BIOLOGY SHS General Biology 2 Laboratory Notes

General Biology 2 (Laboratory) Notes

Table of Contents

Activity 1: The Microscope Activity 2: Animal Cell Structure Activity 3: Membrane Transport Short Quiz #1 Activity 4: Cell Division Activity 5: Animal Histology Activity 6: External Anatomy of the Toad Short Quiz #2

Activity 1: The Microscope Pre-Lab Discussion Microscope ● Used to visualize cells ● 3 important parameters of microscopy ○ Magnification - ratio of an object’s image size to its real size ○ Resolution - measure of the clarity of the image ○ Contrast - visible differences in brightness between parts of the sample ● 4 Types of Objective Lenses ○ Scanner - 4x (Objective/Magnification) x 10x (Eyepiece) = 40x (Total Magnification) ○ Low Power Objective - 10x (Objective/Magnification) x 10x (Eyepiece) = 100x (Total Magnification) ○ High Power Objective - 40x (Objective/Magnification) x 10x (Eyepiece) = 400x (Total Magnification) ○ Oil Immersion Objective - 100x (Objective/Magnification) x 10x (Eyepiece) = 1000x (Total Magnification) ● Parts of a Microscope and their Functions ○ Eyepiece Lens: the lens at the top that you look through, usually 10x or 15x power. ○ Tube: Connects the eyepiece to the objective lenses. ○ Arm: Supports the tube and connects it to the base. ○ Base: The bottom of the microscope, used for support. ○ Illuminator: A steady light source (110 volts) used in place of a mirror. If your microscope has a mirror, it is used to reflect light from an external light source up through the bottom of the stage. ○ Stage with Stage Clips: The flat platform where you place your slides. Stage clips hold the slides in place. If your microscope has a mechanical stage, you will be able to move the slide around by turning two knobs. One moves it left and right, the other moves it up and down. ○ Revolving Nosepiece or Turret: This is the part that holds two or more objective lenses and can be rotated to easily change power. ○ Objective Lenses: Usually you will find 3 or 4 objective lenses on a microscope.

They almost always consist of 4x, 10x, 40x and 100x powers. When coupled with a 10x (most common) eyepiece lens, total magnification is 40x (4x times 10x), 100x, 400x and 1000x. ○ Rack Stop: This is an adjustment that determines how close the objective lens can get to the slide. It is set at the factory and keeps students from cranking the high power objective lens down into the slide and breaking things. You would only need to adjust this if you were using very thin slides and you weren't able to focus on the specimen at high power. (Tip: If you are using thin slides and can't

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focus, rather than adjust the rack stop, place a clear glass slide under the original slide to raise it a bit higher). ○ Condenser Lens: The purpose of the condenser lens is to focus the light onto the specimen. ○ Diaphragm or Iris: Many microscopes have a rotating disk under the stage. This diaphragm has different sized holes and is used to vary the intensity and size of the cone of light that is projected upward into the slide.

The ocular eyepiece will always be 10x.

The field of view is the area that you see when looking through the eyepiece.

The field diameter is essentially the number of millimeters or micrometers you can see in the entire field of view.

Working distance is the distance of the lens from the stage. This can be changed using the coarse adjustment knob and the fine adjustment knob. However, a good microscope would have a parfocal. Parfocal refers to objectives that can be changed with minimal or no refocusing.

When looking in a microscope, the image will be inverted and reversed.

Under a scanner objective, the working distance will still be large regardless Light Microscope ○ Visible light passes through a specimen and then through the glass lenses ○ Lenses refract the light → image is magnified ○ Can magnify up to about 1,000 times (Oil Immersion Objective) the size of the actual specimen ○ Light from the lamp of the microscope as source of illumination ○ Types: Brightfield, Phase-contrast, Differential-interference-contrast, Fluorescence, Confocal, Deconvolution, Super-resolution Electron Microscope ○ Used to study subcellular structures ○ Light from beam of accelerated electrons as a source of illumination

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Worksheet

Types: Transmission electron microscope (TEM) and Scanning electron microscope (SEM) ■ SEM provides detailed images of the surfaces of cells. SEM focuses on the sample's surface and its composition, so SEM shows only the morphology of samples, and provides a 3D image.

■ Transmission electron microscopes are used to view thin specimens (tissue sections, molecules, etc). TEM has a much higher resolution than SEM, and the TEM image shows the interior structure of an organism.

