Collect, Record, and Organize Data Date Table Test Tube

Contents

Starting Color

End Color

Light or Dark

Starting Color

End Color

Light or Dark

Record information from the entire class. Test Tube

Contents

L1 L2 L3 L4 D1

D2 D3 D4

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Student Journal Part II: Implement Your Investigation, continued Analyze Data 1. Summarize the relationship you observed regarding the Elodea set in the light and the Elodea set in the dark as well as the snail set in the light and the snail set in the dark.

Summarize what you observed regarding the Elodea and snail set in the light and the Elodea and snail set in the dark.

Explain under what conditions would you expect for cellular respiration to stop in all test tubes.

Why did the color of the bromothymol blue (BTB) change from green to blue in the test tube with the Elodea set in the light?

Why did the color of the bromothymol blue (BTB) change from green to yellow in the test tube with the Elodea and snail set in the dark?

What evidence did you observe that snails and plants both carry out cellular respiration? Be specific.

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B1E Photosynthesis and Respiration in the Cell

Student Journal Reflections and Conclusions 1.

In your own words, describe the process of photosynthesis and cellular respiration. How do these two processes cycle matter and energy within a cell? Sketch a simple diagram to support your description.

In the investigation, why was bromothymol blue used as an indicator?

Which of the test tubes in the investigation contained a balanced system? Explain your answer.

Why is learning and understanding the process of photosynthesis and cellular respiration, and how matter cycles through an atmosphere important?

What organelle do you think is the most abundant in muscle cells and why?

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STEMscopedia: PHOTOSYNTHESIS AND

RESPIRATION IN THE CELL B1E

Reflect Wind turbines, shown in the photo on the right, are large structures with blades that move in response to air movement. When the wind blows, the blades rotate. This motion generates energy that is converted into electricity. The wind turbine alone does not create energy. Instead, it captures the energy of wind movement and converts that energy into a usable form: electricity. Organisms also transform energy. For example, plants rely on energy from the Sun to survive. They convert light energy from the Sun into chemical energy that is used to maintain life processes. This process is called photosynthesis. How exactly do plants convert energy from one form to another? Do animals convert energy into usable forms? If so, how? Energy in a System Before discussing energy conversions among organisms, it is important to review the laws of bioenergetics. The first law states that energy cannot be created or destroyed. The total amount of energy in the universe is constant. Just as a wind turbine cannot itself create energy, an organism also cannot create energy. Like a wind turbine, the cell only converts (changes the form of) energy that already exists. Energy can, however, move through a system. As mentioned earlier, it can also change forms. For example, chemical energy is a useful form of energy that powers life activities, allowing organisms to do work. When plants convert light energy to chemical energy, the energy changes forms but is not created in the process. Instead, energy flows in one direction from the Sun to producers, consumers, and, finally, decomposers.

As energy moves through a system, the amount of energy decreases at each step. The energy is not destroyed. Instead, it is lost to the environment, typically due to heat being released at each step. Organisms need to constantly convert energy in order to survive. Plants and animals have developed very different ways of addressing their energy requirements. However, all organisms rely on converting energy to a usable form.

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Adenosine Triphosphate: The Energy Currency Cells use energy from adenosine triphosphate, or ATP, to perform work. ATP stores energy in the chemical bonds between the three phosphate groups attached to the ribose molecule. When a cell needs to perform work, such as transporting a molecule across a membrane or driving a chemical reaction, ATP provides the energy for these activities. When a cell needs energy, ATP is broken down into adenosine diphosphate (ADP) and inorganic phosphate (Pi), releasing the stored energy in the reactant: the substance bond between the two outermost phosphate groups. This energy is used that changes during a to drive cellular processes. chemical reaction We now know that organisms use ATP as an energy currency to fuel cellular activity. But where does ATP come from? First, plants convert energy from sunlight into chemical energy. Second, mitochondria in both plants and animals convert chemical energy into ATP. Photosynthesis During photosynthesis, plants convert light energy into chemical energy. The light energy comes from sunlight, and the chemical energy is glucose, a 6-carbon monosaccharide shown in the diagram on the right. The chemical reaction for photosynthesis is:

product: the substance resulting from a chemical reaction

Six molecules of carbon dioxide (CO2) and six water molecules are the reactants. They combine to form glucose and oxygen, which are the products. Sunlight provides the energy to drive the reaction from reactants to products. Note that the above chemical reaction is balanced. Photosynthesis is a two-step process involving light-dependent reactions followed by light-independent reactions. In light-dependent reactions, photons (units of light energy) are absorbed and converted to ATP. This takes place in thylakoids, a series of ﬂat, stacked disks located in chloroplasts. Thylakoids are bound inside a thylakoid membrane, along with the green pigment chlorophyll. Chlorophyll gives plants their green color. When light energy hits the thylakoid membrane, it is used to excite electrons in the photosystems and split water. When the water molecules are split, the oxygen diffuses into the atmosphere, the electrons enter the electron transport chain, and the hydrogen ions are used as an energy source in the production of ATP. As the electrons and hydrogen ions exit the thylakoid membrane, they are picked up and transported to the Calvin cycle on NADPH, a carrier protein molecule.

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In the light-independent reactions, carbon dioxide and the products of the light-dependent reaction (ATP and NADPH) undergo a series of reactions known as the Calvin cycle. The Calvin cycle produces glucose as its end product. The combination of the light-dependent and light-independent reaction results in the overall equation for photosynthesis: 6CO2 + 6H2O + (light energy)

C6H12 O6 + 6O2

Where do the products come from that are used in the photosynthesis reaction? Water enters plants through roots, which absorb water from the soil and move it up and toward the leaves through the xylem. Water is then stored in the leaves for use in photosynthesis. Carbon dioxide enters leafy plants through stomata, tiny openings on the surface of leaves. Once inside the plant, CO2 travels into chloroplasts by diffusion.

Look Out Photosynthesis has a number of variations in nature. Photosynthesis is not limited to plants. It also takes place in algae and some bacterial species. Not all plants are green, either. These plants, as well as red and brown algae, rely on other photosynthetic pigments for photosynthesis, giving them their distinctive colors. aerobic: requiring oxygen Cellular Respiration Cellular respiration converts glucose into ATP. First, a process known as glycolysis occurs. Glucose enters the cell, and while in the cytoplasm, it is broken down into two 3-carbon molecules called pyruvic acid. Although the cell uses some ATP to begin glycolysis, the overall process produces more ATP than was used to initiate it. For each molecule of glucose that enters glycolysis, a net of two ATP molecules are generated. In eukaryotic cells, aerobic respiration is a two-step process that takes place in the mitochondria following glycolysis. The two steps are: •

Krebs cycle: The two pyruvic acid molecules formed during glycolysis move into the mitochondria, where they initiate a series of enzymatic reactions that release electrons and hydrogen ions and produce carbon dioxide and two molecules of ATP. The carbon dioxide diffuses out of the mitochondria. The electrons and hydrogen ions are carried to the electron transport chain on NADH (a carrier protein molecule similar to NADPH).

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•

Electron transport chain: Products from the Krebs cycle move across the inner membrane of the mitochondria. It is called the electron transport chain because electrons are shuttled back and forth across the inner mitochondrial membrane as part of this process. At the end of the electron transport chain, a process known as oxidative phosphorylation takes place. Here, the enzyme ATP synthase adds phosphate to ADP, creating approximately 32 ATP molecules per glucose in the process!

The overall reaction for aerobic respiration is: C6H12O6 + 6O2 6CO2 + 6H2O + 36 ATP Remember, two ATP moles are produced during glycolysis and 34 are produced during aerobic respiration (two in the Krebs Cycle and 32 in the electron transport chain). Photosynthesis and cellular respiration are part of the same cycle. In cellular respiration, the reactants (glucose and oxygen) are the products of photosynthesis and the products of cell respiration (carbon dioxide and water) are the reactants in photosynthesis.

What Do You Think? Humans and other animals rely on atmospheric oxygen to survive. Without oxygen, aerobic respiration cannot occur. Many scientists worry that the destruction of rainforests and other large areas of vegetation will decrease the overall available oxygen in Earth’s atmosphere. How might this affect aerobic respiration? Anaerobic Respiration Aerobic processes require oxygen, while anaerobic reactions do not require oxygen. In cellular respiration, glycolysis is an anaerobic step as no oxygen is required. However, both the Krebs cycle and electron transport chain are aerobic processes that require oxygen. What happens in the absence of oxygen? Glycolysis can still take place, producing pyruvic acid. In a low-oxygen environment, pyruvic acid can be turned into lactic acid as an alternate pathway for making small amounts of ATP. For example, when a person exercises strenuously and the muscles’ demand for oxygen exceeds the body’s ability to deliver the oxygen, lactic acid is produced in the muscles as the body tries to keep up with ATP requirements. The burning sensation often felt in muscles that are exerted is caused by lactic acid. Some organisms, such as certain kinds of bacteria and fungi, live without oxygen under normal circumstances. They produce energy through fermentation, converting a carbohydrate, such as a sugar or starch, into alcohol or acid. The speciﬁc products of fermentation depend on the organism. For example, bacteria convert carbohydrates into lactic acid, and yeasts convert sugar into alcohol. Fermentation is used in the food industry to produce yeast breads and fermented alcohols such as wine and beer.

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STEMscopedia: PHOTOSYNTHESIS AND

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Getting Technical Fermentation is used for more than just food. Scientists grow bacteria and yeast in large tanks called fermenters. The bacteria and yeast cells are genetically engineered to produce human therapeutic proteins. The proteins are then puriﬁed away from the cells. For example, bacteria are used to produce insulin, which is a treatment for diabetes. Yeasts are used to produce erythropoietin, which can stimulate red blood cell production for treating anemia. This approach allows scientists to produce large batches of therapeutic drugs to treat human diseases.

Try Now What Do You Know? In the spaces below, write the products and reactants for photosynthesis and cellular respiration. Photosynthesis: 6_____+ 6_____+ light energy → + 6_____ Respiration: ______ + 6_____→ 6_____+ 6_____+ 36 ______ Next, draw a line to match each term on the left with the correct description on the right. Light-dependent reaction

Energy currency for cells.

Krebs cycle ATP

Takes place in thylakoids within the chloroplasts. Part of aerobic respiration that produces two ATP molecules.

Glycolysis

Produces two pyruvate molecules.

Fermentation Electron transport chain Light-independent reaction

Includes the Calvin cycle, which produces glucose. Part of aerobic respiration that produces 32 ATP molecules. Produces alcohol or acid and does not require oxygen.

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Connecting With Your Child Observing Cellular Respiration During photosynthesis and cellular respiration, gases are released as products of each process. Cellular respiration produces carbon dioxide. This process can be indirectly observed in the kitchen using baker’s yeast. Yeast is a unicellular organism that uses fermentation to convert sugar into alcohol and carbon dioxide. For this activity, gather together two small glass bowls or clear plastic cups, a packet of baker’s yeast, and one teaspoon of white sugar. You will also need a measuring cup and a spoon. Place the two bowls next to each other. Add one cup of warm water to each bowl. The water should not be boiling or scalding hot, but it should be warmer than room temperature. To one bowl, add one teaspoon of sugar and mix with the spoon. Next, add one-half of the yeast packet to each bowl and gently stir to combine. Within a few minutes, bubbles should start to rise to the top of the water. These bubbles are the carbon dioxide (CO2), the product of cellular respiration. More bubbles should be produced in the bowl with sugar than in the bowl without sugar. Table sugar is a disaccharide made up of glucose and fructose linked together. When added to the yeast mixture, it provides chemical energy for driving cellular respiration, resulting in greater production of carbon dioxide bubbles. As you and your child perform this activity, you may wish to discuss the following questions: 1. What are the bubbles that form after adding the yeast? 2. Why was sugar added to one bowl? 3. Which bowl likely produced more ATP? Explain your reasoning. 4. What are some ways that you might be able to indirectly observe the products of photosynthesis?

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B1E Photosynthesis and Respiration in the Cell

Reading Science Name:

Date:

Group:

Glycolysis 1

Cellular respiration is a complex series of chemical reactions that extract energy from foods. All organisms use energy to survive, so cellular respiration is performed by both plants and animals. Let’s concentrate on one process that is part of cellular respiration, glycolysis.

Glycolysis converts the input glucose into pyruvate, producing 2 NADH molecules, 2 ATP, and 2 H2O. It usually happens in the cytoplasm of eukaryotic cells and does not require oxygen. The glucose enters the cell via a protein transporter. The pyruvate is used by the mitochondria and further broken down into more ATP and carbon dioxide. Glycolysis consists of a series of 10 steps, each performed by a different enzyme. Cells regulate the process at three different steps to meet their needs.

The purpose of glycolysis is to extract energy from glucose and produce the molecule required by the mitochondria. Since glycolysis does not require oxygen, it can go on for some period of time even under anaerobic conditions. A sprinter relies on a combination of stored energy and energy from glycolysis to power her muscles. Once the sprint is over, oxygen is used to further process the molecules produced during the sprint.

Disorders of glycolysis are rare because the process is central to cell survival. Some inherited disorders of glycolysis have been described in humans. Mature red blood cells can only obtain energy through glycolysis. When any one of the enzymes in glycolysis is missing, red blood cells don’t have enough energy to maintain cell integrity. The affected cells burst and die. This produces anemia in affected individuals. Since red blood cells carry oxygen to all cells of the body, people with anemia don’t get enough oxygen to their organs.

On the other hand, cancer cells need lots of energy to continue to divide, so they perform more glycolysis than normal tissue. Physicians can introduce radioactive molecules into the body and use instruments to measure which tissues use them. Depriving cancer cells of molecules necessary for glycolysis may halt cancer’s growth.

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Reading Science 1.

Glycolysis take place in __________. A.

mitochondria

the blood

the cytoplasm

the chloroplasts

Which of the following is NOT an output of glycolysis? A.

Glucose

Pyruvate

ATP

Water

Which of the following statements best describes the regulation of glycolysis? A.

Glycolysis is an unregulated process.

Every step of glycolysis is regulated.

Glycolysis is only regulated in certain tissues.

Three different steps are regulated.

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Reading Science 4.

Inherited disorders of glycolysis cause __________. A.

cancer

anemia

premature aging

baldness

How is glycolysis different in cancer cells as compared to normal tissue? A.

Glycolysis consists of fewer steps.

Glycolysis does not produce ATP.

Cancer cells perform more glycolysis.

Cancer cells use different inputs.

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B1E Photosynthesis and Respiration in the Cell

Math Connections Name:

Date:

Group:

Part I: Photosynthesis The chemical equation for photosynthesis is: 6CO2+6H2O+(light energy)

C6H12O6+6O2

Although the amount of molecules may change, the proportions stay constant in the equation. Complete the following equations, given the amount of one of the molecules. CO2+42H2O+(light energy)

C6H12O6+

What scale factor did you multiply by?

2. 30CO2+

H2O+(light energy)

What scale factor did you multiply by?

CO2+

C6H12O6+72O2

H2O+(light energy)

What scale factor did you multiply by?

CO2+

H2O+(light energy)

7C6H12O6+

C6H12O6+

What scale factor did you multiply by?

5. 3CO2+

H2O+(light energy)

What scale factor did you multiply by?

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B1E Photosynthesis and Respiration in the Cell

Math Connections Part II: Cellular Respiration Complete the ATP gain/loss for each step of cellular respiration in the diagram below.

Part III: Cellular Respiration Actual Yield Complete the ATP gain/loss for each step of cellular respiration in the diagram below for the actual ATP yields indicated. 1.72 total net ATP yield:

1.9 total net ATP yield:

1.126 total net ATP yield:

1.18 total net ATP yield:

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B1E Photosynthesis and Respiration in the Cell

Writing Science Name:

Date:

Group:

LOOK

THINK about the cycling of energy through the processes of photosynthesis and respiration. Life depends on energy. Plants transform energy from the sun into energy they can use in their cells through a process called photosynthesis. Sunlight is trapped by the chloroplasts in the cells of the plant. The plant takes in water mostly through the roots and carbon dioxide mostly through the leaves. Energy is transformed into glucose (ATP), and oxygen is released through the leaves. In cellular respiration, when energy is needed by the plant to produce proteins, DNA, cells, tissues, and whatever else is needed for life, growth, and reproduction, the glucose and oxygen react and release water and energy (ATP). WRITE if the plant can use energy from the sun to make ATP, why does it go through the trouble of using the ATP to make glucose? Be sure to • clearly state your central idea; • organize your thoughts; • develop your essay in detail; • choose your words carefully; and • use correct spelling, capitalization, punctuation, and grammar.

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B1E Photosynthesis and Respiration in the Cell

Writing Science

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High School Biology

B2AB

DNA and RNA

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B2AB DNA and RNA

Student Handout Name:

Date:

Copy this statement: “The color of the truck parked next to the football field was blue.

Define “transcribe.”

Use the code below to fill in the blanks on the puzzle. a=1

b=2

c=3

d=4

e=5

f=6

g=7

h=8

i=9

j = 10

k = 11

l = 12

m = 13

n = 14

o = 15

p = 16

q = 17

r = 18

s = 19

t = 20

u = 21

v = 22

w = 23

x = 24

y = 25

z = 26

___ ___ ___ 20 8 5

___ ___ ___ ___ ___ ___ ___ 16 18 15 3 5 19 19

___ ___ 15 6

___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ 20 18 1 14 19 12 1 20 9 15 14 9 19 12 9 11 5 ___ ___ ___ ___ ___ ___ ___ 19 15 12 22 9 14 7

___ 1

What does the sentence say?

Define “translate.”

___ ___ ___ ___ ___ ___ 16 21 26 26 12 5

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B2AB DNA and RNA

Student Journal Name:

Date:

Group:

Part I: DNA Replication 1.

In DNA, adenine always binds with ___________ and guanine always binds with ______________.

Color in and label what the completed DNA looks like below.

In the space below, draw, label, and color the result of step 2 after it is complete.

Compare the two strands of DNA that you have after DNA replication has been completed. Explain any similarities or differences they have to each other as well as to the original strand.

What do the bead and pipe cleaner represent?

The rectangular piece of wood represents the enzyme helicase. Based on this activity, what does this enzyme do?

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B2AB DNA and RNA

Student Journal Part II: Transcription 1.

Represent what your transcription process looks like by drawing, labeling, and coloring a diagram below.

IIn the table below, record the sequences that pair up with those in the coding strand. DNA Coding Strand

T A C C A T T TA CA G G TA A T G CA T T A A C C GA C T

DNA codons

TAC

CAT

mRNA codons

AU G

G UA

What is the purpose of transcription?

What types of results in genetic expression do you think may occur if even one nucleotide is not correctly transcribed from the DNA to the RNA? Explain

What was the purpose of moving from your desk to the other area in the room

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B2AB DNA and RNA

Student Journal Part III: Translation 1.

Represent what your translation process looks like by drawing, labeling, and coloring a diagram below.

What do the staples represent in your amino acid chain?

What was missing from this modeling process?

In the table below, translate your mRNA code from Part II into an amino acid chain. Use the Student Reference Sheet: mRNA Codon Chart. DNA codons

TAC

CAT

mRNA codons

AU G

G UA

Amino acid

Met start

Val

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B2AB DNA and RNA

Student Journal Part IV: Causes of Genetic Variation

Cause

Definition

Drawing

Which type of mutation would you expect to have the least effect on the organism? Why?

In which type of cell would a mutation have to take place for it to be passed onto offspring?

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B2AB DNA and RNA

Student Journal Reflections and Conclusions 1.

Based on what you learned in this activity, why is the following phrase correct? “DNA replication transmits and conserves the genetic information.”

In your own words, describe the importance of proteins to the expression of genes in an organism and explain the connection between proteins and DNA. Make sure to use the following terms: amino acids, codons, mRNA, transcription, and translation.

How would gene mutations have an effect on the expressed traits of an organism?

Explain the different factors that can cause genetic variation in sexually reproducing organisms.

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STEMscopedia: DNA AND RNA

B2AB

Reflect Cookbooks contain the ingredients and steps needed to make many kinds of dishes. Some cookbooks contain hundreds of recipes. However, someone needs to use a cookbook in order to create the dishes. Without a chef as the intermediary, cookbooks are simply words on paper. DNA (deoxyribonucleic acid) is similar to a cookbook. It contains a lot of information. But until an intermediary makes that information useful, DNA is simply a string of nucleic acids. How is DNA turned into something useful? You are probably familiar with the fact that your genetic material determines most of your physical traits. The DNA inherited from each of your two parents dictates your body structure, height, eye and hair color, and even the precise shape of your toes. Furthermore, modern science is discovering increasing numbers of your health characteristics that are influenced by genetics. Predispositions to cancer, heart disease, and even drug addiction have links to specific genetic markers. What about personality traits like calmness, anger, and anxiety? Could these traits be predetermined by our genetic makeup? Social and psychological scientists have long debated the question of “nature versus nurture.” How much of what makes us “who we are” is predetermined by our heredity? How much is influenced by our A balance of the environment and actions? While scientists increasingly discover genetic biomolecules is important in links to both physical and behavioral characteristics, most agree that your diet. lifestyle choices can have a dramatic impact on many of these traits. Consider the role of diet and exercise in preventing diseases that might normally result from certain genetic patterns. Inheriting our genetic material may be akin to being dealt a hand of cards. It is up to each individual to make strategic decisions in order to obtain optimal results for health. But what exactly is the genetic material that determines so much about every living organism? What does it look like, how does it work, and where is it found? The Genetic Blueprint for Life, Deoxyribonucleic acid (DNA) stores all of the genetic information required to grow and maintain a living organism.

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Examples of balanced meals.

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STEMscopedia: DNA AND RNA DNA Structure and Function DNA is a nucleic acid made up of a string of nucleotides. Many nucleotides string together through bonds between the phosphate group of one nucleotide and the sugar of the next. These bonds are called strong covalent bonds. This nucleic acid structure, including the four nitrogenous bases, sugar, and phosphate, is identical in the DNA of all living organisms. Two individual nucleotide strands are joined by weak hydrogen bonds between their respective nucleotide bases. Because of their unique structures, the nitrogenous bases that join two strands of a DNA molecule bind according to the following rules: adenine (A) binds with thymine (T), and cytosine (C) binds with guanine (G). Due to these binding rules, the two strands of DNA are said to be “complementary. Therefore, if the sequence of one strand is known, the other can be deduced. These nucleotides are joined in a double helix configuration, much like a winding staircase. In eukaryotic cells, DNA is packaged in the cell’s nucleus. Each cell in an organism contains the entire genome (the full complement of DNA) for that organism. If all of the DNA within a human cell were laid out in a straight line, it would span approximately two meters in length! In order to fit inside the tiny cellular nucleus, DNA is folded tightly. Individual strands are wrapped around special proteins called histones. Histone complexes are then repeatedly coiled to form chromatin. During prophase of mitosis and meiosis, each strand of chromatin is supercoiled into tightly compact structures called chromosomes. When a cell divides, its chromosomes are replicated, and a complete set of genetic information is passed on to each daughter cell. During meiosis, when the homologous chromosomes are paired up, crossing over can occur. This is a process where the exchange of genes between these two chromosomes results in a mixture of parental characteristics in offspring. This leads to genetic variation in each daughter cell. chromosome: a linear covalent bond: a strand of DNA that is chemical bond formed wrapped around protein between atoms that share structures; carries the gene electrons sequence of an organism Genes are located on chromosomes and are sections of DNA that code for a specific protein. These proteins contribute to a specific hereditary trait or characteristic. When a gene’s code is used to produce a protein, that gene is considered to be expressed.

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STEMscopedia: DNA AND RNA Gene expression takes place in two steps: transcription and translation. Transcription is a process in which RNA polymerase unzips a section of the DNA and a complementary strand of RNA is formed from the section of DNA that contains a gene. The RNA is then used as a template to produce a protein through a process called translation. Each of these processes is tightly controlled. If something goes wrong at any step, the results can be deadly. You will learn more about the steps involved in transcription and translation later in the lesson. Discover Science: The Discovery of the Structure of DNA The discovery of the structure of DNA in the 1950s answered many biologically important questions. For years, the hunt was on to determine what this molecule was made of and what it looked like. By the 1940s, scientists knew that nucleic acids, specifically containing the four bases, A, C, T, and G, comprised the molecule of heredity. However, the arrangement and structure of this molecule remained a mystery until the following decade. Two scientists at Cambridge University, James Watson and Francis Crick, worked hard to reveal DNA’s structure. They used various models, arranging atoms in a variety of ways. They made structural predictions based on what they knew about the atomic makeup of DNA. At the same time, another scientist named Rosalind Franklin was also working hard to determine the structure of DNA. Franklin was using a sophisticated research technique called x-ray crystallography. In this technique, x-rays are shot at crystallized samples of the molecule in question. The technique reveals a vague, shadowy image, based on how the x-rays diffract off of the molecule’s atoms. Franklin generated such an image of the DNA molecule. Her research partner, Maurice Wilkins, showed this image to Francis and Crick. When they saw the image, they quickly deduced that it pointed to a double-helical structure. Watson and Crick soon published their findings that DNA was a double helix, with a sugar phosphate backbone on the outside, and nucleotide bases on the inside. Watson, Crick, and Wilkins shared the Nobel Prize for this discovery in 1962. However, Rosalind Franklin was not included in the honor because she had died before it was awarded. At the time, Franklin did not receive the credit that she deserved, but the scientific community today is well aware of her contribution to this momentous discovery.

James Watson and Francis Crick

Rosalind Franklin

Franklin with research partner, Maurice Wilkins

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STEMscopedia: DNA AND RNA Regulating Gene Expression A strand of DNA does not just contain genes. It also has a number of regulatory elements that help control gene expression. Some regulators help turn genes on, causing genes to be expressed. Certain proteins can make it easier for transcription to occur. These proteins help to increase gene expression. Certain sections of DNA mark where a gene begins and ends. This helps the process of transcription occur in the correct area of DNA. Sections of DNA or proteins can turn genes off, or prevent gene expression. Cells typically produce a specific protein only when it is needed. Some genes are housekeeping genes that are always turned on. These genes code for proteins that are always needed. Genes and the Production of Proteins A major question remains: How is it that DNA controls the traits of living organisms? The answer involves a very important cellular component: proteins. Proteins effectively determine virtually everything about a living cell and, thus, an organism. The proteins within a cell determine the cell’s structure and its function. Proteins regulate which materials will be transported into and out of cells. They determine the products a cell might make (such as hormones, pigments, or mucus). They also determine whether a cell will be motile, like sperm and certain immune cells, or contain large amounts of contractile muscle fibers, like muscle cells. Simply put, DNA controls cellular fate by providing the instructions for making each and every protein within a cell. The process of reading out the information within a cell’s DNA to produce a protein takes place in two stages: transcription and translation. Transcription Transcription uses DNA as the template for making RNA. Recall that DNA is made up of four nucleotides: adenine (A), guanine (G), thymine (T), and cytosine (C). Transcription takes place within the cell’s nucleus and is the first step in a process that will produce a protein with a specific function. First, the complementary DNA strands separate at the site of the gene to be expressed. Then a series of proteins called RNA polymerases move into the now-available DNA and synthesize a strand of RNA based on the DNA template. (In the diagram below and to the right, the RNA strand is shown in green.) This RNA is called messenger RNA, or mRNA, because it is the message used to produce a protein. Similar to DNA, RNA is also made up of nucleotides. However, the nucleotides in RNA are slightly different: adenine (A), cytosine (C), guanine (G), and uracil (U). When mRNA is being formed, guanine is matched to cytosine in the DNA, and cytosine to guanine. Adenine still pairs with thymine in DNA. However, it is uracil that is added to mRNA as the partner for adenine. After it is made, the mRNA separates from the DNA and then leaves the nucleus and enters the cytoplasm for the next steps in the protein production process, translation.

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STEMscopedia: DNA AND RNA Translation The purpose of translation is to convert the information in the mRNA into an amino acid sequence, which will form a protein. Translation takes place in a cell’s cytoplasm after the mRNA has exited the nucleus. Translation is carried out by organelles called ribosomes. Ribosomes either ﬂoat freely in the cytoplasm or, in eukaryotes, can be found attached to the endoplasmic reticulum. Ribosomes are miniature protein production factories made of ribosomal RNA (rRNA). Ribosomes are responsible for “reading” the nitrogenous bases of the mRNA. Translation depends on “translating” three-letter groups of nucleotides in the mRNA, called codons. Most codons correspond to speciﬁc amino acids. Three of the codons are stop codons. When one of these codons occurs, it is the signal to stop adding amino acids. These amino acids are assembled in the appropriate sequence to form the final protein.

Codons are sets of three nucleotides in mRNA that determine which amino acids are linked together to make a protein.

Look Out You can remember transcription if you create a mental image of a scribe rewriting/transcribing your class notes (a scribe is someone who copies). You can remember translation if you think of RNA being a nucleic acid language that is translated into an amino acid language. Complex multicellular organisms contain a huge variety of cell types. Consider the differences between muscle, brain, blood, skin, and bone cells. Each of these cells has a different structure and performs unique jobs. These differences arise from the different proteins expressed in each. However, earlier it was mentioned that all cells contain a copy of the same genome (all of an organism’s DNA). How is it that different cell types contain different types of proteins if all cells contain exactly the same DNA? The answer lies in the control that each cell exerts over which genes are expressed (actively copied to make RNA) and which remain silent. Imagine a group of actors rehearsing a play with each actor holding a copy of the same script. Each actor only reads his own lines, skipping everyone else’s. Similarly, each cell within an organism only expresses the specific genes that it needs to perform its functions, skipping other genes. This discretion is made possible with the help of special proteins called “transcription factors.” Transcription factors bind to genes within the DNA and either promote or hinder the copying of those genes into RNA.

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STEMscopedia: DNA AND RNA Mutations Changes to DNA are called mutations. Think about a recipe for pizza dough in a cookbook. If you substituted sugar for salt, would your dough taste the same? Probably not! In a similar way, if the genetic message changes, the protein may change, or it may not be created at all. Mutations are heritable, permanent changes that are passed on to the next generation of cells when the cell divides. Some mutations are called point mutations. They occur in a single area of DNA. One type of point mutation is a substitution. For example, consider what happens if the codon UAC changes to UAA. UAC codes for tyrosine. UAA is a stop codon. By substituting a single nucleotide for another, the message changes from “add a tyrosine” to “stop adding nucleotides here.” This results in a shorterthan-normal peptide that may not be functional in this shorter form. This single change can “knock out” the protein. Sometimes substitutions do not affect the final protein. Consider a change from UAC to UAU. Although the third nucleotide has changed, both codons code for tyrosine, so the final protein is the same. Sometimes point mutations result in a frame-shift mutation. In this case, a single nucleotide is inserted or deleted from the DNA sequence. This causes a shift in what is called the reading frame. Because DNA is read three bases at a time in a ribosome, an insertion or deletion can cause the wrong amino acids to be added to the chain. This usually results in the assembly of a nonfunctional protein. Mutations happen on a daily basis. Some are caused by errors in the cell replication process or by non-disjunction, which is the failure of one or more pairs of homologous chromosomes or chromatids to separate normally during nuclear division, usually resulting in an abnormal distribution of chromosomes in the daughter cell. Others are caused by exposure to chemicals or ionizing radiation. There are proteins in the cell whose job is to constantly scan DNA looking for damage that needs repair. However, sometimes they miss damaged DNA, and the damaged DNA is passed on to the next generation of cells. Sometimes, the damage takes place in areas of DNA that are not expressed. In these cases, the changes are considered harmless. Mutations that affect cell growth cause cancer, uncontrollable cell division in the body. Getting Technical: Gene Knockouts Scientists will sometimes deliberately cause genetic mutations in an organism. A gene knockout is a process by which a gene in an organism has been made nonfunctional by a directed mutation. This process can help scientists understand the function of a gene. For example, suppose scientists inactivated a particular gene in a mouse genome, and the resulting mouse was hairless. The scientists would know the gene in question was related to hair growth. Knockout organisms can also be used to study diseases. For example, scientists have bred knockout mice with various mutations in the CFTR gene in order to study cystic fibrosis. This disease is caused by mutations in the CFTR gene.

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STEMscopedia: DNA AND RNA A DNA mutation is not always harmful. If a section of DNA is changed that has no real use in a cell, the resulting mutation is harmless. In addition, if the mutation occurs in a noncoding section of the DNA, it is unlikely to cause any harm. Some mutations even increase the survival rates of individuals and are therefore more likely to be passed on to future generations. For example, if a mutation causes a color change in an animal and the color change helps the animal hide from predators, that animal will likely survive and reproduce.

What Do You Think? Part 1: DNA, RNA, or Both Using the following list of phrases and the Venn diagram below, decide whether a phrase belongs in the category “A,” “B,” or “C.” Write the correct letter next to each phrase. 1. Directly translated into protein 2. Double helix 3. A nucleic acid 4. Contains the sugar ribose 5. Wrapped around histones 6. Single stranded 7. Contains nitrogenous bases 8. Double stranded 9. Sugar/phosphate association through covalent bonds 10. Contains adenine, cytosine, guanine, and uracil

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STEMscopedia: DNA AND RNA Part 2: Transcription, Translation, or Both Use what you have learned about transcription and translation to complete the chart below. Read each description in the left column. Then, in the right column, write whether each is associated with transcription, translation, or both. Description

Transcription, Translation, or Both?

A process that is a vital step in protein production. DNA strands separate from each other. Amino acids are linked together in a polypeptide. Takes place in the cytoplasm. Takes place in the nucleus. Involves the use of helicase. Requires tRNA and mRNA. Uses information from a gene to produce a speciﬁc protein.

Connecting With Your Child Activity 1: Building a DNA model To help students better understand the structure of DNA, build a molecule of DNA together. Using construction paper or cardboard, draw the different molecular group components of DNA— phosphate, deoxyribose, and nitrogenous base—and cut them out. You can find templates for these at the bottom of the page. You can decide how long your molecule will be, depending on the amount of time, space, and paper you have available. Try to use each base pair at least once. Since DNA is double stranded, you will need twice the number of components to build the complementary strand. Label the nitrogenous bases either A, C, T, or G. You may want to staple the sugar/phosphate groups together (this would represent your covalent bond) and use tape to connect the nitrogenous bases (this would represent your weak hydrogen bond). When constructing the complementary strand and connecting nitrogenous bases, be sure to pair the bases in the appropriate configuration (A pairs with T, and C pairs with G.) Once your molecule is complete, take hold of each end and twist gently until a double helix is formed. You may want to construct a double helix that reaches from floor to ceiling. If there is a base on which to attach both ends of the molecule, the model can be twisted and maintained in a helix.

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STEMscopedia: DNA AND RNA Here are some questions to discuss with students: 1. When DNA is copied to make a strand of RNA, the double helix must be separated into its two individual strands. Given this, why do you think it is important that the sugar phosphate bonds be strong covalent bonds (as opposed to the weaker hydrogen bonds between bases)? 2. Remember that during meiosis, our DNA is tightly condensed into structures called chromosomes. If a fertilized egg inherits a full complement of chromosomes (23) from both the sperm and the egg, how many chromosomes are contained in the fertilized egg? 3. Looking at your DNA model, in what ways would this model differ if it were a model of RNA?

Activity 2: Codon Bingo Codons are sequences of three nucleotides each in mRNA that code for speciﬁc amino acids. When DNA is transcribed into mRNA, these codons dictate which amino acids should be linked together in the ﬁnal protein. Some codons are “stop” sequences, which end translation at that site. This game reinforces two concepts: a codon is a sequence of three nucleotides that codes for an amino acid, and multiple three-letter codons can code for the same amino acid. To play Codon Bingo, make a large 5 x 5 grid bingo card using construction paper and a marker. Then search for an RNA codon table on the Internet. Government sites usually have accurate, reliable tables. Using the codon table, randomly enter three-letter codon codes into the boxes. Do not repeat any of the codon codes on any one card. Repeat the card-making process for anyone else playing along. A sample table is shown here: UUU

CUU

AUU

GUU

UCU

CCU

ACU

ACA

GCU

UAU

UAA

UAG

CAU

AAU

AAA

GAU

GAC

GAG

UGU

UGC

UGA

CGC

AGU

GGU

GGG

Using the codon table you found on the Internet, begin calling out three-letter combinations at random. You may wish to use the codon chart to cross off each combination as you call it out. Each time a codon is found on the bingo sheet, your child should cross it off, and write the amino acid that codon codes for next to the codon.

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STEMscopedia: DNA AND RNA There are two ways to win the game. The ﬁrst is by “translating” ﬁve codons in a row into amino acids on the bingo card. The second is if the student has a “stop” codon on their card. As you play the game, you may wish to discuss the following questions with your student: 1. What does each codon code for? 2. Do you have any amino acids that appear more than once? If so, what is similar between their codons? 3. What happens when there is a stop codon in mRNA? Activity 3: Construct an Argument Construct an argument based on evidence that inheritable genetic information may result from: • • •

new genetic combinations through meiosis (e.g., crossing over or non-disjunction) nonlethal errors occurring during replication (e.g., insertion, deletion, or substitution) heritable mutations caused by environmental factors (e.g., radiation, chemicals, or viruses)

Once both of you are done constructing your argument, engage in a discussion and share your information.

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B2AB DNA and RNA

Reading Science Name:

Date:

Group:

Heredity Relates to Structure 1

What is DNA, and how does it relate to inheritance? In the 1950s, scientists knew that the molecule deoxyribonucleic acid was a polymer. It is made of a nitrogenous base (a base that contains the element nitrogen), a pentose sugar known as deoxyribose, and a phosphate group. They also knew that the nitrogenous bases consisted of only four specific bases within the molecule. These are adenine (A), thymine (T), cytosine (C), and guanine (G). In 1947, a biologist named Erwin Chargaff noted that the number of certain nitrogenous bases within a species seemed to equal each other. More specifically, the number of adenine (A) and thymine (T) were relatively equal, and the percentage of cytosine (C) and guanine (G) were almost exactly equal. With this finding, he hypothesized that these bases must occur in pairs within the DNA molecule. The fact that A=T and C=G has become known as Chargaff’s rule.

Scientists were also beginning to believe that the DNA molecule itself may be responsible for heredity. Previously, proteins had been thought to fill that role. Why? Scientists had closely observed the process of mitosis, or cell division, in eukaryotic cells. They noticed that not only was the DNA content of each cell precisely doubled, but it was also evenly distributed to each daughter cell created. What they did not know was how these components arranged themselves within the DNA molecule. They also did not know if (or how) the structure of DNA permitted it to be the carrier of genetic information. By the early 1950s, several scientists were taking all of the information known regarding DNA to answer these questions. They were determined to discover the true structure of the molecule, and how this structure may be involved in the passing of genetic information.

Scientists were using a process called X-ray crystallography to study the structure of the DNA molecule. In this process, images are produced from samples of the molecule that have been treated to form crystals. X-rays are passed through the crystals and then photographed as they are deflected from the crystalline structures. This deflection process is also known as X-ray diffraction. The diffracted images did not show the actual structure of the molecules. Instead, they showed distinct patterns that could be used to interpret the structure of molecules. Due to this process, a scientist named Linus Pauling discovered that molecules may have helical shapes.

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Reading Science 4

It was at this time that four scientists stepped into the history books. The first were two scientists working at King’s College in London, named Maurice Wilkins and Rosalind Franklin. Both had been working with the structure of the DNA molecule for quite a long time, but they could not solve the structural puzzle. In 1951, Rosalind Franklin, with a PhD in physical chemistry, was placed in charge of refining the X-ray crystallography work with DNA. Maurice Wilkins, with a PhD in physics, worked with Franklin and her X-ray crystallography technique to study the structure of the DNA molecule.

During this time, a relatively unknown young American scientist named James Watson arrived at the Cavendish Laboratory at Cambridge University in London. He had a keen interest in genetics. Watson had heard that X-ray crystallography images were being made of DNA. At Cambridge, he met a young English physicist named Francis Crick, who was working on X-ray crystallography of blood cells. Wilkins showed Watson an X-ray crystallography image of a DNA molecule created by Franklin. Reportedly, Wilkins did this without Franklin’s permission. This specific image was labeled “Photograph 51.” It was this very image that allowed Watson to determine that the DNA molecule structure was double helical, or twisted.

He used this image to interpret the width of the helix and how the various bases were positioned within the molecule. Based on this information, Watson and Crick quickly built many models. They knew, based on Chargaff’s rule, that the DNA molecule had specific base pairing. This was the key! Watson realized that if he paired the bases according to Chargaff’s rule, then the bonds between the bases would be equal. This, in turn, made the rungs of the ladder of the double helix equal. Therefore, the sugar-phosphate backbone would be smooth. They concluded that it was the specific base pairing that allowed the DNA molecule to duplicate itself. Thus, the structure of DNA enables it to transfer genetic information during the process of replication, as seen in earlier studies of mitosis.

Watson and Crick were the first to solve the puzzle on February 21, 1953. Their findings were published in an article in the April 25, 1953, publication Nature. The article was called “Molecular Structure of Nucleic Acids: A Structure for Deoxyribose Nucleic Acid.” However, it is important to note that Watson and Crick’s findings were primarily based on the previous work of Wilkins and Franklin. Furthermore, Franklin and Wilkins published two articles on the subject in that same issue of Nature. Nevertheless, Watson and Crick still received the credit for being the first to solve the puzzle. James Watson, Francis Crick, and Maurice Wilkins all received the Nobel Prize in Physiology or Medicine in 1962 for their discoveries of the DNA molecule and how its structure related to heredity. Unfortunately, Rosalind Franklin died of cancer in 1958 at the age of 37. Nobel Prizes are only awarded to the living. She was never able to receive this prestigious award, even though her image was the ultimate key to the puzzle.

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B2AB DNA and RNA

Reading Science 1.

Paragraph 1 discusses several important facts regarding the DNA molecule. Which of the following facts relates to Chargaff’s rule? A.

DNA contains a pentose sugar, nitrogenous bases, and a phosphate group.

DNA is a molecule in structure.

DNA contains adenine, thymine, cytosine, and guanine.

Cytosine and guanine appear in equal proportions in DNA.

With any major scientific discovery, the previous work of many different scientists helps contribute to final conclusions. Which of the following scientists’ work did not contribute to the discovery of the structure of the DNA molecule? A.

Gregor Mendel

Linus Pauling

Erwin Chargaff

Rosalind Franklin

X-ray crystallography is a very important process that is used to help identify the structure of molecules. What exactly does this process show? A.

A photograph of the molecule

The atoms within the molecule

Patterns that can be used to interpret structure

The crystal structure of the molecule

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Reading Science 4.

In 1951, four scientists were working on solving the structural puzzle of the DNA molecule. Two of those scientists had worked for many years to try to solve the puzzle, and even though their work became the foundation for the actual discovery of the structure of DNA, they are not often remembered. Who are these two scientists? A.

Watson and Crick

Chargaff and Pauling

Wilkins and Franklin

Mendel and Darwin

In 1962, three scientists who contributed to the discovery of the structure of the DNA molecule were awarded the Nobel Prize in Physiology and Medicine. The fourth scientist who contributed to this discovery, Rosalind Franklin, was not awarded the prize as she had died before this honor could be bestowed. What was her major contribution to this discovery? A.

She determined that DNA was a crystal.

She captured the X-ray crystallography image that led to the discovery.

She determined that nitrogenous bases occurred in pairs.

She determined that DNA was a double helix.

The passage discusses the importance of the discovery of the structure of the DNA molecule. What did this discovery allow scientists to confirm? A.

Specific base pairing allowed DNA to duplicate itself.

If Chargaff’s rule was followed, then the bonds between bases were equal.

Specific base pairing allowed for the transfer of genetic information.

All of the above.