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The microscope must be always held with one hand on the arm and the other below and supporting the base.

Changing the objective lenses increases the clarity of the microscope. Each optical component in a microscope device should have the highest numerical aperture (NA) available to achieve full (theoretical) resolution (taking into consideration the angular aperture).

Furthermore, viewing the specimen with a shorter wavelength of light will enhance the resolution. Lastly, the simplest way would be to clean the lenses of the microscope with lens paper and cleaner before use.

If magnification increases, the working distance decreases. In order to focus, the high-power objective lens must be much closer to the specimen than the low-power objective lens. Magnification is inversely proportional to working distance.

Similarly, the diameter of the field of view shrinks as magnification increases. In other words, when you increase the magnification, you can see less of the specimen.

In the experiment proper, two types of protozoa (amoeba and paramecium) were viewed under low-power objective lenses (100x).

Activity 2: Animal Cell Structure Pre-Lab Discussion ●

Cells ○ ○ ○

All living things are made up of cells.

Fundamental unit of life Cytology - Study of cells

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Cell Theory ○ By Theodor Schwann, Matthias Schleiden, and Rudolf Virchow ○ Points of Cell Theory ■ All organisms are made up of cells and a cell is the structural and functional unit of the organism ■ Cells are capable of self-reproduction (cell division and replication), and cells come from pre-existing cells

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Prokaryotic Domains ○ Bacteria ○ Archaea Eukaryotic Domains ○ Multicellular ■ Plantae ■ Fungi ■ Animalia ○ Unicellular ■ Protists

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Prokaryotic ○ Simple cell ○ No membrane-bound organelles ○ Chromosome not contained in nucleus (chromatin fibers are in the nuclear region)

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Small cells Example: Bacteria

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Eukaryotic ○ Complex cell ○ Membrane bound organelles ○ Chromosomes contained in nucleus (chromosomes are contained in nuclear envelope/membrane) ○ Larger cells ○ Example: All other organisms

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Basic Subcellular Structures of Animal Cells ○ Cell membrane - selectively permeable controlling the movement of materials into and out, also protects the cells ■ Outside covering of the cell (protection) ■ A.k.a. plasma membrane ■ Phospholipid bilayer (hydrophilic and hydrophobic regions) ■ Has embedded proteins and sugar side chains ■ Allows communication with cells nearby ○ Smooth Endoplasmic Reticulum - Transport of materials within the cell, lipid synthesis ■ Proteins are usually transported in the cells ○ Mitochondria - where respiration occurs, in charge of cellular respiration ■ Mitochondrial inheritance - The mitochondria is usually found in the tail of the sperm cell ■ ATP synthesis (energy) ○ Nucleus - controls the normal activities of cells, contains the genes that code the DNA into RNA ■ RNA will be translated into proteins, which will be used in different parts of the cells ○ Ribosome - Protein synthesis ■ Two types: Bound and free ribosomes ● Bound Ribosomes - found along the rough endoplasmic reticulum ● Free Ribosomes - scattered along the cytosol ○ Centriole - plays a role in organizing spindle fiber during mitosis and meiosis ○ Nuclear membrane - Selectively permeable double membrane that bounds into the nucleus ○ Chromatin - condenses into chromosomes during cell division ■ Made up of DNA and proteins (Histone) ○ Vacuole - a fluid-filled space in a cell surrounded by a membrane ■ Types of Vacuoles: ● Food Vacuole - most common type, food enters the cell and forms a membrane around the food, which then becomes the food vacuole

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Contractual Vacuole - present in the protists which allows them to move ● Central Vacuole - found in plant cells which contains water Nucleolus - RNA synthesis, found inside the nucleus Rough Endoplasmic Reticulum - ribosomes attached to it are sites for protein synthesis and products are transported to golgi bodies Golgi Bodies - allow for the modification, manufacturing, and packaging proteins prior to secretion Cytoplasm - Consists of aqueous solution of many substances, providing a medium for chemical reactions to take place inside the cell. It contains a variety of organelles and non-living granules.

■ This is where the organelles are situated ■ Cytosol - liquid portion Lysosome - contains enzymes that digest substances such as macromolecules (e.g. food particles, organelle portions, etc.)

Basic Structure of an Animal Cell

Red Blood Cells - Biconcave - has something to do with the transportation of oxygen to different parts of the body - Anucleated at maturity - more space for oxygen to be carried (adaptation of mammals) Table 2.1. Differences Between Plant Cells and Animal Cells Characteristics

Plant Cells

Animal Cells

Size

Larger

Smaller

Cell shape

Definite

Irregular, indefinite

Cell’s outer covering

Cell Wall

Cell membrane

Others

Autotrophic (chloroplasts) Peripheral nucleus Larger central vacuoles

Heterotrophic Central nucleus Smaller peripheral vacuoles

Worksheet ● ● ●

The specimens in this activity were viewed in 400x magnification (HPO).

Human cheek cells are shell-shaped.

Mammals have no nucleoid red blood cells, since they needed the space for oxygen to be carried (Adaptation of mammals). ○ However, since frogs are amphibians and can breathe underwater, they have nucleoid red blood cells.

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Some cells have no definite shape, thus they are called amorphous.

In a frog’s blood smear, the red blood cells are oval in shape because of the nucleus, while the white blood cells have no definite shape, hence, they are amorphous.

The frog’s ovary is spherical shaped.

In a frog’s testis, the shape is threadlike because of the sperms, who have a whip-like shape for their flagellum. ○ The flagellum aids in the sperm’s locomotion.

For the smooth muscles like in the stomach, its shape is spindle-shaped or fusiform.

For the live cells in the hay infusion, different specimens thrived there, namely protozoa and bacteria.

Activity 3: Membrane Transport Pre-Lab Discussion Passive Transport ● Diffusion of a substance across a membrane with no energy investment (no ATP) ● Diffusion is the tendency for molecules to spread out evenly into the available space ● Example: When spraying perfume, the perfume will spread out in the entire room ● The entire net population moves in a directional manner but the solute movement (single molecule) is random ○ From higher concentration to lower concentration ● Although each molecule moves randomly, diffusion of a population of molecules may be directional (region of higher concentration to a region of lower concentration) ● At dynamic equilibrium, as many molecules cross the membrane in one direction as in the other

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Equilibrium - equal concentrations of both solutes in both sides

Osmosis ● Special form of diffusion ● Movement of water from a dilute solution (hypoosmotic) to a more concentrated (hyperosmotic) one through a semi-permeable or selectively permeable membrane ● The process of diffusion of a crystalloid solute through such a membrane is known as dialysis

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Water and ethanol move the quickest during osmosis The water will continue to move until the concentration of the solutes are equal Water molecules can pass through pores, but sugar molecules cannot Water moves from lower to higher concentration of solute

Hypotonic Solution ● Solute concentration is higher inside the cell ● The animal cell is in a lysed state (or it burst) ● Water is going to go inside of the cell

Isotonic Solution ● Same solute concentration as that of the cell ● The animal cell is in a normal state ● Water is in equilibrium Hypertonic Solution ● Has a higher solute concentration as that of cell ● The animal cell is in a shriveled state ● Water is going to leave the cell

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The larger the molecule, the slower it will diffuse The smaller the molecule, the faster it will diffuse

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An acid-base reaction or neutralization took place when adding the two elements. Thus, the compounds H2O (water) and NH4Cl (ammonium chloride) were formed.

In this experiment, a precipitate in the shape of a "ring" in the tube can be seen, indicating the formation of ammonium chloride.

Heavier molecules move more slowly; therefore, they diffuse more slowly. The opposite is true for lighter molecules.

Both hydrochloric acid and ammonium hydroxide have the similar molecular weights of around 35 grams per mole. Therefore, they diffuse at almost the same rate, with ammonium hydroxide diffusing slightly faster.

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In the second part of the first experiment, potassium permanganate diffused the farthest compared to congo red and methyl blue. ○ The molecular weight for congo red is 697 g/mol, 320 g/mol for methylene blue, and 158 g/mol for potassium permanganate. Since potassium permanganate weighed the least, it diffused across a larger area compared to the other two dyes.

The next experiment used potassium permanganate so it will reveal the state of the crystals in terms of the color that diffuses in the water, as well as the remaining crystals that would be apparent. This is also to make it possible to see how temperature influences diffusion rates.