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B2AB DNA and RNA

Math Connections Name:

Date:

Group:

All living organisms have genes that comprise nucleic acids made from the same nitrogenous bases (adenine, guanine, cytosine, thymine, uracil). The combination of these bases determines an organism’s traits. Determine the strand of nucleotides below by solving the equations and matching the answers with the nucleotides in the chart. Key

Nucleotide

Adenine (A)

Solution

Solve and simplify

Cysteine (C) Guanine (G) Thymine (T) Uracil (U) 5

Nucleotide

3x=6 11=3x – 4 –8(3 – x)=32 x / 3=x – 2 4+3x=19 8x=–10x+36 12+5x – 8=12x – 10

Solve and simplify

2. Is this a DNA or RNA nucleotide strand? Why?

3. What percent of the nucleotides of the strand shown are adenine?

4. What percent of the total nucleotides for both sides of this strand are adenine?

Nucleotide

2x – 6=8 5x – 9=46 2x+8=30 (5x+6) / 4=3x – 2 6x+9=39 9+x=4x – 6 4x+5=33

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6. Is this a DNA or RNA nucleotide strand? Why?

7. What percent of the nucleotides for the strand shown are adenine?

8. What percent of the total nucleotides for this strand are adenine?

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B2AB DNA and RNA

Writing Science Name:

Date:

Group:

LOOK

THINK about the structure and function of the DNA molecule. Deoxyribonucleic acid (DNA), a macromolecule known as a nucleic acid, carries all of the information about an organism. The organism’s individual traits are contained within DNA’s many nucleotides, which are the monomers of nucleic acids. DNA structures comprise a phosphate covalently bonded to a deoxyribose sugar molecule, which is similarly bonded to a nitrogenous base. Four nitrogenous bases are located with a DNA molecule: Adenine, Thymine, Guanine, and Cytosine. The order in which these nitrogenous bases are sequenced determines the differences between organisms. The genome of an organism is its complete set of genetic information, which can include up to tens of thousands of genes. A gene is a sequence of DNA that codes for a protein, thus its ability to determine a trait. These sequences carry all of the information for specifying every organism’s many characteristics. WRITE how information for specifying the traits of an organism is carried in the DNA molecule. Be sure to • clearly state your central idea; • organize your thoughts; • develop your essay in detail; • choose your words carefully; and • use correct spelling, capitalization, punctuation, and grammar.

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B2AB DNA and RNA

Writing Science

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High School Biology

B2C

Biotechnology

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B2C Biotechnology

Student Handout Name:

Date:

After viewing the video on stem cells, write a statement for each.

Should I?

Shouldn’t I?

Make sure to give evidence to support your claim.

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B2C Biotechnology

Student Journal Name:

Date:

Group:

Part I: Biotechnology Applications 1.

Research the following applications in biotechnology. List at least two pros and two cons for each and provide an example of its current use. Technology

Pros +

Cons -

Example

Vaccines

Antibiotics

Gene Therapy

Biofuels

Flowers and Horticulture

Plant and Animal Cloning Pesticide Resistant Crops Nutrient Supplementation Genetically Modified Organisms

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B2C Biotechnology

Student Journal Part I: Biotechnology Applications, continued Research Follow-Up 1.

What was the most interesting application that you researched?

What are some of the benefits of genetic testing?

What are some of the consequences of genetic testing?

Part II: Biotechnology Debate 1.

Write your reflections on biotechnology applications after the class debate/discussion in the space below.

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STEMscopedia: BIOTECHNOLOGY B2C

Reflect Biotechnology is generally defined as the use of biological agents for technological advancement, or more specifically, using artificial methods to manipulate and modify the genetic material of living organisms or cells. This is done to produce new biological compounds or to obtain a new function.

biotechnology: a broad and potentially controversial scientific field in which biological agents (organisms, cells, or processes) are exploited to create new agricultural, medical, or industrial technologies

By this definition, biotechnology has been used to selectively breed livestock and crops for thousands of years, way before the science behind it was fully understood by humans. However, since the discovery of DNA, the biotechnology field has expanded and innovated rapidly in academia as well as private industry. This technology is still used in agriculture to genetically modify crops to increase yields. However, now the newest and most prevalent applications of modern biotechnology are in medicine. Medical uses include the production of enzymes, vaccines, antibiotics, as well as targeted gene therapy. Biotechnology is also used in industrial processes such as fermentation and the production of biofuels. Even common household applications use biotechnology methods, like the production of enzymes in laundry detergent. DNA Structure Review: • Nucleic acids are macromolecules made of nucleotides (sugar, phosphate, and nucleotide base). • Nucleotide bases include adenine, thymine, guanine, and cytosine in DNA. • Phosphate groups have a net negative charge. • All of the DNA in the nucleus of eukaryotic organisms is the genome. • DNA has 2 strands: hydrogen bonds and paired bases. How is genetic material manipulated? How do biotechnologists accomplish these technological applications using biological processes? DNA must first be extracted before it can be studied or manipulated in biotechnology applications. 1. Cells are broken open using a detergent solution with a buffering compound. 2. DNA is brought out of this solution using alcohol. 3. Long, polymer-based DNA forms gelatinous mass. selective breeding: a process in which individuals (usually plants or animals) with preferred traits are bred together in hopes of producing offspring with those traits. It is separate from genetically modified organisms because only the genes already existing in those organisms are used.

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STEMscopedia: BIOTECHNOLOGY Gel electrophoresis is a technique used to separate molecules according to size and charge. This works because of the net negative charge of the phosphate-based DNA. Gene therapy is a genetic engineering technique that may one day be used to cure certain genetic diseases. Some applications of gene therapies are vaccines, antibodies, and hormone production. Traditional vaccination strategies use weakened or inactive forms of microorganisms or viruses to stimulate the immune system. Modern techniques use biotechnology to isolate specific genes of microorganisms, clone them into vectors (like a bacterium), and then mass-produce just the protein needed to make large quantities of specific substances to stimulate the immune system. The substances are then used as a vaccine. Recombinant DNA technology was used to produce large-scale quantities of the human hormone insulin in E. coli as early as 1978. Previously, it was only possible to treat diabetes with pig insulin, which caused allergic reactions in many humans because of differences in the insulin molecule between the two species. Molecular Cloning Cloning allows for the creation of multiple copies of genes. To get the DNA fragment into a bacterial cell in a form that will be copied or expressed, the fragment is first inserted into a plasmid. A plasmid, also called a vector, is a small circular DNA molecule that replicates independently of the chromosomal DNA in bacteria. In cloning, the plasmid molecules can be used to provide a “vehicle” in which to insert a desired DNA fragment. Modified plasmids are usually reintroduced into a bacterial host for replication. As the bacteria divide, they copy their own DNA (including the plasmids). The inserted DNA fragment is copied along with the rest of the bacterial DNA. Genetic Engineering Using recombinant DNA technology to modify an organism’s DNA to achieve desirable traits is called genetic engineering. The addition of foreign DNA in the form of recombinant DNA vectors that are generated by molecular cloning is the most common method of genetic engineering. An organism that receives the recombinant DNA is called a genetically modified organism (GMO). If the foreign DNA that is introduced comes from a different species, the host organism is called transgenic. Bacteria, plants, and animals have been genetically modified in this way since the early 1970s for academic, medical, agricultural, and industrial purposes. Plants are the most important source of food for the human population. Manipulating the DNA of plants (creating GMOs) has helped to create traits such as disease resistance, herbicide, and pest resistance, better nutritional value, and better shelf life.

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STEMscopedia: BIOTECHNOLOGY Transgenic plants have received DNA from other species. Because they contain unique combinations of genes and are not restricted to the laboratory, transgenic plants, and other GMOs are monitored by government agencies to ensure that they are fit for human consumption and do not endanger other plant and animal life. Many people are concerned about applications of GMOs on their grocery shelves, particularly in the produce aisle. When you see an apple whose packaging claims it tastes like grapes or a seedless watermelon, know that these did not come about as a result of putting genes of different organisms together. These “new” foods likely came about as a result of selective breeding. The most common food products that actually have been genetically modified include major staple products that are the base of our commercial food system. These include (but are not limited to) corn, soybeans, wheat, sugar, papaya, and some others. Why not do a little research to find out some more?

Look Out Think About It There are many new useful applications of genomics, such as creating new biofuels, assisting in DNA forensics, increasing crop yields, and creating targeted pharmacological and gene therapies.

It is important that we critique the ethical issues and implications of genomics and biotechnology (stem cell research, gene therapy, and GMOs) to ensure that the tools and technology are not used improperly or carelessly. Scientific discourse and debate on all of these issues should be well informed and supported with scientific fact, yet sensitive to societal concerns. This is where science and the lawmaking bodies of our state and nation intersect. The Human Genome Project Genomics is the study of entire genomes, including the complete set of genes, their nucleotide sequence and organization, and their interactions within a species and with other species. The advances in genomics have been made possible by DNA-sequencing technology.

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STEMscopedia: BIOTECHNOLOGY Look Out Genome mapping is the process of finding the location of genes on each chromosome. The maps that are created are comparable to the maps that we use to navigate streets. A genetic map is an illustration that lists genes and their location on a chromosome. Genetic maps provide the big picture and use genetic markers. A genetic marker is a gene or sequence on a chromosome that shows genetic linkage with a trait of interest. The genetic marker tends to be inherited with the gene of interest. Physical maps get into the intimate details of smaller regions of the chromosomes. Genetic maps provide the outline, and physical maps provide the details. Both types of genome-mapping techniques are important to show the big picture. The introduction of DNA sequencing and whole genome sequencing projects, particularly the Human Genome Project, has expanded the applicability of DNA sequence information. Genomics is now being used in a wide variety of fields, such as metagenomics, pharmacogenomics, and mitochondrial genomics. The most commonly known application of genomics is to understand and find cures for diseases. Human genome maps help researchers in their efforts to identify human disease-causing genes related to illnesses such as cancer, heart disease, and cystic fibrosis.

Some forms of biotechnology are controversial, and the ethics of their use are debated. Based on your knowledge of biotechnical medical applications, evaluate the economic and social benefits of some of the most promising gene therapies for medical conditions such as the following: cystic fibrosis, Alzheimer’s, diabetes, hemophilia, AIDS, diabetes, and cancer. Identify cons of these therapies, too.

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STEMscopedia: BIOTECHNOLOGY What Do You Know?

Economic

Social

Cons

Use your prior knowledge and any new knowledge gained during these lessons to evaluate the ethical use of biotechnology in agriculture. Identify at least one pro and one con of each of these as part of your argument. 1. Herbicide intolerance in soybean plants 2. Insect resistance in corn 3. Drought tolerance in wheat 4. Vitamin enrichment in rice

Connecting With Your Child Have you ever actually seen DNA? In your own kitchen, you and your child can extract DNA just like a biotechnologist would! Gather the following materials: • Rubbing alcohol • Small bowl • 1/2 Teaspoon salt • 1/3 Cup water • 1 Tablespoon dishwashing detergent (such as Dawn) • 3 Strawberries (green tops removed) • Small plastic zip-top bag • Funnel cheesecloth (or a coffee filter) • Tall drinking glass • Test tube or small, clear glass jar • Bamboo skewer (optional)

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STEMscopedia: BIOTECHNOLOGY 1. Put the rubbing alcohol in the freezer to chill while you prepare the rest of the experiment. 2. Mix the salt, water, and detergent in a small bowl. This will be your extraction liquid. 3. Put the strawberries in the plastic bag and squeeze out all the extra air before sealing tightly. 4. Mash the strawberries with your hands for about two minutes until they are mushy. 5. Add three tablespoons of the extraction liquid to the strawberries in the bag. Squeeze out the air and seal the bag again. 6. Mash the strawberry mixture with your hands for another minute. 7. Place a layer of cheesecloth inside the funnel and set the funnel on top of the tall drinking glass (so that it will empty into the glass). 8. Pour the strawberry mixture from the bag into the funnel. Let it drop through the cheesecloth until there is no liquid left. 9. Throw away the cheesecloth and the strawberry pulp inside it. 10. Pour the contents of the glass into the test tube or small jar until it is one-quarter full. Tilt the test tube or jar, and pour rubbing alcohol down the side very slowly. The alcohol will form a layer on top of the strawberry juice. Do not let the alcohol mix with the strawberry juice! Let the contents sit for a few minutes. You should see stringy, whitish stuff collecting between the two layers of liquid. This is DNA! You can gently pull the DNA out with the bamboo skewer if desired. Discuss the following questions with your child: 1. What is biotechnology? 2. How is it used? 3. Which steps of the instructions go with the steps in the image? 4. What is gene therapy? 5. What are some of the pros and cons of biotechnology?

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B2C Biotechnology

Reading Science Name:

Date:

Group:

GMO Medicine 1.

People have been modifying the genetics of organisms for thousands of years through selective breeding. However, they were limited to modifying only genes already present in the plant or animal. More recently, genes from completely unrelated organisms have been inserted into organisms as diverse as bacteria, fish, and goats. For this reading, the definition of genetically modified organism (GMO) includes only those whose genome contains one or more genes from an unrelated organism. Furthermore, these genes must be passed on from parent to offspring.

One use of GMOs is in producing medicines for human consumption. For example, scientists inserted the gene for human insulin into bacteria. Insulin is used to treat diabetes in children and adults. Before bacteria, insulin was extracted from slaughtered cows and pigs. Although cow or pig insulin works, it causes an allergic reaction in some people. Insulin made by the bacteria is human insulin, and therefore does not cause an allergic reaction.

Goats are also being used to produce medicine. About one in 2,000 people are born without a protein that inhibits blood clotting. Those affected are at increased risk of blood clots during surgery or, for women, in childbirth. Genetically modified goats produce a protein called antithrombin in their milk. The goats are milked, and the milk is processed to extract the antithrombin protein.

Another potential use of GMOs is as a source of organs for transplantation. Currently, many people die while waiting for an organ to become available. Transplanting organs from genetically distant species, such as pigs, always results in a strong immune response in the patient, leading to organ rejection and frequently death. Inserting human genes into pigs can make the organ “look” more human to the immune system and therefore lessen rejection.

There are both advantages and disadvantages in using animals to produce medicines or organs. Production can be predictable, making available enough medicine or organs to meet human needs. On the other hand, genetically modifying animals may cause distress to the animals, which are treated similar to factories.

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B2C Biotechnology

Reading Science 6.

Do you think animals should be used to produce medicines and organs? Here are some things to consider before you answer that question. Is using bacteria different from using mammals such as goats or pigs? Goats are not killed to harvest the protein, but pigs must be killed to harvest organs. Is using pigs to grow organs for transplant the same or different from using pigs for food? Different people will arrive at different conclusions, and those conclusions may change as technology continues to advance. For example, one day 3-D printers may make organs using biological materials as “ink.”

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B2C Biotechnology

Reading Science 1.

Which of the following statements best describes the genome of a GMO? A.

It contains one or more genes from another organism.

It contains only genes not found in the wild population.

In contains fewer genes than non-GMO varieties.

It contains more chromosomes than non-GMO varieties.

What was the problem with insulin derived from pigs? A.

It does not treat diabetes.

It was scarce and expensive.

It caused allergic reactions.

It had to be injected.

Antithrombin is harvested from goats by ___________. A.

drawing their blood and processing it

milking them and processing the milk

killing them and eating their meat

shearing them and processing their fur

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B2C Biotechnology

Reading Science 4.

Pig organs cannot be used in humans because ___________. A.

the organs of pigs are much smaller than human organs

pig organs function very differently from human organs

people don’t want pig organs in their bodies

the human immune system strongly rejects pig organs

Which of the following is NOT an advantage to using animals to produce medicines? A.

The medicines produced don’t cause allergic reactions.

Production can match demand for the medicine.

Producing medicine may cause the animal pain.

Medicine may be harvested without killing the animal.

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B2C Biotechnology

Math Connections Name:

Date:

Group:

Biotechnology has increased our knowledge and career opportunities in many fields and has provided economic benefits for Georgia. There are currently more than 650 life-science companies and more than 2,000 additional companies that support life sciences. Since 2001, biotechnology companies have created more than 12,000 jobs in the areas of pharmaceuticals, research, testing and medical labs, agricultural feedstock, and chemicals. The table below shows the Employment Index for Biosciences in Georgia vs. the United States as a whole. Employment Index of Jobs in Biosciences Year Georgia United States 2001 100 100 2002 104 101 2003 107 102 2004 114 104 2005 118 105 2006 121 106 2007 121 107 2008 124 109 2009 123 106 2010 123 106 Use the data in the table to create a line graph comparing the Georgia Employment Index to the United States.

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B2C Biotechnology

Math Connections 1.

How does the employment index for bioscience jobs in Georgia compare to that of the United States?

What does this say about the growth of bioscience in Georgia?

North Carolina has experienced more growth in bioscience jobs than any other state. What percent increase in bioscience jobs did Georgia experience from 2001 to 2010?

What percent increase in bioscience jobs did the United States experience from 2001 to 2010?

What do you think contributes to Georgia being a hub for bioscience companies? Think about what is needed to start and maintain a successful business.

Add the following data about the employment index of all other private sector jobs in Georgia to the graph on page 1.

Year Employment Index

2001

Employment Index of Private Sector Jobs 2002 2003 2004 2005 2006 2007 2008

2009

2010

100

104

106

105

The United States experienced a recession in 2008 and in the following years. How did bioscience jobs compare to those of other private sector companies?

From a pre-recession high of 3.4 million jobs, Georgia’s private sector jobs fell to a low of 3.1 million in 2010. What was the percent decrease in private sector jobs?

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B2C Biotechnology

Writing Science Name:

Date:

Group:

LOOK

THINK about the ethical issues surrounding the use of DNA technology. In 1985, scientists began thinking about sequencing the entire human genome. The Human Genome Project (HGP) was a collaborative research program that included centers in the US, France, and Germany. The goal of HGP was to achieve the complete mapping and understanding of all the genes of human beings. The HGP has revealed that there are probably about 20,500 human genes. The completed human sequence can now identify the genes’ locations. This ultimate product of the HGP has given the world a resource of detailed information about the structure, organization, and function of the complete set of human genes. In 1998, Congress provided the funds for American scientists to work on this project, and by April of 2003, the full sequence was completed. The cost of the research program was $2.7 billion. Today, sequencing a person’s entire genome costs between $1,000 and $5,000, and you can search the Internet for companies that do it. Although we do not fully understand the entire sequence, there are many genes that can tell if you are destined to have specific diseases. WRITE Discuss the advantages and disadvantages of having your genome sequenced. Be sure to • clearly state your central idea; • organize your thoughts; • develop your essay in detail; • choose your words carefully; and • use correct spelling, capitalization, punctuation, and grammar.

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B2C Biotechnology

Writing Science

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High School Biology

B3A

Mendel’s Law

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B3A Mendel’s Laws

Student Handout Date:

Meoisis Board

Name:

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B3A Mendel’s Laws

Student Journal Name:

Date:

Group:

Mendel’s Laws Reproductive Variability 1.

Flip the coin and record your results below. One partner will represent the mother; the other partner will represent the father. If the coin lands on heads, record the dominant allele. If the coin lands on tails, record the recessive allele. Mother’s Allele

Father’s Allele

Genotype After Fertilization

Phenotype

Grey fur (G) or brown fur (g) Straight fur (S) or curly fur (s) Black eyes (B) or brown eyes (b) Hair on paws (H) or bald paws (h) Pointed ears (P) or folded ears (p) Long tail (L) or short tail (l) 2.

Draw a picture of what your guinea pig would look like.

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B3A Mendel’s Laws

Student Journal Reproductive Variability, continued 1.

Compare the result of your guinea pig with the results of other groups in your class. Explain any similarities and differences that you notice.

How is the law of segregation demonstrated during this activity?

How is the law of independent assortment demonstrated during this activity?

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STEMscopedia: MENDEL’S LAWS B3A Reflect Have you ever seen a litter of newborn puppies? Usually, you will notice that all of the puppies have different color markings. This is the same for kittens, and even humans and their siblings. Why is it that two parents can produce such a wide array of offspring? Genetic variability is important for species success. Father of Genetics In a monastery garden, a curious monk discovered some of the basic principles of genetics. The work of the monk, Gregor Mendel, laid the groundwork for the study of genetics, which has advanced our understanding of many related areas of science, including the genetics of certain diseases and the process of selective breeding. Science did not advance enough in Mendel’s lifetime for him to learn of the existence of DNA and genes. Still, he was able to provide us with mechanisms of how traits were passed on from parents to offspring. Mendel’s Law of Segregation Gregor Mendel (1822-1884) Gregor Mendel studied pea plants due to their relatively quick was an Austrian monk who reproductive rates and distinctive varieties. At the time, it was believed developed ideas on genetic that offspring were simply a blend of traits from parents. After studying inheritance patterns. many generations of pea plants crossed from a variety of parent pea plants, Mendel was able to determine that was, in fact, not the case. He noticed that when two hybrid plants—plants that have two alleles for a trait—were crossed, the offspring showed unexpected traits. This meant that if a plant had the dominant and recessive allele for a trait, they would not be passed on to the next generation together. Instead, the alleles separated, or segregated, when the gametes formed. During sexual reproduction, when male and female gametes unite, the resulting offspring will have received one random allele for a trait from each parent, producing the unexpected trait patterns Mendel observed and meaning that two hybrids could produce offspring pure for a particular trait.

What Do You Think? After studying this kind of inheritance pattern, what do you think accounts for the fact that people have so many variations of traits like height, eye color, and hair color? Law of Independent Assortment Mendel thought about the many traits that are observed in pea plants. He came up with his second law, which states that alleles of different traits will be segregated independently of one another. For example, the traits of height (tall and short), flower color (white and purple), and seed color (yellow and green) in a pea plant are all inherited completely independent of each other. No trait in pea plants is dependent on another trait. Just because a plant has a certain seed color does not mean it will have a certain height or flower color.

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STEMscopedia: MENDEL’S LAWS If traits in pea plants are inherited independently of one another, why do certain traits show up in combination in high frequency in people, like dark hair and dark eyes? Meiosis and Genetic Variation Meiosis increases genetic variation in organisms that undergo sexual reproduction. Meiosis is similar to mitosis in that chromosomes replicate and divide into daughter cells. However, during meiosis, cells undergo two divisions (meiosis I and II) resulting in daughter cells with half the number of chromosomes as the parent cell, which is called haploid. These cells are the gametes, or sex cells, referred to as sperm and eggs. When eukaryotes reproduce sexually, the gametes from each parent join together. The two haploid cells combine, giving the offspring a complete set of chromosomes, which is called diploid. Sexual reproduction creates greater genetic variety in two ways. First, an offspring inherits DNA from both of its parents. This causes new random combinations of alleles, resulting in a variety of traits that differ from the mother and the father. Since genes are randomly assorted when they are passed to offspring, even two siblings have different combinations of genes and traits from the same set of parents. Only identical twins have exactly the same DNA. Meiosis also contributes to genetic variation through crossing over. During one phase of meiosis, homologous chromosomes—pairs of chromosomes containing the same genes, but possibly different alleles—line up at the center of the cell. When this happens, sections of the homologous chromosomes can cross over and switch from one chromosome to the other. This results in a reshufﬂing of genes on the individual chromosomes, which provides an even greater variety of genetic combinations that can be passed on to offspring.

Meiosis has an extra step that results in the production of four haploid cells. These are the sex cells, sperm and eggs.

Look Out Mitosis and meiosis are very similar processes that are often confused for one another. It is important to understand that the second phase of meiosis lacks the crucial step of DNA synthesis, which is why the four resulting daughter cells only have half the original amount of chromosomes.

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STEMscopedia: MENDEL’S LAWS Connecting With Your Child Variability in nature due to sexual reproduction is the driving force behind evolution. To help your child learn more about this, have them research the advantages and disadvantages of sexual reproduction over asexual reproduction. Also have them create a chart or Venn diagram, or even write a paper, to compare the two. Make sure your child can explain the difference between the two types of reproduction and explain how sexual reproduction contributes to higher genetic variability.

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B3A Mendel’s Law

Reading Science Name:

Date:

Group:

Gregor Mendel and Heredity 1. Traits are the part of our genetic code that make us who we are. You may have brown or blond hair, dark or light skin, or a blood type of A, B, AB, or O. These are all traits that are encoded on your DNA, your genetic material. Can one predict traits? Are certain traits more likely to be passed from one generation to the next? What exactly are the variations that we observe between organisms? How do they occur? 2. It was once hypothesized that the traits that arose from generation to generation must be blended in the same manner that different colors of paint are blended. According to this hypothesis, if a plant with red flowers reproduced with a plant with white flowers, then all of the flowers of the offspring should be pink. In other words, over time, all of the offspring of those plant parents should produce pink flowers. However, for many organisms, this was not the observed result. Others, including Charles Darwin, thought that an organism’s experiences caused them to produce chemicals in the blood. They thought these chemicals traveled to the animal’s reproductive organs and then were passed to their offspring. Another hypothesis was later described as the “gene” hypothesis. This hypothesis speculated that traits were passed from generation to generation through specific packages known as heritable units. There were three scientific explanations proposed for heredity. It would take careful experimental testing to determine which was most accurate. 3. The process of trait transfer became the life’s work of a monk and genetic pioneer named Gregor Mendel. He is now known as the Father of Modern Genetics. He was curious about the questions of trait transfer and spent his life studying heritability. Gregor Mendel grew up in Austria in the mid-1800s. As a young boy, he learned about agriculture and farming. As a young man, he studied at the University of Vienna. He learned about science, the experimental method, and the causes of variation in plants. Mendel also learned how to use statistics and probabilities to help analyze his data. Once his studies were completed, he moved to a monastery. This is where he began to investigate inheritance and the process of trait transfer, using garden peas as his subjects.

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B3A Mendel’s Law

Reading Science Continued 4. Mendel relied on all of the knowledge he had gained throughout his life. However, his study of statistics proved to be very useful in his final analysis. His choice of garden peas also helped with this process. Garden peas were a good choice for the scientific study of heredity as they came in many varieties. Furthermore, it was easy to control the pollination process due to the structure of the pea flowers. They also produced a lot of offspring (large sample size) and were fast growing. Mendel was able to track the changes in traits from generation to generation, often within one growing season. Mendel was also very wise when he planned his study. He chose traits from the pea plants that were easy to distinguish. For example, he looked at flower color (purple or white), plant height (tall or short), or pea color (green or yellow). In this way, he was able to track the heritability of each specific trait as a heritable unit and could statistically track the results. One of Mendel’s greatest gifts was the ability to see statistical patterns in the results of his breeding program. 5. So how did he conduct these experiments, and what did he learn? Mendel began by crossing what he called “true-breeding” plants. When the true-breeding plants reproduced by selfpollination, the offspring would be identical to the parents. In other words, when plants with white flowers self-pollinated and created seeds, the offspring from those seeds would all produce white flowers. He used true-breeding parents and single traits for his study. His experimental procedures isolated variables and allowed him to decipher his results. 6. Mendel would follow his breeding plants for at least three generations. To test the gene hypotheses regarding inheritance, Mendel would cross two different types of true-breeding parents. The parents would only differ in one trait, such as flower color. The first generation, the true-breeding parents, was known as the P generation. This stood for parental generation. The hybrid offspring of the P generation were known as the F1 generation. This stood for first filial generation, since filial is derived from the Latin word for son. Then Mendel would allow the hybrid F1 generation to reproduce, creating an F2 generation. The second filial generation can be thought of as grandchildren of the original parent generation. 7. If the blending hypothesis were true, then all of the F1 generation should have had light purple flowers, but this was not the case. All of the offspring had purple flowers. How could this be? When Mendel allowed the purple-flowered F1 generation to self-pollinate, some of the resulting plants produced white flowers like one of the plants in the P generation. Mendel realized that there must be specific traits that are dominant over other traits. As the white trait did not fully disappear, this must mean that the purple trait was dominant over the white trait. Mendel compared the numbers of plants with purple flowers to the number with white flowers in the F2 generation. He saw that the flower colors consistently showed up in a ratio of three purple flowers to one white flower. Here is where Mendel used his mathematical knowledge to help him uncover the secret. Mendel found that traits occurred in predictable ratios from generation to generation. Therefore, he concluded that traits must be transferred in discrete units from parent to offspring. In Mendel’s study of garden peas, the gene hypothesis was supported.

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Reading Science 1. Following the sequence of Mendel’s heritability study in paragraph 6, which of the following is true? A Mendel began by breeding two of the same true-breeding parents. B Mendel began by breeding two different types of true-breeding parents. C The offspring of the P generation were known as the first filial generation. D Both B and C.

2. Why were garden peas a good choice for a study of heredity? A They come in many varieties. B They produce a large sample size, or many offspring. C The breeding, or pollination process, is easy to control. D All of the above.

3. The results of Mendel’s study supported the gene hypothesis of heredity because the flower colors of the offspring– A all blended. B appeared in distinct and predictable ratios. C always were either one color or the other. D never changed from generation to generation.

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Reading Science 6. Gregor Mendel studied many things at the University of Vienna. According to the passage, which of the following topics of study was the most crucial to his final analysis? A The study of statistics and probabilities B The study of plant varieties C The study of agriculture D The study of the experimental method

7. Consider the following experiment: True-breeding tall pea plants are cut short before being pollinated to determine if there is an effect on the offspring. Which explanation for trait inheritance is this testing? A Blended inheritance B Gene theory C An organism’s experiences are passed to their offspring D None of the above

8. Which trait did Gregor Mendel examine from the pea plant when he planned his study? A Plant height B Color of the plant flower C Traits that were easy to distinguish D All of the above

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B3A Mendel’s Laws

Math Connections Name:

Date:

Group:

Part I: Chromosomal Abnormalities All eggs (oocytes) a female will have are formed before birth by the ovaries. A baby girl is born with almost 1 million oocytes. As a female matures and ages, her number of potential eggs gradually deteriorates. Only about 400 oocytes will be released during a woman’s reproductive life. However, as a woman ages, so do her eggs. The risk of having a baby with a chromosomal abnormality (such as Down’s syndrome) increases with age. Examine the table below to understand how the age of the mother affects the probability of having a baby with Down’s syndrome. Probability of Having Offspring with Down’s Syndrome Mother’s Age Probability of Down’s Syndrome 20 0.05% 25 0.08% 30 0.11% 35 0.29% 40 1.00% 45 3.33% 50 10.0% 1.

Using the data from the table, create a graph that outlines the risk of Down’s syndrome when compared to a mother’s age.

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Math Connections Use the data from the graph to answer questions 2–4. 2.

Based on this data, how does the age of the mother affect the risk of Down’s syndrome in the child?

On a particular day, there were 5,252 live births by 30-year-old women. How many children would you expect to be born with Down’s syndrome?

How would this number differ if all of the mothers were 45 years in age?

Part II: Meiosis The following graph shows the amount of DNA a cell contains over time while undergoing meiosis. Use the graph to answer questions 5–9.

Amount of DNA per cell

Amount of DNA Per Cell Undergoing Meiosis 4 3 2 1 Time

At which stage(s) would the cell be considered diploid (2n)?

At which stage(s) would the cell be considered haploid (1n)?

Which stage represents the synthesis portion of interphase? What happens at this stage?

Which stage represents meiosis 2?

Which stage represents a sperm cell?

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B3A Mendel’s Laws

Writing Science Name:

Date:

Group:

LOOK

THINK about the role of meiosis in reproductive variability. All organisms strive to reproduce and pass their genes to the next generation, a process known as reproduction. Some organisms (prokaryotes) pass on exact copies of their genetic material through an asexual process known as binary fission. However, this leads to little diversity within the population, as each offspring is an exact copy of its parent. Animals go through sexual reproduction, in which the mother’s and father’s genes are combined to create diverse offspring. The three dogs in the photo have the same parents and were born in the same litter, yet their coats are of various colors. Sexual reproduction creates diversity through the new and unique combinations of genetic material. When animals mate, one chromosome from the father (sperm cell) and one chromosome from the mother (egg cell) join together. The non-identical parent cells combine in new and unique forms in their offspring. As shown above, this may lead to a variety of coat and eye colors, making each offspring unique. WRITE the process of meiosis, and compare the advantages of sexual reproduction versus asexual reproduction. Be sure to • clearly state your central idea; • organize your thoughts; • develop your essay in detail; • choose your words carefully; and • use correct spelling, capitalization, punctuation, and grammar.

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Writing Science

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High School Biology

B3B

Patterns of Inheritance

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B3B Patterns of Inheritance

Student Handout Name:

Date:

Mendel’s Laws 1.

Do genetic combinations affect only our physical appearance, or are there other ways we are like our parents?

Based on your prior knowledge, what is heredity?

What traits do you observe from the large sample of peas shown?

(a.) From the sample of four peas, what traits do you observe?

(b.) The parent plants of these peas produced the four seeds in the picture. What is the probability of the parents producing a round-shaped pea?

(c.) If the parent pea plants were to produce 200 seeds, how many of the offspring would you expect to be wrinkled?

What traits could be studied from these fruit flies?

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B3B Patterns of Inheritance

Student Journal Name:

Date:

Group:

Part I: Traits Below is a list of traits that an individual may possess. For each of the following traits, put an “X” in the column labeled “Nature” if it is an inherited trait or in the column labeled “Nurture” if it is a learned or environmentally influenced trait. Traits

Nature

Nurture

Brown Eyes Athletic Short in Height Red Hair High IQ Overweight Smokes Mental Illness Addiction Cancer 1.

What determined if you placed a “X” in the Nature column or Nurture column?

Are there any factors that you think are both determined by nature and nurture? Explain.

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Student Journal Part II: Predicting Mendelian Genetic Outcomes Earwax Trait Example A man has a genotype of Ww. W will be dominant for wet earwax, and w will be recessive for dry earwax. This means the man has wet earwax. A woman also has a genotype of Ww and also has wet earwax. The pair decides to have offspring. The genotype cross is Ww x Ww. This means it is a cross between two parents who are heterozygous for wet earwax.

Genotype = The letters in the parent boxes represent the parents’ genotypes with both alleles. 1.

Ww W

W w

The single letters in the boxes on the top of the square represent a single allele from each parent.

The double letters within the square represent the alleles of the offspring.

Fill in the Punnett square and then use that information to complete the chart below. Offspring Box Number

Genotype

Phenotype

Homozygous or Heterozygous

1 2 3 4 F1 genotypic ratio: _______ : _______ : _______ F1 phenotypic ratio: _______ : _______ 2.

What percentage of offspring would have dry earwax? ________

What is an allele and how does it relate to a chromosome, a gene, and a trait?

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B3B Patterns of Inheritance

Student Journal Part II: Predicting Mendelian Genetic Outcomes, continued One of the dry earwax offspring decides to marry and have children with a heterozygous wet earwax woman. Determine the chances for their offspring to have wet or dry earwax.

Genotype =

X 1

Fill in the Punnett square and then use that information to fill in the chart below. Offspring Box Number

Genotype

Phenotype

Homozygous or Heterozygous

1 2 3 4 F1 genotypic ratio: _______ : _______ : _______ F1 phenotypic ratio: _______ : _______ 2.

What is the fraction of offspring would have wet earwax? ________

3. State the difference between a genotype and a phenotype, then explain how you would identify each. That is, where would you look for a genotype or a phenotype?

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B3B Patterns of Inheritance

Student Journal Part II: Predicting Mendelian Genetic Outcomes, continued Determine the genotypic and phenotypic ratios of a man that is heterozygous for wet earwax (Ww) and unattached earlobes (Ee) and a woman who is also heterozygous for wet earwax (Ww) and unattached earlobes (Ee).

Genotype =

genotypic ratio:

phenotypic ratio:

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B3B Patterns of Inheritance

Student Journal Part III: Non-Mendelian Genetics Incomplete Dominance Using the information in your Student Guide, cross a pink flower and red flower.

Genotype =

Fill in the Punnett square and then use that information to fill in the chart below. Offspring Box Number

Genotype

Phenotype

Homozygous or Heterozygous

1 2 3 4 F1 genotypic ratio: _____RR : _____R’R’ : _____RR’ F1 phenotypic ratio: _____Red : _____White:____Pink 2.

In your own words, explain why incomplete dominance does not follow Mendel’s laws of heredity.

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B3B Patterns of Inheritance

Student Journal Part III: Non-Mendelian Genetics, continued Codominance Using the information in your Student Guide, cross two black-and-white speckled chickens.

Genotype =

Fill in the Punnett square and then use that information to fill in the chart below. Offspring Box Number

Genotype

Phenotype

Homozygous or Heterozygous

1 2 3 4 F1 genotypic ratio: _____BB : _____WW: _____BW F1 phenotypic ratio: _____Black : _____White:____Black/White Speckled 2.

In your own words, explain why codominance does not follow Mendel’s laws of heredity.

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Student Journal Reflection and Conclusions 1.

You were asked to predict the possible outcomes of genetic crosses. What methods did you use to predict genetic outcomes? Describe those methods.

DNA for all organisms is composed of the same parts. What makes your DNA different from another person’s DNA?

What makes Mendelian inheritance patterns different from non-Mendelian inheritance patterns?

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STEMscopedia: PATTERNS OF INHERITANCE B3B Reflect Have you ever looked into a mirror at your reflection and wondered why you look the way you do? Why do you look similar to your parents or siblings but not identical? The answers to these questions can be gained by looking at a curious monk’s discovery of the basic principles of genetics. The work of the monk, Gregor Mendel, laid the groundwork for the study of genetics, which has advanced our understanding of many related areas of science, including the genetics of certain diseases and the process of selective breeding. Scientists have built upon the discoveries of Mendel, answering some important questions, including why organisms look and act the way they do, why offspring resemble their parents, and what role technology can play in genetics. Let’s explore the answers to these questions. Genotypes, Phenotypes, and Punnett Squares An organism’s traits can be predicted based on its parents’ traits. Mendel conducted breeding experiments with pea plants and concluded that some characters are determined by two factors. For example, the peas he worked with could have either a smooth texture or a wrinkled texture. These different values for the texture character are called traits. Traits are determined by alleles, which are different versions of a gene. Offspring inherit one allele from each parent in sexual reproduction. The combination of the two alleles is the offspring’s genotype and determines what trait the organism will express. In Mendelian genetics, two letters, such as Ss (one letter for each allele), represent genotypes. A capital letter means the allele is dominant. A lowercase letter means the allele is recessive. One possible genotype for the texture of the peas in Mendel’s breeding experiments was Ss, meaning that the offspring could have inherited one dominant allele and one recessive allele. Smooth texture (S) is dominant, and wrinkled texture (s) is recessive. A pea plant with the genotype Ss has smooth peas because the dominant allele masks the recessive one. The smooth texture is the phenotype. The phenotype is the physical expression of the alleles. It is the outward appearance of the genotype. So a pea with a genotype SS will also have smooth peas, but a pea with the genotype ss will express the recessive trait, wrinkled peas. When the genotypes of two parents are known, it is possible to predict the genotypes and resulting phenotypes of the offspring. A Punnett square is used to find and analyze the possible gene combinations of the offspring. How traits are passed from parents to offspring?

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STEMscopedia: PATTERNS OF INHERITANCE Genetic Outcomes The Punnett square on the right shows a monohybrid cross for a single trait represented by a blue “A” for the dominant allele and a purple “a” for the recessive allele. In this monohybrid cross, the parents have one of each allele for the trait, allowing us to examine all possible combinations of the alleles. Therefore, the parents are both heterozygous, meaning that each parent has two different forms of an allele for a particular trait (Aa). Their genotypes are written across the top and down the left side of the Punnett square. The genotypes inside the squares represent the possible allele combinations for the offspring. Notice that two possible genotypes in the offspring are homozygous, meaning they have two of the same forms of an allele for a particular trait: AA and aa.

In this Punnett square, the offspring have a 75 percent chance (three out of four) of expressing the dominant trait and a 25 percent chance (one out of four) of expressing the recessive trait.

Mendelian genetic crosses include dihybrid crosses as well. A dihybrid cross examines the possible inheritance of two specific sets of alleles. The Punnett square below shows the possible genotypes and their frequencies for a trait represented by the letter “A” (“a” for the recessive form) and a trait represented by the letter “B” (“b” for the recessive form).

What Do You Think? For the dihybrid cross on the above, calculate the frequency of each phenotype. For example, combinations containing at least one “A” and one “B” appear nine out of 16 times, giving offspring a 56 percent probability of expressing both dominant traits. What is the probability of the offspring expressing both recessive traits? Dominance In Mendelian genetic crosses, you can observe a dominant and recessive allele. The dominant allele will be expressed when one dominant (capital letters) or both dominant alleles are present. Sometimes the word dominant can be misinterpreted. A dominant allele is not necessarily stronger or better than the recessive allele and does not always occur most often in the population. An example of this is polydactyly, where an individual’s hand or foot will have more than five fingers or toes. Having five fingers and toes is a recessive allele, while polydactyly is a dominant allele that is rarely expressed in a population.

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STEMscopedia: PATTERNS OF INHERITANCE Polydactyly is a condition of having more than five fingers or toes. The allele for this disorder is a dominant allele. Non-Mendelian Genetic Crosses Geneticists soon discovered that some traits do not follow Mendel’s patterns of inheritance. These non-Mendelian traits include phenotypes that are coded by multiple alleles or do not follow the normal rules of dominance. Some alleles display codominance in which both alleles of a gene are expressed completely. Neither alleles is dominant or recessive and are fully and separately expressed in the organism at the same time. An example occurs when a homozygous red flower is crossed with a homozygous white flower. In incomplete dominance, the offspring would be pink, but in a codominant flower, the petals will have some red areas and some white areas. Incomplete dominance Another type of non-Mendelian genetics is incomplete dominance. In this case, a heterozygous genotype results in a blend of the two traits. For example, a certain breed of snapdragon plant produces white flowers and red flowers. When they are crossed, a heterozygous offspring is produced with a third phenotype: pink flowers. Incomplete dominance is popular when breeding plants and animals in order to obtain a blend of desired traits. Polygenic Traits When traits are produced by two or more genes, they are said to polygenic traits. Eye color is an example of a polygenic trait. Scientists have identified as many as 10 genes that play a role in human eye color. Below is a chart showing how three of these genes play a role in green, blue, and brown eyes. The order of dominance for these three eye colors is as follows: brown > green > blue. Gene Name BEY1 BEY2 GEY

Dominant Allele Brown Brown Green

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Recessive Allele Blue Blue Blue

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STEMscopedia: PATTERNS OF INHERITANCE What Do You Think? Some flowers exhibit codominance. Predict what the offspring of a red flower and a white flower would look like if they followed a codominant pattern of inheritance. Meiosis and Genetic Variation Meiosis increases genetic variation in organisms that undergo sexual reproduction. Meiosis is similar to mitosis in that chromosomes replicate and divide into daughter cells. However, during meiosis, cells undergo two divisions (meiosis I and II) resulting in daughter cells with half the number of chromosomes as the parent cell, which is called haploid (n). These cells are the gametes, or sex cells, referred to as sperm and eggs. When eukaryotes reproduce sexually, the gametes from each parent join together. The two haploid cells combine, giving the offspring a complete set of chromosomes, which is called diploid (2n). Sexual reproduction creates greater genetic variety in two ways. First, an offspring inherits DNA from both of its parents. This causes new random Crossing over during combinations of alleles, resulting in a variety of traits that differ from the meiosis I in the cells shown mother and the father. Since genes are randomly assorted when they here resulted in sections are passed to offspring, even two siblings have different combinations of of the two homologous genes and traits from the same set of parents. Only identical twins have chromosomes switching exactly the same DNA. Meiosis also contributes to genetic variation places. through crossing over. During one phase of meiosis, homologous chromosomes—pairs of chromosomes containing the same genes, but possibly different alleles—line up at the center of the cell. When this happens, sections of the homologous chromosomes can cross over and switch position from one chromosome to the other. This results in a reshuffling of genes on the individual chromosomes, which provides an even greater variety of genetic combinations that can be passed on to offspring.