Higher temperatures increase the energy and therefore the movement of the molecules, increasing the rate of diffusion. The opposite is also true: The lower the temperatures are set, the lower the energy will be. Thus, decreasing the rate of diffusion. ○ The speed of a molecule is proportional to the square root of the absolute temperature and temperature is the measure of the average kinetic energy of molecules in an object, therefore when the temperature increases the molecules will have more kinetic energy, so they move faster and due to more spontaneous spreading.

The addition of IKI to the cellulose sac resulted in a color transition. ○ Since the difference of color occurred within the container, signaling the entry of IKI due to its smaller size, it can be inferred that iodine has smaller molecules. ○ Iodine ions diffused from the heavily concentrated beaker to the cellulose sac with a lower concentration. The iodine was then absorbed by the starch in the cellulose sac, resulting in the color transition.

Iodine has fewer molecules than starch, according to the observations. ○ The smaller molecular size of the iodine caused the color difference in the cellulose sac, allowing it to move through. ○ The starch molecules, on the other hand, are complex and, owing to their larger size, are unable to move through the cellulose sac.

Short Quiz #1 1. This is the natural tendency of the molecules to spread out evenly across the membrane a. Diffusion 2. This is the size of the area that the lens views. The higher the magnifying power of an objective lens, the smaller the area viewed a. Field of View 3. What is the staining material used to make the pointed cellular structure more visible under the microscope? a. Methylene blue 4. Which among the statement/s is/are true about the part labeled as B? a. Single layer of phospholipids and is permeable b. Semi-permeable phospholipid layer c. Consist of phosphate heads that are hydrophilic and lipid layer that hydrophobic 5. Which among the following is the least diffused chemical compound? a. Congo red 6. Which of the following materials acts as the cell membrane in determining the relationship between diffusion and molecular size? a. Cellulose sac 7. In the experiment Diffusion and Molecular Size where a starch solution in cellulose sac is submerged in an iodine solution, which substance has larger molecules? a. Starch 8. This refers to the movement of water from a dilute solution to a more concentrated one through a semi-permeable or selectively permeable membrane a. Osmosis 9. Identify the cellular part or the structure that gives the frog spermatozoa a hair-like or thread-like gross appearance in the section of the frog’s testis. a. Flagellum 10. What is the descriptive term that refers to the shape of the pointed cells? a. Amorphous

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a. Eyepiece b. Revolving Nosepiece c. Stage d. Stage Controller 12. You were tasked to view a specimen under the microscope. Your eyepiece’s magnification is 25 times. What would be your total magnification under HPO? a. 1000x 13. In a light compound microscope, the coarse adjustment knob does not have to be readjusted when changing the magnification. What is this phenomenon called? a. Parfocal 14. Give the magnification of each objective lens. Follow A-D order. a. 4x - 10x - 100x - 40x 15. Which is NOT TRUE about the field of view? a. If you switch to a higher lens, the center portion of what is being viewed decreases in size 16. What do you see in a cheek cell under a higher magnification? a. Nucleus and cytoplasm 17. What is the total magnification of a Scanner? a. 40x 18. The relationship between the magnification of the objective lens and the field of view is... a. Inverse 19. What happens when you shift to an objective of a higher magnification? a. The diameter of the field of view decreases 20. A student wants to view cells under the compound microscope at a total magnification of 400X. If the eyepiece is 10X, which of the following objective lenses should be used? a. 40x 21. Give the primary function of the pointed “hair-like” structure of this unicellular organism. a. For mobility 22. Nucleus of cheek cell function a. Control center of the cell 23. In terms of molecular weight, which is lighter: NH4OH or HCl? a. NH4OH 24. What could be the resulting product/s of the reaction of hydrochloric acid and ammonium hydroxide as indicated by the formation of a white ring? a. The resulting product of the reaction is ammonium chloride and water.

25. What explains the bluish-black color inside the starch-filled cellulose sac? a. Diffusion of IKI molecules through the cellulose sac tiny pores, reacting with starch molecules

bAActivity 4: Cell Division Pre-Lab Discussion

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In interphase, the cells are prepared for cell division. (i.e. preparing spindle fibers and centrioles)

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Karyokinesis (division of the nucleus) Cytokinesis (division of the cytoplasm)

Interphase ● The genetic materials inside the nucleus appear as thin, thread-like structures appropriately called chromatin fibers. ● Nucleus is surrounded by a nuclear membrane. Within the nucleus can be found 1 to 2 nucleoli, which are dense, darkly stained bodies formed by several chromosomal materials that code for certain RNA’s. ● Near the nucleus is the centrosome which contains a pair of centrioles. The centrioles may not be readily seen using the light microscope.

Prophase ● The chromatic fibers start to appear as coiled, thickened condensed structures forming chromosomes that are visible under the light microscope. Each chromosome has sister chromatids that are bound at the center by the centromere. ● Near the centromere, kinetochores are proteins that are holding the chromosome to the spindle fibers. ● The pair of centrioles divide and are seen in the opposite poles. ● Locate ray-like microtubule bodies called asters radiating around each centriole and mitotic spindles forming between centrioles. ● The nucleoli and nuclear membrane disappear at this stage.

Metaphase ● Metaphase plate/Equatorial plate - The chromosomes are aligned at the equatorial region of the nucleus. ● At this stage, the replicated chromosomes, which are much shorter and more condensed, are known as sister chromatids. ● They are joined together at their central region called centromere. ● Closely associated with centromeres are kinetochores, protein complexes to which the spindle fibers are attached to.

Anaphase ● The sister chromatids are separated and pulled apart toward the opposite poles. ● This stage is differentiated into early and late stages depending on the distance travelled by the chromatids.

Telophase ● Cleavage furrow, a constriction of the plasma membrane at the region of the equatorial plate, starts to appear (caused by the actin in the cytoskeleton) ● At this stage, the nuclear membrane and the nucleus start to reappear. ● The chromosomes begin to uncoil and assume a threadlike appearance. ● The asters and mitotic spindle disappear. At late telophase, the cleavage furrow becomes more constricted leading to the formation of 2 daughter cells.

Cytokinesis ● Which is the division of the cytoplasm, usually occurs along with telophase ● Completely separated daughter cells are formed soon after mitosis Mitosis ● Reason for growth and repair of tissues Worksheet

Activity 5: Animal Histology Pre-Lab Discussion ●

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Histology ○ Science that deals with the microscopic anatomy of tissues of plants and animals ○ Refers to animal tissues Tissues - a group of cells that serve one function, that vary in shape and function per each kind. They are differentiated and classified by function. ○ Aggregations of cells with similar shape functional association, and inter-cellular components ○ Tissues combine to form larger functional units called organs

4 Types of Tissues 1. Epithelial ○ This type of tissue is composed of tightly packed cells with very little intercellular substance. ○ It covers the outer surface (skin) and inner lining of the body ○ It is also the principal tissue of the glands ○ Epithelial tissues are characterized by: i.

Different shapes of cells ranging from squamous (flattened), cuboidal, columnar to intermediate (transitional) types which are arranged in either a single layer (simple, pseudo stratified) or in 2 or more layers (stratified) ii.

Presence of a basement membrane and apical surface 1. Apical surface (Upper portion) is associated with fluids 2. Basement membrane (bottom portion) - extension of the ECM forming epithelial wall/tissues iii.

Presence of specializations on its apical surface such as cilia and microvilli 1. Cilia is found in the lining of the digestive tract while both cilia and microvilli can be found in the trachea iv.

Extremely coherent intercellular adhesions 1. Cells are tightly packed together because of the different intercellular junctions (Tight/Gap junctions, desmosomes) ○ Transitional tissues can change arrangement, giving the tissue different forms/layers. ○ Simple Squamous i.

Example: The lining of lungs and blood vessels ii.

Flattened shape iii.

Single layer of cells lying upon a basement membrane iv.

The cells are very thin and rectangular in profile and are arranged closely together to form a sheet allowing for filter.

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Simple Cuboidal: i.

Example: Kidney tubules, lining of the circular thyroid follicles ii.

These cells appear as box-like or tube-like with more or less equal height and width. iii.

Simple cuboidal cells are found in the lining of each thyroid follicle and kidney lining.

Simple Columnar i.

Example: Lining of the intestine. ii.

Under the LPO, identify finger-like projections on the inner surface of the intestine. These are called Villi iii.

Focus on one villus under HPO and examine the surface layer of tall and slender epithelial cells with darkly stained nuclei more or less at the same level, near the bases of the cells iv.

Among tall columnar cells are “pitcher-like” mucus glands called goblet cells 1. Secrete mucus that creates a protective layer from the digestive juices Stratified Squamous i.