Look Out Sexual reproduction is beneficial to organisms because it increases genetic variation, but asexual reproduction has advantages as well. In asexual reproduction, a single parent produces offspring that are genetically identical to the parent and to one another. This type of reproduction is mostly associated with prokaryotes. Other simple life forms, such as the hydra and sponge, may reproduce sexually or asexually at various stages of their lives. Although genetic variation is compromised in asexual reproduction, there are benefits to the parent organism. Animals that are immobile, such as sponges, would have great difficulty finding a mate. Asexual reproduction allows them to produce offspring without having to travel. Another advantage is that in asexual reproduction the parent expends much less energy compared to sexual reproduction.

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A bud, or offspring, grows out of the left side of this hydra. What do you know about the bud’s genetic makeup?

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STEMscopedia: PATTERNS OF INHERITANCE This allows organisms to produce many offspring without greatly taxing their energy or time. Finally, in a stable environment, asexual reproduction produces offspring with the necessary genetic traits to survive and thrive in their environment. Mutations can also occur during meiosis. This is a change in an organism’s DNA and can affect a single gene (replication) or a group of genes or chromosomes. Chromosomal mutations take place during the crossing over process in meiosis. Two types of this are gene duplications and gene translocation. Remember, not all mutations will impact phenotype. Discover Science Mapping the human genome and other genetic technology identifying 25,000 genes and sequencing three billion base pairs of the human genome is no simple task. But in 2003, after 13 years of research by scientists in more than 18 countries, the Human Genome Project was completed. In addition to identifying and sequencing all of the genetic material, the project’s goals included creating a database to store the information, improving the tools used for analyzing the data, sharing the technology with companies who could advance the research, and addressing the ethical issues involved with advancements in genetics. Although the project has been completed, analyzing the data and applying it will continue for many years to come. There are a variety of techniques that are used to study the genomes or smaller sections of genetic information in organisms. •

Gel electrophoresis: One of the most popular DNA technologies is gel electrophoresis, in which sections of DNA are sliced into differently sized fragments and placed in a gel-covered plate. An electric current is passed through the gel, causing the fragments to separate according to size. Gel electrophoresis is commonly used in DNA fingerprinting to determine the degree to which two samples of DNA are related based on the number of matching fragments in their patterns.

•

Recombinant DNA technology: DNA can be altered to produce desirable proteins through recombinant DNA. Small sections of DNA called plasmids containing desired genes are inserted into host bacterial cells. As the bacterium undergoes protein synthesis, the inserted genes are translated right along with the host’s own DNA. This technology is used to study genetic disorders and to explore the possibility of using recombinant DNA to replace mutated genes.

•

DNA and RNA probes: Chosen segments of genetic material are used to label specific nucleicacid sequences. These labels can then be followed and examined in more complex genetic processes and sequences. Nucleic acid probes are often used during experiments in order to conduct a chromosomal analysis.

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STEMscopedia: PATTERNS OF INHERITANCE •

Bioinformatics: This field of science combines genetics and computer technology to store, analyze, and model the wealth of information held within the nucleotide sequences of genetic material. Since DNA is so small, yet so complex, bioinformatics allows scientists to gain insight into the functions and changes of genetic material through computations.

•

Karyotyping: This technology provides a picture of an organism’s chromosomes allowing for visual analysis. The karyotype, or chromosomal image, can show genetic abnormalities and can be used to diagnose genetic disorders.

What Do You Know? Genetic outcomes are the result of combining chromosomes from two different parents who reproduce sexually. The processes that take place during meiosis help contribute to genetic variation among offspring. Use what you have learned about genetic outcomes and Punnett squares to solve the following mystery. A newborn child was brought to the hospital nursery before he was marked with his parents’ names. The hospital workers must use what they know about genetic outcomes to determine whom the child belongs to. They use his traits to help them. The baby has freckles (F dominant), and attached earlobes (l recessive). They believe that one of the baby’s parents is a man who has attached earlobes but no freckles. It is known that the woman is heterozygous for freckles and earlobe type. Complete the Punnett square below to determine the probability that the child belongs to this couple. List the possible combinations of the man’s alleles across the top and the possible combinations of the woman’s alleles down the left side. Then write your answer in the space below. Include a brief statement explaining how you reached your answer.

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STEMscopedia: PATTERNS OF INHERITANCE fl fl fl fl

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STEMscopedia: PATTERNS OF INHERITANCE Connecting With Your Child Studying a Genetic Disease To help students learn more about genetic outcomes, have your child create an informational brochure about a genetic disease. Begin by conducting online research to find a list of the more commonly known genetic diseases and have your child choose one of them to research further. Instruct your child to gather specific information about the disease such as its symptoms, management, potential cures, and the type of chromosomal abnormality that causes the disease. Have your child organize the information in a colorful trifold brochure that might be distributed in a doctor’s office or by a health organization. Make sure two Punnett squares are included in the brochure to illustrate the chances that a child will inherit the disease if one parent carries the disease and if both parents carry the disease. Here are some questions to discuss with your student: • What causes the disease in your brochure? • How can doctors use what they know about the disease to counsel couples who want to have children, knowing that one or both of them carry an allele for the disease? • What technologies are under development regarding the treatments and/or cures for the disease?

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B3B Patterns of Inheritance

Reading Science Name:

Date:

Group:

Domination! 1.

Have you ever asked someone where she got her blue eyes or her curly hair? Maybe you’ve seen a teenage boy and wondered how it was possible for him to be six inches taller than his dad and counting! Sometimes a child can look like a “mini-me” of a parent, and sometimes a child doesn’t look anything like either parent. How does this happen? Heredity! What is heredity? Heredity is the passing of traits from one generation to the next. Genetics is the study of heredity.

The “father of genetics” is Gregor Mendel, a 19th-century Austrian monk. He worked and experimented in the extensive gardens at the monastery where he lived. He investigated how pea plants passed traits on to their offspring. He chose pea plants because they are easy to breed and grow quickly. They are flowering plants that reproduce through pollination. Pea plants can cross-pollinate (through the wind or insects) or self-pollinate. Mendel studied the following traits that had only two forms: flower color (purple or white), seed shape (smooth or rough), seed color (yellow or green), and pod color (green or yellow). He ensured that he began his experiments with true-breeding plants—plants that are homozygous, or only produce the same kind of offspring when they are self-fertilized.

To summarize his investigation, he carefully crossbred pea plants. What he discovered led him to envision and understand the concept of genes (though he did not use the term genes). For the parent generation, he crossbred true-breeding purple flowers with white flowers. The first generation offspring were all purple flowers. He carefully self-pollinated the second generation and was surprised to see that one-quarter of the flowers produced were white even though all the parent flowers were purple! He theorized that some unit was being passed down from parent to offspring that was determining plant color. There were two color choices for each unit. Mendel conducted his investigation again and received the same data and percentages for seed shape, seed color, and pod color that he did for flower color. He determined that purple color, round shape, yellow seeds, and green pods were dominant traits for pea plants.

Our knowledge of genetics has greatly advanced since Mendel’s discoveries. Scientists now call those units genes and the different options for each gene alleles. Dominant alleles are always expressed (or shown) and may cover up the existence of recessive alleles. Recessive alleles may be covered up if a dominant allele is present. Mendel differentiated between an organism’s genotype and phenotype. A genotype is the alleles for a gene that an organism actually contains. A phenotype is the type of the trait that an organism displays. When bred, results for genotypes and phenotypes for generations can be predicted using a Punnett square. A Punnett square is a tool that puts one parent’s genotype at the top and the other parent’s genotype at the left. In the middle it shows all the possible combinations of alleles for offspring based on the parents’ alleles.

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Reading Science 5.

Certain organisms, like the pea plants that Mendel observed, have strictly dominant and recessive alleles. In pea plants, a capital “P” represents the dominant allele, which is the color purple. The lowercase “p” represents the recessive allele, which is the color white. That means every time a “P” is included in a genotype, the phenotype will be a purple flower. In order to create a white flower, the genotype must contain a “p” from both parents. Look at the Punnett square below. Think carefully about the genotypes and phenotypes of the parents and the possible outcomes for offspring.

Mendel was fortunate that he chose to study pea plants because they have several easily observed traits that are determined by two alleles, which are distinctly dominant or recessive. Not every organism has such a simple genetic makeup. In some cases, incomplete dominance is expressed. Incomplete dominance occurs in an organism when two alleles are both expressed by blending in the phenotype. One example is pink roses. The red allele is dominant, but when it is paired with a recessive white allele, the rose’s phenotype is pink. R is red and R’ is pink. Therefore, RR = red; R’R’ = white; RR’ = pink.

Codominance is a situation in which genes act differently from the genes in pea plants. Codominance occurs in an organism when two different alleles from a gene are displayed simultaneously in the phenotype. One example of this is roan fur in cattle. Cattle can have all red fur (genotype RR) or all white fur (genotype WW), but when a cow with red fur (RR) is crossed with a bull with white fur (WW), the result is not red or white or even pink. Both traits are displayed so that the offspring possesses roan fur, which is red and white at the same time (RW).

Why do we use Punnett squares? Punnett squares help scientists check the probability of particular genotypes and phenotypes occurring when certain organisms are bred. Probability is the mathematical chance that an event will occur. It may be expressed as a fraction or a percentage. Although not every situation regarding heredity is as simple as Mendel’s pea plants, his ideas led to the science of genetics. What would he say if he knew his experiments on pea plants eventually led to such complex genetic studies as the mapping of the human genome?

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Reading Science 1.

Look back at the Punnett square of the pea plants and answer the following question. What is the probability that the offspring will be a true-breeding plant? A.

25%

50%

100%

Gregor Mendel was a _________. A.

farmer

lord

astronomer

monk

The phenotype of an individual organism ALWAYS shows you _________. A.

what traits are expressed

what the genotype is

what the offspring will be

what the genotypes of its parents were

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Reading Science 4.

Carefully study the Punnett square of the roses and then answer the following question. What is the probability that the offspring of the parent flowers will be pink? A.

1/4

3/4

1/2

They will all be pink.

Which answer choice is the best summary of the passage? A.

Gregor Mendel was a monk who studied pea plants in his home—a monastery in Austria.

Dominant and recessive alleles decide what traits will be expressed in organisms.

Pea plants hold the answers to genetics.

Gregor Mendel discovered principles of heredity, propelling us forward to learn about genes and how various traits are passed on to the next generation.

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B3B Patterns of Inheritance

Math Connections Name:

Date:

Group:

Punnett squares can be used to determine genotypic and phenotypic ratios. The dominant alleles will mask recessive alleles. Freckles are a dominant trait inherited from a set of parents. The tree diagram below shows the genetic combinations passed from one generation to the next. Use this diagram to answer the questions below and figure out the genetic combination each child received.

Create a Punnett square to describe the outcomes for Child 1, Child 2, and Child 3. X

Child 1 and Child 2 inherited the genotype predicted to be present in 50% of the offspring. What is their genotype for having freckles?

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Math Connections 3.

Child 3 did not inherit freckles. What is the chance of the offspring of Child 3’s parents not inheriting freckles?

Create a Punnett square to describe the outcomes for Child 4. X

Child 4 inherited the double recessive genotype. Did the child have freckles? What is the chance of other offspring from these parents inheriting freckles?

Create a Punnett square to describe the outcomes for Child 5 and Child 6. X

Child 5 did not inherit freckles. If he married someone who was heterozygous for freckles, what would be the genotypic ratio of his offspring? X

What chance did Child 6 have of not inheriting freckles?

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B3B Patterns of Inheritance

Math Connections 9.

What percent of the entire family is heterozygous?

10. A heterozygous freckled man marries a heterozygous freckled woman. If they have 19 kids, approximately how many of those children would have freckles? How many would not have freckles? X

11. A dihybrid Punnett square displays the genotype of more than one trait. Construct a dihybrid Punnett square for a parent who is homozygous dominant for red hair and heterozygous for freckles (RRFf) and a parent who is homozygous recessive for red hair and homozygous dominant for freckles (rrFF). x

rF rF rF rF 12.

Determine the phenotypic ratio of all offspring represented in the Punnett square above.

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B3B Patterns of Inheritance

Writing Science Name:

Date:

Group:

LOOK

THINK As genetic information is passed from parent to offspring, dominance, codominance, and incomplete dominance are evident. Think about the traits you and your siblings have inherited from your parents. Do you all look exactly like your dad or exactly like your mom? Do you and your sibling have the same eye color? Do you all have detached earlobes? Most likely, unless you are an identical twin, there are some differences and some similarities present. Use the table of traits below as a reference.

WRITE Use a math model to explain patterns of inheritance as you analyze dominance, codominance, and incomplete dominance seen in the table of traits above. Be sure to • clearly state your central idea; • organize your thoughts; • develop your essay in detail; • choose your words carefully; and • use correct spelling, capitalization, punctuation, and grammar.

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B3B Patterns of Inheritance

Writing Science

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High School Biology

B3C

Advantages and Disadvantages of Sexual and Asexual Reproduction

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B3C Advantages and Disadvantages of Sexual and Asexual Reproduction

Student Handout Name:

Date:

EGGcellent Eggs Questions 1.

Based on the information provided, does the chicken egg go through asexual or sexual reproduction? How do you know?

Thinking about sexual reproduction, are the offspring created through this process genetically identical or genetically different from the parents?

Thinking about what you know about asexual reproduction, are the offspring created through this process genetically identical or genetically different from the parent?

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B3C Advantages and Disadvantages of Sexual and Asexual Reproduction

Student Journal Name:

Date:

Group:

Reproduction

Background 1. What two factors determine the traits inherited by an organism?

What is asexual reproduction?

What is binary fission?

What are spores?

What is budding?

What is vegetative propagation?

What is sexual reproduction?

Offspring from asexual reproduction are _____________________________; offspring from sexual reproduction are _______________________________.

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B3C Advantages and Disadvantages of Sexual and Asexual Reproduction

Student Journal Part I: Guess Who 1.

Which organism reproduced asexually?

Were the offspring of this organism uniform, meaning they look the same as each other and the parent, or were they diverse, meaning they express a variety of appearances? Explain your answer.

Which organism reproduced sexually?

Were the offspring of this organism uniform or diverse? Explain your answer.

Offspring of asexual reproduction may differ from offspring of sexual reproduction in whether they are uniform or diverse. However, they may also share some similarities. What similarities do these organisms share?

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Student Journal Part II: Did You Say “Flesh-Eating Bacteria”? Draw and label the observations from the patient’s lab work in the Petri dishes and include your analysis of the cell type and prescription.

Patient 1: Condition ________________ Type of cell ☐ prokaryotic (no nucleus) ☐ eukaryotic (has nucleus)

Prescription ☐ antibiotic ☐ antifungal

Patient 2: Condition ________________ Type of cell ☐ prokaryotic (no nucleus) ☐ eukaryotic (has nucleus) Prescription ☐ antibiotic ☐ antifungal

2 Patient 3: Condition ________________ Type of cell ☐ prokaryotic (no nucleus) ☐ eukaryotic (has nucleus)

Prescription ☐ antibiotic ☐ antifungal

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Student Journal Part II: Did You Say “Flesh-Eating Bacteria”?, continued 1.

What differences did you observe between prokaryotic and eukaryotic cells?

What similarities did you observe between prokaryotic and eukaryotic cells?

Eukaryotic fungi can cause fungal infections. Human cells are eukaryotic. How can this information cause problems with treatment?

Eukaryotic fungi can reproduce sexually, creating diverse offspring. How might this complicate treatment?

Bacteria are prokaryotic and reproduce quickly and asexually through binary fission, during which one cell becomes two cells with identical DNA. How does this reproduction strategy promote survival of the species?

Antibiotics can be very successful in treating bacterial infections. What is it about the reproductive strategy of bacteria that allows antibiotics to be so successful?

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B3C Advantages and Disadvantages of Sexual and Asexual Reproduction

Student Journal Part III: Advantage or disadvantage? That is the question. 1.

Do you think that humans could benefit from being able to multiply without the need for reproducing sexually? Why?

2. In which sort of condition or situation would each method of reproduction be most disadvantageous or advantageous?

3. Is one method of reproduction usually better do you think? Explain your reasoning.

Reflections and Conclusions 1. What type of offspring results from sexual reproduction? How is this different from offspring resulting from asexual reproduction? Explain your answer.

2. How do scientists determine if offspring result from sexual or asexual reproduction? What evidence would scientists use to determine this? Explain your answer.

3. Do some organisms have the ability to reproduce both sexually and asexually? Are they prokaryotic or eukaryotic? Use examples to explain your answer.

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B3C Advantages and Disadvantages of Sexual and Asexual Reproduction

Student Journal Reflections and Conclusions, continued 4.

After a forest fire, plants quickly begin to repopulate the disturbed area. What advantage would plants that can reproduce asexually have over plants that only reproduce sexually?

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STEMscopedia: ADVANTAGES AND

DISADVANTAGES OF SEXUAL AND ASEXUAL REPRODUCTION B3C

Reflect Have you ever cut a picture in half so you could give each piece to someone? Did either piece look like the original? Probably not. Look at the image above. Do its halves look alike either horizontally or vertically? All organisms reproduce. If they didn’t, no species would survive past a single generation. Reproduction allows organisms to pass on their traits, or characteristics, to their offspring. Parents pass on their traits through their genetic material, or DNA. Asexual Reproduction In asexual reproduction, the one parent passes its genetic material to its offspring. Therefore, the offspring have the same traits as their parent and as each other. The offspring are uniform, or the same. Think of it as making a copy on a copy machine. The parent is like the piece of paper you put into the machine. The offspring are like the copies that come out. The offspring, like the copies, all look like their parent and like each other. There are different forms of asexual reproduction, including binary fission, budding, and spores. Prokaryotic organisms, such as bacteria, go through a process called binary fission. First, a singlecelled bacterium makes a copy of the DNA it has in its cell. Then the bacterium splits in half, forming two cells. Each cell gets the original DNA. Eukaryotic organisms reproduce asexually in several ways. Fungi, such as molds, form spores. Spores are tiny reproductive structures that contain a copy of the parent DNA. Some organisms reproduce by budding. In budding, a smaller version of the parent organism grows out of the parent. Eventually, it separates from the parent and begins to function on its own. This would be similar to another exact organism growing out of your body!

eukaryote: cells that have an organized nucleus with a membrane and specialized organelles

asexual reproduction: a type of reproduction in which one parent makes an exact copy of itself

prokaryote: a microscopic single-cell living organism that does not have a definite nucleus or nuclear membrane with no exact organelles reproduction: a living process in which a new organism is formed from a parent or parents either sexually or asexually

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STEMscopedia: ADVANTAGES AND

DISADVANTAGES OF SEXUAL AND ASEXUAL REPRODUCTION Sexual Reproduction Sexual reproduction requires two parents. Unlike asexual reproduction, sexual reproduction requires a male and female. Each parent contributes half of their genetic material, or DNA, to the offspring. The female contributes her DNA in an egg cell. The male contributes his DNA in a sperm cell. When the egg and sperm combine, they form the new offspring. Offspring may look similar to their parents, but they are not exact copies. In sexual reproduction, each offspring has a mixture of its parents’ traits. Parents may pass on dominant traits or recessive traits to their offspring. Each offspring may be different from its siblings. For example, suppose the father in a human family does not have freckles, but the mother does. Among their children, one child might not have freckles, but the other children might have them. In sexual reproduction, the offspring have a unique combination of their parents’ traits. This is why organisms that reproduce sexually have diverse offspring.

sexual reproduction: a type of reproduction in which two parents of the opposite sex contribute to the characteristics of the offspring with their egg and sperm uniting

Look Out In looking at asexual and sexual reproduction, what are some of the advantages and disadvantages of each? Remember, in asexual reproduction, only one parent is needed. That parent simply splits into two new cells and the offspring is an exact copy of the parent. However, in sexual reproduction, a male and female each contribute DNA material to produce their offspring. Advantages and Disadvantages of Asexual Reproduction There are several advantages to asexual reproduction. The first one might be obvious to many: fast population. Sometimes an event happens causing the invasion of “trespassers.” To protect themselves and the area, the organisms will rapidly reproduce new organisms. This action safeguards the continuation of the organisms. Many organisms live in isolated or desolate areas. To find a mate might be extremely difficult due to the environmental conditions, including extreme drought, extreme cold, or deep oceans. Asexual reproduction takes away the need to hunt for a mate and allows for the continued survival of the organism. It takes a period of time for the growth of an organism in sexual reproduction. This is not so with asexual reproduction. Reproduction time is much quicker, as it entails one organism simply dividing into two new organisms. Lastly, in some plants and animals (hydra), when no other plants or animals of the same are around, asexual reproduction takes place. In plants, if pollination cannot take place due to an extreme event, the plant can then replicate itself by asexual reproduction. 238

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STEMscopedia: ADVANTAGES AND

DISADVANTAGES OF SEXUAL AND ASEXUAL REPRODUCTION As there are several advantages, there are equally several disadvantages to asexual reproduction. One such disadvantage is the exact replication of all the traits of the parent to the offspring. That means the exact strengths and weaknesses are copied. Predators or parasites that hunt or feed off the organism, can take out the whole species. Since total replication takes place in asexual reproduction, there is no variance in traits among the organisms. Lastly, if there is an environmental change, these organisms cannot adapt to the changes, thus they all die and become extinct. Advantages and Disadvantages of Sexual Reproduction Sexual reproduction, which involves male and female parents, has several advantages. The first is variation in the offspring. This allows the offspring to adapt if the environment changes and helps prevent the extinction of the species. With this type of reproduction, the organism must look for a mate, and this takes energy. Another advantage is that the offspring are formed from a combination of traits from both parents or crossing over (exchange of chromosomal material during meiosis). This helps when the environment is not stable, which causes a slower rate of reproduction but does not stop it. One final advantage allows for the elimination of bad or harmful mutations such as sickle-cell anemia or cystic fibrosis. Disadvantages can include the time it takes for sexual reproduction to occur, finding a mate, and lack of positive genetic replication. Sexual reproduction takes time to conceive and give birth to their offspring. This may take days to months––unlike asexual reproduction. This could be a disaster to the species if the population is low. Another disadvantage is finding a mate. Other organisms of the same species must be present. Organisms that are in an isolated environment are not well matched for this type of reproduction. Finally, errors in gene replication. This may cause serious consequences to the offspring such as Down’s syndrome.

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STEMscopedia: ADVANTAGES AND

DISADVANTAGES OF SEXUAL AND ASEXUAL REPRODUCTION What Do You Think? Match the vocabulary. reproduction sexual reproduction eukaryote prokaryote asexual reproduction

A. a form of reproduction in which one organism makes copies of itself B. single-celled organism with no organized nucleus, nuclear membrane, or organelles C. a form of reproduction in which a male and female unite their sperm to form a new organism D. cells that have an organized nucleus surrounded by a membrane and specialized organelles E. a process by which a new organism is formed

Connecting With Your Child To help your child learn more about asexual reproduction, let’s plant some potatoes. Choose either a red potato or a sweet potato with sprouting “eyes.” If you have a large five-gallon bucket, fill it with soil. Cut your red potato in pieces, each containing a sprouting “eye.” Place the potato pieces about four inches down into the soil and cover. Water and place outside where it can receive sunlight at least four hours a day. Check for moisture and water when needed. Do not overwater, or the potato pieces will decay. Watch for new potato plants within 10 days. If you can, let the potatoes grow until the tops die (three to four months). Carefully pull up the dead plant and you should have potatoes. As you watch your potatoes grow, discuss with your child what is going on and how these potatoes will be making copies of the parent potato. For the sweet potato, choose a sprouting sweet potato. Place the sprouting end in a jar of water filled one-third of the way up. Put it in a window with direct or indirect sunlight. Watch what happens. Continue discussion with your child about the changes going on. With whichever project you choose, have your child keep a notebook and draw pictures of the potato through the growth period. Write down descriptions of anything you see happen. Discuss these with your child as the project continues.

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B3C Advantages and Disadvantages of Sexual and Asexual Reproduction

Reading Science Name:

Date:

Group:

Sexual vs. Asexual Reproduction 1.

The process of creating the next generation is called reproduction. In sexual reproduction, male and female gametes unite to produce offspring that are genetically different from both parents. In asexual reproduction, an individual produces offspring that are genetically identical to the parent. Both types of reproduction have advantages and disadvantages. Let’s look at a group of animals that can reproduce both sexually and asexually, the sea anemones.

Sea anemones live in salt water. They are carnivorous and eat animals such as fish and crustaceans. The majority of sea anemones are sessile as adults, attaching by means of a pedal disk. The oral disk is surrounded by tentacles that contain small poison sacks. When prey touches the tentacles, small hairs are bent. A harpoon-like structure attaches to the prey and injects the poison. Once the prey is paralyzed, it is moved into the sea anemone through the oral cavity for digestion.

When reproducing sexually, the fertilized egg develops into a planula, which is a freeswimming larval form. The planula matures and becomes a polyp, growing into another mature sea anemone. During sexual reproduction, genes are shuffled randomly. Asexual reproduction can take a variety of forms. Sometimes, a planula is produced; more often, however, the parent sea anemone buds off one or more individuals. Large sea anemones may separate into two equally sized individuals through binary fission. The two individuals crawl apart over time, leaving each room to grow.

Scientists studying sea anemones examine the genetic diversity of polyps of the same species living in close proximity. If individuals reproduce mostly asexually, genetic diversity will be low. On the other hand, if multiple planulae produced by sexual reproduction have settled in an area, genetic diversity will be high. Computer models can be used to estimate the percentage of individuals created from sexual reproduction.

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Reading Science 5.

Sea anemones living on stable shores displayed lower levels of genetic diversity. Scientists think that the sea anemones living there have evolved a combination of genes that are particularly well suited to the environment. Think about playing a card game and drawing a winning hand. If you pass that hand onto the next player, he or she is more likely to win than by drawing a hand randomly from the deck. Sea anemones living on unstable shores display higher levels of genetic diversity. With instability comes unpredictability, and therefore sea anemones doing the equivalent of drawing a new hand of genetic cards for each individual are more likely to have at least some winning hands when the environment changes.

In general, sexual reproduction is better for dealing with changing or unpredictable environments, while asexual reproduction works well in a stable environment. Other factors that influence reproductive strategy include availability of mates and abundance of food.

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Reading Science 1.

Which of the following is a characteristic of asexual reproduction? A.

It involves male and female gametes.

It produces genetically identical offspring.

It produces large numbers of offspring.

It is most common in humans.

In paragraph 2, the word “sessile” means ___________. A.

having both male and female organs in a single organism

reproducing by budding off new individuals

remaining attached to the bottom like a coral reef

being moved by wind and currents from place to place

Scientists can determine whether a colony of sea anemones was produced sexually or asexually by ___________. A.

counting the number of individual polyps

examining the diet of each polyp

examining the genetic diversity between polyps

looking at environmental stability over time

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Reading Science 4.

In an unstable environment, sea anemones will most likely produce ___________. A.

planulae through sexual reproduction

planulae through asexual reproduction

offspring primarily through binary fission

offspring primarily through budding

Climate change is leading to greater environmental instability in many regions of the globe. Which of the following would likely happen to sea anemones and their reproductive strategies? A.

They would produce smaller numbers of offspring.

They would produce offspring more frequently.

They would produce physically larger offspring.

They would reproduce sexually more often.

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B3C Advantages and Disadvantages of Sexual and Asexual Reproduction

Math Connections Name:

Date:

Group:

Both asexual (alone) and sexual (with a mate) reproduction have advantages and disadvantages. Asexual organisms procreate individually, allowing them to populate an environment quickly and avoid extinction or population decline. However, an asexual organism’s offspring has no diversity; all progeny are identical to the parent organism. This lack of diversity is a problem during times of competition, predation, and natural selection. Organisms that reproduce sexually have a slower propagation rate, but these organisms are richly diversified, and they benefit from characteristic traits that help them to adapt and survive in their environments. The organisms listed in the table below reproduce asexually. A scientist monitored the rate at which each organism reproduced over the course of two months after an initial count of a sample population. Use the table below to help you answer the following questions.

Organism

Initial Population

Protists Fungi Rotifers

80 55 175

Population at 1 Month 240 220 1,050

Population at 2 Months 720 880 6,300

Determine the rate of reproduction for fungi in the chart above. Use the rate to calculate how many organisms the scientist would expect to see in the fungi population after 3 months of reproduction if the initial population started with only 5 organisms.

Organism

Initial Population

Fungi

Population at 1 Month

Population at 2 Months

Population at 3 Months

Rotifers are near-microscopic organisms that live in water. During times of low population, rotifers practice asexual reproduction. Using the reproduction rate from the first table, calculate how many organisms the scientist would expect to see in the rotifer population after 6 months of reproduction if the initial population started with only 12 organisms.

Organism

Initial

Rotifers

1 Month

2 Months

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3 Months

4 Months

5 Months

6 Months

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Math Connections Use the first table from the previous page to help you answer the following questions. 3.

Protists are found almost anywhere there is water. Using the reproduction rate from the table, calculate how many organisms the scientist would expect to see in the protist population after 9 months of reproduction if the initial population started with only 7 organisms.

Organism

Initial

Protists

Some rotifers are capable of also producing sexually when their population is plentiful. By changing to sexual reproduction, these rotifers can build diversity to help sustain their population through environmental challenges. The scientist believes that once the rotifer population exceeds 50,000, they will stop reproducing asexually. Using an initial population of 175, during which month can the scientist expect to see a switch in the rotifers’ reproduction style? Answer: _______________

Using the information in the table, during which month will the fungi population exceed 10,000? Answer: _______________

Using the information in the table, during which month will the protists population exceed 125,000? Answer: _______________

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B3C Advantages and Disadvantages of Sexual and Asexual Reproduction

Writing Science Name:

Date:

Group:

LOOK

THINK Asexual reproduction occurs when offspring are created from only one parent. Sexual reproduction occurs when offspring are created using genetic material from two parents. Dandelions are a special plant because, unlike other plants, they are able to self-pollinate. Each flower has a male part and a female part which enable asexual reproduction to occur. However, if an insect does pollinate from one dandelion to another, sexual reproduction has taken place. WRITE Describe the advantages and disadvantages related to asexual and sexual reproduction for a population. Explain which type of reproduction is more advantageous for a dandelion. Be sure to • clearly state your central idea; • organize your thoughts; • develop your essay in detail; • choose your words carefully; and • use correct spelling, capitalization, punctuation, and grammar.

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Writing Science

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High School Biology

B4A

Structure, Function, and Classification

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B4A Structure, Function, and Classification

Student Handout Name:

Date:

Animal Cookie Classification Create a graphic organizer of the classification system you created. Drawings of each of the animal cookies with labels should be used to create the graphic organizer.

What was the largest group of cookies that you started with? Why?

What were some limitations of using animal cookies?

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B4A Structure, Function, and Classification

Student Journal Name:

Date:

Group:

Part I: Similarities and Differences List traits specific to each species in the labeled boxes. List similarities shared by all the organisms in the middle box. Algae

Bacteria

Similarities

Paramecium

Mitochondria

Use the activity above to write a working definition of a molecular homology.

What are the two most common structures you noticed in the photos in your Student Guide?

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Student Journal Part I: Similarities and Differences, continued

Pair Connections Thymine - __________ Guanine - ___________ Adenine - ___________

Label each nucleobase on the diagram using the key to the right.

Observe which nucleobases pair up like puzzle pieces. Write out the pair connections in the spaces to the right of the diagram.

How could this diagram and similar ones be used to explain molecular homology?

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B4A Structure, Function, and Classification

Student Journal Part II: Anatomical Homologies

Anatomical Homologies Skeletal Structure

Number of Joints

Movement Direction

Human Horse Cat Bird Whale

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B4A Structure, Function, and Classification

Student Journal Part III: Developmental Homologies 1.

Use the Student Guide to label the developmental homologies below.

Observe the structures on the diagram and list at least four animals that could be represented by this diagram in their early stages.

List four other organisms that possibly have at least two of the developmental homologies.

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Student Journal Reflections and Conclusions 1.

Describe the type of homologies that many organisms share at the very base of life.

How does the function of movement play a role in anatomical homologies between animals with forelimbs and hindlimbs?

How can developmental homologies influence anatomical homologies based on the activities and observations that were completed in Part II and Part III of the Student Journal?

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STEMscopedia: STRUCTURE, FUNCTION, AND

CLASSIFICATION B4A

Reflect Classifying and naming organisms is a practice that dates back to ancient Greece. Aristotle was one of the first to group and categorize living things based on their characteristics. After Aristotle, scientists and academics continued his work by adding to classification systems and creating new ones as discoveries were made. By the 18th century, there were multiple classification systems in place, each with its own way of categorizing and naming species. In order for collaboration in the scientific community to advance, changes had to be made. What changes to classification were necessary? What tools could scientists use to organize organisms consistently? What characteristics represent different groups of organisms?

A Standardized System of Classification and Naming In the past, scientists were unable to properly communicate about living organisms. Newly discovered species were randomly named. In fact, some may have been discovered multiple times due to the lack of ability to distinguish the classification systems. A standardized system of grouping and naming life was necessary in order to allow scientists to communicate and maintain organization of the wide diversity of life on Earth. Carolus Linnaeus was an 18th-century scientist who focused his studies on plants. However, he is known best as the father of taxonomy. Taxonomy is a systematic process of classifying living organisms into different groups based on their physical traits and genetic relationships. Over the years, Linnaeus’ original system has been modified as new discoveries were made, but the basic system is still intact. The groupings of living things begin as broad classifications and become narrower and more specific as they continue. The highest and broadest level of classification is called the domain. It is followed by kingdom, phylum, class, order, family, genus, and species. The table below shows the classification of the domestic dog from domain to species. Domain Eukarya

Kingdom Phylum Animalia Chordata

Class Order Family Mammalia Carnivora Canidae

Genus Species Canis Familiaris

Organisms are commonly referred to according to the two most speciﬁc taxonomic levels: genus and species, which are often Latin. This is called binomial nomenclature. The taxonomic name of modern humans is Homo sapiens. The genus is always capitalized, the species is lowercase, and the whole name is written in italics. By using this same system, scientists around the globe can freely communicate with certainty that they are referring to the same organisms.

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STEMscopedia: STRUCTURE, FUNCTION, AND What Do You Think?

CLASSIFICATION

Imagine that, before the establishment of taxonomy, a scientist working in Africa writes a letter to a biologist in England claiming that he has discovered a new organism. It is unique, and he has never seen one before. He has named the animal glotchbot. The British biologist spreads the word about the glotchbot through the scientific community, and everyone in the community becomes excited about this new discovery. The scientist returns from Africa with a picture of the glotchbot shown on the right. Suddenly, the scientific community loses all interest, and both the scientist and the biologist lose respect. How would a standard system of taxonomy have changed the outcome of this scenario? Career Corner: Taxonomist Scientists who study taxonomy and use the classification system to identify and name organisms are taxonomists. Taxonomists are first and foremost scientists. They have a fundamental knowledge of biology or other related fields. They often have advanced degrees in zoology, animal physiology, botany, or other life sciences. Museums, zoos, aquariums, and universities are common places of employment for taxonomists. Here they can study DNA, environments, and other influences that have contributed to characteristics of life. Taxonomists’ knowledge is often used to educate others through lectures and publications about conservation of endangered or threatened species. Classification Into Domains: Bacteria, Archaea, and Eukarya The three domains differ fundamentally in their cellular structures and genetic makeup. The domains are so broad that all life can be separated into just three different categories. Let’s examine the basic differences between these three categories of life. Patterns in Structures of Clades Domain Bacteria: This domain consists of unicellular prokaryotes. They lack a cell nucleus and membrane-bound organelles, but they are surrounded by a thick cell wall. Bacteria can be found nearly everywhere on Earth, including living inside human beings’ mouths and stomachs. Bacteria are incredibly diverse. Some are free living, while others rely on a host to survive. Many use oxygen, while others are killed by the presence of oxygen. Like plants, some bacteria are photosynthetic. Many bacteria cause infections, such as strep throat (Streptococcal pharyngitis), food poisoning (Escherichia coli and Salmonella enterica), and plant wilt in sweet corn (Erwinia stewartii). Most bacteria are beneficial and serve a necessary role in their environment. There are a wide variety of characteristics and functions among the members of domain Bacteria. Domain Archaea: Like domain Bacteria, the members of domain Archaea are unicellular prokaryotes. They also have a cell wall, but it differs in composition from those of bacteria. Archaean cell walls lack the substance peptidoglycan found in bacteria. Their cell membranes also differ, containing unusual lipids that are not found in any other organisms on Earth. (A lipid is a type of biomolecule; fats, oils, and waxes are examples of lipids.)

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One of the most distinct features of domain Archaea is that they are able to survive in some of the most extreme environments on Earth. Archaea have been found in the hot springs of Yellowstone National Park in Wyoming and in deep oceanic hydrothermal vents measuring over 100 degrees Celsius (212 degrees Fahrenheit). Others live in environments with extremely high salinity and acidity. Domain Eukarya: This domain differs from the others because its members’ cells contain a nucleus and membrane-bound organelles. Most eukaryotic species are multicellular, but some are unicellular. Domain Eukarya is quite diverse and contains the most well-known organisms. Eukaryotes are found all over the world in a variety of environments. The domain is so diverse that it is best to study the organisms of domain Eukarya in their narrower classiﬁcation groups.

Archaea are thermophiles because they thrive in hot environments like this geothermal pool.

Suppose a group of scientists discovered a new prokaryotic organism in a highly acidic sulfur vent in Antarctica. Which domain does the organism most likely belong to? The Four Kingdoms of Eukaryotes Domain Eukarya is incredibly diverse. it includes organisms from daffodils to dragonflies and orangutans to oak trees. It is divided into four kingdoms based on the most general characteristics. The kingdoms are Protista, Plantae, Fungi, and Animalia. Each kingdom is further divided into phyla, then classes, orders, and so on. The members of each kingdom have distinct enough characteristics to allow us to begin identifying organisms. Protista: These ancient eukaryotes have some characteristics not shared by many other members of the domain, including the fact that many are unicellular. Even within the kingdom there is great diversity. In fact, many protists are classified in this kingdom just because they do not fit in any of the others. They vary greatly in their appearance, mobility, reproduction, and methods for obtaining food. Some protists are even photosynthetic. Examples include many phytoplankton, red and brown algae, and dinoflagellates. Plantae: Plants are very common eukaryotes. They include a wide variety of organisms with unique characteristics and functions, as well. But there are some properties of kingdom Plantae that they all share. Plants are multicellular organisms that are able to photosynthesize. Since plants can use energy from the Sun to produce food, they are considered autotrophs. Plants lack mobility and often must rely on the wind or animals to help them reproduce through cross pollination. All plants have the same basic parts, including roots, stems, and leaves. Their cells are unique from other eukaryotes because they are surrounded by a rigid cell wall made mostly of cellulose. The cell wall gives plants structure and support, allowing them to grow tall and expose their green leaves to the Sun for photosynthesis.

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Fungi: Fungi, such as mushrooms, are often confused for plants. They do share some similarities. Most, for example, are multicellular, although yeasts, a type of fungi, are unicellular. Like plants, the cells of fungi have a cell wall, which is usually made of chitin instead of cellulose. Fungi, however, cannot produce their own food through photosynthesis, so they are called heterotrophs. This kingdom has some characteristics that differ from any of the other eukaryotes. A primary difference is that fungi grow long ﬁlaments called hyphae. Many fungi feed by releasing enzymes outside of their bodies. The enzymes break down and digest nearby leaves, fruits, and other substances. Once digested, the molecules of food are absorbed into the fungal body. These enzymes are also important to decomposition. Fungi break down dead, organic matter and return nutrients to the soil. They help maintain the balance with organisms like plants that take nutrients from the soil.

A mushroom is actually the fruiting body, or reproductive organ, of a fungus.

Animalia: The animal kingdom is undoubtedly the most well-known because it includes humans. Like all the kingdoms, Animalia is quite diverse. In addition to humans, it includes birds, ﬁsh, insects, and a wealth of other animals. What they all have in common is that animals are multicellular, are heterotrophic, and have cells lacking a cell wall. Also, animals are motile at least at some point in their lives. Beyond these characteristics, animals vary greatly in their body plans, reproduction, methods for obtaining food, and many other factors. This sea sponge is in the Scientists in the Spotlight: Lynn Margulis same kingdom as humans. In the 1960s, biologist Lynn Margulis proposed the endosymbiotic theory. She suggested that mitochondria, which convert food into energy in cells, and chloroplasts, which convert sunlight into energy in plant cells, have more in common with prokaryotes than eukaryotes. In fact, she suggests that mitochondria and chloroplasts were once free-living bacteria that evolved a mutualistic relationship with early eukaryotic cells. Over time, the reproductive cycle of the endosymbiont became completely tied to that of the host, and the endosymbionts lost the ability to live outside of the host cell. Support for the endosymbiotic theory is found in the DNA and ribosomes of mitochondria—both of which are similar to that found in Rickettsia, a parasitic endosymbiont. Like mitochondrial DNA, chloroplast DNA is also similar to prokaryotic photosynthetic cyanobacteria.

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Look Out Anyone who has visited tide pools or snorkeled in the ocean knows that some animals, such as sponges, barnacles, and coral, are fixed in place. However, these organisms all belong to kingdom Animalia, which is characterized by motility. The caveat is that animals are motile at some point in their lives, but not necessarily their entire lives. Adult sponges and coral, for example, are sessile— that is, immobile or fixed in one place. However, as zygotes they have cilia allowing movement through the water to find a preferred location. Barnacles are somewhat similar. They have two larval stages during which they are able to swim through the water using setae, which are hairlike bristles used for movement. In the second larval stage, barnacles cannot take in any food, so they have a limited amount of time to find the best place for their adult form to become fixed in place. Tools for Classifying Organisms Two methods scientists rely on to identify and classify organisms are dichotomous keys and cladograms. These tools help scientists determine how organisms are related through common ancestry. A dichotomous key is a type of flow chart made up of questions or paired statements about an organism. Following each of the steps of a dichotomous key helps scientists identify organisms based on their traits.

What Do You Think? Use the dichotomous key below to identify the ﬁsh shown on the right.

1. Is the ﬁsh’s body long and thin?

Yes

Go to step 2

Go to step 3

2. Does the ﬁsh have pointed or rounded ﬁns?

Pointed

Trumpet ﬁsh

Rounded

Moray eel

3. Are the eyes on top of the ﬁsh’s head?

Yes

Go to step 4

Go to step 5

4. Does the ﬁsh have a long tail or a short tail?

Long tail

Spotted eagle ray

Short tail

Witch ﬂounder

5. Does the ﬁsh have spots?

Yes

Go to step 6

Glassy sweeper

Yes

Spotted goat ﬁsh

Bandtail puffer

6. Does the ﬁsh have whiskers?

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A cladogram is a branched diagram resembling a tree that shows the evolutionary relationship among organisms. It is often used to show how similarities are derived from common ancestry. Places where a lineage branches off in a cladogram are called nodes. They represent speciation events. The fewer the number of nodes between organisms, the more closely they are related. Cladograms provide scientists with a visual summary of how organisms in any taxonomic grouping are related.

What Do You Think? Look at the cladogram below. Which two organisms are more closely related, a hagﬁsh and a lizard or a pigeon and a chimp? How do you know?