Example: Lining of the skin, frog’s skin ii.

Two or more layers of epithelial cells specifically named based on the shape of the cells at the surface. iii.

Usually, their function is for protection. Another example includes the lining of the vagina. iv.

Basement membranes - extension of the extracellular matrix

Cross section of the frog’s skin tissue

2. Connective ○ Connective tissue comprises a diverse group of tissues that serve to maintain and support the body ○ Function: connect, bind, and pack body parts together ○ It is generally made up of cells and an extracellular matrix (fluid form) composed of protein fibers, an amorphous ground substance and tissue fluid ○ This group includes the connective tissue proper, connective tissues with special properties, and supporting connective tissues ○ The dots refer to the cells. They are easy to find because of the fibroblast shape. ○ Loose connective tissue (areolar tissue) i.

This tissue is composed of a great deal of ground substance with several types of protein fibers ii.

Almost all types of cells are found in this tissue but the most numerous and easy to find cells are the spindle-shaped fibroblasts 1. Can be identified because of their large ovoid nuclei iii.

Areolar tissues bind the skin to the muscles

Connective Tissue with Special Properties ○ Adipose Tissue i.

Found beneath the dermis of the skin and may be found around the other organs of the body ii.

Cells are called adipocytes, which have the ability to hold or fold fats/lipids which can hold the insulation of the body iii.

These cells have a thin ring of cytoplasm surrounding a very large vacuole/space left by the dissolved lipid droplets. iv.

Nuclei are flattened and often seen at the sides or periphery of cells. v.

Depository of fats. These tissues are removed during liposuction.

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Blood i.

This specialized tissue is composed of blood cells and fluid matrix, the plasma (water, salts, and protein) 1. WBC, RBC (transportation of oxygen), and Platelets ii.

Remember that RBC are enucleated at maturity, while white blood cells are nucleated. iii.

Some white blood cells are granular.

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These are protectors of the body that will fight foreign substances (anything unusual in the body).

Supporting Connective Tissues ○ Hyaline Cartilage i.

This is one of the three types of cartilages ii.

The firm, gel-like extracellular matrix is bluish-white and translucent with predominance of collagen fibers iii.

The cartilage cells or chondrocytes (progenitor: chondroblast) occupy small cavities called lacunae which are filled with tissue fluid in life

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Bone Tissue i.

The hard calcified matrix deposited with inorganic salts makes it a supporting connective tissue ii.

Made up of calcium carbonate salts iii.

Harder and more elastic compared to cartilage iv.

Bone cells or osteocytes (progenitor: osteoblasts) occupy lacunae with several canaliculi (interconnecting small canals) radiating from it v.

In life, these lacunae are filled with tissue fluid. Unlike cartilage, the bone is rich in blood vessels and nerves

3. Muscle ○ The muscle tissue’s main function is to contract to provide movement. i.

They will always PULL and NEVER PUSH. ○ There are three types of muscle tissues differentiated, among others, by the shape of cells, rate of contraction, and control (whether voluntary or involuntary). ○ Three types: i.

Skeletal/Striated Muscle (Voluntary) 1. This type of muscle tissue is primarily found attached to the bone to provide body movements and locomotion.

2. Note that the long, cylindrical muscle fibers, each containing 2 or more nuclei located near the plasma membrane 3. The fibers also show alternating light and dark bands or striations (skeletal and heart muscles).

4. Microfilaments composed by actin and myosin enable the muscles to move by shortening or lengthening the muscles.

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Visceral (Involuntary)

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Cardiac (Involuntary) 1. The heart muscle is a muscle that is involuntary, and striated in cardiac muscle tissues.

4. Nervous ○ A living organism responds to stimulus, by the delivery of impulse. ○ Function: i.

Reception of stimuli ii.

Conduction of impulses in the body ○ The nervous tissue’s main function is conductivity. i.

The conduction of impulses. ○ The main components are the nerve cells or neurons i.

Comprise of dendrites and axons, protected by myelin sheath. ○ The supporting cells are called neuroglia. ○ Three types of neurons: i.

Sensory 1. Receives impulses from the different sense organs of the body 2. Carry impulses toward the spinal cord and brain ii.

Motor 1. Carry impulses away from the Central Nervous System 2. Usually terminate in muscles or glands of the body iii.