What Do You Know? The characteristics used to classify organisms into taxonomic groups help scientists identify and organize living things. With the information gathered, they can construct tools such as cladograms that show the evolutionary relationships of living things, including common ancestry. Fill in the table with information about the three domains. Domain

Bacteria

Kingdom

Eubacteria

Archaebacteria

Cell type Number of Cells

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Plantae

Fungi

Eukaryote

Unicellular

Presence of Cell Wall Mode of Autotroph & Food Intake heterotroph

Protista

Multicellular Yes

Autotroph & heterotroph

Eukaryote Multicellular

Yes Heterotroph

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Connecting With Your Child Taxonomy in the Real World To help students learn more about taxonomy, have them visit a zoo, botanical garden, plant nursery, or even a local pond or stream where they can observe the characteristics of many different organisms. Have students collect the binomial nomenclature of the species they observe where possible. These are commonly posted at zoos, botanical gardens, and some nurseries. Students should gather as much information about the different species’ physical appearances they encounter as possible. Encourage students to use a camera to take pictures of the different species or draw pictures of what they see. At home, have students identify the domain for each of the organisms they observed. Most likely every organism will belong to domain Eukarya. Then have students classify the organisms into kingdoms, phyla, and so on, as far as they can go with the information they gathered. Next, have students research the genus and species names for the organisms. Using this information and online resources, students can check their own classiﬁcations against the true taxonomy. Once complete, have students build either a cladogram or a dichotomous key for organisms they observed. Encourage students to analyze the cladogram to determine which characteristics evolved latest and which organisms are most closely related. Here are some questions to discuss with students: 1. How does a standard system of classiﬁcation help you do research? 2. What characteristics can you use to classify organisms into domains? Into kingdoms? 3. What role would a cladogram play for a scientist who discovers a fossil of an extinct organism?

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B4A Structure, Function, and Classification

Reading Science Name:

Date:

Group:

Endosymbiotic Theory

Geologists have found rocks containing fossil evidence of cellular organisms that lived on the Earth approximately 3.5 billion years ago. The fossils show that the early cells resembled modern prokaryotes. Prokaryotes have a cell wall, a cell membrane, and a fluid interior containing deoxyribonucleic acid (DNA) and other organic molecules. Some of the ancient cellular organisms are thought to have obtained nutrients by consuming organic compounds in the environment. Others are thought to have obtained nutrients through chemosynthesis: the synthesis of organic compounds from inorganic molecules such as methane, ammonia, and carbon dioxide.

The first photosynthetic organisms, ancestors of the modern cyanobacteria, appear in the fossil record about 1 billion years after the first cellular organisms appeared. Cyanobacteria are bacteria that perform photosynthesis, a series of chemical reactions that uses energy from the Sun to synthesize nutrients in the form of glucose from water and carbon dioxide. Molecular oxygen is a by-product of photosynthesis. The proliferation of photosynthetic organisms in the fossil record suggests that the ability to perform photosynthesis was a great advantage because sunlight, water, and carbon dioxide were abundant and easy to obtain. Geological, isotopic, and chemical evidence suggest that as the photosynthetic organisms became more and more abundant, they produced more and more oxygen, which began to accumulate in the atmosphere about 200 million years after the first photosynthetic organisms appeared. The accumulation of oxygen changed the nature of the atmosphere from a reducing atmosphere to the oxidizing atmosphere that exists on Earth today. The oxidizing atmosphere was toxic to many organisms. Organisms that were not wiped out by the oxidizing atmosphere began to use the oxygen for metabolic processes (e.g., cellular respiration) that increased their metabolic efficiency.

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Reading Science Continued 3

The fossil record indicates a dramatic change approximately 2 billion years ago, nearly 1.5 billion years after the first cells appeared in the fossil record. The diversity of prokaryotes increased greatly and the first eukaryotes appeared. The eukaryotes differed from the prokaryotes because the eukaryotes had internal membranes.

Unlike prokaryotic cells, eukaryotic cells enclose their DNA within a membrane-bound nucleus. Prokaryotic cells do not have a nucleus or other membrane-bound organelles. Modern eukaryotic cells have other membrane-bound organelles, including the endoplasmic reticulum, Golgi body, and vacuoles, which form an interconnected endomembrane system. Each membrane has structural and functional specializations that help the organelle perform its functions. Each organelle in the endomembrane system is enclosed within a singlelayered membrane. Mitochondria and chloroplasts, however, differ from the organelles of the endomembrane system because they have a double-layered membrane.

The endosymbiotic theory states that eukaryotic cells originated from endosymbiotic interactions among prokaryotic cells. Endosymbiosis is an interaction where one organism lives inside the body of another organism, and both organisms benefit from the relationship. The endosymbiotic theory got its start more than 100 years ago, in the late 1800s. Scientists observed that the membranes of mitochondria and chloroplasts are similar to those of prokaryotes. The scientists hypothesized that the ancestors of the eukaryotes ingested smaller prokaryotes for food. Some of the smaller prokaryotes survived being eaten, however, and began living inside the larger cells. Some of the ingested prokaryotes were able to use oxygen to produce chemical energy via respiration. If a larger cell ingested a smaller cell that could perform respiration, the larger cell could benefit from the energy that the smaller cell produced. If the smaller cell could survive inside the cytoplasm of the larger cell, it would be protected from the external environment. The endosymbiotic theory states that mitochondria were once free-living prokaryotes that could perform respiration; they were ingested by larger cells and survived inside the cytoplasm providing energy to the larger cells through respiration. Similarly, the endosymbiotic theory states that chloroplasts were once free-living prokaryotes that could perform photosynthesis; they were ingested by larger cells and survived inside the cytoplasm providing food in the form of glucose to the larger cells through photosynthesis. Not much attention was paid to the endosymbiotic theory until Lynn Margulis published a book entitled Origin of Eukaryotic Cells in 1971.

Margulis argued for the endosymbiotic theory using observational and experimental evidence. She showed that some present-day prokaryotes are similar in size and appearance to mitochondria and chloroplasts. Experimental evidence revealed that chloroplasts and mitochondria both contain ribosomes. The ribosomes within mitochondria and chloroplasts are more similar to those of prokaryotes than they are to those of eukaryotes. Mitochondria and chloroplasts contain their own DNA, which is similar to that of prokaryotes. Mitochondrial replication and chloroplast replication are similar to prokaryotic binary fission, and their enzymes also resemble those of prokaryotes. Overall, there is a considerable amount of evidence supporting the endosymbiotic theory.

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Reading Science 1 A process by which organisms create carbohydrates from sunlight, carbon dioxide, and water is called– A photosynthesis. B biogenesis. C chemosynthesis. D metamorphosis.

2 Why did cyanobacteria gain an advantage over their chemosynthetic competitors? A Chemosynthetic bacteria are too large and unable to diffuse organic compounds across their membranes. B Cyanobacteria rely on ammonia and methane for photosynthesis. C Chemosynthetic bacteria require oxygen for survival. D Cyanobacteria are able to produce glucose using abundant and easily obtained materials.

3 Which type of cell does not contain membrane-bound organelles? A Animal cells B Prokaryotic cells C Eukaryotic cells D Plant cells

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Reading Science 4 Which of the following characteristics make mitochondria and chloroplasts different from other organelles? A They are part of the endomembrane system. B They are found in both prokaryotic and eukaryotic cells. C They have a double-layered membrane. D None of the above.

5 The endosymbiotic theory states that early eukaryotic cells ingested prokaryotic cells called endosymbionts. This led to a symbiotic relationship between the larger and smaller cells. Endosymbiotic relationships may have led to mitochondria and chloroplasts. Which of the following statements is NOT true of mitochondria? A They replicate by binary fission. B They are independent and can survive on their own. C They have their own unique DNA. D They have ribosomes similar to other prokaryotes.

6 Which of the following is evidence to support the endosymbiotic theory? A Prokaryotes have the same numbers and types of enzymes as eukaryotes. B Mitochondria and chloroplasts have their own DNA, which is similar to prokaryotic DNA. C All eukaryotic cells have a double-layered membrane composed of phospholipids and proteins. D Fossil evidence shows that the first forms of life were prokaryotic cells.

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B4A Structure, Function, and Classification

Math Connections Name:

Date:

Group:

Taxonomy is a systematic scientific process that groups living organisms by different levels of classification according to their traits and genetic relationships. A cladogram is a branched diagram showing the phylogenetic relationships between organisms. It can be used to show homologies among species and gene sequences and to reflect common ancestry based on observed similarities. The following cladogram shows the similarities among organisms in the phylum Arthropoda. The names associated with each type of arthropod are missing. Solve the systems of equations to figure out where the names are correctly located. Refer to the answer bank below. Write the name of the organism on the line provided.

3 Pairs of thoracic appendages 5 Pairs of head appendages Head, thorax, abdomen Tripartite brain Mandibles Unique ommatidial structure Body not divided into three lobes Segmental sclerites Jointed Legs Metamerically arranged appendages Ecdysial glands

Answer Key (6,2) Myriapoda

(1,8)

(7,−3)

(−5,3)

Hexapoda Onocophora Crustacea

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(2,−3)

(−2,−4)

(−4,−1)

Tardigrada Trilobitomorpha Chelicerata

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B4A Structure, Function, and Classification

Writing Science Name:

Date:

Group:

LOOK

THINK about the similarities and differences among the organisms classified according to the various domains and kingdoms. Biologists use a classification system called taxonomy to name organisms and group them logically. Organisms are designated scientific names mainly to establish a common language among scientists. Classification systems are universal criteria for grouping similar things. For example, one may refer to fruit, but more specifically, citrus fruit. A six-kingdom system of classification (Eubacteria, Archaebacteria, Protista, Fungi, Plantae, and Animalia) has been developed under the larger threedomain system (Eukarya, Bacteria, and Archaea). Living organisms are classified according to cell type, cell structure, and number of cells. Some groups share one or more traits with others. Bacteria domain members are unicellular and prokaryotic, but within the domain exists an ecologically diverse kingdom. Archaea members are also unicellular and prokaryotic, but have no peptidoglycan in their cell walls. Eukarya, organized into four kingdoms, comprises eukaryotic (nucleus-containing) and multicellular organisms. WRITE how similarities and differences in characteristics of organisms are important in the application of taxonomy. Be sure to • clearly state your central idea; • organize your thoughts; • develop your essay in detail; • choose your words carefully; and • use correct spelling, capitalization, punctuation, and grammar. © Accelerate Learning Inc. - All Rights Reserved

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Writing Science

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High School Biology

B4B

Relationships Among Groups Of Organisms

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B4B Relationships Among Groups of Organisms

Student Handout Name:

Date:

Skeleton Sort! Ever wonder how a dog evolved from a wolf? Or how a horse has changed over time? By studying fossils, we can learn how a species changed to adapt to its environment. A paleontologist is a scientist who studies fossils to identify the age and species of these organisms. In this activity, you act as a paleontologist and try to determine the chronological order of a series of horse skeletons. Procedure 1. Place the cards with the series of horse skeletons in front of you on your desk. 2.

Try to arrange them in chronological order from the earliest species to the most current species. When complete, have your teacher check if you are correct.

3. Answer the questions below. Questions 1.

What similarities did you notice in the horse skeletons over time?

How do the horse skeletons differ from each other?

What other tools or information could help you determine that these species are ancestors of the horse?

Early horses lived in jungle areas with soft, wet ground. Eventually they moved out of the jungle onto the drier grasslands and steppes. Observe the pattern of the horses’ toes. Identify the cause and effect of this change.

What patterns can be used to identify the ancestry line of an organism?

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Student Journal Name:

B4B Relationships Among Groups of Organisms

Date:

Group:

Part I: Leafy Similarities and Differences: 1.

Briefly describe the method that you used to sort the leaves pictured in the cards into categories. What are the types of trees represented in your categories?

Build a flow chart for sorting classroom items into progressively smaller groups in the space below. Be sure to label everything very clearly.

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B4B Relationships Among Groups of Organisms

Student Journal Part II: Organism Comparisons Within the Animal Kingdom 1.

Using the chart of organisms below, fill in the blanks along the cladogram based on similarities between organisms. Organism

Shark

Ray finned fish

Primates

Birds

Amphibians

Crocodiles

Vertebrate

Four Limbs

Amniotic Egg

Bony Skeleton

Eggs with Shells

?____

Fish

?____

Primates ?____

Birds

What characteristics do amphibians and primates share?

Which two species, represented by the above data, are more closely related? How do you know?

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B4B Relationships Among Groups of Organisms

Student Journal Part III: Creating a Phylogenetic Tree 1.

Construct your phylogenetic tree below. Hint: Start with the vertebrates first.

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B4B Relationships Among Groups of Organisms

Student Journal Reflections and Conclusions 1.

Describe how you analyzed the leaves to determine groupings for Part I.

Can this classification system be used to accurately identify organisms that are extinct? Why or why not? Explain your answer.

In what ways could new technologies change the current system for classifying organisms? Suggest at least one possibility.

Explain the benefit of cladograms.

Explain the difference between a cladogram and a phylogenetic tree.

Why are the more specialized traits listed toward the top of a cladogram?

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Reflect

B4B

Take a moment and make a list of as many living things as you can. How many of the organisms on your list are animals? How many are plants? How many represent one of the other kingdoms of living things? While making your list, you should not have had too much trouble coming up with organisms, as there are millions of different species that inhabit the planet along with humans. We humans have come up with a system for grouping organisms based on their similarities. Kingdoms are the largest of those groups. Historically, organisms were grouped by how they looked. When fossils were found and studied, the knowledge gained from them went on to change human understanding of how to group some organisms. Today, and in the past hundred years or so, genetic and other biochemical information is changing our current groupings as well.

Look Out Before we had technology to help us understand the DNA and other biochemical information of organisms, we could only base our classification system on appearance. The body form, or appearance, of an organism is known as its morphology. Classification is constantly changing based on new understandings of how morphology is connected to biochemistry. Scientific names (genus and species) and even some families (or even larger groups) are being revised as scientists unlock genetic information about organisms.

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The birds pictured here were first discovered by Charles Darwin as he traveled through the Galapagos Islands aboard a ship that was sailing around the world on a five-year voyage. He thought the birds were completely unrelated until he brought them to a bird specialist back in England when he returned home from this trip. The specialist pointed out some morphological similarities that indicated they are actually close relatives. Genetic information has been found, in more recent times, to help scientists understand how close the relationship between these two species of finches actually is.

Do these birds appear to be very different or very similar? These groupings start in very broad groups, with organisms that share particular characteristics. The biggest groupings used to be called kingdoms. There are currently six kingdoms, based on our best scientific information. You should be familiar with animals, plants, and fungi. Perhaps you are also familiar with protists and bacteria. Because of biochemical information discovered in recent decades, the bacteria have been split into two separate groups. The differences in these two types of bacteria are considered so big that a new category that was even bigger than the kingdoms was agreed upon: the domain. There are only three domains. These are the archaea, which are bacteria that include the most primitive of bacteria; the bacteria, which include most of the bacteria we humans encounter regularly; and the eukaryota, which includes the other four kingdoms.

While grouping organisms had been done throughout human history, the current system in use was developed by Carl Linnaeus, a Swedish botanist. He decided in the 1700s to develop a system that organised all living things, as well as rocks and minerals. Today, we only use it to organize living things. Linnaeus came up with seven levels of categories, starting with the kingdoms. He then subdivided the kingdoms into groups called phylums, the phylums into classes, the classes into orders, the orders into genuses, and the genuses into species. A species is the smallest group, and all organisms in a species are so similar that they can reproduce, and their offspring are also able to reproduce (i.e., they are not sterile).

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When it was introduced, Linnaeus’ system of sorting and grouping organisms was used worldwide in a matter of a few years. This is remarkable at a time when information traveled much slower—there were no computers or Internet!

What Do You Think? Fungi and plants were once in the same kingdom. What are some ways that flowering plants and mushrooms look alike? Do they share other similarities? In what ways are they different? Ultimately, because plants conduct photosynthesis and fungi rely on other organisms for their source of calories, the groups were made into two different large groups that we know as kingdoms. There are other differences, as well. In science, we often need to update knowledge to reflect the best, most current understanding of the world around us.

Linnaeus had to build his system using the appearance of organisms to guide him. Fossils were understood at the time, but not as many were available during his lifetime. The third main type of evidence used to classify organisms is biochemical data, like DNA, and it was completely unknown at the time. Organisms in smaller groups are typically more related, but that’s not always the case. A cladogram is a diagram that shows these relationships. You may see a cladogram that has species that don’t look related, but just like organisms can look similar and be unrelated, there can be related organisms that don’t look all that similar. © Accelerate Learning Inc. - All Rights Reserved

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In this cladogram, the oldest species would be at the bottom, but we don’t necessarily know what it looks like. It is an ancestor of all of the organisms in this cladogram. The first branching off to the left represents all of the ancestor species that led to the modern hagfish (which is a fish without a jaw, and considered to be one of the simplest vertebrate animals). When the hagfish ancestor branched off, other species continued to change through time, and eventually one of them developed the first jaws. Notice where the cladogram says the word “jaws.” All species after that mark have jaws, and only the hagfish (and it’s ancestor species) comes before it. None of them had jaws. The line leading to the perch, similarly, represents all of the species between the ancestor with the first jaws and today’s modern perch fish. The branching in the rest of the diagram also show these evolutionary relationships. These diagrams are based on evolutionary history and the branching of species. Notice that this cladogram does not show the hagfish turning into the perch and the perch turning into the salamander. It shows that there is history behind these modern species. Something happens in the environment of the ancestor to cause different genes to be favored by the breeding individuals. Over time this can cause individuals to look different. The modern salamander isn’t going to just start being a lizard. This is like your family tree. Whether you know all of the members of your family tree or not, know a generation or two, there are a lot of members of your family who lived before you did. Your cousin can’t become you any more than the salamander can become a lizard. There were biological events that happened to cause the salamander to be what it is, and events that happened a long time ago (millions of years) that led to today’s modern lizards.

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STEMscopedia: RELATIONSHIPS AMONG GROUPS OF ORGANISMS

Application: Reading a Cladogram In the cladogram seen here, the skeletons of a few species of bird ancestors can be seen. Aves is name for the modern class of birds (refer to the classification groupings described above). 1. What ancestral group did birds come from? 2. Name a bird ancestor that is older than archeopteryx. 3. What changes do you see in the skeletons of these species? Consider the “wings,” but also the skulls and other features.

Look Out The diagram you see here provides information that is different from the information most people expect from it. Like a cladogram, it is meant to explain the progression of organisms that led to modern human beings. On the right side of the diagram, you see an early human, Homo sapiens. On the left side of the diagram is an organism that looks a lot like a modern chimpanzee; however, it is not meant to be a chimpanzee. Humans and modern chimps share an ancestor and our morphology, fossil evidence, and biochemical data all back that up. The organism on the left side is meant to represent an ancestor of modern humans. About five million years ago there was an organism that encountered change in the environment and led to both modern humans (Homo sapiens) and modern chimpanzees. The diagram shows a relationship, but it doesn’t suggest that modern chimpanzees are going to become humans.

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STEMscopedia: RELATIONSHIPS AMONG GROUPS OF ORGANISMS

Connecting With Your Child What does your pantry look like? Do you have food stored in a few cabinets, a walk-in pantry, a small closet-like space, or some other arrangement? How do you organize the food you keep in the refrigerator? Are there specific places items should go or is it a bit haphazard? Your way of storing food, like in most homes, probably follows some kind of system. There is often a “right” place for at least some of the foods you use on a regular basis. Are the pastas kept a certain place? Are the canned items stored on a particular shelf? Discuss with at least one adult family member what the major groups of foods are in your home. Decide together what subgroups there are and why or why not similar items in the major groups may be kept apart or together. To Do: 1. Draw a branching tree to show your system. Include your names for the levels of your groups (like kingdoms, phyla, classes, orders, families, genuses, and species). 2. List places where these things are stored in your kitchen and add a key at the side of your tree diagram, one color for each location. Circle the types of foods in your tree with the proper color. 3. List at least three ways you can make your current classification/storage system more effective.

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B4B Relationships Among Groups of Organisms

Reading Science Name:

Date:

Group:

Cladograms 1.

Evolution is the complex and lengthy process that describes how organisms adapt and differentiate. Adaptations are inherited traits that help animals survive in their environments. Adaptations may include structural changes to protect, feed, or transport an organism.

Scientists have determined that Earth formed 4.6 billion years ago. Fossil evidence shows that after about a billion years, prokaryotic bacteria cells appeared as the first form of life on Earth. Scientists believe that all living organisms on Earth evolved from a common ancestor—a prokaryotic bacterium. After the passage of another billion years, prokaryotic bacteria evolved into eukaryotic cells with prokaryotic bacteria as organelles. Fastforward another billion years (one billion years ago), multicellular organisms began to appear. Larger plants and animals first developed about 500 million years ago.

How can evolution and the relationships of organisms be tracked and displayed? One option is a cladogram. A cladogram is a diagram used to classify organisms based on shared derived traits and evolutionary relationships among species and their ancestors. The cladogram’s branches show many evolutionary paths and display evolved traits of organisms. Lines connecting to the branch indicate an ancestor that supposedly shared all of the traits of the organisms above it on the cladogram. The individual lines show where certain species diverged from common ancestors.

Cladograms were originally used for physical adaptations. Now scientists use three types of cladograms—morphological, molecular, and behavioral. Morphological refers to the form of the organism such as whether it is a vertebrate, has claws, or is warm-blooded. Molecular means genetic information such as DNA or RNA. Technology has advanced and become more affordable, convenient, and accurate. This type of cladogram has become a popular way to investigate evolutionary questions and hypotheses. Behavioral cladograms are only used for animal actions.

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Reading Science 1.

What do you notice about all of the animals that are above the “claws or nails” spot? A.

They are predators.

They are herbivores.

They are land animals.

They are small animals (under 5 lbs.).

What do the hagfish and perch lack that all other animals higher on the cladogram possess? A.

Jaws

Fur

Feathers

Lungs

What could replace the mouse on the cladogram? A.

Snake

Eagle

Goat

Turtle

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Reading Science 4.

Why do you think the pigeon has “feathers” labeled in a different spot? A.

It is the only organism on the cladogram with feathers.

Feathers are an extra special adaptation.

Feathers are halfway like fur.

There was no room on the correct spot on the cladogram.

What could have been inserted between the mouse and the chimp? A.

Cold-bloodedness

Eggs

Scales

Opposable thumbs

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B4B Relationships Among Groups of Organisms

Math Connections Name:

Date:

Group:

Part I: Evidence of a Common Ancestor Researchers compare DNA and RNA base sequences, in addition to anatomy, to determine closely related species. Below is a table that depicts amino acid sequences for three different species— species A, B, and C. Use this information to answer the questions that follow. Species A Species B Species C

avllgmfasythkksdctcr vvlIfpwdcytrkrsectch avllgffawythrksdctcr

How many differences in amino acid sequences are there between species A and species B?

How many differences in amino acid sequences are there between species B and species C?

How many differences in amino acid sequences are there between species A and species C?

Draw a phylogenetic tree that best represents the possible evolutionary relationship between species A, B, and C.

Name three animals that could match this phylogenetic tree.

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Math Connections Researchers compare DNA and RNA base sequences, in addition to anatomy, to determine closely related species. Below is a table that depicts amino acid sequences for six different species— species A, B, C, D, E, and F. Use this information to answer the questions that follow. Species A Species B Species C Species D Species E Species F Species G

avllgmfasythkksdctcrlglfp lpfIgfgIsytqktyecdcrlmlfw avllgmfpcyttkksdsdcrlglfp abllgmfpsyttkksdsdtrlglfp ablIgmfpsythkksdstcrlglfp abllgmfhsythkksdctcrlglfp lpfIgvgmsytrkrsecdctlflfw

Complete the table below that cites the number of differences between each of the species.

A B C D E F G

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Math Connections 7.

Create a phylogenic tree that depicts the relationships among species A–G.

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Math Connections Part II: Rates and Patterns of Evolution The fossil record reflects that the rates and patterns of evolution are not constant over geologic time. Species can change very little for long periods of time (evolutionary stasis); they can change very little for a long time, and then undergo dramatic change over a relatively short period of time, followed by another long period of little change (punctuated equilibrium); or they can change gradually and sequentially (gradualism). Use the graph below to answer questions a–k.

a) What is the domain of this graph? b) What is the range of this graph? c) When is the species population increasing? d) When is this species population decreasing? e) When is the species population constant? f) When is the species population at its maximum? How many members does the population have at this time? g) When is the species population at its minimum? How many members does the population have at this time? h) What is the average rate of change on the interval 2 million years to 20 million years? i) On what interval (over what years) does this population go through evolutionary stasis? j) On what interval (over what years) does this population go through punctuated equilibrium? k) On what interval (over what years) does this population go through gradualism?

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Writing Science Name:

Date:

Group:

LOOK

THINK Common ancestry refers to the concept that groups of organisms may share a common descent. From observing the warthog and the rhinoceros above, you may notice that similar physical characteristics are present. Both animals have a tail, four limbs, and a protective structure on their bodies. Both are also similar in color and have similar diets. Warthogs eat berries, grass, and plants, and rhinoceroses eat plants. Although there are some similarities, there are also differences. The rhinoceros’s horn is made of keratin, while the warthog’s horn is made of ivory. They also differ in size and skin coverings.

WRITE Using the data from the table, construct a model such as a cladogram or a phylogenetic tree to determine relationships between the organisms listed in terms of common ancestry and/or evolution. Be sure to • clearly state your central idea; • organize your thoughts; • develop your essay in detail; • choose your words carefully; and • use correct spelling, capitalization, punctuation, and grammar. © Accelerate Learning Inc. - All Rights Reserved

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Writing Science

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High School Biology

B4C

Viruses

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B4C Viruses

Student Handout Name:

Date:

Label the following pictures as a virus, bacteria, or cell.

a.___________________ b.__________________ c. ___________________ 2.

In your own words, define a virus. Are viruses considered to be alive? Explain.

In what ways do you think the following viruses are transmitted (airborne, bloodborne, mosquito bite, animal bite, or contaminated food/water)? West Nile virus______________________________________________________________ Rabies____________________________________________________________________ Influenza___________________________________________________________________ HIV _______________________________________________________________________ Hepatitis A_________________________________________________________________

What is the difference between a vaccine and an antibiotic?

Circle all the diseases caused by a viral infection. Anthrax

Chicken Pox

Influenza (flu)

Lyme Disease

West Nile

Tetanus

Hepatitis B

Cholera

Measles

Rabies

Mononucleosis

Whooping Cough

Hepatitis A

Bubonic Plague

Gonorrhea

Common Cold

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B4C Viruses

Student Journal Name:

Date:

Group:

Part I: Viruses and Cells Using your Student Guide, fill out the Venn diagram. List the similarities and differences of viruses and cells.

Part II: Viral Replication 1. What are the two methods of viral replication?

2. What two stages of replication do both cycles have in common? Describe the virion action at each of these stages.

3. What determines whether or not an organism is in a virus’ host range?

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Student Journal Part III: Investigating Viruses Record facts about your disease in the boxes provided below.

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Disease Background

Treatment

Prevention

Symptoms

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B4C Viruses

Student Journal Reflections and Conclusions 1. What does it mean for a virus to have a lysogenic reproductive cycle? Describe the process.

2. Suppose you were to breathe in a flu-causing virion. How is it possible that a single lytic virion could infect thousands of your cells, leading to illness?

3. Is a virus considered to be a living or nonliving entity? Explain your answer.

4. Using all of the following terms, develop a graphic organizer. Use another sheet of paper, if needed. Terms: Virus, capsid, DNA, RNA, lytic cycle, lysogenic cycle, host cell, antibiotic, vaccine, bacteriophage, influenza, pathogen.

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STEMscopedia: VIRUSES B4C

Reflect Imagine a military base designed to keep invaders out. Soldiers patrol the fences and gates. Cameras are set up along the borders of the base to capture video of anyone who tries to get in. Sensors in the ground set off alarms if someone jumps over the fence. But every day, the tiny invaders get past these complex security measures and take over the base. In this analogy, the military base is the human body and the tiny invaders are called viruses. What are viruses? Are they alive? How do they make us sick? Characteristics of Viruses Viruses are nonliving particles. They do not eat, they do not have a metabolism, and they cannot move on their own. Viruses are not able to reproduce without living cells. They lack cytoplasm and membrane-bound organelles. Viruses depend on living things to survive, and in doing so harm their cell hosts. This characteristic makes viruses parasites. Viruses are also very small. They are so small, in fact, that they are measured in nanometers (nm). One nanometer is 1×10–9 meters. The common cold virus is 75 nm, about 100 times smaller than a red blood cell! Their tiny size is part of what makes viruses so good at invading living things. A virus is fairly basic in structure and contains only what it absolutely needs to survive.

Host: organism that supports a parasite

• Protein coat: The outside of a virus is composed of a protective protein coat called a capsid. The capsid has surface proteins on it that help the virus invade cells. Protein coats come in many shapes and sizes. Some viruses are spherical in shape, while others look like rods. Some viruses also have a lipid envelope surrounding the protein coat.

• Surface proteins: Surface proteins are located on the virus’s protein coat. They act as “keys” that bind with the host cell’s receptor proteins, or “locks.” The surface proteins allow the virus to bind to the host cell. Then, the virus can insert its genetic material into the cell or enter the cell itself. The surface proteins only match up with specific cells. This is why a virus can only infect certain cells in the body. For example, a virus with surface proteins that match up with liver cells cannot infect red blood cells.

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STEMscopedia: VIRUSES • Genetic material: Like cells, viruses have genetic material. The genetic material in a virus may be single-stranded or double-stranded RNA or DNA. As with prokaryotic cells, the genetic material is not contained within a nucleus. It is found inside the protein coat. Viruses vary in the size of their genome. Some viruses have as few as four genes, while others may have a thousand genes. Viruses can only copy their genetic material while inside a host cell.

Prokaryotic cell: a cell that does not contain a membrane-bound nucleus or other organelles

Look Out Not all viruses are bad. Scientists have found a way to use viruses to prevent disease. Most children in the United States are required to have certain vaccines before they enter school. A vaccine contains a weakened or inactive virus that is injected or sprayed into the body. The virus is not strong enough to cause the disease, but it does cause an immune response. The body learns to recognize and fight the virus. So, if the strong, active version of the virus ever attacks the body in the future, the body will be able to fight it off without getting the disease. Viral Reproduction A virus can make copies of itself in two ways: lytic infection and lysogenic infection. Both of these methods involve the virus taking over a living cell in order to reproduce. • Lytic infection: The lytic infection is so named because it causes the host cell to lyse, or be destroyed. First, the virus attaches to the host cell (A) Then, it either enters the cell or injects its genetic material into the cell (B) The virus takes over the host cell and causes the cell to make viral proteins and genetic material. (C) New virus particles are assembled (D) Think of this process as similar to breaking into a car factory and using the machinery to make your own kind of car. Eventually, the viral genes direct the production of enzymes that cause the release of newly produced viruses from the cell. The newly produced viruses escape the host cell either by causing it to burst or by encasing themselves within a piece of the cell membrane and then breaking away from the cell. (E) Each of these new virus particles is capable of infecting another cell.

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STEMscopedia: VIRUSES • Lysogenic infection: Think of the lysogenic infection as a sneaky Daughter cells: attack compared to the lytic infection. In a lysogenic infection, the virus the cells produced does not immediately kill its host cell. As in the lytic infection, the virus during cell division either enters the cell or injects its genetic material into the cell. Then, the viral genetic material is inserted into the host cell’s DNA. This is how the lysogenic infection differs from the lytic infection. Whenever the host cell replicates its DNA, the viral genome is copied, too. All of the host cell’s daughter cells have a copy of the virus genome. Eventually, something triggers the viral DNA to remove itself from the host’s DNA. Common triggers include cellular stress or exposure to ultraviolet radiation. Once triggered, the infection takes the path of a lytic infection. The host cell and all of its daughter cells begin to make copies of the virus. Eventually, the cells lyse and release the viruses. Lysogenic viruses that you may be familiar with are those that cause cold sores and shingles.

What Do You Think? Viruses depend on living things for survival. Viruses can only reproduce if they are inside a living cell. Do you think viruses evolved before living things or after? Explain your reasoning. Viral Diseases Like a military base, our bodies have many defenses to prevent viruses from infecting our cells. The skin and the mucus lining the respiratory tract help prevent viruses from invading the body. But every now and then, these tiny invaders slip past our defenses. Viruses are the cause of a variety of diseases. Some you may have had yourself—the common cold, influenza (flu), chicken pox, and measles. Viruses can also cause more serious diseases such as dengue fever (a disease spread by mosquitos characterized by high fever), encephalitis (a disease characterized by swelling of the brain), small pox, and AIDS. Some viruses can even cause cancer by disrupting the normal cell cycle. Usually, a cell’s DNA contains information about when the cell should stay at rest and when it should replicate. Some cancer-causing viruses are able to direct the cell to keep dividing over and over. The result is a large mass of cells called a tumor. © Accelerate Learning Inc. - All Rights Reserved

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STEMscopedia: VIRUSES The symptoms of a disease are often due to the type of cell that is attacked by the virus. Remember that different viruses can only infect specific cells. Viruses that attack nerve cells, such as the polio virus, can cause paralysis, or loss of movement. When a nerve cell is killed by a viral infection, it is not replaced because nerve cells do not reproduce. When enough nerve cells are killed, a person experiences paralysis. Some viruses infect white blood cells. White blood cells are part of a human body system that fights infections. When a virus kills white blood cells, the body can become more susceptible to further infection. The virus that causes the common cold infects cells in the respiratory tract. When attacked, these cells release mucus, which can result in a runny nose or cough. In this case, the symptoms are due more to the immune system response than to the actions of the virus itself! The Immune System: Fighting Infections How does your body cope with a viral infection? As mentioned previously, the body’s immune system fights the virus. Special cells in the immune system try to find and destroy any body cell that contains a virus. These immune cells can also direct an infected cell to self-destruct before the virus inside can make copies of itself. This process of self-destruction is called apoptosis. Some viruses have developed special proteins that inhibit apoptosis. This allows the virus to continue using the cell for reproduction. Sometimes the ways in which the body tries to fight the virus can end up hurting the body, too. For example, a fever is the body’s way of trying to “cook” the virus to death. This attempt to control the infection can cause discomfort and may cause serious damage to the body, though that’s rare. However, very high, prolonged fevers can cause seizures and brain damage. Acquired Immunodeficiency Syndrome: AIDS AIDS is caused by the human immunodeficiency virus (HIV). This virus causes a deficiency in the body’s defenses by targeting and killing cells in the immune system. HIV targets helper T-cells, the very cells in the body that would be useful in fighting the viral infection. The virus is also able to hide from the immune system, allowing it to replicate without being detected.

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STEMscopedia: VIRUSES HIV is a retrovirus. What does this mean? The prefix “retro” means “backward.” It refers to the backwards way in which the virus transcribes DNA. In most viral infections, a virus first injects its genetic material into the cell, and the cell then makes mRNA and proteins from the viral genes. In a retrovirus infection, the retrovirus injects its genetic material, RNA, along with an enzyme called reverse transcriptase into the host cell. The host cell then makes double-stranded DNA from the viral RNA using the reverse transcriptase. The viral DNA is then incorporated into the genome of the host cell. Some of the medicines that are used to treat HIV and other retroviruses attempt to inhibit reverse transcriptase. This prevents the virus from incorporating its DNA into the host cell’s DNA and making copies of itself. Although AIDS cannot be cured, it can be delayed with treatments that inhibit virus replication. For example, a drug called AZT inhibits the function of reverse transcriptase. Career Corner: Virologists Do you like solving medical mysteries? Do you like using laboratory equipment? Then, a career as a virologist might be in your future. A virologist is a scientist who studies viruses. They may study the origin of a virus, its shape, its method of infection, the diseases it causes, and how to fight the diseases. Some virologists work in laboratories. Others travel to places where viral diseases are widespread within the population to learn more about the viruses. A virologist may work with other scientists to develop anti-viral medications and vaccines. Virologists work with sophisticated technology. Because viruses cannot usually be seen with a compound light microscope, virologists must use powerful electron microscopes to visualize viruses. By studying viral diseases, these scientists make a huge difference in the world. The work they do saves lives and prevents the spread of diseases.

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This model shows HIV (green) attacking white blood cells (blue). Transcribe: to convert the genetic information in DNA into RNA Enzyme: a protein that helps control a chemical reaction in the body

This virologist is using a micropipette to infect a culture of human cells with a virus.

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STEMscopedia: VIRUSES What Do You Know? Use what you know about viruses to fill out the table below. First, decide if you agree or disagree with the statement in the left column. Then, provide an explanation for your decision in the right column. Agree/Disagree?

Explanation

Viruses are nonliving. Agree Disagree Viruses are larger than most living cells. Agree Disagree A lytic infection involves incorporating viral DNA into a host cell’s DNA. Agree Disagree

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STEMscopedia: VIRUSES Connecting With Your Child Viruses and Infection To help students learn more about viruses, work with them to make a scale model comparison of several viruses and the human body cells they infect. First, research three viruses that infect the human body. Try to choose viruses that are well known or cause common diseases—these viruses will have the most information available. Here are some examples of diseases caused by viruses: the common cold, flu, chicken pox, cold sores, shingles, Ebola, and AIDS. You may select from these examples or use others that interest you. Health websites ending in “.gov” are typically very informative and accurate. Have students research the following questions about each virus: • What is the size of the virus and the type of host cell it infects? • What symptoms does the virus cause, and are they a result of viral action or the immune response? • Are there any ways to prevent infection or treat infection once it has happened? Next, make a scale paper model of each virus and the host cell it infects. For example, if you make a model of the virus that causes the common cold, the virus would be 75 nanometers in diameter. You could make a scale in which 10 nanometers equals 1 centimeter. Because cells might be measured in micrometers, it would be useful to know that 1 micrometer equals 1,000 nanometers. It might be best to use a roll of brown postal packing paper to make the models, as the body cells might be quite large in comparison to the viruses. Have students add the information about the virus, host cell, infection, and treatment to the models. Here are some questions to discuss with students: • How does the size of viruses compare to the cells they infect? • How are the viruses and the cells they infect similar in structure? How are they different? • Do any of the viruses infect more than one type of host cell?

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B4C Viruses

Reading Science Name:

Date:

Group:

Viral Replication and Treatment 1. Viruses have been in the news a lot lately, from the West Nile virus, to H1N1, to the bird flu. But, what exactly is a virus, and why is there such concern over the spread of these pathogens? The concern has to do with the structure and reproductive cycle of these diseasecausing agents. Viruses are not structured like other biological organisms. In fact, viruses are not considered biological organisms at all. Let us take a closer look at the structure and reproductive systems of viruses. Then we can discuss why these factors make viruses so difficult to treat. 2. Most biological cells consist of a membrane that encloses genetic material in the form of a double-helix strand of DNA. This is true whether the cell is a prokaryotic bacteria, or a eukaryotic cell in a plant, animal, fungus, or protist. Viruses are different. First of all, viruses do not have cell membranes. The material inside the virus is enclosed in a protein shell called a capsid. Within the capsid is another structure called the viral envelope. Second, viruses do not always contain a double-helix strand of DNA. The genetic material inside the virus can come in a variety of forms: from a single strand of DNA to a strand of RNA. Third, viruses have no mechanisms for metabolism. They also do not have ribosomes. But, what truly distinguishes viruses from other biological structures is that viruses cannot replicate on their own. They can only reproduce within another cell, or a host cell. This is why many do not consider viruses to be living cells at all. 3. Viruses do not have metabolism while all bacteria and other cells do. Also, viruses (unlike other biological cells) rely on other organisms to survive and replicate. They are considered a type of parasite because they need another organism to survive. Let us look at a specific type of virus: the bacteriophages, or phages. These types of viruses infect bacteria and are highly structured. Their replication methods are well documented. There are two main ways that these types of viruses can replicate within a host organism. Both of these methods make it very difficult to treat and destroy the virus once it has entered the host cell. 4. The first type of replication cycle seen in phages is the lytic cycle. Let us assume that this virus is infecting an E. coli bacterium. The phage has specific structures that fit into receptors on the plasma membrane of its host cell. It will land on the surface of the E. coli and inject its genetic material straight into the cell. The genetic material of the virus will form a circle and take control of the protein synthesis “machinery” of the host cell.

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B4C Viruses

Reading Science

5. At this point, the new genetic material will direct the host cell to start replicating viral parts from the host cell’s molecules. The viral components will be replicated in pieces. They will then assemble within the cell. Once the cell produces 100 to 200 phage products, the cell will burst (lyse). This kills the host cell and releases the newly formed viruses, which will then infect other nearby cells. 6. he second type of replication cycle is the lysogenic cycle. In this cycle, the host cell is not killed. Instead, it is used to produce more of the viral genome. As with the lytic cycle, the virus will attach to the host’s receptors and release its genetic information into the host cell. However, the viral genome will then become incorporated into the host cell’s genome. Host cells with embedded viral genomes are called lysogens. Each time the host cell reproduces, it copies the viral genome and passes this information to each daughter cell. In this way, the information for creating more viruses is carried in a host organism without killing the host organism. However, at certain points, the viral replication cycle can switch from lysogenic to lytic and back again. 7. The viral replication cycle is the reason that viruses are so difficult to treat. Once the host cells are infected with the viral genetic material, it is almost impossible to remove. In other words, viral infections cannot currently be cured. They can, however, be treated with medicines to lessen the symptoms. Often, certain lymphocytes in the body’s immune system make enough antibodies to destroy more viruses than are being made. In this way, the disease is overcome. Sometimes viral infections can be prevented by immunizations or vaccines. People are exposed to pieces of specific disease-causing viruses. The body’s immune system is triggered to prepare to fight the actual specific virus if it encounters one in the future. This is why many people in the United States are vaccinated against such viral diseases as chicken pox, the measles, and the flu. Unfortunately, HIV, the human immunodeficiency virus, infects and causes the death of the very cells that form antibodies to protect you. That is why people who are infected with HIV become sick due to infections that otherwise healthy people could successfully fight.

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Reading Science 1. In which replication cycle is the viral genome reproduced without damage to the host cell? A The lytic cycle B The attachment cycle C The parasitic cycle D The lysogenic cycle

2. Which of the following statements is false? A Viruses have metabolism. B Viral infections can be treated with vaccines. C Viruses are a type of parasite. D Viral replication cycles can switch from lysogenic to lytic and back again.

3. Considering the information given in paragraph 1, we know that viruses– A are all of the following. B are disease-causing pathogens. C are not considered biological organisms. D cause a great deal of concern.

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Reading Science 4. A virus is a pathogen that contains several components. Which of the following could NOT be a component of a virus? A A strand of RNA B A protein shell C A ribosome D A viral envelope

5. How do immunizations work with viruses? A They cure the person by killing the virus cells and preventing the symptoms. B They show the body virus pieces to prepare it to fight that virus in the future. C They treat all of the symptoms of the virus so that they are not as severe. D They provide a chemical that keeps any virus from infecting the cells.

6. What is the main reason that viruses are not considered to be living organisms? A They are too small to be living. B They do not have DNA. C They need the host cell to replicate. D They kill the host cells.

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B4C Viruses

Reading Science 7. Why is the human immunodeficiency virus so deadly? A It cannot be broken into pieces to make antibodies. B It is too small to identify the white blood cells. C It is not recognized as a virus by the body. D It kills the cells that make antibodies.

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Carbon and Nitrogen Cycle

B 4B(3)

STEMscopedia The story of Goldilocks and the Three Bears describes how the little girl, Goldilocks, preferred the porridge that was neither too cold nor too hot, but “just right.” Much like Goldilocks, certain conditions within an ecosystem cannot tilt too far to one or another extreme. Ecosystems thrive when conditions are balanced, or “just right.” Take a look at the photograph on the right. What are some of the components—living and nonliving—of this ecosystem? How might conditions in the ecosystem—the amount of rainfall, the nutrients in the soil, the number of organisms within each population—fall out of balance? How might such changes affect the ecosystem? Elements such as carbon cycle through the atmosphere and biosphere. Systems on Earth are healthiest when their various components are balanced. One important element that contributes to this balance is carbon. Carbon moves between living and nonliving things on Earth. These movements make up the carbon cycle. Like all cycles, the carbon cycle has neither beginning nor end. Instead, it consists of a number of related processes. One part of the carbon cycle centers on photosynthesis. Carbon exists in Earth’s atmosphere primarily within molecules of carbon dioxide (CO2). During the Calvin cycle of photosynthesis, plants use Carbohydrates such as this molecule of glucose the carbon (C) from CO2 to make organic (left) have a carbon backbone. Foods made from compounds called carbohydrates. One of grains, such as bread and pasta (right), are the most important of these carbohydrates complex forms of carbohydrates. is glucose (C6H12O6), a sugar that plants use for food. Plants can store glucose for later consumption in the form of starch, another type of carbohydrate. Another important part of the carbon cycle occurs when organisms consume carbohydrates produced by plants. These consumers use the energy held within the chemical bonds of the molecules to fuel their cellular activities. For example, in an animal’s cells, carbohydrates undergo a series of chemical reactions that break down the molecule to release energy. This process is called cellular respiration. One of the waste products of cellular respiration is carbon dioxide. Because animals cannot use

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Carbon and Nitrogen Cycle

carbon dioxide, they exhale it into the atmosphere where plants can once again use it to make carbohydrates. In this way, carbon cycles continually between the atmosphere (as carbon dioxide) and the biosphere (as carbohydrates).

B 4B(3)

Atmosphere: the layer of gases that surrounds Earth

Biosphere: the living Carbon in biomass—the living (or recently living) matter in things on Earth and their an ecosystem—is also returned to the environment through environments decomposition. The bodies of organisms are primarily made up of carbon. When an organism dies, worms, bacteria, and other decomposers break down the body into its component elements. In this way, carbon moves from biomass into the ground, where it can remain buried for thousands of years. Over millions of years, extreme heat and pressure from Earth’s interior transformed buried plants and animals from the Carboniferous period (approximately 300–350 million years ago) into fossil fuels such as coal, petroleum, and natural gas. When humans burn fossil fuels—to power machines, generate electricity, and heat buildings—the carbon cycles back to the atmosphere, where it can be used again by plants during photosynthesis.

Photosynthesis, respiration, and decomposition happen in the oceans as well as on land. In the oceans, carbon cycles between the surface ocean, the deep ocean, and the seafloor. These movements are part of the carbon cycle.

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Carbon and Nitrogen Cycle

B 4B(3)

Humans contribute to the carbon cycle by burning fossil fuels and other forms of biomass, such as wood. (Biomass also burns through natural processes. For example, a bolt of lightning can spark a forest fire.) However, over the past few centuries, humans have released huge quantities of carbon into the atmosphere—more than can be absorbed through photosynthesis and other natural processes. Scientists have evidence this excess carbon dioxide is trapping heat at Earth’s surface, leading to global climate change. Nitrogen also cycles between Earth’s atmosphere and biosphere. Both plants and animals require nitrogen to survive. It is a key component of DNA, RNA, and amino acids, which are used to form proteins in living organisms. Approximately 78% of Earth’s atmosphere is nitrogen gas (N2), but most living things cannot use nitrogen in this form. Only certain types of bacteria can take nitrogen directly from the atmosphere. For this reason, if it were not for these bacteria, nitrogen would not cycle through the biosphere for other organisms to use. Many legumes—plants such as peas, soybeans, peanuts, and alfalfa—coexist with bacteria called Rhizobia. The bacteria live in the soil on the roots of the legumes. These bacteria are able to take nitrogen directly from the atmosphere and convert it into ammonia (NH3); this process is called nitrogen fixation. Other bacteria in the soil change the ammonia into nitrites (NO2–) and nitrates (NO3–) in a process called nitrification. Plants absorb the nitrogen compounds through their roots and use them to synthesize amino acids; this process is called assimilation. As consumers eat plant producers, nitrogen passes up through the food chain for other living things to use. In addition, some bacteria in the soil convert nitrates into nitrogen gas through a process called denitrification. The nitrogen gas is then released back into the atmosphere. The decomposition of organic material is also a crucial part of the nitrogen cycle. When organisms die, nitrogen compounds held in their bodies are broken down by detritivores and returned to the soil as nitrates and nitrites. Bacteria in the soil can also convert nitrogen compounds from decaying matter into ammonia through a process called ammonification. The nitrogen cycle continues as plants reabsorb these compounds into their bodies.

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The roots of legumes contain tiny nodules where the Rhizobium bacteria is found.

Detritivore: an organism that feeds on dead organic matter (detritus)

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Carbon and Nitrogen Cycle

B 4B(3)

Organisms need nitrogen to carry out their life functions—for example, nitrogen is an important component of proteins. Several key processes in the nitrogen cycle make nitrogen available for all organisms to use. A symbiotic relationship is one in which organisms live together in such a way that their actions affect each other. How is the relationship between legumes and Rhizobia symbiotic? Everyday Life: Disruptions to the Carbon and Nitrogen Cycles As mentioned previously, ecosystems thrive when conditions are balanced. The carbon and nitrogen cycles are crucial to maintaining this balance. Disruptions to these cycles can have devastating effects on an ecosystem. Unfortunately, too often these disruptions result from human activities. The total amount of carbon actively moving through the carbon cycle decreases when people bury organic materials in landfills rather than allow them to decompose naturally outdoors. Ideally, fallen leaves and discarded food should be used for compost, allowing nutrients in the decomposing biomass to return to the ecosystem.

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Compost: a mixture of decaying organic matter, air, and water that may be used to fertilize soil

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STEMscopedia

Carbon and Nitrogen Cycle

A much larger problem, however, is excessive carbon in the atmosphere. Recall that burning fossil fuels releases carbon dioxide gas into the air. In the last 150 years, there has been a dramatic increase in the burning of coal, oil, and natural gas for factories, cars, airplanes, heat, and other technologies invented by humans. Not only does this excessive use deplete Earth of its natural fossil fuel resources, but it also pollutes the air and creates unbalance in the carbon cycle. During the last few decades, governments and individuals in the United States and other countries have worked at reducing the amount of CO2 emissions from refineries, factories, and automobiles. Additionally, efforts are being made to make homes and office buildings more energy efficient using “green” technology. Burning fossil fuels also results in excessive nitrogen buildup in the atmosphere, which leads to destructive acid rain. Overusing nitrogen-based fertilizers in agriculture also disturbs the nitrogen cycle. The availability of nitrogen can be a limiting factor to the growth of crops. To combat this, farmers use fertilizers with high concentrations of nitrogen and other nutrients. The fertilizers may help with farming, but the nitrogen compounds in the soil get carried away by rainwater. The runoff causes nitrogen to build up in estuaries, lakes, and streams. This change in water composition is called eutrophication. Algae thrive on the excess nitrogen concentrations and reproduce uncontrollably, resulting in an algal bloom. As the algae die, the decaying matter and decomposers use up most of the available oxygen, choking out other organisms in the water such as fish.

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B 4B(3)

Exhaust from vehicles releases lots of carbon dioxide into the atmosphere.

This algae bloom—the over-reproducing of algae in a water body at the expense of other organisms—is the result of eutrophication.

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Carbon and Nitrogen Cycle

B 4B(3)

What Do You Know? Use the Venn diagram to compare and contrast the carbon and nitrogen cycles. Add 3–5 responses that show how each cycle is different, and 3–5 responses that show how the cycles are similar. Be sure to include consequences that result from human activities or other disruptions. Carbon Cycle

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Both

Nitrogen Cycle

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STEMscopedia

Carbon and Nitrogen Cycle

B 4B(3)

Your Role in Nutrient Cycles To help your child learn more about the carbon and nitrogen cycles and the effects of human activities on them, work together to develop carbon and nitrogen recycling programs around your home, school, or community. You may begin by creating a place to store a compost pile. Have your child choose a convenient place that is shaded, well drained, and not too close to any tree roots or wooden fences. For a home compost pile, 1 square meter is an acceptable size. A larger area may be appropriate for compost piles at school or in a community location. Begin the compost pile with a thick layer of organic materials such as dead leaves, yard clippings, or vegetable scraps. When ready, add a thin layer of fertilized soil to activate the compost. Then, layer a thin covering of topsoil, which may include microorganisms. All organic waste from uneaten food including leftovers, eggshells, and peelings can be added to a compost pile. Important: Never include human or animal waste products in compost used on food plants.

You can recycle biomass at home by making a compost pile.

You will need to water the compost and turn it every couple of weeks. To turn the compost, use a garden tool to move the inside material to the outside and vice versa—all parts should be exposed to oxygen. Within a couple of months, the compost pile should be ready to use. You can also research your carbon footprint and find ways to reduce it. Encourage your child to think about ways he or she can personally reduce fossil fuel emissions into the atmosphere. Suggestions include walking or riding a bike instead of driving and recycling materials made in factories such as plastics. Encourage your child to expand a personal program to the entire family, the school, or the community. Here are some questions to discuss with your child: • How do the carbon and nitrogen cycles keep nutrients balanced between the atmosphere and biosphere? • What roles do humans play in the carbon and nitrogen cycles? • What can you do to help maintain balance in the nutrient cycles?

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B4C Viruses

Math Connections Name:

Date:

Group:

In March of 2014, the Ebola virus began to spread quickly in the West African countries of Sierra Leone, Senegal, Liberia, Guinea, and Nigeria. The virus, known as hemorrhagic fever, is spread through contact with skin and body fluids of infected individuals or animals. The symptoms can appear between 2 and 21 days after infection and may include high fever, headache, muscle aches, sore throat, and stomach pain. As symptoms progress, the infected individuals will experience a decease in the number of blood-clotting cells, which will lead to internal and external bleeding. The mortality rate of Ebola victims is up to 90% of those infected. The data below show the number of total cases per month in the countries named above. Infection and Mortality of Ebola Cases in 2014 Month

Total infected individuals

Total Deaths

First report

March

137

April

241

162

May

421

226

June

759

467

July

1,603

887

August

3,707

1,848

1. Calculate the percentage of the those infected who have died from the disease. Record the figures in the table below. Month

Percent fatalities

First report March April May June July August

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Math Connections 2. The mortality rate of Ebola victims is about 90%. However, your figures from question 1 do not support this figure per month. Why? What other conditions need to be taken into account for this data? 3. Graph the relationship between the number of infected individuals vs. the number of deaths for the seven months of the Ebola outbreak in West Africa.

Ebola Virus 2014: Infected Persons vs. Mortality

4000 3800

3600 3400 3200 3000 Number of infected persons

2800 2600 2400

2200 2000 1800 1600 1400 1200 1000

800 600 400 200 0

200

400

600

800 1000 1200 1400 1600 1800 2000 2200 2400

Number of deaths

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Math Connections 4. What is the percent increase from the number of first reported cases to the number of cases in August?

5. Draw a line of best fit through the data on the graph. 6. What is the rate of increase on your graph (slope)?

7. What is the y-intercept of your graph? (How many deaths will there be if no one is infected?) 8. Create an equation to describe the line.

9. What does this equation represent? 10. Graph the total number of people infected per month on the chart below.

4400

Total Number of Ebola-Infected Individuals per Month

4000 3600 3200 2800 2400 2000 1600 1200 800 400

Mar Apr

May Jun

Jul

Aug

Sep

Oct

Nov Dec

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Math Connections 11. Is the relationship linear? If not, describe the relationship.

12. What does the pattern seem to be from one month to the next? (Use estimation; the relationship does not have to be exact.)

13. An estimated 20,000 people will become infected with the Ebola virus before the disease can be controlled. In what month will the number of infected people reach a total of 20,000?

14. What are some measures the countries involved can take to decrease the spread of the Ebola virus?

15. How might these measures affect the people living in or visiting those countries?

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Writing Science Name:

Date:

Group:

LOOK

THINK about the different types of infections and how they may be treated. Your throat starts to hurt, your body aches, and, suddenly, you have a high fever. You realize that you have been infected by some sort of pathogen, or disease-causing agent. Treatment depends on the origin of the infection. If it is bacterial infection, an antibiotic will stop the symptoms of the illness, as the antibiotic will kill the bacteria. Viral infections have no cures. Usually, once infected with a virus, only the symptoms may be treated, though some treatments for viral infections, like HIV, are available (AZT). Your best defense against a viral infection is good hand-washing habits. Soap and warm water will wash most viruses off of your skin before they enter your body. Vaccines are also an option for prevention. They “train” your immune system to recognize a specific virus, so if you are infected, your body is ready to defend itself. When you are vaccinated, a dead or weakened version of the virus is injected into your body. This triggers your immune system to create antibodies for that specific virus, which are then manufactured in your body. If (or when) that virus shows up again, the body is ready to attack and stop the virus from entering your cells. WRITE the various types of infections, and explain why it is difficult to halt the spread of viruses. Be sure to • clearly state your central idea; • organize your thoughts; • develop your essay in detail; • choose your words carefully; and • use correct spelling, capitalization, punctuation, and grammar.

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Writing Science

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High School Biology

B5A

Biodiversity and Populations in Ecosystems

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B5A Biodiversity and Populations in Ecosystems

Student Handout Name:

Date:

What Affects an Ecosystem? Directions: As you observe the picture below, brainstorm answers to the questions that follow.

What factors are in an ecosystem?

What do you think limits the number of factors in an ecosystem?

What types of interactions are there between the factors in an ecosystem?

What do you think would happen if there were more organisms than an ecosystem could handle?

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Student Journal

B5A Biodiversity and Populations in Ecosystems

Name:

Date:

Group:

Part I: Carrying Capacity Read the article in your Student Guide, then answer the following questions. 1.

Write a definition of carrying capacity.

On which factors does carrying capacity depend?

“The carrying capacity of this lake equals 250 minnows.” a. Can less than 250 minnows live in this lake? ____________ b. Can more than 250 minnows live in this lake? ___________ c. Let’s say that there are 240 minnows in this lake when the amount of resources in this lake decreased and the carrying capacity drops from 250 to 200 minnows. What will happen to the minnow population? Why will this happen? ____________

What do you think will happen if we did not have hunting seasons?

What are some other ways to help “control” certain species from reaching their carrying capacities?

How would introduction of a new species in an ecosystem affect the carrying capacity of the other species in that environment?

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B5A Biodiversity and Populations in Ecosystems

Student Journal Part I: Carrying Capacity, continued 1.

Refer to the following graphs for the next set of questions.

What is the carrying capacity (approximately) for Graph A?

Approximately during which year did the population in Graph A reach the carrying capacity of its ecosystem?

About how many years did it stay at the carrying capacity in Graph A?

What is the carrying capacities for Graph B?

How many years did this population in Graph B spend at the first carrying capacity?

During which year did the population reach the next carrying capacity in Graph B?

Which carrying capacity is more stable in Graph B? Why do you think so?

What do you think caused a shift in carrying capacity for Graph B?

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B5A Biodiversity and Populations in Ecosystems

Student Journal Part II: A Squirrely Game 1.

What are some of the abiotic factors that a squirrel interacts with in its environment?

What are some of the biotic factors that a squirrel interacts with in its environment?

What strategies might a squirrel use to survive?

Year (Round)

1 2 3 4 5 6 7 8 9 10 11 12 13 14

Number of Native Squirrels

Number of Invasive Squirrels

Number of Predators

x x x x x x x x x x x x x x

Notes

x x x x

15 16 17 18 19 20

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Student Journal 4.

In the space provided below, draw a food web diagram of the relationship between squirrels and the biotic and abiotic factors in the natural world. What do they depend on?

Revisit the prediction you made before the game. How does it compare to the game’s actual results? Explain.

When was it easiest for the squirrels to find resources? When was it hardest?

When do organisms within the same population compete for resources?

When do different populations compete for resources?

How are resources affected by competition?

10. To avoid extinction from competition, how would the native squirrel’s niche need to change? 11. How might data collected from the So Squirrely game differ from data collected from the natural world?

12. Are the squirrels considered a keystone species? Why or why not?

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B5A Biodiversity and Populations in Ecosystems

Student Journal Reflections and Conclusions 1.

What is a climax community?

What is a keystone species?

How do biological competition and limiting factors affect species and populations in the ecosystem?

Why is species diversity important in an ecosystem?

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STEMscopedia: BIODIVERSITY AND

POPULATIONS IN ECOSYSTEMS

Reflect

B5A

Every living organism on the planet depends on its surroundings, living and nonliving alike, to sustain its life. Most organisms, including humans, do best in environments high in biodiversity. Imagine two types of forests. One has only one type of tree, a maple tree. Maple trees are deciduous, meaning they lose all of their leaves every winter. The other type of forest has many types of trees, including deciduous and evergreen. Which of these forests could sustain more life? Biodiversity Biodiversity, or biological diversity, is the term we use to describe the variety of different species found on Earth. Biodiversity involves not only the number of different species but the variability in genetics, the ecosystems in which the organisms live, and the natural resources found in the ecosystems. All natural resources are connected, and all organisms are dependent on them. Therefore, it is safe to assume that any change, positive or negative, will have an impact on more than just one species or organism. All living things and their environments are interconnected. Why is biodiversity important? All living things depend on each other, and high biodiversity helps the sustainment of most species and strengthens their ability to withstand environmental change. Factors Affecting Biodiversity A balanced ecosystem, meaning an ecosystem maintaining itself over time through the emergence or migration of new species and loss of others, is ideal. Many different factors can affect biodiversity, including man and nature. Limiting Factors A limiting factor is anything in the environment that will limit the amount of organisms the environment can sustain. Limiting factors include, but are not limited to, space, water, food, and air. Space is a limiting factor in self-contained environments, such as a lake or pond. Biodiversity plays a great role in food as a limiting factor. Ecosystems high in biodiversity can support more life simply because there is more food. High biodiversity can also support a population because of the variety of food sources. For example, if a certain species of beetle feeds on a certain plant but that plants suffers a disease and dies out, a highly diverse environment would allow that beetle to go feed on another plant.

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STEMscopedia: BIODIVERSITY AND

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Population Size Since some environments are conducive to population growth, some species will outgrow their environment. All ecosystems have a carrying capacity. This is the maximum amount of life a certain habitat can support. Most of the time, populations take care of staying below the carry capacity through immigration and emigration, but sometimes the population gets too high, and mass die-offs or even extinction can occur. Certain types of species play seemingly more important roles in an ecosystem than others. Keystone species are generally a predator that acts as a control on other population sizes. Fire ants are a good example of a keystone species. They keep insect populations under control. Without fire ants acting as a predator on certain insects, they might decimate the plant populations, leading to the destruction of habitats and food sources for other populations.

The systematic removal of the gray wolf by the U.S. government is an excellent example of population disruption following the elimination of a keystone species.

The Chinese tallowtree is a highly invasive species that was originally introduced in 1776 to the American South. It competes with native trees for space and nutrients, eventually taking over native hardwood forest. Invasive species also play big roles on biodiversity. These are nonnative species that take over. An invasive species can move into an area that it is not naturally a part of and cause harm to its new home. Native species, or species that are naturally from that area, already have an established food web. Introducing a new species will throw off the balance of the food web, causing competition for food, habitat, and other resources. Human Disturbance The Great Barrier Reef extends over 2,000 kilometers just off the northwestern Australian coast. It is the largest reef system on the planet and has been in a constant state of growth and development for thousands of years—until recently. Over the past two years, the reef has been steadily losing living coral, the basic reef-building organism. As coral disappears, so do many other populations, including fish, mollusks, This brain coral is mostly marine mammals, and many more. dead. Once the coral dies off, all that is left behind is the white, calcium carbonate skeleton.

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STEMscopedia: BIODIVERSITY AND

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The main culprits of coral bleaching—living coral dying off and leaving the reef to appear bright white—are ocean pollution, acidification, and rising ocean temperatures. To grow and thrive, most species of coral need clean, clear ocean water at just the right pH and temperature. Pollution makes the water murky and can choke out the sunlight that symbiotic, photosynthetic algae needs to feed the coral organism. Ocean acidification due to increase in carbon dioxide alters the pH of shallow waters, disrupting coral growth.

What Do You Think? There are many ways in which humans can help reduce negative impacts on biodiversity and help increase it instead. Sustaining biodiversity to maintain the ecosystem’s functions and productivity is essential to supporting and enhancing life on Earth. It also benefits humanity by preserving landscapes of recreational or inspirational value. What are some actions you can personally take to reduce negative impacts on the ecosystems? Application Determine the limiting factors that might exist in the example ecosystems below. 1. A community of mussels, starfish, and algae exist in a small tide pool. 2. An oasis thrives around a small spring-fed pool in the middle of a desert. 3. A population of elk is reproducing rapidly in a section of forest due to the absence of any predators.

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STEMscopedia: BIODIVERSITY AND

POPULATIONS IN ECOSYSTEMS

Connecting With Your Child Your Role in Biodiversity Impact To help your child learn more about the effects of human activities on biodiversity, as well as his or her role in these activities, research together what your local community is doing to minimize human impact and maintain biodiversity in your area. You may begin by researching what environmental protection efforts that currently exist in your community. Find what interests your child and check out different organizations together. If your local area is lacking in this department, suggest ways your child can help. There are things your child can do at home that will conserve energy and water, which helps to maintain natural resources. You and your child can do things together at the local level to lessen human impact and maintain biodiversity. Consider starting a club at school to help raise awareness, creating more accessible recycle bins and locations in the neighborhood, or supporting organizations that promote natural wildlife and resources. You can also research your carbon footprint and find ways to reduce it. Encourage your child to think about ways he or she can personally reduce fossil fuel emissions into the atmosphere. Suggestions include walking or riding a bike instead of driving, as well as recycling materials made in factories such as plastics. Here are some questions to discuss with your child: 1. How does human impact influence biodiversity? 2. What roles do you play in impacting biodiversity? 3. What can you change to lessen your impact?

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B5A Biodiversity and Populations in Ecosystems

Reading Science Name:

Date:

Group:

Wolves and Willows 1

As human beings, we depend on the living world for our survival. We use the wood from trees to build our homes. We use the water from lakes, streams, and groundwater for drinking water. We use fertile soils to plant our crops. But the natural world also has benefits besides the material things that we can gain from it. We enjoy hiking in beautiful landscapes. We enjoy watching wild animals in their habitats. We love to play in clean rivers and lakes. But human activity has affected the biodiversity of the world in which we live. Let us look at one way in which humans had a negative effect on biodiversity and what was learned from that effect.

In order for any ecosystem to function normally, it must have many different parts that work together. In terms of an ecosystem, we call this biodiversity. The prefix “bio-” relates to the biological organisms that live within the ecosystem. The suffix “-diversity” refers to the many diverse, or different, parts. For example, what do you think of when you think of a forest? You most likely think of trees, but this is only part of the picture. In a healthy forest ecosystem there are many, many organisms that work together. There is a variety of tree types in the forest. There are also shrubs, grasses, flowers, mosses, and fungi. There is also a variety of animals, from large herbivores and predators, to birds, fish (in streams and creeks), amphibians, and insects. All of these living things contribute to the biodiversity found within this ecosystem, and all of these living organisms play a crucial role in the health of the forest.

Forests are not the only ecosystems with biodiversity. The oceans are teeming with life and biodiversity. Cold alpine areas are a delicate ecosystem with many life forms that work together. Even deserts contain more biodiversity than you may realize. Far-reaching problems can arise if the delicate balance of these ecosystems is thrown off. The balance can be thrown off by something as simple as removing one species from the ecosystem, be it a plant or an animal. Unfortunately, human activity in the last few hundred years has affected the balance of many ecosystems through habitat destruction, overexploitation, and the introduction of invasive species. Fortunately, however, humans are also coming up with many solutions to lessen these adverse effects.

One main solution to protecting biodiversity is creating national parks and wildlife preserves. Back in 1872, President Ulysses S. Grant signed an act of Congress known as the Act of Dedication. This act established Yellowstone National Park, the first national park in the United States. The president and Congress were so taken with the reports of the landscape and wildlife of the area that they wanted to make sure that the land in the park would not be sold during public auction. In other words, they wanted it to remain intact for future generations to enjoy. The creation of Yellowstone National Park set a precedent for preserving wild places in this country.

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B5A Biodiversity and Populations in Ecosystems

Reading Science 5

Even though the creation of the national park system was a good start, biologists and ecologists found that simply setting land aside was not enough. The species of organisms within the park had to be protected as well. When the park was created, there were many different types of animals within the ecosystem. Cutthroat trout were plentiful in the waterways. These trout formed the base of a complex food chain that included grizzly bears, black bears, otters, eagles, and hawks. Large herbivores such as elk, bison, and deer were plentiful. Moose did live in the area, but the population was small. Other top predators such as wolves, coyotes, and fox could be found in large numbers. The park was teeming with many types of birds, insects, and plants.

At the time of the park’s creation, people were not aware of how each of these individual organisms depended on the other. In the early days of the park, many people who lived in the area would poach (illegally hunt) the animals within the park. The bison were hunted almost to extinction. Many other animal populations declined due to fur trapping and hunting. In an effort to save many of the animals in the park, the government forbade the hunting of any wildlife, except for two animals––the wolf and the grizzly bear. The United States government actually paid hunters to kill as many wolves and bears as possible. These early officials did not realize that it was the extermination of these apex predators that created the largest disruption to the biodiversity of the park.

After the 1920s, when the wolves and grizzly were completely removed from the park, the herbivore population exploded. In fact, the moose population grew at an alarming rate. As a result, those herbivores needed more food, so they began to eat small tree saplings, mainly aspen and willow trees. This led to a decline in these and other small trees, which affected the beavers in the area. As the beavers had fewer small trees for dam building and food, the beaver population declined. As a result, the small wetlands created by the beavers drained, which affected the bird populations. As you can see, the elimination of one animal had large cascading effects on many other types of organisms.

How do we know that the removal of the wolves had such a huge impact on the biodiversity of Yellowstone National Park? In 1986, wolves traveling from Canada recolonized the park. At that time, wolves were an endangered species. Since that time, the wolf population has made a remarkable comeback. The result? The deer, elk, and moose populations have declined as the wolves have hunted them, and the aspen and willows have returned, as have the beavers and songbirds. The bird of prey populations are increasing as well. This new understanding of the role that wolves play in that ecosystem have park managers from across the country reevaluating their management practices. Many are now understanding the importance of biodiversity in national parks and wildlife refuges, and steps are being taken to ensure that biodiversity is maintained for the future

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B5A Biodiversity and Populations in Ecosystems

Reading Science 1.

Which of the following is not a way that human activity has negatively affected the biodiversity of ecosystems? A.

Introduction of invasive species

Habitat destruction

The planting of trees

Overexploitation

What must a healthy ecosystem contain in order to function properly A.

A variety of animals

A variety of plants

Many organisms working together

All of the above

Which type of ecosystem needs biodiversity? A.

Oceans

Deserts

Alpine areas

All ecosystems

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Reading Science 4.

At the time that Yellowstone National Park was created, there was a crucial factor that the park managers did not fully understand. What was that factor? A.

How many grizzly bears were in the park

How the organisms depended on each other

How many aspen and willows were in the park

What food each type of animal ate

Which of the following was not one of the ways that the extermination of the wolf population affected the biodiversity of the park? A.

An increase in the grizzly bear population

A decline in the willow population

A decline in the beaver population

A shift in bird populations

A student and a team of conservationists want to set up a park to preserve a specific area. What would be the most important step to take to make sure that the park had adequate biodiversity? Use the information in this reading to help. A.

Count the number and types of organisms that live in the area when they set up the preserve

Consult historical records of the area and introduce organisms that existed in the area before human activity.

Plant many fragrant flowering trees for shade for the animals.

Make sure to remove all of the predators from the area before setting up the park.

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B5A Biodiversity and Populations in Ecosystems

Math Connections Name:

Date:

Group:

Part I: Biodiversity Index The biodiversity index is used to provide information regarding the diversity of species in a given area. If the biodiversity index of a species becomes too low, the species may become endangered or extinct. To calculate biodiversity-species richness index: 1. Determine the number of species in a certain area. 2. Determine the number of individual organisms in a given area. 3. Biodiversity index = number of species/number of individuals Simpson’s index is another way researchers can calculate biodiversity of a given area. The Simpson’s index includes both species richness and species evenness. The formula for Simpson’s index is: D = Σn(n-1)/N(N-1) Where D is the Simpson’s index, n is the total number of organisms of a particular species, and N is the total number of organisms of all species. Use this information to answer the questions that follow. 1.

A researcher explores a section of the forest that is 50 square feet. There are 2 oaks, 2 pines, and 1 cedar tree. What is the biodiversity index of this area?

You have studied a specific site and have counted the individuals of five different species. Determine the Simpson’s index of this site.

Species A Species B Species C Species D Species E

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n 12 3 7 4 9 N=

n(n-1)

Σn(n-1)

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Math Connections Part II: Is Pisaster ochraceus a keystone predator? Certain species have an especially significant influence on the structure of entire communities, either because they are highly abundant or because they play a pivotal role in community dynamics. The effect of these species can result either from their trophic interactions or through their influences on the physical environment. Keystone species exert strong control on community structure not by sheer number of individual organisms, but by their ecological roles, or niches. One way to identify a keystone species is by removal experiments, in which species richness (number of species) is compared with and without the species being studied. The following data was collected from the removal experiment that sought to determine if Pisaster ochraceus is a keystone predator. Read the background, graph the results, and support your conclusion. Background: In rocky intertidal communities of western North America, the relatively uncommon sea star, Pisaster ochraceus, preys on mussels such as Mytilus californianus, a dominant species and strong competitor for space. Robert Paine, of the University of Washington, removed Pisaster from an area in the intertidal zone and examined the effect on species richness. Results from Paine’s Experiment: Table 1. With Pisaster ochraceus (control) Year 1963 1964 1965 1966 Number of 16 16.5 17 18 Species Present

1967

1968

1969

1972

1973

18.5

19.50 19.75 19.90 19.90

1969

1970

1971

1972

1973

3.5

1.5

2.25

Table 2. Without Pisaster ochraceus (experimental) Year 1963 1964 1965 1966 1967 1968 Number of 17 13.5 6 4 3.75 3.75 Species Present

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B4B Relationships Among Groups of Organisms

Math Connections 1.

Graph the data.

Is Pisaster ochraceus a keystone species? Provide a rationale for your response.

Based on the graph, if the study were continued for five more years, hypothesize if species richness would increase, decrease or remain stable for the control and experimental treatments. Provide a rationale for your response.

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Math Connections 4.

Population numbers for species were also recorded and graphed for each treatment (control and experimental). Based on the background and data provided, hypothesize whether mytilus would have an increasing or decreasing population trend over time. Provide a rationale for your response.

Suppose an invasive fungus killed most individuals of Mytilus at these sites. What do you think would happen to species richness if Pisaster ochraceus were then removed?

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B5A Biodiversity and Populations in Ecosystems

Writing Science Name:

Date:

Group:

LOOK

THINK Biodiversity is important to the survival of many organisms such as plants and animals. The variety of organisms found in an ecosystem is controlled by factors such as the availability of resources, predation, and the amount of space available. Another factor is keystone species. If left alone, the sea urchin population can grow to a size too large for its ecosystem to sustain. The sea otter feasts on urchins which help control the size of the urchin population to a level that can be supported. Think about factors that affect biodiversity in an ecosystem, such as carrying capacity, size, limiting factors, and keystone species. WRITE Describe how carrying capacity, size, limiting factors, and keystone species affect the biodiversity and populations in an ecosystem. Be sure to • clearly state your central idea; • organize your thoughts; • develop your essay in detail; • choose your words carefully; and • use correct spelling, capitalization, punctuation, and grammar.

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Writing Science

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High School Biology

B5B

Photosynthesis and Respiration in Ecosystems

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B5B Photosynthesis and Respiration in Ecosystems

Student Handout Name:

Date:

Carbon—It’s a Cycle! Directions: Use your knowledge of photosynthesis and cellular respiration to model the cycling of carbon between the rabbit and the grass in the image below.

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B5B Photosynthesis and Respiration in Ecosystems

Student Journal Name:

Date:

Group:

Part I: Your Role in the Ecosystem 1.

Fill in the table below with each of your group members' roles and a description of how each role influences or affects the carbon, nitrogen, and phosphorus cycles. The number of roles filled in will vary based on your group size. Use your Student Reference Sheet for additional help. Role

Influence on Carbon Cycle

Influence on Nitrogen Cycle

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Influence on Phosphorus Cycle

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B5B Photosynthesis and Respiration in Ecosystems

Student Journal Part I: Your Role in the Ecosystem, continued 2.

Using your Student Reference Sheet, briefly illustrate the carbon, nitrogen, and phosphorus cycles.

Carbon Cycle

Nitrogen Cycle

Phosphorus Cycle

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B5B Photosynthesis and Respiration in Ecosystems

Student Journal Part I: Your Role in the Ecosystems, continued 3.

Explain how hydrogen and oxygen is cycled during cellular respiration and photosynthesis.

Explain why organisms need oxygen and hydrogen to survive.

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B5B Photosynthesis and Respiration in Ecosystems

Student Journal Part II: Food Webs

Describe the food web in your own words.

Using the above food web, explain how organisms arranged according to energy flow in food webs.

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B5B Photosynthesis and Respiration in Ecosystems

Student Journal Part III: Energy Pyramids 1.

How much energy is lost as you move up each trophic level in the energy pyramid?

Explain why energy is lost and not gained in energy pyramids as you move up trophic levels.

Describe each trophic level of an energy pyramid.

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Student Journal Part IV: Calculating Energy Flow Calculate the energy lost and the energy available for each trophic level. Use the example in your Student Guide, if needed. Primary Consumer Energy

_____ KCal

Primary Consumer Energy

_____ KCal

Secondary Consumer Energy - _____ KCal

= _____ KCal

_____KCal ÷

______KCal

= _________

_____KCal ÷

(total energy)

_______ x

100 =

______KCal

= _________

(total energy)

_______%

Energy lost

_______ x

100 =

_______%

Energy lost

Energy Available:

Available 100% - ________ = _______% energy

Primary Consumer Energy

_____ KCal

Primary Consumer Energy

_____ KCal

Secondary Consumer Energy - _____ KCal

= _____ KCal

_____KCal ÷

______KCal

= _________

_____KCal ÷

(total energy)

_______ x

100 =

_______%

______KCal

= _________

(total energy)

Energy lost

_______ x

100 =

_______%

Energy lost

Energy Available:

Available 100% - ________ = _______% energy

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B5B Photosynthesis and Respiration in Ecosystems

Student Journal Part IV: Calculating Energy Flow, continued

Total Energy _____ KCal

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Reflect

B5B

What would happen to Earth without the Sun? It would be a desolate place. The temperature of Earth would drop to about -400 degrees Fahrenheit. The oceans would slowly but completely freeze. Photosynthesis would halt, and all life on Earth would cease since there would no longer be a food source. So if the Sun is the source of energy on Earth, how does that energy become our energy? Cycles Water Cycle The water cycle is fueled by energy from the Sun. It is the process by which water moves back and forth between Earth’s surface and the atmosphere. Water can be cycled in many ways. One simple way is for organisms to drink water and then excrete it back to the environment. A more complex pattern is for water to evaporate from the ocean, condense in a cloud, precipitate onto land below, percolate through soil and infiltrate permeable rock to become groundwater, eventually return to become surface water at a spring, and then evaporate again, starting the cycle over. Water is the basis of life on Earth, and the water cycle recycles water to ensure a water supply and survival for organisms. Carbon Cycle Like all cycles, the carbon cycle has neither a beginning nor an end. Instead, it consists of a number of related processes. One part of the carbon cycle centers on photosynthesis. Carbon exists in Earth’s atmosphere primarily within molecules of carbon dioxide (CO2). During the Calvin cycle of photosynthesis, plants use the carbon (C) from carbon dioxide to make organic compounds called carbohydrates. One of the most important of these carbohydrates is glucose (C6H12O6), a sugar that plants use for food. Plants can store glucose for later consumption in the form of starch, another type of carbohydrate. Another important part of the carbon cycle occurs when organisms consume carbohydrates produced by plants. These consumers use the energy held within the chemical bonds of the molecules to fuel their cellular activities. For example, in an animal’s cells, carbohydrates undergo a series of chemical reactions that break down the molecule to release energy. This process is called cellular respiration. One of the waste products of cellular respiration is carbon dioxide. Because animals cannot use carbon dioxide, they exhale it into the atmosphere where plants can once again use it to make carbohydrates. In this way, carbon cycles continually between the atmosphere (as carbon dioxide) and the biosphere (as carbohydrates).

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Carbon in biomass—the living (or recently living) matter in an ecosystem—is also returned to the environment through decomposition. The bodies of organisms are primarily made of carbon. When an organism dies, detritivores (such as earthworms) and decomposers (such as fungi and bacteria) break down the body into its component elements. In this way, carbon moves from biomass into the ground, where it can remain buried for years. Over millions of years, extreme heat and pressure from Earth’s interior transform buried plants and animals into fossil fuels such as coal, petroleum, and natural gas. When humans burn fossil fuels—to power machines, generate electricity, and heat buildings—the carbon cycles back to the atmosphere, where it is once again available to plants for photosynthesis. Humans contribute to the carbon cycle by burning fossil fuels and other forms of biomass, such as wood. Biomass also burns through natural processes. For example, a bolt of lightning can spark a forest fire. However, over the past few centuries, humans have released huge quantities of carbon into the atmosphere—more than can be absorbed through photosynthesis and other natural processes. Scientists have evidence that this excess carbon dioxide is trapping heat at Earth’s surface, leading to global climate change.

Nitrogen Cycle Important terms: nitrogen fixation: a process in which nitrogen in the atmosphere (N2) is converted to ammonia (NH3) by certain bacteria assimilation: the process in which plants absorb nitrogen through their roots and use nitrogen to synthesize amino acids ammonification: the process of decomposition by bacteria resulting in the formation of ammonia nitrification: the biological process of bacteria transforming ammonia to nitrites (NO2) and then nitrates (NO3) denitrification: the biological process of bacteria transforming nitrates (NO3) into nitrogen gas Both plants and animals require nitrogen to survive. Nitrogen is a key component of DNA, RNA, and amino acids, which are used to form proteins in living organisms. Approximately 78 percent of Earth’s atmosphere is composed of nitrogen gas (N2). Unfortunately, most living things cannot use nitrogen in this form. Certain types of bacteria can take nitrogen directly from the atmosphere. Were it not for those particular bacteria, nitrogen would be unable to cycle through the biosphere for other organisms to use.

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Many plants are hosts to bacteria, which are found in the soil and live on the roots of plants. There, they convert nitrogen gas to a more usable form of nitrogen in a process called nitrogen fixation. The plants absorb this form of nitrogen through their roots to synthesize amino acids, in a process termed assimilation. When consumers eat producers, nitrogen passes up through the food chain for other living things to utilize. When organisms die, the vital work of decomposition begins. Detritivores and decomposers work to break down the waste and dead organisms and release nitrogen back into the soil and water in a process called ammonification. The cycle continues as nitrogen is converted back into a usable form during the process of nitrification, in which bacteria convert ammonia to nitrites and nitrates. Some of the nitrates are further altered to become nitrogen gas in a process called denitrification. The nitrogen cycle continues as plants reabsorb these compounds into their bodies.

Organisms need nitrogen to carry out their life functions. For example, nitrogen is an important component of proteins. Several key processes in the nitrogen cycle make nitrogen available for all organisms to use.

Look Out Detritivores and decomposers are often confused. They are related organisms only in that both aid in processing waste or dead organic material. Detritivores are invertebrates that practice physical decomposition of the soil by breaking it into smaller particles. For example, earthworms perform fragmentation, which breaks up waste or dead organic material into smaller particles. This, in turn, increases the surface area upon which decomposers work, speeding up the decomposition progression. Decomposers, such as fungi and bacteria, are microscopic. Their task is chemical decomposition. Decomposers use enzymes to break down decaying matter, carry out respiration, and release carbon dioxide into the environment.

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What Do You Know? Ecosystems thrive when conditions are balanced. The nitrogen cycle is crucial to maintaining this balance. Disruptions to the nitrogen cycle can have devastating effects on the environment. Unfortunately, too often these disruptions result from human activities. Overusing nitrogen-based fertilizers in agriculture is one way humans disturb the nitrogen cycle. The availability of nitrogen can be a limiting factor to the growth of crops. To combat this, farmers use fertilizers with high concentrations of nitrogen and other nutrients. The fertilizers may help with farming, but nitrogen compounds in the soil get carried away by rainwater. The runoff causes nitrogen to build up in estuaries, lakes, and streams. This change in water composition is called eutrophication. Algae thrive on the excess nitrogen concentrations and reproduce uncontrollably, resulting in an algal bloom. As the algae die, the decaying matter and decomposers use up most of the available oxygen, choking out other organisms in the water, such as fish. • • •

What can humans do to avoid the problem caused by excess fertilizers? What are other imbalances in the nitrogen cycle caused by humans? What are some solutions to those problems?

Ecosystems What is an ecosystem? An ecosystem is all the living and nonliving factors that interact within a specific region. The living things in an environment include all organisms, including plants and animals. The nonliving things include air, sunlight, temperature, soil, water, and nutrients. Energy Sunlight is usually the source of energy for an ecosystem. Plants absorb the light from the Sun and perform photosynthesis. Photosynthesis is the process in which plants utilize the energy from the Sun, water, and carbon dioxide from the air to produce food in the form of carbohydrates (sugars and starches). Photosynthesis is performed by plants called producers, organisms that possess the ability to make food. Other members of ecosystems are unable to make their own food. They must eat other organisms to get energy. These beings are called consumers. Consume means to eat or drink. There are three types of consumers: herbivores, carnivores, and omnivores. Herbivores are consumers that just eat plants such as rabbits, deer, caterpillars, sheep, cows, and bees. Carnivores are consumers that only eat animals such as lions, wolves, sharks, spiders, and ladybugs. Omnivores are consumers that eat both plants and animals such as bears, skunks, pigs, rats, turtles, chickens, robins, and humans.

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Another group of organisms that exist in all ecosystems are decomposers. Decomposers are organisms that consume waste and dead organisms to get energy. In doing so, they break down waste and dead organisms and return nutrients to the environment. Decomposers are vital to ecosystems because everything dies, but without decomposers, there would be no way to recycle the nutrients. Examples of decomposers are bacteria and fungi. Nutrient Cycle + Energy Flow Nutrients are materials that provide nourishment for organisms’ growth and development and for the maintaining life-sustaining functions. Nutrients are different than energy when it comes to the nutrient cycle and energy flow. Unlike energy that is constantly “lost” during the process, nutrients are able to be recycled. Carbon, oxygen, hydrogen, and nitrogen are all recycled during the water cycle, carbon cycle, and nitrogen cycle, as explained above. Energy flows from the Sun to producers to consumers to decomposers. For example, when a plant uses the Sun’s energy to perform photosynthesis, energy transfers from the Sun to the plant. Then, when a rabbit eats leaves, the energy from the plant flows to the rabbit. When a coyote eats the rabbit, the energy from the rabbit goes to the coyote. When the coyote dies, its energy moves to the decomposers through waste and dead matter. A food chain is a simple diagram that demonstrates the transfer of energy and nutrients. Plant

Rabbit

Coyote

Earthworm/Bacteria

In reality, the food chain should be in the shape of a circle, since it is a cycle. Because food chains are too simplified to represent the realistic options in an ecosystem, scientists have adopted food webs to more accurately depict what occurs in nature. A food web is a diagram that shows numerous interconnected food chains. The arrows in food chains and food webs go from the food to the consumer of the food because the arrows show where the energy flows.