Associative 1. Link the sensory neurons to the motor neurons

Cow’s Nerve Smear

Activity 6: External Anatomy of the Toad Reminders: ● First Long Exam is on April 16 (from Activities 1 to 6) ○ 60 minutes ○ 7:30 am to 9:00 am ● Short Quiz 2 covers Activities 4, 5 and 6. Set on April 12 (D1: 2:30 to 3 pm; D2: 3:40 to 4 pm) ○ Pointers: ■ Cell Division ■ Animal Histology ■ External Anatomy of the Toad Pre-Lab Discussion

Why are frogs important? ● More than 70 frogs are known to have medicinal value (i.e. Rana plancyi) ● Importance in the environment (predator & prey) ● Play important role in culture and tradition of many countries Order Anura: Frog vs. Toad (Same phylum amphibia and order anura) Frogs ● Northern Leopard Frog (Rana pipiens) ● Smooth or slimy skin (mucus) that is moist (because of the environment that they are in: areas that have or are near water)

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Long, strong hind legs that aid them in leaping Big, bulging eyes

Cane Toad (Bufo marinus/Rhinella marina) Thicker, bumpy skin that is usually dry Shorter hind legs more suitable for walking More subtle eyes The bulging structure behind the eyes is the parotoid gland (poisonous)

Skin of the Toad ● Epidermis and Outer Layer ○ Made up of stratified epithelium with thin dead squamous cells that are constantly removed when the toad sheds skin ● Inner Layer (Dermis) ○ Living cuboidal to columnar cells that continuously divide to replace the shed off layer of the skin ● Melanophores ○ Black pigment containing cells found at the junction (in between) of the dermis and epidermis

Terms to Know ● Dorsal ○ The back or upper surface of an organism ○ “Dorsal lateral” - lateral, upper side of an organism. ● Ventral ○ The stomach or lower surface of an organism ● Anterior

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○ The head end of an organism Posterior ○ Tail end of an organism

Determining Sex

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The sex of a frog may be determined externally by examining the thumb pads on the front feet. The thumb pads of males are enlarged at the base.

Females DO NOT have a swollen thumb Males HAVE a swollen thumb

External Anatomy of the Frog Bilateral Symmetry ● It can be differentiated into two mirrored portions (right and left halves) 3 planes of the toad body ● Frontal - into dorsal and ventral sections ● Sagittal (longitudinal) - into right and left sections ● Transverse (cross) - into anterior and posterior sections With reference to the location relative to the center of the body:

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Medial - near the middle Lateral - to the sides Proximal - part of a structure that is near to the origin Distal - part farther from the origin

1. Axial Region ○ Structural functions ○ Head ■ Snout - blunt apex found on the tip of the head ■ Mouth - function: feeding 1. Tongue - sticky structure in the inside of the mouth that protrudes to catch preys (insects) ■ External nares - paired opening at snout connected to internal nares (breathing) ■ Browspot - circular spot between the eyes, displays where part of the skull development took place ■ Tympanic membrane - serves as frog’s ear, protects inner ear from outer environment ■ Parotoid gland - behind tympanic membrane; large aggregate of poison glands (only on toads) ■ Did you know that only male frogs croak?

1. They do this to either: a. Find a mate b. Defend their territory

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Trunk ■ Hump - pelvis is elongated and higher at the spine which causes the sacral hump ■ Anus - serves as exit cavity for excretory, urinary, reproductive system Eyes ■ Used to push down food; close their eyes when they swallow 1. Upper eyelid - thicker, does not move

2. Lower eyelid - thinner, moves 3. Nictitating membrane - thin, transparent, protects eyeballs from external materials or objects, it protects the toad’s eyes when underwater, due to the absence of eyelids.