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What Do You Think? Study the food web below, and then answer the questions that follow. What is the original source of energy for this food web? What are the two producers of this food web? Name five consumers from the food web. What animal is at the top of the food web? What vital role is missing from the web? Why is this important? What organisms would you fill in for the missing role? Utilizing the same food web, classify each organism in the following table. Be sure to include the detritivore and/or decomposer you added. Organism Grass

Producer

Herbivore

Carnivore

Decomposer

Fly Daisy Frog Eagle Grasshopper Raccoon Snake Butterfly

Now redraw the food web to include all possible energy flows, including the very important roles of the detritivores and/or decomposers. Remember, the arrows point in the direction the energy flows. Refer back to the original simple food chain: Grass → Rabbit → Coyote → Earthworm/Bacteria Does the coyote capture all of the energy transferred by the Sun to the plants the rabbit consumed? No, most of the energy is lost. At each step of the food chain, some energy is lost as heat. The heat is not recoverable in a usable form for organisms in the environment, so we say it is “lost.” However, we know that energy can be neither created nor destroyed—it simply changes forms.

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Think of what happens when dogs run. They burn calories for energy. Their body temperatures increase, and they pant, losing heat energy to the environment. In order to survive, all organisms use some energy and store some energy. The energy that is used is lost to the environment as heat. The energy that is stored is passed on to the organism that consumes it. What does this mean? As you go further up the food chain, less and less energy is available. Therefore, in every food chain or food web, producers contain the greatest amount of energy. This means the base (widest part) of the pyramid is always dedicated to producers. A primary consumer is an herbivore, or an animal that eats producers. A secondary consumer is a carnivore, or an animal that eats other herbivores. A tertiary consumer is one that eats secondary consumers. A quaternary consumer is one that consumes tertiary consumers. Usually, quaternary consumers are the top predators in a food chain. Carefully study the energy pyramid. Note how there are fewer organisms the further up the pyramid you look. Scientists estimate that each level of the pyramid contains only 10 percent of the energy from the level below it. In other words, if the pyramid has five levels and the base of the pyramid (producers) contains 10,000 energy units, the next level (herbivores) would possess 1,000 energy units, the next level (secondary consumers) would only have 100 energy units, the fourth level (tertiary consumers) would include 10 energy units, and the top carnivores on the 50 level would only contain one energy unit. Obviously, the higher the level of the pyramid, the lower the energy level. If there are too many levels, there is potential that there will not be enough food/energy for all organisms.

Look Out Based on many food webs, it often appears that the largest animals are always at the top of the food chains as top predators. However, this is untrue. Lions are top predators in Africa, but elephants are larger. Sharks and orcas are top predators, and they often attack larger animals. The massive animals—elephants, giraffes, hippos, pandas, and manatees—are all herbivores. Why? The greatest amount of energy available is the base of the pyramid (producers). Therefore, herbivores actually have the greatest amount of energy available to them. In fact, top predators have less energy available to them than large herbivores.

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Connecting With Your Child To better understand food chains, food webs, and energy pyramids, you and your child will imagine a complete ecosystem. Write out a brief description of the abiotic factors, such as rain, wind, soil, temperature, altitude, nutrients, sunlight, and pollution. Then describe the biotic factors, especially animal and plant life. You may also sketch your ecosystem if it helps you better imagine it. Next, draw a food web from your ecosystem. Make sure to include producers, consumers (incorporating herbivores and carnivores), and detritivores/decomposers. Remember that the arrows point the way the energy flows. After you have completed the food web, choose one food chain from within the web. For this specific activity, you do not need to include the detritivores and decomposers. Begin with the producer and finish with the top predator. Finally, create an energy pyramid based on your chosen food chain. Recall that each level only contains 10 percent of the energy of the level underneath it. After you complete your projects, answer the following questions: 1. How many different food chains can you find in your food web? 2. Within your energy pyramid, how many times more energy does your base level contain than your pinnacle level? 3. Why is a pyramid an appropriate shape for an energy pyramid? 4. What factors could throw your ecosystem, food web, and energy pyramid out of balance?

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B5B Photosynthesis and Respiration in Ecosystems

Reading Science Name:

Date:

Group:

Carbon Interrupted 1. The element carbon is one of the most important elements for biological life because it is so versatile. Carbon can form up to four chemical bonds by the nature of the way that it bonds to other elements. This large number of bonding possibilities makes carbon able to form varied, large, and intricate molecules. Some form of carbon is found in all forms of life, and most organisms require some form of carbon for a large part of their food sources. But, where does all of the carbon come from, and where does it go? Let us take a journey and follow a single carbon atom through the many stages and forms in which it may find itself. This carbon atom will be referred to as “our carbon” atom. 2. Our carbon atom begins its journey in the atmosphere as an element in the compound CO2, or carbon dioxide gas. As a naturally occurring gas in the atmosphere, CO2 is the carbon source for a surprisingly large number of biological organisms. The CO2 with our carbon atom will remain in the atmosphere until it reaches the outer surface of a leaf of a tree. Here, the CO2 gas will enter the leaf through an opening called a stoma. 3. An amazing transformation occurs once the CO2 molecule enters the leaf. The carbon dioxide enters a chloroplast within the leaf and is drawn into a photosynthetic process called the Calvin (light-independent) cycle. Here the carbon atom from the CO2 molecule is added to a sugar molecule that is synthesized during this process. In the leaf of a plant, the carbon is moved from a CO2 molecule to a glucose sugar molecule, or C6H12O6. 4. The carbon of that sugar molecule may attach to such molecules as starch, cellulose, or lignin inside the tree. On this journey, our carbon atom will remain attached to the glucose sugar and will move to the fruit of the tree through the xylem system. The glucose will remain in the fruit until the fruit drops onto the grass. Animals find the fruit sweet and good to eat. In this case, an animal eats the fruit containing our carbon atom, which is a part of the sugar molecule. The fruit is digested in the stomach and intestine of the animal. Then the nutrients are absorbed and carried to the animal’s cells. Our carbon atom then goes through another incredible transformation. 5. The carbon in the sugar (C6H12O6) enters a cell of an animal. In the cytosol of the cell, the sugar is broken down into two smaller molecules called pyruvate, one of which holds our carbon. Once the sugar unit is broken down into the smaller molecule pyruvate, it can enter into the mitochondria where it goes through a process of further breakdown. This process is called the Krebs cycle and breaks the pyruvate into CO2 molecules. Again, our carbon atom becomes part of a CO2 molecule. The CO2 is released back into the atmosphere with the animal’s next breath. © Accelerate Learning Inc. - All Rights Reserved

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B5B Photosynthesis and Respiration in Ecosystems

Reading Science 6. Not long after the animal breathes out the CO2 molecule, the molecule travels over the surface of a shallow ocean and is absorbed by a photosynthetic phytoplankton, in much the same process as the plant leaf. Our carbon atom is integrated into a sugar molecule again during photosynthesis. It is carried by this phytoplankton until a larger organism, a zooplankton, eats it. This organism is then eaten by a small fish that is then eaten by a larger fish, a salmon. Once inside the salmon, our carbon atom is incorporated into a protein. The carbon atom is used over and over inside this salmon. For instance, once the original protein degrades into amino acids, it can become yet another protein. Once the amino acids degrade, however, our carbon becomes part of a fat molecule, a hydrocarbon. Here, the carbon stays for quite some time. 7. Our carbon atom is carried up a river in the body of the salmon during the salmon “mating run” as hormones signal to the salmon that it is time to mate. As the fat stores of the salmon are consumed during the journey, our carbon atom moves within the cells to become part of the hormone (a lipid or protein) that triggers the salmon to spawn. The salmon eventually dies after spawning in the stream in which it was born. The salmon’s body washes ashore and decomposes. 8. Our carbon atom from the decomposing biomass of the fish now becomes available in the soil for microorganisms. Bacteria consume the carbon atom in the hormone in the salmon’s blood, and our carbon atom finds a resting place in the soil. Eventually, the carbon will return to the atmosphere as either CO2 or CH4 (methane), and the carbon atom will begin another incredible journey. Our carbon atom may have been traveling for millions of years, and over the next million years, it will have many new and exciting adventures. The movement from atmosphere to plant to animal to another location is all a part of what we refer to as the carbon cycle.

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B5B Photosynthesis and Respiration in Ecosystems

Reading Science 1. Based on a close reading of paragraphs 2–5, which of the following statements is true? A Carbon atoms move between the atmosphere and organisms connecting Earth’s biosphere and atmosphere. B Carbon atoms move through several locations, but remain in the atmosphere for their long journey. C Once a carbon atom becomes a part of a sugar, it will remain chemically bonded in that form. D Carbon can only enter an animal’s body when it takes in sugars from photosynthesis in plants.

2. Which of the following statements is NOT true regarding the element carbon? A Carbon can only form a few types of chemical compounds. B Carbon may be found in many types of molecules. C Carbon can bond to other molecules in a variety of ways. D Carbon is a critical element found in all biological organisms.

3. What happened to the carbon atom when it entered the plant through the stoma on the leaf? A It moved from a sugar molecule to a carbon dioxide molecule. B It moved from a gas molecule to a protein molecule. C It moved from a carbon dioxide molecule to a sugar molecule. D It remained a carbon dioxide molecule in the leaf.

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Reading Science 4. Carbon may appear in more than one form on Earth. Several of those forms were discussed here. What was one form that was not discussed? A Carbon dioxide—CO2 B Glucose sugar—C6H12O6 C Calcium carbonate (limestone)—CaCO3 D A hydrocarbon—a CH chain

5. Carbon is an important element for biological life because it – A is always attached to oxygen atoms. B can form varied, large, and intricate molecules. C is stable and does not easily go through changes. D is only found in plant species such as trees.

6. Which of the following statements is false? A Carbon can be stored in the body fat of a salmon. B Carbon can move within the cells of an organism. C Carbon is degraded by amino acids. D Carbon can remain in soil bacteria for a long time.

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B5B Photosynthesis and Respiration in Ecosystems

Math Connections Name:

Date:

Group:

Part I: Biomass Pyramid and Energy Flow in an Ecosystem A biomass pyramid is a chart, drawn to scale, showing the biomass at each stage of the food chain. The pyramid below is a generic pyramid showing the different levels of organisms in the food chain and the amount they consume and retain from the pre-occurring organisms.

If you begin with 250,000 g/m2 of corn, how many grams of that biomass would be available to a primary consumer? Use a proportion to help you calculate your answer.

How many grams of the corn would be consumed by the secondary consumers?

How many grams of the corn would be consumed by the tertiary consumers?

Based on the pattern above, how many grams of the corn would be consumed by the quaternary consumers?

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B5B Photosynthesis and Respiration in Ecosystems

Math Connections Part II: The Carbon Cycle: Components and Functions Before you begin the activity, cut out the cards below. Solve the quadratic functions, match them to their solutions, and glue them onto their graph on the diagram on page 3. The completed diagram will display the processes in the carbon cycle and how they relate to each other. Quadratic Equations Photosynthesis

Burial

x2 + 2x + 1 = 0

x2 + 2x = 99

Cellular Respiration 2x2 + 8x = -6

Dissolution x2 – 3x = 0

Decomposition

Combustion

x2 – 36 = -16x

x2 + 8x +7 = 0

Solutions Burning of vegetation and fossil fuels add CO2 to the atmosphere.

Animals consume plant or animal tissues that contain carbon compounds.

x = -1, -7

x = 2, 1

Used by autotrophs to combine CO2 and H2O to produce carbohydrates; removes carbon from the atmosphere and adds oxygen. x = -1 CO2 is emitted into the atmosphere.

Weathering and Erosion

Digestion of Organic Matter

x2 – 2x = 24

x2 – 3x = -

Atmosphere Accumulation

Geologic Processes (e.g. volcanoes)

Ocean water absorbs CO2 from the atmosphere, forming carbonic acid.

x2 – x = 12

x = 3, 0

x2 – 3x – 10 = 0

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x = 4, -3

Decomposers break down organic matter and release CO2. x = -18, 2 Carbon is building up in the atmosphere from various processes. x = 5, -2 Protects organic matter from being respired/decomposed. Can become a rock or (with enough heat, pressure and time) fossil fuels. . x = -11, 9

Combines carbohydrates with O2 to produce H2O and CO2.

CO2 from the atmosphere dissolves in water to break down rock.

x = -1, -3

x = 6, -4

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B4B Relationships Among Groups of Organisms

Math Connections

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Lithosphere

Biosphere

Atmosphere

Hydrosphere

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B5B Photosynthesis and Respiration in Ecosystems

Writing Science Name:

Date:

Group:

LOOK

THINK about the roles of the carbon and nitrogen cycles and how a disruption of them may affect living organisms. Biochemical cycles, such as the oxygen, carbon, and nitrogen cycles, are important because nutrients are passed between organisms through these cycles. Every living organism depends upon nutrients to fulfill life functions. Oxygen is a part of all biochemical cycles, as it continuously combines with each cycle. Although both carbon and nitrogen cycles are also important, they play different roles for living organisms. Carbon, a key element of living tissue, plays many roles. These roles include linking the atmosphere and biosphere. Some processes that involve the movement of carbon are photosynthesis, erosion, decomposition of dead organisms, and burning forests. Amino acids are composed of nitrogen to build proteins. Nitrogen comes in many forms, such as gas, decaying organic matter, and an ingredient in plant fertilizers. On Earth, the most abundant form of nitrogen is atmospheric nitrogen gas. WRITE predict the effect the overuse of plant fertilizer in an ecosystem would have on the nitrogen cycles.

Be sure to • clearly state your central idea; • organize your thoughts; • develop your essay in detail; • choose your words carefully; and • use correct spelling, capitalization, punctuation, and grammar. © Accelerate Learning Inc. - All Rights Reserved

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Writing Science

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High School Biology

B5CDE

Changes In Ecosystems and Environments

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B5CDE Changes in Ecosystems and Environments

Student Handout Name:

Date:

Instructions: 1.

Think about human impacts on the environment and biodiversity that you have seen or heard about in the media. List as many of these human impacts as you can in the space below.

Pair up with a partner close to you. Share your list and add any ideas that were not on your list in the space below.

If there are any ideas on either list that you or your partner feels are not a human impact to the environment or to biodiversity, discuss whether these ideas should be removed. Explain your reasons for removing any human impacts below, making sure to back up your reasons with evidence.

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B5CDE Changes in Ecosystems and Environments

Student Journal Name:

Date:

Group:

Part I: Environmental Debate Scenario: __________________________________

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B5CDE Changes in Ecosystems and Environments

Student Journal Part II: A Solution to the Problem 1.

What are the main ways humans negatively impact the ecosystem?

What are two of your possible solutions to your problem?

Sketch the prototype for your solution below.

Identify the conclusions have you come up with based on your research.

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B5CDE Changes in Ecosystems and Environments

Student Journal Part III: Stability Street My Energy Wallet Energy units = joules (J)

My ID Name:

________________________

Title:

________________________

Company:

________________________

Role:

________________________

Starting amount: _____________________ Granted: _____________________ Deducted: _____________________ Other: _____________________ Total: _____________________

Predict how a catastrophic event would affect your role.

Identify and summarize your group’s selected specific catastrophic event.

Predict how your role may be affected by this event. Make a claim, identify evidence, and apply reasoning to explain how the evidence supports your prediction claim. Use additional paper, as needed.

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B5CDE Changes in Ecosystems and Environments

Student Journal

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28.

27.

26.

25.

24.

23.

22.

21.

20.

19.

18.

17.

16.

15.

14.

13.

12.

11.

10.

Name

Title

Company

Role

Part III: Stability Street, continued

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B5CDE Changes in Ecosystems and Environments

Student Journal Reflections and Conclusions 1.

How did the catastrophic event affect other roles in your group? Summarize.

In what ways did the event affect the ecosystem’s overall stability? Explain.

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STEMscopedia: CHANGES IN ECOSYSTEMS

AND ENVIRONMENTS

Reflect

B5CDE

An organism’s habitat provides not only shelter but also the food resources the organism needs to obtain nutrients. Habitat is particularly important to the giant pandas of China. These large creatures survive almost exclusively on the bamboo plant, which makes up 99 percent of their diet. Bamboo is not rich in nutrients, so the pandas must eat large quantities of the plant to adequately nourish themselves. Pandas spend about 12 hours a day eating, consuming up to 38 kilograms (84 pounds) of bamboo. Unfortunately, their food source is becoming more difficult to find in their habitat. Too often, human activity is the external factor affecting populations of plants and animals in their natural environment. The pandas’ bamboo forest habitat is being destroyed as the demands of the farming and timber industries grow. Although bamboo is a fastgrowing plant, it only grows in particular climates at specific altitudes. Two breeding pandas need approximately 30 square kilometers to support them, the equivalent of about 15,000 football fields! The destruction of the bamboo forests decreases the shelter and food resources available to the panda population in China. As a result, the panda population is dwindling. Scientists estimate that the wild panda population consists of less than 2,500 individuals, which makes this unique creature an endangered species. The saying “No man is an island” means that people need each other to survive. Everyone on Earth is interconnected in some way. This is not only true of human beings but all living and many nonliving things on Earth. In an ecosystem, individual organisms, populations, and entire communities interact with each other and their environments. In fact, much of how living things behave is in response to changes in their environment. Biodiversity Biodiversity is the term we use to describe the variety of different species found on Earth. Biodiversity involves not only the number of different species but the variability in genetics, the ecosystems in which organisms live, and natural resources found in the ecosystems. All natural resources are connected, and all organisms are dependent on them. Therefore, it is safe to assume that any change, positive or negative, will have an impact on more than just one species or organism. All living things and their environments are interconnected. Why is biodiversity important? All living things depend on each other, and high biodiversity helps the sustainment of most species and strengthens their ability to withstand environmental change.

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STEMscopedia: CHANGES IN ECOSYSTEMS

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Human Impacts on Biodiversity and Ecosystems Humans depend on the living world for the resources and other benefits provided by biodiversity. But human activity also has adverse effects on biodiversity through overpopulation, overexploitation, habitat destruction, pollution, introduction of invasive species, and climate change. Food Webs Removing one species from a food web has a dramatic effect on the health and stability of that food web and its ecosystem. Plenty of evidence demonstrates the effects of predator and prey populations in food webs when one species becomes extinct. For example, consider the removal of the lion, a top predator, from the savannah (which has been the unfortunate target of poachers). What do you think will happen? The animals that typically fall prey to these lions, such as zebras, will increase in population. However, the land that supports these animals cannot handle so many at once. A problem is now created. There is an imbalance in this ecosystem. It is important that food webs maintain a balance to support a healthy ecosystem. Invasive Species Invasive species ranks second to habitat destruction in regards to endangering native species in the United States. An invasive species can move into an area that it is not naturally a part of and cause harm to its new home. Native species, or species that are naturally from the area they inhabit, already have an established food web. Introducing a new species throws off the balance of the food web, causing competition for food, habitat, and other resources. The cane toad is a prime example of humans introducing a species for a specific purpose and then watching helplessly as the introduced species went horribly wrong. Cane toads were introduced to several tropical islands (Hawaii, the Philippines, and some islands in the Caribbean) to control pests that were attacking sugarcane. The cane toad accomplished its task of controlling those pests, so it was imported to several other areas. Unfortunately, people realized too late that no natural predator existed to control it, partially because it produces toxins that can kill animals of all sizes (and has even been responsible for a few human deaths). In addition, the cane toad did not just eat the sugar pests. It also ate any animal small enough to eat. Overpopulation and Habitat Destruction The human population is growing by about 75 million people per year! With more people come more houses. More houses require more resources. It’s easy to see why overpopulation has had a significant and negative impact on biodiversity. Not only are we encroaching on land that is supporting other life, we are also destroying the very land we need to live. Imagine if we were to build a road in the middle of this picture, to get from one city to the next. What changes in biodiversity do you think will happen? 388

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STEMscopedia: CHANGES IN ECOSYSTEMS

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Pollution Pollution occurs when contaminants enter the natural environment and have a negative impact. Contaminants can be chemicals, noises, heating, or lights. Pollution has many forms such as: air, water, noise, or land. Pollutants can be the result of natural impurities or man-made toxins. Because different countries value different things, the level of pollution varies among them. Some countries may be more technologically advanced, but that can result in more opportunities for negative impacts, such as increased carbon dioxide emissions.

Climate Change Climate change and biodiversity go hand in hand. Any change in the climate will have a direct effect on organisms in the area. Some species may be able to withstand this change, while others cannot. Because of human impact, water resources are decreasing, which is causing a drier climate in some areas. Drier climates in turn change which species are suited to live there. Some species may not adjust to the change and thus become extinct, resulting in decreased biodiversity. Global warming is another climate change through which humans are having a devastating effect on ecosystems. As humans burn fossil fuels, they add carbon dioxide to the air, contributing to the greenhouse effect, which traps more and more of the Sun’s heat in Earth’s atmosphere.

What Do You Know? Reducing Human Impact on the Environment By driving excessively, overusing energy, buying more products than we need, developing and building on more and more land, and creating increasing amounts of waste without thought of consequences, we are using increasing amounts of the natural resources around us. These are resources that we are sharing with all species on Earth.

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• How does human impact influence biodiversity? • What roles do you play in impacting biodiversity? • What can you change to lessen your impact?

There are many ways in which humans can help reduce negative impacts on biodiversity and help increase it instead. Sustaining biodiversity to maintain the ecosystem’s functions and productivity is essential to supporting and enhancing life on Earth. It also benefits humanity by preserving landscapes of recreational or inspirational value. Look at the items in the list below. Which of these would have a positive impact on biodiversity? Why? Eat only organic foods Purchase only supplies you need them

Water your yard only when necessary and not for aesthetic appeal Carpool to school instead of walk

Cut down only the smaller trees

Reduce use of harmful pesticides

Purchase supplies from companies that give back to their environment Reduce the use of nitrate-rich fertilizers made from ammonia. Plant nonnative plants in your yard and garden Utilize renewable energy sources whenever possible

Introduce new competition for food

Recycle

Start your own compost pile in your backyard Use fossil fuels as much as possible Set aside areas for wildlife refuges, national parks, and nature preserves Plant native trees and plants

How can people help? A basic rule of thumb for lessening the negative impact humans have on their environment is to try to leave Earth as unchanged as possible. Think of a sign often seen on trails at national parks: “Take only pictures and leave only footprints.” Here is a list of real-world practices you can try to do your part in protecting our planet: • • • • •

Walk or bike as much as possible Consolidate errands and car trips Plant native trees and plants Water your yard sparingly Plant a garden

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STEMscopedia: CHANGES IN ECOSYSTEMS

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• • • • • • • • • • • • • • • •

Buy local, organic food Turn off lights and electrical appliances when not in use Start a compost pile Limit time in showers Recycle Repurpose items Reuse things Stop using plastic shopping bags Buy only what you need Carpool Look into renewable energy resources Turn off water while you brush your teeth Invest in “low-flow” toilets, showers, and faucets Learn about local wildlife Reduce the use of pesticides Reduce the use of harmful chemicals (such as those found in cleaners and detergents) and use biodegradable products

What other habits can you think of that you could put into practice in your daily life?

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STEMscopedia: CHANGES IN ECOSYSTEMS

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What Do You Think? Sometimes humans’ best intentions to be good stewards of Earth end up backfiring. Look at the example of forest fires. Forest fires have two causes: natural sources (such as lightning) and human carelessness or apathy. Human causes can be attributed to smoking, campfires, and even arson. When most people think of forest fires, they think of raging, destructive fires destroying entire ecosystems. Throughout the last century, people have hired firefighters and launched anti-forest fire advertising campaigns, such as Smokey the Bear, in an effort to prevent or halt forest fires. The effect has been fewer, but larger, more dangerous fires.

Some forest fires are actually beneficial. When less intense, local fires burn, they clear out brush and small trees. Those minor fires are nature’s way of preventing huge catastrophic fires. When smaller fires are allowed to burn, they clear the forest floor of fuel for fires, such as pine needles, pine cones, fallen, dead trees, and small, young trees. That leaves less of an energy supply for future fires. In addition, fires enrich soil. Plus, some plants, like lodgepole pines and redwood trees, require the heat of fire to allow their seeds to be released or to sprout. Natural fires are part of the natural cycle of damage and regrowth. When natural fires are prevented or put out prematurely (not allowed to burn themselves out), there is too much debris that builds up. Therefore, when a fire does start, it burns hotter and larger. It kills trees and other animal and plant life and threatens human life and property. In certain circumstances, people are learning to let nature take its course. For example, Yellowstone National Park adopted a policy on its 100th anniversary in 1972. Whenever a fire is detected in the park, rangers investigate to determine the cause. If it is a natural cause, the fire is permitted to burn—unless it poses a great risk to humans. If people started the fire, firefighters put it out. Scientists continue to learn about natural processes from this policy. Even though there was a huge fire in 1988 and people were afraid of the damage it caused, the native wildlife flourished after the fire. The soil was rich, plants grew back quickly, and animals returned to their habitat.

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STEMscopedia: CHANGES IN ECOSYSTEMS

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• • • •

Should people attempt to stop all forest fires? Why or why not? How can fire harm a forest and its inhabitants? How can fire benefit a forest and its inhabitants? Find and read about an organism (plant or animal) that needs fire in order to thrive.

Connecting With Your Child Changes in an Ecosystem To help your child learn more about the ways in which abiotic and biotic factors affect the stability of an ecosystem, work together to conduct an investigation of an ecosystem that has experienced a major change or sudden event. Research how this change or event affected the ecosystem. Work together to develop a digital slideshow presentation documenting this change or event. (If you do not have access to digital resources or appropriate software, your child can create a trifold poster display.) Begin by conducting research to find an example of an ecosystem that was affected by a dramatic change or event. This change could be abiotic or biotic. Some examples of changes in abiotic factors could include flooding, drought, hurricanes, wildfires, or volcanic eruptions. Some examples of changes in biotic factors could be overfishing, cattle grazing, introduction of invasive species, or extinction of keystone organisms. Next, find information about the structure of the ecosystem before the change by addressing the following questions: 1. What kinds of abiotic and biotic factors did it contain? 2. How were these factors interconnected? 3. What organisms made up the ecosystem’s food web? Describe how the change affected the abiotic and biotic factors in the ecosystem. For example, overfishing may have caused a collapse of organisms that depended on the fish for food and an increase in the organisms that were once preyed upon by the fish. Work together to find information from a variety of sources and media, such as: • photographs • sound recordings • video clips (for example, from a newscast about a natural disaster) • scientific data (graphs or tables) • eyewitness accounts

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STEMscopedia: CHANGES IN ECOSYSTEMS

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Here are some questions to discuss with your child: • How did the change in the ecosystem affect the abiotic and biotic factors for both the short term and the long term? • How did the change in the ecosystem affect competition among the organisms that lived there? • Were any organisms well adapted to the ecosystem after the change? If so, how and why did this happen? • Did any new organisms enter the ecosystem? What were they and under what circumstances did they join the ecosystem?

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B5CDE Changes in Ecosystems and Environments

Reading Science Name:

Date:

Group:

Coral Reefs and Climate Change 1

There are many different types of environments on the planet, and often many ecosystems within each environment. Ecosystems all contain a mixture of abiotic and biotic factors. The organisms within each ecosystem rely on natural resources in that ecosystem for survival. They are interdependent. Changes in the environment can affect both the stability and the equilibrium of that ecosystem. It is also important to note that the amount of natural space, food, shelter, and water within these ecosystems is limited. Species compete for these resources as they struggle to survive. These aspects are known as limiting factors. Limiting factors affect every level of organization: from organism to ecosystem.

One of the most diverse ecosystems on the planet is found in the ocean’s coral reefs. Unfortunately, they are also one of the most threatened ecosystems. Why? The bounty of life that lives in these ecosystems is changing due to warming ocean waters and changing ocean currents. Coral reefs house over 25% of the ocean’s marine species, yet they are found in only one-tenth of the ocean’s area. That is a lot of diversity for such a small space. Changes in the delicate balance of shallow waters, light, and sea temperatures can threaten the equilibrium that holds this ecosystem together. To understand why coral reefs are so threatened, it is important to first understand what makes a healthy coral reef ecosystem.

The world’s coral reefs are found in very specific areas in the world. They are only found in the zone 30 degrees south and 30 degrees north of the equator. The warm, shallow seas that the corals require for growth are found in these latitudes. Corals are very small animals that belong to the phylum Cnidaria. This same phylum contains other marine animals, such as jellyfish and sea anemones. They live in very large colonies. Corals reproduce by producing polyps that float in the sea until they reach a solid resting place. Once attached, they create a hard calcium carbonate structure that forms the backbone of the coral reef. Since each coral cannot move from its anchor spot, it feeds on passing debris by extending its tentacles. As the corals eat, they produce more calcium carbonate, building the coral reef.

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B5CDE Changes in Ecosystems and Environments

Reading Science Continued 4 In a healthy coral ecosystem, the corals have a symbiotic relationship with a specific type of algae called zooxanthellae. Over time, the algae and the corals have adapted to work together. The algae lives inside the “skin” of the coral, performing photosynthesis in the light that shines through the water of the shallow seas. The sugars produced from the photosynthetic process are then available to the coral. In return, the corals house the algae, protecting them and giving them access to light. However, these algae can only live within a very narrow temperature range within the ocean. Along with the zooxanthellae, corals and the reefs that they build provide important habitat for many other ocean creatures. The reefs provide shelter and food sources, and reduce wave action around the reef. 5

As the ocean organisms consume energy through eating corals and other food sources housed on and around the reef, energy flows from the Sun through all trophic levels, creating a food web. If the corals die, then the entire system is affected. Unfortunately, this has been associated with a variety of environmental changes. In some places, the ocean waters near the reef are becoming warmer. In other places, the currents have changed bringing different water temperatures and nutrients to the reefs. Temperature change is not the only problem. In some parts of the ocean, the water near reefs has become more acidic. The delicate zooxanthellae algae sometimes leave the corals. This is known as “coral bleaching.” The corals cannot survive without their symbiotic partners. As a result, the corals on the reef die. Soil erosion or fertilizer runoff that promote seaweed growth over the coral can also be a problem. As these types of environmental changes happen, the reef structures fall apart. Many marine creatures lose their shelter and food source. Fish and other reef inhabitants are forced to move affecting the entire balance of the coral reef ecosystem.

People are working to repair and rebuild coral reefs around the world. Many successful artificial reefs are being placed in locations where natural reefs had never developed before. Some are farther from the equator, outside the normal growth zone. Others are in deeper water, such as off the Texas coast in the Gulf of Mexico. There are two approaches to artificial reefs. The first is used in zones where natural reefs have been damaged or destroyed. The primary goal is environmental restoration. Pieces of healthy corals are attached to an artificial substrate, similar to a large metal cage. Within as little as a year, the corals will grow. As they grow, marine animals will return to live in and around the structures. This has been a very positive step toward saving this important ecosystem.

A second type of artificial reef is created simply by sinking objects to the seafloor. Sometimes this includes the specially designed substrate. More often this is a way to reuse items that would be difficult to dispose of otherwise. This includes retired drilling rigs and cargo ships. It also includes large chunks of concrete from demolition projects. Coral polyps, as well as immature oysters and barnacles, will attach to the surfaces and begin to grow. Eventually, a reef system will develop. While this will benefit the environment by providing new habitat, the building of these reefs is often motivated by a desire to generate tourism income for a coastal city. Scuba diving on artificial reefs is part of a growing industry called ecotourism.

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Reading Science Continued 8 These reefs also generate income as destinations for offshore fishing trips. Deep sea fish are easier to catch in these locations. They are attracted to the ready food supply of smaller reef fish. 9

There is controversy about the environmental impact of fishing on artificial reefs. There are two main concerns. The first is that it may contribute to the depletion of the deep sea game fish. Some biologists argue that these new reefs do not lead to increased populations of these larger fish. Instead, they fear that the artificial reefs may simply lure these marine predators into one place where they can more easily be caught. The second concern is for people eating fish caught off of reefs made from sunken vehicles. Before becoming a potential reef, a train car or ship must be thoroughly cleaned. Even so, small amounts of chemicals can come from the materials and be added to the water. Some studies have found these chemicals to be concentrated in the flesh of the game fish. They worry that these fish may not be safe to eat.

In general, the ecotourism industry tries to attract your vacation spending by advertising fun outdoor adventures that claim to have a very low impact on the environment. Many will even state that some of the money you pay for a vacation with their company will even benefit wild animals and ecosystems. This is also true of artificial reef diving.

In some popular areas, natural reefs have been damaged by too many visitors. The system can recover when divers are diverted to artificial reefs. You should do your homework before booking any trip however. Always research the site your dive will visit. Some older artificial reefs were made by chaining used tires together. These are not as safe for divers or for wildlife. They can shift unexpectedly or break free and crash into natural reefs causing damage. Most of these are being removed and replaced. All told, scuba diving does a good job of living up to its claims of pairing fun with environmental benefit. Remember, though, that you should evaluate any type of vacation services for yourself before you endorse them with your dollars.

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Reading Science 1 According to paragraph 1, which of the following factors limits the abilities of populations within an ecosystem to survive? A The frequency of reproduction of each species B The number of organisms becomes too large C Availability of space, shelter, food, and water D Availability of a diversity of species

2 Corals are related to other commonly found marine animals. What other animals are found in the phylum Cnidaria? A Polyps B Jellyfish C Zooxanthellae D They are not related to other marine animals.

3 Based on this passage, evaluate the following vacation activities. Which one would cause the least disruption of the balance of the coral reef? A Sport fishing on the reef B Scuba diving to view the reef species C Collecting rocks and shells as souvenirs D Attracting sharks to the reef with bait for photos

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Reading Science 4 The balance of the coral reef ecosystem is being affected by warming oceans, changing ocean currents, and what other external factor? A The acidification of the oceans B The light that enters the system C Marine animals leaving the reef D Not enough information is given

5 Why are coral reefs important? A Coral reefs house over 25% of marine species. B Coral reefs provide important habitat for many ocean creatures. C Coral reefs create important food webs. D All of the above.

6 Healthy ecosystems depend on– A a balance of abiotic and biotic factors. B coral reefs. C zooxanthellae. D warm oceans.

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Math Connections Name:

Date:

Group:

Part I: Recycling Cans Recycling centers store the used cans they buy from can collectors in trailers. A full trailer holds 15,350 pounds of loose cans. There are approximately 24 aluminum cans in a pound. When the trailer is full, it is hauled to a processing plant where the loose cans are pressed into huge 850-pound bales. Bales are loaded into rail boxcars for a trip to an aluminum company remelting plant. Cans are melted down into ingots weighing about 30,000 tons and are then rolled into new aluminum for new cans. If you are in a state with a bottle bill, the value of each container is five or ten cents. If your state does not have a bottle bill, use a computer to research how much per pound your nearest recycling center pays for aluminum. You may have to use the information from a recycling center in a neighboring state if your state does not have one. 1.

Suppose you own a recycling center with large and small trailers. The small trailers hold 68% of the larger trailer’s capacity. If you want to fill two larger trailers and twice the number of smaller trailers full of used beverage cans, how many cans will you need?

Create an equation that could be used to find, a, the least and most amount of cash you can collect for the aluminum in these trailers. Use this equation to find those amounts.

Best Trailers is having a sale for 20% off used large trailers that holds 17,750 pounds and used smaller trailers that hold 52% of the larger trailer’s capacity. Should you buy Best Trailers’ trailers or continue to use your own? Defend your answer.

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Math Connections 4.

If purchasing a large trailer from Best Trailer, the capacity of your new larger trailer would have how much of a percent of increase?

If purchasing a small trailer from Best Trailer, your new small trailer would have how much of a percent of increase or decrease in capacity?

How much money can be made from filling five larger trailers and two smaller trailers from your answer choice in the previous question?

Create an equation to determine, p, the number of pounds of melted aluminum that are needed to make an ingot. Use this equation to determine how many collectors must visit the center before enough aluminum cans are collected to make an ingot if each can collector brings 33 pounds.

How many tons of aluminum are there in 458.3 bales of aluminum?

How many cans would be in this number of bales of aluminum?

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Math Connections Part II: Human Activity and the Environment Use the table below, taken from the 2002 Annual Statistics on Human Activity and the Environment published by Statistics Canada.

Decide what type of graph would best display this information (i.e., line graph, bar chart, circle graph/pie chart) and create a graph based on the information in the table. Make sure to title and label your graph. a) If you are using a computer to graph, you could use a spreadsheet program such as Microsoft Excel. b) If you are graphing by hand, you must use graph paper and a ruler. This ensures that your graph is accurate and neat.

Toluene, Xylene, and Zinc make up what percentage of the total on-site releases to air in 1996?

What was the total amount of releases to air in 1996? What percentage of the releases are not listed in the table above?

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Writing Science Name:

Date:

Group:

LOOK

THINK about the properties of ecosystems that exist in the oceans and how climate changes affect those ecosystems. The world’s vast oceans contain many types of ecosystems: cold-water arctic, deep-water, thermalvent, and shallow warm-water. Due to their color, their wide variety of life forms, and their delicate coral reefs, shallow warm-water ecosystems are some of the most beautiful ecosystems on the planet. Coral reefs live in some of the most diverse ecosystems, containing a wider variety, or greater diversity, of species than any other place on Earth (even more than rainforests, as rainforests have more species but coral reefs have more diversity) and nearly 25% of all the marine species in the oceans. Coral reefs are also one of Earth’s most endangered species. They depend on algae for survival, so climate changes and the warming of shallow water areas can have devastating effects on coral reefs. If the temperature rises higher than the level in which the algae can produce food, the reef may perish. Coral bleaching may also occur if the temperature increase causes corals to starve and die. This bleaching leads to a cascade of events for the coral in the warm-water ecosystem. These changes in the coral reef environment can alter the equilibrium of that ecosystem. WRITE an event that negatively affects a coral reef ecosystem and the steps needed to restore it to a stable system. Be sure to clearly state your central idea; organize your thoughts; develop your essay in detail; choose your words carefully; and use correct spelling, capitalization, punctuation, and grammar. © Accelerate Learning Inc. - All Rights Reserved

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Writing Science

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High School Biology

B6A

Our Evolving Understanding of Biology

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Student Handout Name:

Date:

Directions: Write at least four concepts or ideas you already know about biology around the inside circle.

Biology

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B6A Our Evolving Understanding of Biology

Student Journal Name:

Date:

Group:

Part I: History of Earth 1.

What were the different theories and experiments that helped explain how life on Earth began?

What were some possible problems with the theory of spontaneous generation that led Louis Pasteur to challenge its validity?

Why was it proposed that an energy source such as lightning need to be present for spontaneous generation to take place?

What was a major limitation to the Miller/Urey experiment?

What could Miller and Urey have done to make their experiment more acceptable to the scientific community?

What could the iron-sulfur world hypothesis explain about organic matter?

What was the main challenge for the RNA world hypothesis? Why?

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Student Journal Part I: History of Earth, continued 8.

What does the term “endosymbiotic” mean?

What types of obstacles did Margulis possibly face in advancing the endosymbiotic theory?

10. Write the correct number in each box to indicate the progression of cell formation according to the endosymbiotic theory.

11. What observations can be made about the specialization of the structure from the beginning of the process to the end?

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Student Journal Part I: History of Earth, continued Write the unique characteristics to the left and the similarities to the right. Answer the “What if” statements at the bottom.

What if you were in charge of developing a theory or hypothesis from the two most closely related explanations above? Which two would you choose? What would your theory propose?

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Student Journal Part II: The Emergence of Species from Pre-existing Species 1.

What evidence do scientists use to explain that species emerge from pre-existing species?

Examine the picture below. Why do scientists believe that these organisms shared a common ancestor?

Look at the amino acid chart below. Which two organisms would you suggest are most closely related to the human? Explain your reasoning.

How has the understanding of how species emerge from pre-existing species influenced our understanding of biology?

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Student Journal Part III: Advances in Genetics 1.

DNA for all organisms is composed of the same parts. What makes your DNA different from another person’s DNA?

Scientists use gel electrophoresis to determine paternity or who may have committed a crime. Observe the image of a gel electrophoresis below to determine which sample is the likely father of the child. Remember, the baby can acquire the band from the mother OR the father. Hint: If the mother does not have the band, the father must have the band.

Which sample is the father? Explain your answer.

How do you think scientists can benefit from the completion of the human genome?

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Student Journal

What similarities and differences do you notice between the two karyotypes? What do you think caused the person to develop Patau Syndrome?

Patau Syndrome Karyotype

Normal Karyotype

Part III: Advances in Genetics, continued

Compare the karyotypes of a person without any mutations to someone who has Patau Syndrome.

How have the advancements in genetics influenced our understanding of biology?

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Reflect

B6A

Have you ever wondered why organisms that are alive today are so different from those long ago? Biology is the study of living organisms. As life is constantly changing, it is important to know that so is our understanding of biology. Many different branches of science contribute to our understanding of life on this planet. Age of Earth To understand how and when life began, it is important to look at how old Earth is, and when it became habitable to different forms of life. Scientists as early as Aristotle (384–322 BCE) have come up with calculations for Earth’s age. As different methods of calculations became available, different numbers have been accepted as true and then later changed. Middle Age scholars only had human records to base their theories on and, using these, placed Earth at a few thousand years old. This estimate was widely accepted until new evidence could be examined. Leonardo da Vinci (1452–1519) studied sedimentation in the Alps and along rivers and concluded that a few thousand years was not long enough for all he observed. Da Vinci’s thoughts on the matter were not published until many years later. Once scientist noticed the geological events of deposition and sedimentations, they began to calculate the rates of these events. Many realized that geological processes must stay the same over time, and that tens of thousands, if not millions, of years would be required to reconcile with what they observed.

Rock layers like this are due to sediment deposition over many millions of years.

In the middle of the 20th century, scientists started looking at layers in ice core samples taken from glaciers. In Antarctica, they found that the oldest layer of ice is 740,000 years old, much older than Earth was believed to be! In the early 1900s, physicist Lord Rutherford suggested that radioactive elements could be used to measure the age of rocks and other geologic formations. Once isotopes of radioactive elements were discovered, and half-lives became known, relatively precise measurements could be made on organic and nonorganic material. Radioactive elements are highly unstable atoms that decay, or break down into more stable elements, over time. Half-life describes exactly half the amount of time it takes for an unstable radioactive element to decay into a stable daughter element. Carbon-14 is the most common known element used to date, but due to a relatively short half-life, we use it more for organic artifacts.

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Ice core samples like this one, taken from ice sheets in Greenland, show thousands of years of winter layering. Scientists use the cores to study Earth’s atmosphere from times before recorded history.

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Uranium isotopes and potassium isotopes have much longer half-lives, so these can be used to date rocks and meteorites, which give us our most currently and widely accepted date of Earth at 4.56 billion years old. Evolution of New Species Until the theory of evolution was postulated and widely studied by scientists throughout the 19th and 20th centuries, most people assumed that all species existed as they always had, unchanged. Over the years, the distinct field of biology emerged and certain traits became unexplainable. Though it was not widely accepted until much later, many scientists in the late 1700s started to look into the biological evolution of species. Although scientists studied the idea of evolution since the early days of Anaximander, Lucretius, and Aristotle, it wasn’t until Charles Darwin (1809-1882) provided a plausible mechanism for this process that the general population began to accept the idea. Darwin was a naturalist who traveled the world, making observations on nature and collecting specimens. It was his study of many different types of finches on an island off the coast of South America that led him to believe each finch was a descendant of a single species from the mainland. This changed so many views on biology and led him to develop his theory on natural selection.

The finches Darwin studied were all uniquely adapted for their individual niches on the islands. Some had beaks that allowed them to eat insects from the sand. Others had strong enough beaks to crack open shells. This specialization reduces completion among the finches.

The theory of evolution by natural selection stated that small changes proving to be beneficial to the organism had a higher chance of being passed on to offspring. Eventually these accumulated small changes might give rise to an all new species over long periods of time.

Look Out Many people equate natural selection to “survival of the fittest.” While this is technically correct, it does not mean that only the strongest of a species will survive. Strength is not necessarily beneficial to survival. Survival of the fittest means refers to traits that allow an organism to best adapt to its environment, giving the organism a greater chance at survival.

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Genetics While Darwin’s theory was revolutionary and still the best theory of evolution, he was unable to provide adequate proof during his lifetime. He had no way to address the mode of inheritance of these advantageous traits he observed. The discovery of genes allowed us to expand on the theory of evolution. Gregor Mendel (1822–1884) developed fundamental laws of inheritance with his work on pea plants. In 1866, he published his ideas on these laws of inheritance, stating he could predict offspring traits based on parent generations. Mendel’s work also went unrecognized in his lifetime. Without adequate technology to see these yet unnamed genes, there was no way to prove his accurate theory. Once better microscopes were developed in the late 19th century and we understood better how traits were passed from parent to offspring, our view of biology was, again, changed. This was reinforced by the discovery of the actual structure of DNA in 1953. Watson and Crick are commonly given the credit for this discovery, but their work was aided by many scientists, including Miescher, Levene, Chargaff, and Rosalind Franklin.

A double helix is sometimes referred to as a “twisted ladder.”

The structure of DNA was discovered to be a double-stranded deoxyribonucleic acid, twisted into a helical shape. The shape is important because it lends to the method of self-replication and transmission of genes.

Once the structure was known, the mechanism for passing along genetic traits became understandable. It is now known that DNA consists of four recurring nitrogen bases—adenine, cytosine, guanine, and thymine— arranged in infinite patterns in the human nuclei. The order in which these bases appear make every organism its unique self. In a few short years, technological advances turned our understanding of biology around. New discoveries may very well cause another shift in the future or advance our understanding of what we already know. As life evolves, so does our view of the natural world around us.

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Connecting With Your Child With the discovery of DNA came the discovery that DNA was also universal to all living things. The same four base pairs that give you your unique characteristics can be found in other animals, plants, fungi, and bacteria. You can see this at home with your child using only a few simple items found around the house! Using your own saliva, we can extract you or your child’s DNA. A strawberry will be used to see DNA represented in the plant kingdom. Note: Strawberries are octoploid, meaning they have eight copies of each set of chromosomes. Humans are diploid because we only have two copies of each chromosome. This will be evident in the amount of DNA you extract from the strawberry, which will be much higher than what you get from the saliva! Materials: 2 Clear glasses or jars 1 Zip-top bag Dish soap Salt High-proof alcohol Grapefruit juice, meat tenderizer or contact saline solution A few strawberries Procedure: Prepare the buffer solution In one glass, mix about one cup of water, two tablespoons of dish soap, a pinch of salt, and either the grapefruit juice or contact solution. (The soap acts to break apart cell membranes. DNA is trapped inside of the nuclei of cells, which are surrounded by a lipid membrane. Soap pulls these lipids apart, freeing the DNA. Salt will bind to the DNA, making it possible to pull the DNA out of the solution. The juice or contact solution will act as a protease. This will help break down enzymes in the cell to essentially get them out of the way, allowing you to see more DNA.) Part I: 1. Put one or two strawberries in the zip-top bag, seal the bag, and mash them up. 2. Add about half of the buffer solution to the bag. 3. Add about one teaspoon of alcohol to the bag (Alcohol will draw the DNA out of the water solution, allowing it to become visible.) 4. Gently swirl the bag and observe the white thread-like material. Strawberry DNA! Part II: 1. Have you or your child spit into the second glass. 2. Add the remainder of the buffer solution. 3. Add a teaspoon of alcohol. 4. Gently swirl the glass and observe the white frothy strands that will form near the surface.

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B6A Our Evolving Understanding of Biology

Reading Science Name:

Date:

Group:

Small Genome, Big Trouble 1.

It all began with a boy and some insectivorous bats. The largest outbreak of Ebola started with a single animal-to-human transmission in a small village in Guinea in December 2013. As of March 2016, more than 28,000 people were infected, and more than 11,000 died. How did scientists arrive at this conclusion?

The Ebola virus is a member of the family Filoviridae. Its genome consists of RNA and produces only eight different proteins. Viruses use host cells to transcribe and translate their genome and produce more viruses. Viruses have to enter a host cell in order to take advantage of its machinery. One particular cellular protein, named NPC1, appears critical for Ebola and other filoviruses to enter cells.

The first recorded outbreak of Ebola happened in 1976 in Central Africa. The genome of the virus responsible for this outbreak was sequenced, along with the genomes of the Ebola virus from more recent outbreaks. Comparing the genome of the Ebola virus of 2013 to other outbreaks showed that this new virus diverged from previous viruses in 2004. For nine years it was transmitted from animal to animal and moved from Central to West Africa. In December 2013, it infected one little boy.

Scientists not only used genetics but also epidemiology to pinpoint the origin of the outbreak. First, they sequenced the genome of viruses from different people infected at various times during the outbreak. All of the virus genomes were very similar to each other. Next, they visited the village where the first cases of Ebola were reported and interviewed the inhabitants. They found that villagers had little contact with large wildlife such as monkeys previously thought to transmit infection. Instead, children played with bats, and a large colony of bats lived in a hollow tree close to the boy’s house.

While Ebola kills between 50% and 90% of those infected, some people do survive. People who survive have fewer viruses in their blood than those who die. Again, genetics appear to play a role. In the laboratory, cells that lack the NPC1 protein survive in the presence of the Ebola virus, and mice without the NPC1 protein do better than those that have NPC1. Drugs that block NPC1 may help prevent virus replication and ultimately save lives. Those drugs will most likely be given by a health worker in a village.

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Reading Science 6.

The ability to rapidly and accurately sequence the genome of a virus has been critical in understanding the most recent Ebola outbreak. Genetics appear to play a role in whether a person survives the infection. Genetics is involved in producing vaccines and drugs for candidates. Hopefully by the time the next person becomes infected with Ebola, he or she won’t be the start of another outbreak.

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Reading Science 1.

Scientists think the 2013 Ebola outbreak began in __________. A.

multiple locations through bites from infected monkeys

multiple locations through people eating bats

one location through contact with a bat colony

one location through people eating monkeys

Which of the following statements best describes the genome of the Ebola virus? A.

It consists of DNA and codes for more than 100 proteins.

It consists of DNA and codes for only eight proteins.

It consists of RNA and codes for more than 100 proteins.

It consists of RNA and codes for only eight proteins.

What is the first step in viral replication? A.

Entering a host cell

Copying the viral genome

Mutating the viral genome

Destroying the host cell

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Reading Science 4.

People who survive the Ebola virus ___________. A.

are generally younger and male

have fewer viruses in their blood

are infected with multiple viruses

are usually older and female

Which of the following is LEAST likely to help prevent the next Ebola outbreak? A.

A vaccine that protects people

Killing all large animals around villages

A drug that blocks the protein NPC1

Increasing the number of health workers

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B6A Our Evolving Understanding of Biology

Math Connections Name:

Date:

Group:

Geologic Life History The history of life on Earth is based on the discovery of both the fossil record and geology. The changes on Earth generally happen over millions of years, but about five times throughout Earth’s history, there have been huge catastrophes that have caused mass extinctions. Life on Earth has continued to evolve. Paleontologists are scientists who study fossils. They created the Geologic Time Scale, which separates Earth’s history into eras and periods. The eras are the larger blocks of time, based on the dominant life forms of that time. Eras are then divided into periods, which are based on fossils from each specific era. Era Cenozoic Cenozoid Mesozoic Mesozoic Mesozoic Paleozoic Paleozoic Paleozoic Paleozoic Paleozoic Paleozoic Precambrian

Period Quartenary (1.8 million years ago [mya] to present) Tertiay (65 to 1.8 mya) Cretaceous (146 to 65 mya) Jurassic (200 to 146 mya) Triassic (251 to 200 mya) Permian (299 to 251 mya)

Dominant Life Forms Mammals

Mammals Flowering Plants Birds and Dinosaurs Dinosaurs Therapsids Tropical Plants and Carboniferous (359 to 299 mya) Foraminifera Devonian (416 to 359 mya) Ferns and Horseshoe Crabs Silurian (444 to 416 mya) Fish with backbones Ordovician (488 to 444 mya) Ice Age, but still trilobites Cambrian (542 to 488 mya) Trilobites Prokaryotic and than Eukaryotic Precambrian (4570 to 542 mya) Cells

Using the table above as a reference, answer the following questions: 1.

From the formation of Earth 4.57 billion years ago, what percentage of that time was occupied by the Precambrian Era?

What percentage of time of Earth’s existence was spent in each of the eras?

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Math Connections 3.

Which period throughout Earth’s history was longest? How long was it? What percentage of Earth’s history was it?

Create a bar graph of the periods of the geologic history that shows how long each period was in millions of years. Then write two questions based on the graph you make.

a) _____________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ b) _____________________________________________________________________________ _______________________________________________________________________________ 5.

Take the data you used for the bar graph and transform it into a horizontal time line that accurately represents the length of time for each era and period. Then create two questions to ask based upon your timeline.

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B6A Our Evolving Understanding of Biology

Writing Science Name:

Date:

Group:

LOOK

THINK Many factors have changed the field of biology. Concepts such as the emergence of new species from pre-existing ones, genetic findings, and the age of Earth have shaped biology into what it is today. The age of Earth is relevant to allow ample time for speciation to occur. Genetic findings have found links between animals such as the African elephant and the extinct mammoths of long ago. Look at the diagram above that shows the emergence of modern horses from a species long ago. WRITE Explain how the emergence of a species from a pre-existing species and our understandings of the age of Earth and genetics have influenced biology. Describe how each is inextricably linked to support findings in evolutionary theory. Be sure to clearly state your central idea; organize your thoughts; develop your essay in detail; choose your words carefully; and use correct spelling, capitalization, punctuation, and grammar.

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Writing Science

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High School Biology

B6B

Speciation

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B6B Speciation

Student Journal Name:

Date:

Group:

Part I: From One Species to Another 1.

Compare and contrast a new species and a subspecies by completing the Venn diagram below.

New Species

Subspecies

How did the geography of the Galápagos Islands affect the genetic diversity of the Galápagos tortoises over thousands of years?

What is the relationship between natural selection and speciation? Explain.

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B6B Speciation

Student Journal Part II: A New Species 1.

Is it possible that all of the tortoises came from the original species of tortoise? Why or Why not?

Which turtle of the three species (A, B, or C) is the oldest? How do you know?

How does biodiversity result from speciation in this scenario?

Giant tortoises live over 100 years in the wild and usually do not start to reproduce until around 40 years of age. Brown rats only live up to three years and can produce offspring after they are five weeks old. Suppose a brown rat had drifted to the Galápagos Island from the mainland at the same time as the tortoise. In which organism do you think speciation would likely occur first? Why?

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STEMscopedia: SPECIATION B6B

Reflect Imagine that you and your classmates are taking a nature hike through a nearby desert ecosystem. The hot sun is beating down on you, and you begin to wonder how anything could live in this harsh climate. But as you look around, you see that the desert is teeming with life. There are cacti, lizards, rats, foxes, beetles, ants, snakes, coyotes, and antelope. And there are so many different variations within the species: big lizards, small lizards, birds of different colors, some cacti that are taller than you, and other cacti that stand only three inches tall. Earth has such an amazing diversity of species. What causes all this diversity? Speciation Earth is home to an astounding array of species. Over time, some species have become extinct, while new species have emerged. Recall that a species is a group of organisms that can interbreed and produce viable, fertile offspring. Viable means that the offspring are able to survive. Fertile means the offspring are able to produce their own offspring. One species may look very much like another, but if they cannot produce viable, fertile offspring, they are considered separate species. Take the mule, for example. It is the offspring of a male donkey and a female horse, which are members of two different species. The mule offspring can survive, so it is viable, but it cannot typically reproduce. In these cases, it is clearly demonstrated that a donkey and a horse are not members of the same species. However, there are rare examples of mules being fertile, which means that there are exceptions to the rule when defining the word species. New species emerge through a process called speciation. Speciation occurs when multiple gene pools originally from a single population diverge, or separate, to the point at which individuals from each population can no longer produce viable, fertile offspring. Eventually, the two gene pools are permanently isolated, and what was once a single population consisting of one species has become two populations, each consisting of a different species. Speciation can occur as a result of geographic isolation. For example, suppose a species of salamanders is living in a forest. A flood results in a new, large river flowing through the middle of the forest. The river separates the salamanders into two populations. Over time, genetic changes occur in both salamander populations. Natural selection acts on each population, but since they no longer intermix, the changes in allele frequencies are unique to each population. As each population accumulates unique adaptations, they become so different that they can no longer interbreed. This type of speciation is called allopatric speciation.

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STEMscopedia: SPECIATION Speciation can also occur without geographic isolation. Any factor that causes a reproductive barrier between two populations of the same species can result in speciation. Suppose you have a population of songbirds. Some of the birds experience a genetic mutation that results in a change to their courtship song. Birds without the genetic change will not respond to the unfamiliar song. Over time, the population may split into two species: one with the original courtship song and one with the new courtship song. Speciation that occurs without geographic isolation is called sympatric speciation. Biodiversity Biodiversity is the assemblage of different organisms within an ecosystem. High biodiversity implies many different species, each with different sets of adaptations that give them different fitness advantages. Low biodiversity implies fewer species. However, it does not mean that each species is not highly adapted to its environment. Biodiversity also includes the diversity among members of the same species, e.g., individuals with different sizes, markings, or behaviors. The study of biodiversity often centers on asking why it exists at all. Why does one species not achieve a higher fitness than the other species and become the only species in the habitat? Biodiversity also involves variation among the individuals within a population. Why do all of the individuals within a population not have the same optimum combination of beneficial alleles?

What Do You Know? Charles Darwin and the Theory of Natural Selection Charles Darwin was a biologist who studied biodiversity and proposed the theory of natural selection to explain the existence of the many different species on Earth. Darwin suggested that, just as livestock breeders could enhance or increase certain traits in their animals by only allowing animals that possess the desired traits to produce offspring, nature could select which individuals produce the most offspring in any given environment. If nature selects different trait values for high reproductive success in different, isolated environments, then the individuals in the different environments will begin to diverge, eventually becoming different species. The existence of DNA and genes was still unknown in Darwin’s time, but Darwin successfully introduced the idea that new species form when existing ones form divergent subpopulations in which different trait values are favored by natural selection.

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STEMscopedia: SPECIATION Microevolution and Macroevolution Understanding how Earth, once devoid of life, now teems with biodiversity is based on two areas of study: microevolution and macroevolution. In general, evolution is the change in the gene pool of a population that results in successive change over time. Microevolution focuses on studying genetic variation due to recombination, gene flow, genetic drift, natural selection, and mutation at the species and subspecies level. Macroevolution is the result of large numbers of changes, and focuses on large changes in a population or species over a longer period of time due to adaptive radiation, coevolution, and convergent evolution. Continue reading to learn more of these patterns.

Try Now Look at the examples below, and determine if the example is caused from a large macroevolutionary shift or a small microevolutionary shift. A baby bird is born missing a wing. Fossil records are found linking modern-day chickens with the prehistoric T-Rex. Geographic barriers separate a species of squirrels. Three Main Patterns of Macroevolution When two or more species evolve because of each other, this is known as coevolution. For example, bees rely on the nectar of a flower in the same way the flowers are in need of the bees’ ability to spread the pollen. These two species count on each other, they will also increase or decrease in species diversity together. Adaptive radiation can be defined by the rapid evolution of one species into many new ones. Darwin saw this through his recordings of the finches on the Galapagos Island. Convergent evolution shows us how organisms that are not as closely related can still show similarities in structural morphology. For example, a bird wing and a whale flipper share similar morphology but are used for two distinct purposes.

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STEMscopedia: SPECIATION Connecting With Your Child Illustrating Speciation To help your child learn more about speciation, have him or her create a digital slideshow presentation that includes illustrations of the mechanisms and patterns that impact biodiversity: speciation, natural selection, and macroevolution. The illustrations should each include a description, an illustration or diagram, and a specific example. If you do not have access to digital resources to create the slideshow presentation, your child can use cardstock paper and colored pencils to create a “mock” slideshow. It should include five quiz questions about the material in the presentation. Have your child present the slideshow. When finished, try to answer the quiz questions. Here are some questions to discuss with your child: 1. How does biodiversity impact species survival? 2. How does natural selection increase biodiversity? 3. What three patterns of macroevolution help maintain biodiversity?

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B6B Speciation

Student Handout Name:

Date:

Moving to a New Environment 1.

Design a species that would live in a prairie ecosystem like what is pictured below. Make a drawing of your species in the picture.

Write down at least five phenotypic traits of your species that help it survive.

A group of your species has been isolated into a desert ecosystem. Individuals with traits that are more adapted to live in the dry heat have a higher chance to survive and reproduce. Which of the traits above, if any, does your species possess that will help it survive? Which traits does your species currently not possess that could help with its survival?

Traits that your species currently possesses that Traits your species does not have but could help help it survive in the new ecosystem. it survive in the new ecosystem.

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Student Handout 4.

The population of your species has reproduced 600 times. Over time, it has incorporated beneficial mutations into its gene pool. Draw what an individual of this new population would look like in its ecosystem.

List five mutations that happened within your population.

What is happening to your species over many generations?

How do the beginning generations differ from the ending generations?

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Reading Science Name:

Date:

Group:

Lemur Diversity 1.

Lemurs are primates native to the island of Madagascar. About 100 species of lemur exist, ranging from the mouse lemur, which weighs about 30 g, to the indri, which at 9 kg is the largest living lemur. Lemur anatomy and physiology are diverse, but most lemurs share the following anatomical and physiological traits. Most lemurs have long tails. Unlike other primates, they don’t use their tail to hold onto branches. Instead, their tails are used for balance. Although lemurs have large eyes, their vision is poorer than that of other primates. Their sense of smell is well-developed, and scent is used for communication particularly in nocturnal species. Lemurs groom each other using a specialized set of teeth known as a toothcomb. The brains of lemurs are generally small when compared to body size.

Most lemurs are herbivorous, although some eat small insects. Although some lemurs have a finger adapted as a tool, objects are not used as tools in the wild. Lemurs are generally social, with female dominance in groups. Because Madagascar has a strongly seasonal climate, lemurs breed seasonally so all young are born at a time when food is more plentiful. Some lemurs will even hibernate, and they are the closest relative to humans to do so!

Geologic evidence suggests that Madagascar has been an island for the last 88 million years. Fossils and some DNA evidence suggest that lemurs arrived on Madagascar between 52 and 40 million years ago. A small population of ancestral lemurs is thought to have been stranded on a raft of vegetation and floated out to sea. Ocean currents would have carried them to Madagascar in about a month. Note that lemurs are not ancestral to modern monkeys and apes, which evolved independently from their own ancestor.

How do scientists arrive at this conclusion? All lemur species are closely related. This suggests that a single ancestral population arrived on the island and subsequently evolved to fill the available niches. If multiple populations of ancestral lemurs had arrived on Madagascar at different times, some living lemurs would be more closely related to species on the nearest continent, Africa.

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Reading Science 1.

Lemurs use their tails _________. A.

to hold onto branches

for balance

for grooming each other

during mating

Which of the following traits allows lemurs to survive in a strongly seasonal climate? A.

They use scent for communication.

They have a smaller brain when compared to body size.

They bear young only at certain times.

They have relatively poor vision.

Scientists believe that lemurs most likely arrived in Madagascar by _________. A.

rafting from Africa

walking across a land bridge

riding ships

hopping between islands

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Reading Science 4.

What is the evolutionary relationship between modern apes and lemurs? A.

Modern apes evolved from modern lemurs.

Modern lemurs evolved from modern apes.

Modern lemurs and apes share a common ancestor.

Modern apes are not related to modern lemurs.

Which of the following facts argues for a single ancestral population for all lemurs? A.

Some lemurs on Madagascar have become extinct.

There are about 100 species of lemurs today.

Lemurs groom each other to maintain social ties.

All lemurs are closely related.

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Math Connections Name:

Date:

Group:

Speciation Speciation is the founding of a new species through evolution from an existing species. This can happen through a variety of ways. One way is the Founder Effect. This situation occurs when a small portion of the population is physically removed from the main population of a species. The genes possessed by the removed (or founder) group may be less common than the majority of the population. Once breeding occurs within the founder group, less common traits may become more common—especially if they are useful for survival, but this is not necessary. Look at the picture below. Then answer the questions.

In the original population, there was a trait called trait X that was very rare. It is designated by the dark dot on the front of the person. 1.

What percentage of the original population possesses trait X? ___________________________________________________________________________

What percentage of the founder group possesses trait X? ___________________________________________________________________________

What percentage of the founder group after three generations possesses trait X? ___________________________________________________________________________

Is trait X most likely a dominant or recessive trait? _______________________ What mathematical evidence do you have to support your answer? _____________________ ___________________________________________________________________________

What percentage of the population will probably possess trait X after three more generations? ___________________________________________________________________________ Explain your thought process. ___________________________________________________ ___________________________________________________________________________

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Math Connections Draw a line graph that shows the percentage of people with the X trait in the founders group, after three generations (as depicted in the picture), and the projected percentage of the population after three more generations. Make sure to include a title, titles for the x-axis and y-axis, and the units.

What are some potential traits that would fit as trait X? _______________________________ ___________________________________________________________________________

Choose one of the traits that you listed in question 6. Draw a punnett square for a cross between the original member of the founder group that possessed trait X and another member of the founder group.

What would be the likely genotypes for each of the two people? What evidence do you have to support your view? ___________________________________________________________ ___________________________________________________________________________

What would happen if no one else in the founder group possessed any form of trait X? ___________________________________________________________________________

10.

Write a question based on the graph you drew or the punnett square you created. ___________________________________________________________________________ ___________________________________________________________________________

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B6B Speciation

Writing Science Name:

Date:

Group:

LOOK

THINK Charles Darwin discovered speciation in finches on his voyage to the Galapagos Islands. At the time, he thought he had simply found three different types of birds. Upon returning home and giving the finches to the Geological Society of London, it was discovered that the birds were actually all finches. Speciation, or macroevolution, refers to the phenomenon of a species splitting to produce two or more new species. WRITE Looking at the specimens in the photograph above, explain biodiversity as it relates to speciation. Be sure to clearly state your central idea; organize your thoughts; develop your essay in detail; choose your words carefully; and use correct spelling, capitalization, punctuation, and grammar.

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Writing Science

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High School Biology

B6C

Common Descent

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B6C Common Descent

Student Handout Name:

Date:

The Great Race 1.

In the space below, please sketch out the race path and the location of the checkpoints using clues from The Great Race: Stamp Cards.

How is this Great Race similar to what scientists do to analyze the history of living organisms?

What is considered evidence for scientists to study how organisms are similar and different over time?

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B6C Common Descent

Student Journal Name:

Date:

Group:

Part I: Anatomical Homologies 1.

What are homologous structures? What are some examples?

What are analogous structures? What are some examples?

Humans are mammals. Mammals are defined by having a certain set of anatomical homologies. Think about some familiar mammals. What are some homologous structures that are shared by all mammals? List them.

How is the human forelimb similar to that of the other three mammals you examined?

Why does this suggest a distant, common ancestry to other vertebrates? Explain your answer. Analyze the forelimbs you constructed and labeled. What similarities would you expect to find in the forelimb of a reptile such as a small gecko? Identify and explain.

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B6C Common Descent

Student Journal Part II: Developmental Homologies 1.

What are developmental homologies? How are they studied?

What is a chordate? What do all chordates have in common? Explain.

List five familiar organisms that are in the phylum Chordata.

What is a notochord? Where is it found?

Title, color, and label the diagram below TITLE: _______________________________________

What do all chordates have in common during embryonic development?

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B6C Common Descent

Student Journal Part III: Molecular Homologies Number of Differences in Cyt C Amino Acid Sequences

Human and Chimpanzee Rhesus Monkey

Human and Chimpanzee

Rhesus Monkey

Cow, Pig, Sheep

Kangaroo

Bullfrog

Cow, Pig, Sheep Kangaroo Bullfrog

0 0 0

Why are organisms with similar genetic sequences likely to have similar protein configurations? What is an example of this?

Cows, pigs, and sheep have identical amino acid sequences for cytochrome c. What does this say about their evolutionary relatedness? What other properties do these species have in common?

Look at the table you completed above. If you were to sequence the amino acids for a snapping turtle, which organism would you predict the sequences to most closely resemble? Why?

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Student Journal Reflections and Conclusions 1.

List the three main categories of homologies in living organisms.

If a new single-celled organism was discovered in a lake and scientists determined it contained DNA, would it share a common ancestry with other living species? Why or why not? Explain your answer.

How do developmental homologies suggest common ancestry? Cite two specific animals that show such a homology.

Explain how using homologies is a valid method for helping to determine relationships and ancestry between organisms.

Use all of the following terms to develop a graphic organizer on a separate sheet of paper.

Terms: common ancestry, homologies, anatomical, developmental, molecular, forelimb, DNA, chordates, vertebrates, fossil record, bacteria, plants, animals

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STEMscopedia: COMMON DESCENT B6C

Reflect Take a look at the photographs below. Do you think the elephant on the left is a direct descendant of the woolly mammoth on the right? Explain your reasoning.

What Do You Think? common ancestor: Comparative Morphology a predecessor that a A 2005 study of mitochondrial DNA conﬁrmed that woolly mammoths creature shares with and African and Asian elephants share a common ancestor. Scientists another creature compared the mitochondrial DNA sequences of both animals and found strong similarities. Mitochondrial DNA is particularly valuable to make these determinations because only the mother passes mitochondrial DNA down to her offspring. Scientists looked at the DNA sequences of each organism and compared their similarities or differences. Similarities in anatomical structure, gene sequences, developmental stages, or any other criteria that point to a common ancestor are called homologies. Paleontologists have compared bone structures in organisms for years to determine common ancestry among organisms. A likeness between the bone structure of one creature and that of another may indicate a common ancestor. Mammals, birds, and reptiles all show similar anatomical patterns. Although the function of each forelimb is different, this diagram shows similarities in the anatomical structure of forelimbs in mammals (bat and human), birds (penguin), and reptiles (alligator).

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STEMscopedia: COMMON DESCENT Look Out Homologies: The fossil record is not the only evidence that supports the common ancestry of organisms. Homologies, or similarities in characteristics between two organisms because they originated from a common ancestor, also support the common ancestry of organisms. A homologous structure is something that is similar in position or form to a structure in a different organism because of a common evolutionary origin. There are three main categories of homologies among organisms: anatomical, developmental, and molecular. Anatomical homologies: Species with common origins (e.g., birds, reptiles, and mammals) all show similar patterns of anatomy, such as those in the bones of the forelimbs. Anatomical homologies are similar anatomical structures that exist between species and can be identified as a link to a common ancestor. Anatomical homologies exist between modern Asian and African elephants and the extinct woolly mammoth. All three are distinct species, but they belong to the same family of organisms, Elephantidae, which has large skeletons, trunks, and tusks. These similar features indicate relatedness among the organisms. Mammals are a class of organisms that all share certain traits, such as breathing air, having hair or fur, and producing milk for their young. All mammals show similar patterns of bone structures in their forelimbs.

Similarities in bone structure demonstrate anatomical homologies.

What Do You Know? However, mammals also show forelimb similarities to birds and reptiles. Not all common structures are indicators of a common descendant. Unlike the homologous structures discussed above that show a common ancestor, analogous structures are similar structures found in

What Do You Think? species that formed independently of one another. What similarities do we as humans share with chickens? Your initial thought may be that there are none or very little. However, sometimes viewing the embryo of a species provides insight into relationships you may not have easily seen in fully developed organisms. Look at the image of the chick embryo on the right. What similarities do you see between it and humans? Maybe you noticed the vertebrae running along the back of the developing chick, or possibly you noted the ribs look similar to ours. embryo: the developing organism between fertilization and birth

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STEMscopedia: COMMON DESCENT The chick’s skeletal system in general has multiple similarities to ours, including having one bone in the upper leg and upper wing and two bones in the lower leg and lower wing. This mimics our arm and leg skeletal structure. Embryology Species with similar origins also show similar embryonic development patterns. Paleontologists can learn a lot about a species by studying the embryo and patterns of development. For example, certain snake embryos have small buds that look like limbs. The buds disappear in later developmental stages. This suggests that snakes evolved from an ancestor that had limbs. Biochemistry and Genetics In addition to evidence from comparative morphology and embryology, evidence from biochemistry and genetics also support the theory that all living organisms are related by way of common descent. All organisms are made up of DNA and RNA. The protein sequences between bacteria, plants, animals, and humans varies relatively slightly. Because of this, biochemists argue their must be some common descent that predates all of these organisms.

What Do You Know? Look at the two pictures below of parents with their offspring. What homologies do you see between the two families? Fill in the space below with ideas.

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STEMscopedia: COMMON DESCENT Connecting With Your Child Evolutionary Trees To help your child learn more about common ancestry, work together to create an evolutionary tree. Also called a phylogenetic tree or a tree of life, this diagram shows how species may be related to each other through physical characteristics, genetics, or character traits. According to Darwin’s theory of evolution by natural selection, all species share a common ancestor. First, have your child choose 12 organisms to include in his or her evolutionary tree, including three aquatic animals, three land mammals, three insects, and three reptiles. Search for photographs of these creatures on the Internet or in old magazines. Get a piece of large poster board, a ruler, glue, and a pencil. This evolutionary tree will focus on the physical characteristics of organisms. Brainstorm with your child different characteristics to use on the tree. Some ideas include: • Presence or absence of a backbone • Presence of hair, fur, or scales • Warm or cold bloodedness • Lungs or gills • External structures such as ﬁns, claws, or hooves • Food preference (omnivore, carnivore, or herbivore) With the poster board in landscape orientation, write “Common Ancestor” at the bottom of the poster board and draw a large “Y” above the term. Leave plenty of room above the “Y” to draw your tree “branches.” Now choose a characteristic for each side of the “Y” (e.g., presence or absence of a backbone). Separate the 12 organisms into two piles according to this characteristic. Now look at the organisms in each group and choose a characteristic to separate each of the two groups into smaller groups. You might ﬁnd that one group, such as the organisms without backbones, cannot be further separated. If this is the case, glue these organisms onto the correct side of the “Y” at the top. For any group(s) that can be further separated, draw a “V” on the correct side(s) of the “Y” at the top. Place the organisms on either side of the “V.” For characteristics such as hair, fur, or scales, you will need to draw an extra line or two on the “V”—one line for each form of the characteristic. Continue with this process until only one organism is left and glue the picture of the organism at the end of the branch. For ideas about how evolutionary trees are drawn and organized, you may want to do an Internet search prior to this activity using the term, “evolutionary tree.” Here are some questions to discuss with your child: • What surprised you the most about the relationships of the organisms in the evolutionary tree? • What surprised you the least? • Do you think an evolutionary tree based on genetic information might look different than the tree based on physical characteristics? Explain your reasoning.

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B6C Common Descent

Reading Science Name:

Date:

Group:

Common Descent: Proof Through Comparative Anatomy 1. Evolution is a theory that describes how different organisms developed and differentiated from ancestors, with all organisms eventually originating from a common ancestor. There is great variety among living species on Earth today. How did this diversity arise? Adaptations are inherited traits that help organisms change to survive in their environments. Adaptations occur slowly over time. Mutations, which are changes in the genetic material of organisms, happen at random throughout a population and add to that population’s genetic variation. It helps promote survival of a population—since a population with a great variety has more hope of surviving a change in environmental conditions. Mutations can be helpful, harmful, or neutral. When a mutation is helpful to an organism, survival is encouraged and the trait is passed down to its offspring. Natural selection favors organisms with favorable adaptations, so they survive and reproduce at higher rates than organisms without favorable adaptations. Eventually, after a long period of time and under the right conditions, a new species may form. 2. Do scientists have evidence that all life forms evolved from a common ancestor? Comparative anatomy is one line of reasoning that indicates that evolution is true. What is comparative anatomy? Comparative anatomy is the study of similarities and differences of the anatomies of various species. 3. One branch of comparative anatomy studies homologous structures. What does your arm have in common with a bird’s wing or a dolphin’s flipper? At first glance, they appear to be very different. They do not have a similar appearance or function. Birds have feathers and wings to help them fly. Humans have skin and hair and arms to help them lift, grasp, and carry. Dolphins have thick, smooth, rubbery skin and flippers to help them swim. However, upon careful examination of bone structure, great resemblances may be noted. Homologous structures are body parts that have a common origin even though they may not perform the same functions. Look at the picture below and note the similarities of the bone structures. Homologous structures make the argument that species are related by a common ancestor.

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Reading Science 4. Homologous structures are important because they are in direct contrast to analogous structures. Analogous structures seem, at first glance, to have much in common. For example, a bird’s wing and a butterfly’s wing seem fairly similar. In truth, the two wings have parallel functions; however, upon closer examination, the structures are extremely different. Both were adapted and developed to achieve similar functions in response to their environments, but they did not descend from a common ancestor.

5. Another method scientists use to compare anatomy is to examine embryos of different species. All embryos of vertebrates share many common skeletal and muscular characteristics. Mammals look even more similar to one another. A calf and a rabbit look almost identical as embryos, even though they appear very different as adults.

6. Even so, all adult vertebrates (and especially adult mammals) share similar formations in their skeletons and muscles. This is more proof that vertebrates descended from a common ancestor. 7. Comparative anatomy is only one way that scientists can demonstrate evidence for evolution. Comparing and contrasting homologous structures and embryo development have shown how vertebrates are structurally similar. This is proof of a common ancestry. The fossil record and DNA evidence are additional lines of evidence that point to the truth of the complex theory of evolution.

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Reading Science 1. What are homologous structures? A Structures that look different but perform similar functions B Structures that look different and perform different functions C Structures with similar forms that perform different functions D Structures from the right side and the left side of the same organism

2. Which of the following pairs demonstrates homologous structures? A Bats and birds B Butterflies and birds. C Bats and butterflies D Butterflies and flying fish

3. Which of the following pairs demonstrates analogous structures? A Bats and birds B Moths and butterflies C Bats and butterflies D Bumblebees and Honeybees

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Reading Science 4. Which embryos would appear most similar during development? A Fish and crabs B Sheep and rabbits C Squid and lions D Shrimp and elephants

5 Why is comparative anatomy important to the scientific community? A It demonstrates how animals that look alike are really different. B It shows what an incredible variety of organisms exist on our planet. C It gathers proof of how organisms are related by a common ancestor, providing evidence for the theory of evolution. D It presents evidence of how organisms are so different that they could not have developed from a common ancestor.

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Math Connections Name:

Date:

Group:

Our fossil records reflect that the rates and patterns of evolution are not constant over geologic time. Species can: a. change very little for long periods of time (evolutionary stasis); b. change very little for a long time, then undergo dramatic change over a relatively short period of time, followed by another long period of little change (punctuated equilibrium); or c. change gradually and sequentially (gradualism).

Megalodon tooth fossil 1. Modern great white sharks, on average, measure 14 feet long and weigh 5,000 pounds, and their teeth measure up to 3 inches long each. The largest ever reported Megalodon (“Meg”) tooth fossil was 7.1 inches long. Set up a proportion using the data from its modern-day cousin, and estimate the size and weight of the prehistoric fish from which it evolved.

2. When archeologists dig for fossils, the location of each fossil must be carefully recorded using a grid method. Solve the following problems to identify the location of each fossil pictured on page 354. Draw each fossil under its corresponding problem. ∕7x+2=−46∕7

2+1∕5x=24∕11

x+5=2+2x

−6x+2=6x−118

2x−¼=−3∕2

−6x−½=−67∕14

−4x+3=7

9+x=6x−21

3x+2∕3=38∕3

−7−2x=−7

−7x+6=¾

8+3x=−2x−32

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Math Connections Use the answer bank to locate the fossil in the grid. Solution

Fossil

x=−10

x=10∕11

x=−1

x=−5∕8

x=10

x=3

x=6 x=4

x=5∕7

x=¾

x=−8

x=0

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B6C Common Descent

Writing Science Name:

Date:

Group:

LOOK

THINK about the fossil record and the evidence it provides for evolution. The fossil record indicates that, over geologic time, species have either stayed the same or changed gradually or suddenly. The theory of punctuated equilibrium states that evolution may not proceed at a regular and steady rate. There are two major types of evolutionary change: stasis and sudden appearance. The fossil record indicates that some organisms exhibit little or no change over a long period of geological time. This is known as “stasis.” Other times, the fossil record contains evidence identifying organisms that are new and fully complex that seem to have no link to ancestors from the fossil record. This is called “sudden appearance.” These two aspects of the fossil record have become a topic of discussion among the scientific community, and several scientific explanations concerning this data have been advanced. WRITE the implications of stasis and sudden appearance within the modern fossil record. Be sure to • clearly state your central idea; • organize your thoughts; • develop your essay in detail; • choose your words carefully; and • use correct spelling, capitalization, punctuation, and grammar.

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B6C Common Descent

Writing Science

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High School Biology

B6D

Natural Selection and Genetic Drift

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B6D Natural Selection and Genetic Drift

Student Handout Name:

Date:

The Gummy Bear Conspiracy Humans have been driven by brain cravings since the beginning of time (Eve, the apple, etc.). The development of candies brought about an evolutionary process that no human could have possibly imagined. The gummy bear community began in the early 1920s. Their origins were thought to be in Eastern Europe, but that is considered a highly biased speculation globally. Eventually, gummy bears realized that human cravings for their sweet little bodies would lead to population issues worldwide. Instinctively, the little fellas had to find ways to adapt and survive. The problem with candies is that they have many appealing qualities to humans. There would be no way to determine from a gummy bear’s standpoint what would be a most delicious trait versus an only mildly appealing yet acceptable tasty treat. Human consumption would lead to the genetic creativity of the gummy bear world. The following data was collected from a global assortment of gummy bears from Europe, China, and the United States. It became obvious that the red gummy bear was the most populated throughout the assortment and orange was clearly the endangered population until two factors came into play. The addition of a rough coat that emits a sour taste shifted the population slightly in favor of orange with an increase of three to five bears. In this case, the red population was reduced by half. The second factor was a larger body size with facial variation. The Albanian bears were larger, and some of them had flat faces while others had pointed noses. The Albanian orange and yellow bears dominated the community. The red population of bears in the community was one-third of its normal population in other areas. All kidding aside, there are serious genetic implications in regards to gummy bears globally. Take your pick from taste and size to color and texture. Consider the genetic concepts of natural selection and genetic drift, which are defined below, and come up with some fun yet accurate possibilities for the gummy bears of the world. Write a brief explanation based on one community of bears and pair share with a partner. Pictures of the different gummy bear populations can be found in the Teacher Printout; each has a label of known origin attached. Genetic drift is the occurrence of a trait increasing or decreasing due to a species leaving more or less offspring with that trait, depending on various situations in the population and environment. Natural selection refers to the fact that organisms better adapted to the environment will survive and most likely produce more offspring over the same species with weaker traits that struggles to survive in the same environment.

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B6D Natural Selection and Genetic Drift

Student Handout My gummy bear population story: Population Origin:____________________________ Traits Observed:

The story of the ____________________ populations of ______________________:

Pair Shift

Genetic Drift

Similarities/DIfferences

Partner 1

Partner 2

Partner 3

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B6D Natural Selection and Genetic Drift

Student Journal Name:

Date:

Group:

Part I: Survival of the Fittest 1. Fill in the table below.

Number of Removed Grains

Number of Replaced Grains

Percentage of Each Colored Grain

Color 1

Color 2

Starting After Trial 1 After Trial 2 After Trial 3 After Trial 4 2.

What did you notice about each trial? What happened with the colored rice grains?

In your own words, describe natural selection.

What does survival of the fittest mean?

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B6D Natural Selection and Genetic Drift

Student Journal 5.

Graph your results below.

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B6D Natural Selection and Genetic Drift

Student Journal Part II: Getting the Genetic Drift

Generation 1

Generation 2

Generation 3

Ratio _________________

Generation 4

Generation 5

Ratio _________________

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B6D Natural Selection and Genetic Drift

Student Journal Part II: Getting the Genetic Drift, continued 1.

How did the ratios of red beans to black beans change between the starting population and the five generations?

How would genetic diversity be affected if, by chance, all red beans or all black beans were selected?

Does this simulation demonstrate genetic drift? Why or why not?

In your own words, how would you define the founder effect in terms of genetic drift?

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B6D Natural Selection and Genetic Drift

Student Journal Reflections and Conclusions 1.

Why are mutations considered the raw materials for natural selection?

How does genetic drift affect genetic variation? Why does it affect only small, isolated populations?

Do you think genetic drift in the human population is more or less common in the 21st century? Explain your answer.

Explain how a species, other than humans, might experience genetic drift. What effect might this have on both the local population and the species as a whole?

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STEMscopedia: NATURAL SELECTION AND

GENETIC DRIFT

Reflect

B6D

Suppose you are standing outside on a beautiful spring day, taking in the sunshine and observing the surrounding wildlife. After doing this all season and again the next, you notice a change. There are less red ladybugs compared to yellow ones. You may begin to wonder if that is a coincidence, or whether it is evolution occurring right before your eyes! You begin to wonder what other small changes in the flora and fauna around you are occurring. What is causing the changes? Is this change the reason we have so much diversity on the planet? It is estimated that approximately 8.7 million species of eukaryotes and about 10,000 species of prokaryotes live on Earth today, according to a 2011 study. This report also suggests that 86 percent of all species on Earth and 91 percent of all species in the ocean have not been classified yet. What led to this incredible diversity of species on Earth? This is an example of microevolution, evolution on a small scale. The process of evolution, or genetic change over time, has resulted in the wide variety of living things that make their home on this planet. Scientists describe five mechanisms that drive evolution-causing populations to change over time. These mechanisms are essentially how evolution “works”: natural selection, mutation, genetic drift, gene flow, and recombination. Let’s take a look at each of these patterns to learn more about how they contribute to genetic changes in populations. Natural Selection and Mutations The first scientist to suggest the concept of evolution was fascinated by the similarities and differences in organisms. Naturalist Charles Darwin was an explorer who spent five years aboard a ship, HMS Beagle, traveling across the world from his native Britain. As he went, he described every species that he came across, ultimately cataloging them in his book, The Zoology of the Voyage of HMS Beagle. Darwin introduced the theory of evolution by natural selection in 1859. He suggested that all species descended from one common ancestor and claimed that organisms diversified, or evolved, through a process called natural selection. In natural selection, organisms with characteristics that are well suited for their environment tend to survive and reproduce. When they reproduce, they pass their characteristics on to their offspring through genes. Organisms with characteristics that are not well suited to their environment are not as likely to survive to reproduce and pass on their characteristics.