2. Appendicular Region ○ Functions for movement ○ Forelimbs ■ Used to raise or support the body when the frog is at rest ■ Composed of the following: 1. Upper arm (Brachium) 2. Forearm (Antebrachium) 3. Manus (Hands) ○ Hindlimbs ■ Well adapted for jumping and swimming ■ Composed of the following: 1. Thigh (upper leg) 2. Shank/Crus (lower leg) 3. Pes (long foot) - divided into tarsus (long ankle), metatarsus (instep) and 5 fully-webbed toes or digits 4. Prehallux - appears as a rudiment of a toe (not used as a toe appendix)

Male vs Female Male ● The skin on the ventral side of the head near the angles of the jaw has a distinct dark pigmentation due to concentration of pigment ● Sexually mature male toads/frogs are generally smaller than the females ● Thumb pads are swollen, which has a patch of textures skin called a nuptial pad that helps the male cling to the back of the female during amplexus Female ● The pigments are diffused, no distinct dark pigmentation at this area ● Sexually mature female toads/frogs are relatively bigger than the males ● Thumb pads of the inner fingers are not swollen

Internal Anatomy of the Frog

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Flow of Food: Mouth → Glottis → Esophagus → Stomach External nares or nostrils - anterior openings for the entry or exit of air.

Esophagus - the tube that connects the mouth to the stomach Tympanic Membrane - the eardrum - receives sound waves Glottis - the opening from the mouth into the respiratory system Tongue - muscular structure attached to the front of the mouth which is extended to catch insects (its food) Maxillary Teeth - sharp teeth in the maxilla of a frog’s mouth that function in holding captured prey

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Vomerine Teeth - small projections in the top of a frog’s mouth that function in holding captured prey Eustachian tube openings - openings in the mouth that lead to tubes that connect to the middle ear to equalize air pressure Nictitating Membrane - a transparent part of a frog’s lower eyelid that moves over the eye to clean it and protect it Cloacal Opening - opening of the cloacal through which undigested food, urine, eggs, and sperm are passed Vocal Sacs - the vocal sac is the flexible membrane of skin possessed by most male frogs ● The purpose of the vocal sac is usually as an amplification of their mating or advertisement call

Initial Frog Skinning

Short Quiz #2 1. It is the stage in the interphase of the cell cycle by which the DNA has just been replicated. a. G-2 Phase 2. If a cell with 12 chromosomes divides, how many cells are formed, and how many chromosomes are there per daughter cell? a. 2, 12 3. The cell in its G2 phase has already copied its DNA. a. True 4. Which represents the correct sequence of stages in the cell cycle? a. G1, S, G2, M 5. What structure is responsible for moving chromosomes during mitosis? a. Spindle fiber 6. Name the pointed structure of this tissue.

a. b. Osteocyte 7. Name the featured tissue below.

a. b. Simple columnar epithelial tissue 8. Identify the type of tissue being featured.

a. b. Areolar

9. Name the pointed tissue.

a. b. Stratified epithelial tissue 10. What is the matrix fluid of this tissue?

a. b. Plasma 11. The major region of the toad’s body which refers to the tail end. a. Posterior 12. Statement A: Male toads have a distinct dark pigmentation due to the concentration of pigments.

Statement B: Female toads are usually bigger in size compared to male counterparts. a. Both statement A and B are correct.

13. The forelimbs are posterior to the hindlimbs. a. False 14. Name the pointed structure.

a. b. Tympanic membrane 15. The frog and toad have no external ear, only the middle, and internal ears. a. True 16. Give the event indicated by the label C.

a.

b. Cleavage furrow formation 17. Why is fish blastula stage frequently used in the study of mitosis? a. This particular stage shows various stages of mitosis.

18. The cell below is on what stage of mitosis?

a. b. Anaphase 19. Which of the following occurs during PROPHASE? a. Disintegration of the nuclear membrane 20. This is found in which organ?

a. b. Kidney tubules or Thyroid follicles 21. Which contains tissue with rich nerve and blood vessels. A or B?

a.

b. c. B 22. What is/are the substance/s that fills this cell?

a. b. Lipids 23. Name the specific structure pointed.

a. b. Nictitating membrane 24. Toads perform internal fertilization known as amplexus. a. False 25. Which event occurs in metaphase in mitosis? a. Chromosomes line up along the equator of the dividing cell.

26. Which of the following is an event that occurs during INTERPHASE? a. DNA replication 27. What is the structure being pointed to?

a. b. Haversian Canal 28. Name the featured cell.

a. b. Nervous tissue 29. Identify the cell being pointed.

a. b. Red blood cells 30. Which is considered as an Epithelial tissue? A or B?

a. b. A (?)

31. The following are located in the axial region, except the ________. a. Shank 32. This region of the toad is made up of the forelimbs (anterior pair) and the hindlimbs (posterior pair). a. Appendicular