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STEMscopedia: NATURAL SELECTION AND

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The “selection” in natural selection refers to the selective pressure the environment places on populations of organisms. The environment cannot support all of the individuals in a population. There may not be enough food, space, or water for everyone, and predators kill members of the population. These factors place pressure on the population. The organisms that are well adapted to the environment are, in a way, “selected” by the environment to survive. Scientists have been able to observe natural selection in action on the Galapagos Islands. When a drought occurred, researchers noticed that the characteristics of the local finch population changed. The drought caused the finches’ food source, seeds, to become dry and tough. The researchers observed that finches with large, strong beaks were better able to crack open the seeds than finches with small, weak beaks. The finches with large, strong beaks survived to reproduce and passed on genes for large, strong beaks to their offspring. Fewer finches with small, weak beaks survived. Over time, the population changed to include more finches with large, strong beaks than finches with small, weak beaks. Mutations generate the raw material for natural selection. A mutation is any change in the sequence of DNA in a cell. Mutations can be harmful, beneficial, or neutral, meaning they have no effect on the organism in which the mutation occurs. Mutations occur at random. According to Darwin, when an individual is born with a beneficial mutation, that individual will be more likely to survive than others without the mutation, a principle called “survival of the fittest.” The beneficial mutation will likely be passed on to the next generation.

Look Out Natural selection does not result in the “best” organisms. Organisms only need to be “good enough” to survive and pass on their genes. For example, consider the finches described above. A finch’s beak only had to be large and strong enough to open the dry, tough seeds. As long as it could still get food, the bird could survive. It didn’t matter if it had the largest and strongest beak of all the other finches as long as its beak was large and strong enough. Mutations are random. They do not occur as the result of a “need.” For example, if an organism’s environment suddenly turns much colder than it was before, its DNA will not simply generate a mutation that results in thicker fur. A mutation may naturally arise that results in thicker fur, but an organism cannot generate a mutation for a specific purpose.

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STEMscopedia: NATURAL SELECTION AND

GENETIC DRIFT

Genetic Drift Genetic drift is another mechanism of evolution resulting in population change. In contrast to natural selection, which favors certain traits, genetic drift is a random process. Genetic drift refers to the idea that specific traits, controlled by alleles on a chromosome, can become more or less common in a population completely by chance. This process can change the diversity of a species, particularly in small populations. As the population gets smaller, the random elimination of a few individuals could eliminate a trait altogether if no other individuals happen to have the trait to pass it on to the next generation.

alleles: different forms of a gene that can occur in an individual

Consider the diagram of frogs shown here. Suppose that a chance occurrence, such as a temporary drought, happens to kill the three brown frogs in the population. The brown frogs do not survive to pass on their traits to the next generation. As a result, the brown allele for skin color is lost from the population. The diversity of the population of frogs has decreased. Discover Science: Cuckoo Bees and Genetic Drift in Action Evolution and the mechanisms that drive it can be difficult for scientists to observe because they typically occur over long periods of time. The small, isolated populations found on island ecosystems can provide an opportunity to see these mechanisms in action. For example, five new species of cuckoo bees were recently discovered in the Republic of Cape Verde, an island nation off the coast of West Africa. Cuckoo bees, much like cuckoo birds, lay their eggs in the nests of other bee species. When the cuckoo bee larva hatches, it eliminates the host’s eggs and consumes the food resources in the nest. One of the recently discovered species, Chiasmognathus batelkai, is a giant in comparison to the other species in its genus (though it is still quite a small insect). Scientists theorize that its relatively massive size is a result of genetic drift. Gene Flow Gene flow is the movement of alleles into and out of populations. It can either increase or decrease the genetic diversity of a population. Genes may be added to the gene pool of a population when individuals enter that population (immigration). In contrast, genes may be removed from the gene pool of a population when individuals leave that population (emigration).

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Peppermint is a cross between spearmint and watermint plants.

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What Do You Know? Many farmers and gardeners rely on gene flow to produce hybrids. Hybridization is the act of bringing two species together with different traits to produce offspring that have both traits. Think back to the change in ladybug color you noticed around your home. Knowing what you know now, predict what patterns may have caused the change you noticed? Recombination Recombination is the process by which genetic material from different individuals becomes combined during sexual reproduction and some forms of asexual reproduction. Recombination can result in enormous diversity in species. Through sexual recombination, alleles are shuffled and produce multitudes of new combinations within every generation, and organisms are able to generate millions of new allele combinations in their gametes (sex cells). During prophase 1 of meiosis, sections from one arm of a homologous chromosome break off and cross over to the matching section on the corresponding homologous chromosome. This act of crossing over dramatically widens possibilities for new gene combinations when egg and sperm come together to form a zygote.

This diagram shows crossing over between homologous chromosomes.

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STEMscopedia: NATURAL SELECTION AND

GENETIC DRIFT

Try Now Read the descriptions of concepts in the left column below. Match each description with the correct term in the left column. (Please make a chart for the following info)

Terms:

Concepts:

Genetic drift

•

Genetic material breaks and trades places with other genetic material

•

An allele is eliminated from the population entirely by chance

•

The movement of alleles into and out of a population

•

Produces the raw material for natural selection

•

An organism survives and reproduces because of inherited characteristics that make it well suited to its environment

Natural selection Crossing over Gene flow Mutation

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STEMscopedia: NATURAL SELECTION AND

GENETIC DRIFT

Connecting With Your Child Illustrating Patterns of Change in Populations To help your child learn more about population changes (evolutionary mechanisms), have him or her create a digital slideshow presentation that includes illustrations of the five mechanisms of biological evolution: natural selection, genetic drift, gene flow, mutation, and recombination. The illustrations of the mechanisms of biological evolution should each include a description, an illustration or diagram, and a specific example. If you do not have access to digital resources to create the slideshow presentation, your child can use cardstock paper and colored pencils to create a “mock” slideshow. It should include five quiz questions about the material in the presentation. Have your child present the slideshow. When finished, try to answer the quiz questions. Here are some questions to discuss with your child: 1. How are mutations and natural selection related? 2. Why does genetic drift have more of an effect on small populations? 3. How is genetic drift different from gene flow? 4. Why is it difficult for scientists to study the mechanisms of evolution?

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B6D Natural Selection and Genetic Drift

Reading Science Name:

Date:

Group:

Bottleneck Effect and Founder Effect 1.

Evolution is the process by which organisms adapt to changing environmental conditions over an extended period of time. Genetic drift, natural selection, crossing over, gene flow, and mutations are all components of evolution. Genetic drift happens entirely by chance in a relatively quick period of time. Rapid, sometimes violent, changes in environmental conditions may cause extreme alterations to populations of organisms. Random events can cause certain alleles to be permanently exterminated from populations. Genetic drift is more likely to result in the disappearance of alleles in a population if the population is small. There are two types of genetic drift: bottleneck effect and founder effect.

A population bottleneck (or bottleneck effect) happens when there is a sudden, unexpected event. The population is reduced to a fraction of its original population. The variety of alleles left is much lower than the alleles of the population before the catastrophe struck. Thus, genetic variation is greatly reduced, which leaves the population vulnerable to further reduction since variation is one of the characteristics that allow populations to survive changes in their ecosystems.

Imagine that there was a bottle of mixed nuts containing peanuts, cashews, pecans, walnuts, almonds, pistachios, and macadamia nuts. You shake a handful of nuts into your hand before a couple of large macadamia nuts converge and plug the neck of the bottle and the rest of the nuts are trapped. All that is left of the “population” of nuts is in your hand. A few almonds, two pistachios, three cashews, and two pecans are the only nuts that made it out of the bottle. By random chance, no peanuts, walnuts, or macadamia nuts were in the handful. This is a simulation of the bottleneck effect.

What kinds of events can cause a population bottleneck? Natural causes include disasters like forest fires, floods, droughts, earthquakes, and volcanic eruptions. Humans can also cause population bottlenecks through deforestation, overhunting, and taking over organisms’ habitats for development. One well-known, real-life example of the bottleneck effect occurred in the 1800s when northern elephant seals were hunted almost to extinction. Although the population later rebounded from less than two dozen seals to over 30,000 seals, the genetic variation in this population is far lower than it was before the seals were hunted.

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B6D Natural Selection and Genetic Drift

Reading Science 5.

The founder effect occurs when a small group breaks off from the main group and establishes a new population. The small group may possess alleles that exist frequently in the new population but were uncommon in the main group. In fact, the newly founded group may not have had any alleles at all that were dominant in the original group.

Pretend a group of 12 families (composed of 48 individuals) purchased an island in the Caribbean to live the “simple life.” They did not let anyone else on their private island. Forty of the family members had blue eyes, four had green eyes, and four had brown eyes. The families live successfully in isolation on the island, and several generations are born. Most of the individuals in the successive generations also have blue eyes, even though brown eyes were much more common in the population where the 12 families originated.

A real-world example of the founder effect happened during the 1980s on one of the Galapagos Islands. Finches had a pattern of stopping for rest on the island but never stayed to lay eggs and raise young. In 1982, five finches randomly stayed on the island to reproduce. The founder birds and then their offspring had measurably larger beaks than the main population of finches that did not remain to breed on the island. This change in the size of beaks was so rapid that it must have come from the genes of the founder birds, which just happened to have larger beaks, rather than slow adaptation and natural selection.

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B6D Natural Selection and Genetic Drift

Reading Science 1.

What could cause genetic drift? A.

Earthquakes

Floods

Overhunting

All of the above

Which of the following is an example of the founder effect? A.

A small group separating from a larger group and starting their own population

A large population with many different alleles

A small population with a large variety of alleles

A group that becomes extinct because there are not enough to survive

What is true of genetic drift? A.

Genetic drift happens slowly over millions of years.

Genetic drift happens quickly with a sudden event.

Genetic drift only happens when natural disasters strike.

A group becomes extinct because there are not enough organisms to survive.

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B6D Natural Selection and Genetic Drift

Reading Science 4.

Which is NOT an example of the bottleneck effect? A.

Northern elephant seals being hunted almost to extinction

Antibiotic-resistant bacteria

Two squirrel populations interbreeding

A tsunami hitting a remote island and wiping out 95 percent of the population

Which of the following can be a result of genetic drift? A.

Genetic variation decreases.

Genetic variation increases.

New species are created within a few generations.

Populations must interbreed with other species to survive.

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B6D Natural Selection and Genetic Drift

Math Connections Name:

Date:

Group:

Applying the Hardy-Weinberg Principle The Hardy-Weinberg principle is often used to test whether evolution is occurring in a population. The Hardy-Weinberg equilibrium states that, at a locus with two alleles, the three genotypes will appear in the following proportions: p2 Expected frequency of homozygote 1 (dominant) 1.

2pq

Expected frequency of heterozygotes

q2 Expected frequency of homozygote 2 (recessive)

Fill in the missing values in the Hardy-Weinberg diagram below. Hardy-Weinberg Principle Parent Generation Phenotype

Genotypic Frequency

.49

.42

.09

Number of Individuals (total=500)

245

210

Number of alleles in gene pool (total=1,000)

Y=490+210=700

Allelic Frequency Hardy-Weinberg Analysis

(700Y/1,000) = 0.7 = p

p(0.7)

q(0.3)

2pq

p(0.7)

q(0.3)

p2=0.49

pq=0.21

q2=0.09

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Predicted Predicted Predicted frequency frequency frequency of YY of yy of Yy offspring offspring offspring 485

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B6D Natural Selection and Genetic Drift

Math Connections Use the Hardy-Weinberg principle to help you answer the questions below about the following scenario: In plants, violet flower color (V) is dominant over white (v). If p = 0.8 and q = 0.2 in a population of 500 plants: 2.

How many individuals would you expect to be homozygous dominant (VV)?

How many individuals would you expect to be heterozygous (Vv)?

How many individuals would you expect to be homozygous recessive (vv)?

How many plants would you expect to have violet flowers?

How many plants would you expect to have white flowers?

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B6D Natural Selection and Genetic Drift

Writing Science Name:

Date:

Group:

LOOK

THINK about the factors involved in the formation of new species. Evolution is the process by which organisms are descended from organisms of the past. Earth is filled with organisms of many different shapes, sizes, and habitats; this is called biological diversity. Charles Darwin, through observations and evidence, proposed a hypothesis to explain the way life changes. The theory of natural selection scientifically explains how living things evolve over time. Darwin saw vast amounts of evidence that pointed towards natural selection being a mechanism of evolution. Since Darwin’s time, several pivotal studies have supported natural selection as a means of organism evolution. The formation of new species, called speciation, can be caused by natural selection. A species is a group of organisms that breed with one another and produce offspring that is fertile, or able to continue reproduction. These populations of individuals share genes, but as genetic changes happen, new genes are spread through new offspring. As the gene pools continue to separate, new species evolve, and reproductive isolation occurs. This means that two or more populations of species are incapable of breeding and producing offspring. Through isolating mechanisms, such as behavioral, geographic, and temporal isolation, reproductive isolation occurs. WRITE the process of speciation. Be sure to • clearly state your central idea; • organize your thoughts; • develop your essay in detail; • choose your words carefully; and • use correct spelling, capitalization, punctuation, and grammar.

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B6D Natural Selection and Genetic Drift

Writing Science

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High School Biology

B6E

Biological Resistance

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B6E Biological Resistance

Student Journal Name:

Date:

Group:

Biological Resistance 1.

What is your prediction about the surviving normal bacteria and the surviving resistant bacteria?

Fill in the table below.

Start of Generation

Normal Bacteria

Dead

Survivors

Reproduction

Resistant Bacteria

Generation 1 Generation 2 Generation 3 Generation 4 Generation 5 3.

Graph your results on the next page.

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B6E Biological Resistance

Student Journal Biological Resistance, continued

How did the proportions of normal bacteria and resistant bacteria change over time?

If you were to do this activity for another five generations, what do you think would happen to the populations of each type of bacteria?

How does natural selection play a role in biological resistance in these bacteria populations?

Why do you think the level of antibacterial resistance has risen recently?

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STEMscopedia: BIOLOGICAL RESISTANCE B6E

Reflect Your class is taking a virtual field trip today since the weather is not good for an on-location trip. Your trip begins in the mountains of Georgia. As you begin your virtual hike at a lower level of the mountain, you notice a lot of greenery such as shrubs, trees, grass, and undergrowth. When the camera zooms in, you see many animals, both small and large, living in the area. You see a lot of different birds overhead, including vultures circling. You watch as large and small lizards catch insects to eat. There are so many different animals here. Looking inside the soil, you see many worms, larva, and even ants teeming around the tunnels. You see so many different variations among the species and begin to wonder if there had been more before now. Earth has such an amazing diversity of species. What causes this diversity? Do species change over time? If so, how?

species: a group of organisms that can interbreed and produce viable, fertile offspring

abiotic: factors that are neither living nor produced by living things

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biotic: factors that are living or produced by living things

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STEMscopedia: BIOLOGICAL RESISTANCE One element that changes the diversity of a species is biological resistance. Within biological resistance are several elements that come into play. These elements can be abiotic or biotic causes. Natural Selection The amazing diversity of species on Earth is due in part to a process called natural selection. First described by the scientist Charles Darwin in the 1850s, natural selection is a process by which populations change over time as those organisms with traits best suited for their environment survive and pass their genes on to the next generation. Let’s closely examine how this process works. Organisms have inherited characteristics, or traits. Genes control these traits, and parents pass their traits on to their offspring through genes. Some traits help an organism survive, find a mate, protect itself, or locate food and shelter.

The change in a population or species over time is called evolution. An individual organism cannot evolve in its lifetime, and natural selection does not act on individuals but on populations. evolution: a species comes from a preexisting species and their characteristics are due to their adaptable ability over successive generations traits: inherited characteristics of an organism

Look Out You wonder how living organisms continue to survive with all the environmental changes throughout time. Organisms reproduce on a regular basis. In doing so, their genes are passed on throughout generations. When environmental changes happen, such as pesticides sprayed to prevent insect attacks from harming the growth of plants, some of the organisms will die. Others will be strong enough to survive the pesticide. This happens if the same pesticide is used over and over on the same pests. The gene pool changes. These pests that survive will adapt to the pesticide and pass on this genetic change to the next generation, until eventually they will be resistant to the pesticide.

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STEMscopedia: BIOLOGICAL RESISTANCE These pests are stronger than their ancestors, and the next generation will evolve to be stronger than the previous. When a new pesticide is used, the cycle begins again. Some will survive, and the survivors will be strong and genetically changed to continue to resist the new pesticide as they reproduce. Antibiotics and influenza vaccines can also evolve over time. Antibiotics are used to fight bacteria. As in pesticides, some bacteria are genetically stronger than others and will survive the antibiotic. If a person is repeatedly sick with the same infection, and he or she is given the same antibiotic, the bacteria will become resistant to the antibiotic and the gene pool becomes stronger. Every year, new antibiotics are created to fight a stronger strain of bacteria or influenza because the illness is resistant to the older antibiotics or “flu shots.” What Do You Do? Suppose you see a huge peanut farm on your virtual hike. It’s growing on the side of the mountain. You then see something eating part of the peanuts. The other half of the peanuts have leaves that are turning yellow. What do you think is happening to this farm? Why do the leaves have holes and “chew” marks on them? Why do some have yellow leaves? Looking back to what you have learned, think about pests and disease. Could the peanut plants have armyworms or a leaf fungus? What do you need to do? Will it change the gene pool if you use a pesticide to get rid of the armyworms and a fungicide to get rid of the leaf fungus? Over the next several generations, the genetic makeup will get more resistant to the pesticide/fungicide the more it is used. Are there advantages/disadvantages to biological resistance? Discuss this with your study buddy and then make an argument for/against it to your class.

Look Out The discovery of antibiotics in 1928 changed human medicine forever. Antibiotics are medicines that kill bacteria. Patients take antibiotics to treat various infections caused by bacteria. However, the overuse and misuse of antibiotics have created a problem. Some bacterial populations are becoming resistant to antibiotics. In other words, the antibiotics do not destroy these bacteria as successfully as they once did. In any given bacteria population, there may be a few individuals that have the trait related to antibiotic resistance. These are called “resistant” bacteria.

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STEMscopedia: BIOLOGICAL RESISTANCE If a person does not take antibiotics, the bacteria living in that person’s body do not experience antibiotics in their environment. In that case, the few resistant bacteria will not have any advantages over “nonresistant” bacteria and will not reproduce more than others. As such, this trait for resistance to antibiotics will not be “favored” and passed on to offspring over time. In other words, the bacteria population will not adapt to become resistant to antibiotics. If a person does take antibiotics, the resistant bacteria will survive and reproduce, while the nonresistant bacteria will die. If this process continues, eventually most of the bacteria population will have the trait for antibiotic resistance. If antibiotics are taken rarely, the population will not have time to adapt to the antibiotic resistance and the bacteria will be killed. The more often antibiotics are taken, the more chances the bacteria have to adapt and develop resistance.

Connecting With Your Child Help your child learn more about biological resistance. Together, talk about a virtual hike through a forest, a farm, woodlands, etc. See if you can locate one in your area on your computer. Then look for one you can visit and hike when the weather is pleasant. See if you can pick out plants and animals on your real hike as well as your virtual hike. Watch the YouTube video https://www.youtube.com/watch?v=_PwQwcTm2vw, which shows crop dusting. Discuss with your child if this is good for the crops. What would happen if they did not spray the vegetation? Over the next several years, will the insects or fungi become resistant to the pesticide/fungicide used. What will need to happen then? Then watch the video about bacteria vs. antibiotics: https://www.youtube.com/watch?v=znnp-Ivj2ek. This video explains how bacteria can become antibiotic resistant. These two videos will get your child thinking about the issues. Help your child think of ways to solve some of these biological resistance problems in our world. Who knows—maybe your child will become a scientist!

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B6E Biological Resistance

Reading Science Name:

Date:

Group:

Pesticide Resistance and Evolution 1.

Farmers lose a significant percentage of their crops to insect pests before harvest. Pesticides are commonly used to reduce the loss. However, insects develop resistance to pesticides over time. Pesticide resistance involves two strategies: breaking down the toxin, or having the ability to tolerate its effects. Some insects develop resistance faster than others. Evolution has provided these insects with a genetic head start.

Take, for example, the Colorado potato beetle (Leptinotarsa decemlineata). Colorado potato beetle adults overwinter in the soil. After emerging in the spring, they feed on potato shoots, where they mate and lay eggs. The eggs hatch, and larvae feed on the potato plants until they mature through several molts. Mature larvae drop into the soil and pupate into adults. Depending on the location, two to three generations of beetles occur per year.

Before the advent of potato fields, Colorado potato beetles fed on a variety of host plants from the nightshade (Solanaceae) family. In addition to potatoes, these include common nightshade, tomato, and belladonna. Plants in this family produce two related phytotoxins, solanine and chaconine. Depending on the concentration of toxins in the plant, even large herbivores such as cows and horses can be affected.

In mammals as well as insects, messages are transmitted from nerves to muscles using the molecule acetylcholine. Acetylcholine is broken down very quickly by an enzyme. Inhibitors of the enzyme increase the amount of acetylcholine and how long it is present, leading to tremors, convulsions, and paralysis. Solanine and chaconine inhibit the enzyme. The enzyme present in Colorado potato beetles is much less sensitive to these naturally occurring phytotoxins.

Certain pesticides used by humans also target the enzyme. Insects that have evolved to resist the phytotoxins are already less sensitive to the pesticide. Within a given population, some beetles will be even more resistant due to mutations in the enzyme. These will be more likely to survive and reproduce, thus increasing resistance in subsequent populations.

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B6E Biological Resistance

Reading Science 1.

Farmers use pesticides to __________. A.

prevent crop loss before harvest

increase the number of beneficial insects

fertilize their crops

assist insect evolution

Potato plants are food for Colorado potato beetle’s __________. A.

eggs and larva

larva and adults

pupa and adults

eggs and adults

Diazoxon inhibits the enzyme that breaks down acetylcholine. What is the expected effect of diazoxon on adult insects? A.

Increased fertility

Smaller body size

Faster and farther flight

Tremors and paralysis

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B6E Biological Resistance

Reading Science 4.

What mechanism do Colorado potato beetles use to resist phytotoxins? A.

They don’t eat plants that produce large amounts of toxins.

They break down the toxins before they are harmed.

They produce an enzyme that is less sensitive to toxins.

They eat only at night when the toxins are less poisonous.

June bugs are beetles that feed mostly on plants without phytotoxins. Which of the following statements best describes their expected sensitivity to pesticides and their ability to evolve resistance? A.

They are highly resistant and evolve resistance quickly.

They are highly resistant but evolve resistance slowly.

They are highly sensitive but evolve resistance quickly.

They are highly sensitive and evolve resistance slowly.

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B6E Biological Resistance

Math Connections Name:

Date:

Group:

A highly controversial branch of biotechnology is genetically modified (GM) foods. From seedless oranges and watermelons to the enzymes used to make bread, genetically modified food is all around us and readily available in stores. There have been many arguments in support and against GM foods. The science of GM food is still relatively new and consistently improving; however, the effects from eating GM food are still being discovered. Read and work through the following problems to decide if you are for or against genetically modified foods. Use scientific notation when necessary to ease calculations. Benefits: 1.

Pest Resistance-

Crops can be genetically modified to resist pests that attack crops. The chemical is introduced into the genetic make-up of the plant. As a result, the need for spray pesticides in the U.S. has dropped by 1.13 x 106 kg per year. •

If U.S. farmers used 4.8 x 108 kg in 2013, how many pounds will they use in the year 2020?

•

What is the percent decrease?

Disease Resistance-

The cassava plant serves as a main food staple in many African countries. The crop is easily susceptible to a disease called mosaic virus. Genetically modified cassava plants could be engineered to withstand and fight off the mosaic virus. •

If every person in Africa eats about 80 kg of cassava per year, how many kilograms of cassava needs to be harvested to feed 1.1 billion people?

•

If 1 ton = 907 kg, how many tons will need to be harvested?

•

About 1.18x108 tons of cassava are produced in Africa annually. If half of the crop is lost due to mosaic virus, how many people will not have enough to eat?

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B6E Biological Resistance

Math Connections 3.

Nutrition-

Genetically modified foods yield higher crop production and can be engineered to contain more nutrients and minerals like iron, Vitamin A and iodine. A strain of rice the has been engineered with these nutrients have helped more than 100 million children worldwide. People in underdeveloped countries suffering from lack of nutrition could benefit from the added nutrients and heartier plants. •

The world’s production of corn is about 5.71 x 108 tons per year. The European corn borer (an insect) destroys about 7% of the world’s corn crop. How much of the crop is destroyed?

•

If the average caloric intake for one person is equivalent to 0.667 tons of corn, how many people could be fed from the amount of corn destroyed?

Pharmaceuticals-

“Pharming” is a method of genetically modifying plants and animals to carry genes for useful production of pharmaceuticals. Bioengineers have engineered goats to produce as much antithrombin (used to prevent blood clots) in one year as from 90,000 human blood donations. •

How many blood donations can a herd of 200 take the place of?

•

About 1 in 5,000 people will develop a need for drugs made with antithrombin. In the U.S. population of 313.9 million people, how many will need a drug made with this protein?

Based on the benefits listed above, what do you think about the need for genetically modified food?

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B6E Biological Resistance

Math Connections Cautions: 6.

Unintended Harm to Nature –

Crops genetically modified to resist herbicide (weed killer) have resulted in a strain of resistant weeds. Instead of decreasing the need for herbicide on crops, it increased the need. From 2003 to 2008, the amount of herbicide used in the U.S. increased from 2.785x108 lbs to 3.304x108 lbs. •

What was the rate of increase per year?

•

If the amount of herbicide used continues to increase at the same rate, how much will be used in the year 2015?

Contamination to Food Supply-

In 2002, a company producing pharmaceutical corn unknowingly contaminated other crops in Nebraska and Iowa through cross pollination of the crops. They were growing the crop in an openair farm. As a result, 155 acres of corn and 500,000 bushels of soybeans had to be destroyed. •

If the corn crop was valued at $17,400 per acre, how much money was lost?

•

What additional information would be useful in assessing the level of risk to humans from this contamination?

Small Farmers Forced Out of Business-

While certain crops have been engineered to increase yields, the cost of genetically engineering these seeds are passed on to the farmers. The data below show the cost difference in planting GM vs. Non-GM corn seed. 1 acre of Herbicide crops Non-GMO 32.50 Corn GMO Corn 32.50

Pesticide

Fertilizer

Insurance

Rent

Seed

15.00

184.00

42.00

350.00

57.45

15.00

184.00

42.00

350.00

138.30

Total

•

What is the difference in cost per acre?

•

How much money would a farmer save by planting 1000 acres with Non-GM Corn seed?

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B6E Biological Resistance

Math Connections 9.

Unknown Human Health Risks-

Genetically modified soybeans are grown on about 91% of U.S. soybean fields. These seeds are modified to withstand the Roundup herbicide sprayed on plants to prevent weeds. In a study done in Russia, hamsters were fed the GM soy and compared to control groups. The results from the study are shown in the chart below. Group Control - No Soy Diet Non-GM Soy Diet Low GM Soy Diet High GM Soy Diet

Number of Pups 52 78 40 16

Deaths 3 4 10 3

•

Fill in the column in the chart with the percent of deaths to pups born.

•

What do you notice about the data?

•

What could this potentially mean for humans?

Mortality Rate

10. Based on the benefits and cautions about GM foods, what is your opinion about GM foods?

11. What additional information could be helpful to you in forming an opinion?

504

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B6E Biological Resitance

Writing Science Name:

Date:

Group:

LOOK

THINK about how natural selection can lead to changes in an organism’s ability to survive. WRITE Explain how natural selection can lead to bacteria becoming resistant to antibiotics. Be sure to • clearly state your central idea; • organize your thoughts; • develop your essay in detail; • choose your words carefully; and • use correct spelling, capitalization, punctuation, and grammar.

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B6E Biological Resistance

Writing Science

506

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abiotic factors

GLOSSARY OF TERMS asexual reproduction

abiotic factors – nonliving factors that affect the ecosystem, such as light, space, temperature, shelter, water, and soil composition

anaphase – the phase of mitosis in which spindle fibers begin to shorten, separating the sister chromatids and pulling them to opposite ends of the cell

active transport – the movement of substance across animals – multicellular the membrane that requires the eukaryotic organisms in kingdom Animalia use of energy; moves against the concentration gradient antibiotic resistance – the agriculture – the science, art, ability of a bacterium to and business of cultivating soil, withstand the effects of an antibiotic producing crops, and raising livestock archaebacteria – single-celled prokaryotic organisms in the allele – a single, distinct kingdom Monera version of a gene analogous structure – various structures in different species that have the same appearance, structure, or function but have evolved separately and do not share common ancestor

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asexual reproduction – the reproductive process that involves one parent and produces offspring identical to the parent

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binary fission

GLOSSARY OF TERMS

binary fission – a form of a asexual reproduction where a single-celled organism replicates its DNA and divides into identical cells

carbohydrate

biotechnology – the use of living systems and organisms to develop or create useful products or processes biotic factors – factors that are living or produced by living things

binary fission – a type of asexual reproduction in which one cell divides to form two identical cells, such as it occurs budding – a type of a sexual reproduction in which an in prokaryotic cells offspring grows out of the parent organism biochemistry – branch of science that studies the chemical and physicochemical calvin cycle – a set of reactions by which energy processes that occur within captured previously from living organisms sunlight is used to make glucose from carbon dioxide biodiversity – the sum of the different forms of living things in and water a given area or population carbohydrate – a biomolecule containing hydrogen, carbon, biodiversity – the variety and oxygen in a 1:2:1 ratio and or range of life within an is used as a primary energy ecosystem or for the entire source planet

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carbon cycle

GLOSSARY OF TERMS

chemical reactants

carbon cycle – the continuous movement of carbon among the abiotic environment and living things

cell reproduction – the process by which a single cell divides into two daughter cells

cell – the basic structural and functional unit of living organisms

cellular respiration – the process of obtaining energy from the breaking of chemical bonds in nutrients

cell wall – a tough, protective barrier that surrounds the outer carrying capacity – the maximum number of organisms membrane of some types of cells an ecosystem can support

cell cycle – the process by which cells grow and divide to produce more cells cell division – the production of two daughter cells from a single progenitor cell

cellular respiration – the process by which cells use electron transport chains to transfer the energy in nutrient molecules to the chemical bonds of ATP

cell membrane – a lipid barrier cellular transport – he movement of materials across that encloses the cytoplasm cell membranes and controls what enters and exits the cell chemical reactants – a substance that takes part in and undergoes change during a reaction © Accelerate Learning Inc. - All Rights Reserved

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chemical reaction

GLOSSARY OF TERMS

chemical reaction – a substance that takes part in and undergoes change during a reaction chemical reaction – processes in which one or more chemical substances are transformed into different chemical substances without changing the nuclei of the atoms

comparitive morphology

climate change – long-term change in the prevailing weather patterns clone – an organism that is genetically identical to its progenitor codominance – a form of allelic interaction in which both alleles are equally expressed in a heterozygous

chloroplast – a membranebound organelle in plants that is the site of photosynthesis

common ancestry – when organisms are descended from a single ancestor

cladistics – a classification system based on shared characteristics between groups of organisms and their common ancestor

common descent – the concept that all life on Earth is descended from the last universal ancestor

cladogram – A branching diagram representing a hypothesis about the evolutionary descent of groups of organisms from a common ancestor 510

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comparative morphology – the analysis of patterns of the locus of structures within the body plan of an organism; this forms the basis of taxonomical categorization © Accelerate Learning Inc. - All Rights Reserved

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concentration

GLOSSARY OF TERMS

concentration – a measurement of the amount of solute that is dissolved in a given quantity of solvent

domain

diffusion – the movement of particles from an area of higher concentration to an area of lower concentration; does not require energy; the particles will continue to move until they are evenly dispersed

concentration gradient – the process in which particles move through a solution/gas dihybrid cross – a genetic from an area with a higher number of particles to an area cross between two parents with a lower number of particles that are each homozygous for alternative alleles of two cytokinesis – the division of dominant-recessive traits the cytoplasm into two separate cells during cellular replication divergence – when a population of species diverges cytoplasm – the jelly-like into two or more descendant material inside the outer subspecies, resulting in once membrane of a cell that holds similar species but becoming the nucleus, organelles, and more and more dissimilar other components of the cell dna – contains information that deletion – a mutation in which forms the hereditary material of a part of a chromosome or a all cells sequence of DNA is missing domain – a classification that is larger than a kingdom

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dominance

GLOSSARY OF TERMS

dominance – a form of allelic interaction in which both alleles are equally expressed in a heterozygous individual dominant – an allele that is always expressed

energy

electron transport chain – the transfer of electrons through a series of electron donors and acceptors, which is coupled to the transfer of protons across a membrane, creating a proton concentration gradient that is used to produce ATP

ecoystem – a system comprising all the biotic and embryology – the study of abiotic factors in an area and the similarities and differences all the interactions among them in the stages of embryonic development amongdifferent ecosystem – a system species consisting of all the interactions that occur between the abiotic emigration – to leave one’s and biotic factors within an country or region for another environment endosymbiotic theory ecosystem – the environment – states that several key and all of the populations in an organelles found in eukaryotes area and all of the interactions originated as a symbiosis among them between separate single-celled organisms

energy – controls the amount of change that can occur within a system; without enough energy, change cannot occur 512

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energy flow

GLOSSARY OF TERMS

energy flow – the flow of energy between organisms in an ecosystem energy pyramid – a representation of an ecological community showing the total amount of energy contained within each trophic level

fossil

expression – the process by which genetic information generates a specific protein or trait fertilization – the combination of male and female gametes to form a new individual organism

eubacteria – prokaryotic cell, lacking a nucleus, commonly referred to as “true bacteria”

food web – overlapping food chains with different pathways for the flow of food energy in an ecosystem

evolution – change in the frequencies of alleles in a population over time

forensics – application of biological sciences to the law and crime enforcement

fossil – preserved parts or exocytosis – the transport traces of animals and plants of material out of a cell by means of a sac/vesicle that first that lived in the past swallows the material and then exits through a gap in the cell membrane

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fossil record

GLOSSARY OF TERMS genetically modified organisms

fossil record – the mineralized remains of organisms and the rock layers in which they are found that show when and where long-dead organisms lived and how their bodies were structured fungi – eukaryotic organism that includes microorganisms such as yeast, mold, and mushrooms gel electrophoresis – a technique used in DNA fingerprinting and other processes in which molecules migrate through a gel (such as a polyacrylamide gel) and separate into bands according to size

gene – a sequence of DNA that encodes a functional molecule and occupies a specific location on a chromosome gene flow – the transfer of alleles or genes from one population to another genetic drift – the change in the frequency of an allele in a population due to the random change survival of certain organisms within the population genetic variation – the reproductive process involving two parents whose genetic material is combined to produce a new organism different from themselves

gene – a segment of DNA that contains specificinstructions for building a functional molecule; the basic unit of heredity

genetically modified organisms (GMO) – an organism whose genetic material has been altered using genetic engineering techniques

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genetics

GLOSSARY OF TERMS

genetics – the study of genes, heredity, and variation in living organisms genetics – the science about inheritance of traits through genes and the environment glucose – C6H12O6 is a monosaccharide sugar that is produced in photosynthesis and used during cellular respiration for energy production glycolysis – the breakdown of glucose into pyruvate to produce ATP and NADH; the first step in both cellular respiration and fermentation golgi body – organelle that packages and sorts materials for transport outside of the cell

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homologous structure

hardy-weinberg principle – states that the allele and genotype frequencies of a population remain constant from generation to generation in the absence of other evolutionary influences heterozygous – a form of allelic interaction in which both alleles are equally expressed in a heterozygous individual homeostasis – the tendency of an organism or cell to maintain a balanced state so as to maintain health and function homologous structure – an organ or bone that appears in different animals, underlying anatomical commonalities demonstrating descent from a common ancestor

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homozygous

GLOSSARY OF TERMS

homozygous – when an individual has two of the same allele for a trait, whether it be dominant or recessive host – an organism in which a parasite resides and/or from which it derives nutrients human genome project – a federally funded U.S. scientific project to identify both the genes and the entire sequence of DNA base pairs that make up the human genome hypertonic– a type of solution in which there is more solute outside of the cell; water will move out of the cell, causing it to shrink hypotonic – a type of solution in which there is more solute inside of the cell; water will move into the cell, causing it to swell

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interphase

immigration – the movement of organisms into an area incomplete dominance – a form of allelic interaction in which neither allele is dominant, resulting in a phenotype that is an intermediate between the two homozygous phenotypes inheritance – what is passed on from parent to offspring insertion – the addition of one or more nucleotide base pairs into a DNA sequence interphase – the longest phase of the cell cycle, in which the cell grows, performs its functions, and, if it is going to divide, replicates its DNA

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isotonic

GLOSSARY OF TERMS

isotonic – a type of solution in which there is equal amounts of solute both inside and outside the cell; there is no net movement of water into or out of the cell keystone species – species that are relied on heavily within an ecosystem; if removed, the ecosystem would change drastically. kingdom – the highest level of organism classification; contains the greatest amount of species and the highest biodiversity krebs cycle – a part of aerobic respiration that uses the products of glycolysis and fatty acid oxidation to generate ATP and NADH for oxidative phosphorylation

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lytic cycle

limiting factors– biotic or abiotic factor that restricts the growth of a population lipid – a biomolecule composed of glycerol and fatty acids that is hydrophobic lysogenic cycle – viral reproduction resulting in viral genetic material being integrated into the host cell’s genetic material; a long latent period lysosome – membranebound organelles that contain enzymes capable of breaking down many types of molecules lytic cycle – viral reproduction resulting in the lysis (splitting) of the host cell and the production of more virus particles manufactured by the host cell

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macromolecules

GLOSSARY OF TERMS

nature resources

macromolecules – very large mitosis – a process of cellular molecule created by combining division whereby a single diploid cell divides into two smaller molecules identical diploid cells matter – has mass and takes monohybrid cross – a mating up space; matter occurs as between individuals that have elements, compounds, and different alleles of a single gene mixtures meiosis – a process of cellular division whereby a single diploid cell divides into four haploid gametes metaphase – the phase of mitosis when chromosomes line up along an imaginary line (the metaphase plate) in the middle of the cell

mutation – a change in the DNA sequence of a chromosome natural selection – a process by which organisms with favorable traits produce more successful offspring than organisms with less favorable traits, causing the favorable traits to become more common in the population

mitochondrion – an organelle in the cytoplasm of eukaryotic nature resources – resources cells that functions in energy production; the power factory of that exist in the environment without human intervention the cell

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nitrogen cycle

GLOSSARY OF TERMS

nitrogen cycle – the process by which nitrogen is converted among various chemical forms as it cycles among the soil, biosphere, lithosphere, and atmosphere nucleic acid – a biomolecule composed of nucleotides and carries the genetic information of an organism nucleus – a membrane-bound structure in eukaryotic cellsthat contains the DNA oparin-haldane hypothesis – states that life began with simple organic compounds formed from atmospheric gases, followed by more complex compounds formed in the seas through multiple reactions

pathogen

organelles – a membranebound structure inside a eukaryotic cell that performs a specific function or set of functions osmosis – the movement of a solvent across a semipermeable membrane from an area of low solute concentration to an area of high solute concentration to equalize the solute concentration on both sides of the membrane overexploitation – use of a natural resource at a level that results in the unwanted depletion or destruction of the resource passive transport – movement across a cell membrane without using energy pathogen – anything capable of causing infectious diseases

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pesticide

GLOSSARY OF TERMS

pesticide – substance used for killing insects or other organisms harmful to the cultivation of plants or animals photosynthesis – a chemical reaction during which plants convert radiant energy from the Sun to chemical energy; a reaction that converts carbon dioxide and water to sugar (glucose)

prion

phylogeny – the evolutionary development of a species plants – multicellular eukaryotes of the kingdom Plantae pollution – harmful substance that contaminate a natural environment

population – a group of interacting individuals of the photosynthesis – the process same species located in the by which autotrophic organisms same area capture light energy to convert population – members of carbon dioxide and water into glucose, thereby storing some the same species that live in the same geographical area; of the captured energy in may be distinctly different than chemical bonds populations living elsewhere phylogenetic tree – a diagram due to the spread of local adaptations within a population that displays the inferred evolutionary relationships prion – a protein shell without among biological species any nucleic acids that can based onthe similarities and differences in their physical and cause diseases genetic characteristics 520

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probability

GLOSSARY OF TERMS

probability – the likelihood of something happening products – the ending substance(s), written on the right side of the chemical reaction arrow, that are created during a chemical change prophase – the first phase of mitosis in which chromosomes condense and become visible, the nuclear membrane dissolves, and the centrosomes move to opposite ends of the nucleus and spindle fibers form

recessive

protist – a large group of eukaryotic organisms which belong to the kingdom Protista punnett square – a chart that shows the likelihoods of all possible genotypes and phenotypes for a certain trait or traits resulting from a cross between two parents with known genotypes radiant energy – energy from the Sun that reaches Earth as visible light, ultraviolet, and infrared (heat) radiation

protein – a biomolecule composed of amino acids connected by peptide bonds

radiation – the emission or transmission of energy as particles or waves

protein pumps – proteins that work against a concentration gradient to transport materials in/out of a cell (from areas of low concentration to areas of higher concentration)

recessive – the inherited characteristic that is only expressed when no other characteristic is present

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replication

GLOSSARY OF TERMS

replication – the synthesis of a new DNA molecule that has the same nucleotide sequences as a pre-existing DNA molecule reproductive success – the ability to produce fertile offspring retrovirus – a virus that contains reverse transcriptase and RNA

species

rna world – refers to the selfreplicating ribonucleic acid molecules described to have been the precursors to all current life semi-permeable – a barrier that will allow specific things to pass through solute – a substance that dissolves in another substance (solvent) to form a homogeneous mixture

ribosome – a structure made of RNA that converts speciation – the divergence messenger RNA sequences into amino acid sequences with of multiple populations or subpopulations of the same the help of transfer RNAs species to the point where they rna (ribonucleic acid) – can no longer interbreed to messenger carrying instructions generate fertile offspring from DNA for controlling the species – a group of synthesis of proteins; in some organisms that are similar to viruses RNA rather than DNA carries the genetic information one another and can combine to produce more of their kind

522

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spores

GLOSSARY OF TERMS

spores – small organisms that can survive under unfavorable conditions for a long time and then grow into new organisms stem cells – an undifferentiated cell that can differentiate into one or more specialized cell types or divide to produce more undifferentiated cells subspecies – groups of organisms of the same species that have diverged to have different characteristics but can still interbreed to produce fertile offspring

theory of evolution

survival of the fittest – the continued existence of organisms that are better adapted to their environment, with the extinction of others whom are not taxonomy – the branch of science that formally names and classifies organisms by their structure, function, and relationships telophase – the phase of mitosis in which the genetic material has been separated, and the nuclear membrane begins to reform to create two separate but identical nuclei

substitution – a point mutation theory of evolution – an in which one base pair in the explanation for how living DNA sequence is replaced by things change over time another

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theory of natural selection

GLOSSARY OF TERMS

theory of natural selection – states that organisms with favorable traits produce more successful offspring than organisms with less favorable traits, causing the favorable traits to become more common in the population

virus

vacuole – a large water filled organelle present in all plant and fungal cells and some animal and bacterial cells virus – a nonliving particle dependent on host cells for replication of genetic material

transcription – the process in which a strand of DNA is copied into an RNA strand for the purpose of protein synthesis transgenic organism – an organism into which an exogenous gene has been introduced for the purpose of introducing a new trait that will be passed on to the organism’s offspring vaccine – an injection of a killed or weakened pathogen

524

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Biology STEMscopes Georgia Student Notebook

I belong to:

a part of STEMscopes NGSS

Georgia_Biology_Book.indd 1

Biology

My teacher is:

developed by Accelerate Learning, Inc. & Rice University

Notebook

(800) 531-0864

6/23/17 9:59 AM