Grade 9 Biology by infinity-learn

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BIOLOGY

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Contents 1.

The Fundamental Unit of Life

2. Cell Cycle and Cell Division

3. Tissues

4. Diversity in Living Organisms

5. Why Do We Fall Ill?

159

6. Improvement in Food Resources

188

THE FUNDAMENTAL UNIT OF LIFE

1.1 INTRODUCTION Living organisms exist in various environments. They are composed of different organs that perform different tasks. These organisms are made up of small units called cells. These are the smallest units of life and play an important role in maintaining an organism's health and functioning. The study of cells, cell components, and their functions is called cytology or cell biology.

1.2 DISCOVERY OF THE CELL The discovery of the cell and its components was made by the contributions of several scientists. In 1590, F. Janssen and Z. Janssen invented the first useful compound microscope. In 1665, Robert Hooke discovered the non-living cell in cork slices, which he called cellula or cell. He documented his findings in the book 'Micrographia'. Based on Hooke's work, Antonie van Leeuwenhoek observed living cells such as bacteria, protozoa, and red blood cells in 1675. Alfonso Corti and F. Fontana, in 1772, further observed living matter within cells, providing additional insights into cellular structures. F. Fontana discovered nucleolus in 1781 within the skin cells of eels. In 1831, Robert Brown discovered the nucleus in the plant Tradescantia. In 1835, Felix Dujardin named the living matter present in cells as 'sarcode'. Finally, in 1839, J.E. Purkinje coined the term 'protoplasm' to describe the essential substance found within cells.

1.3 MICROSCOPES The invention of the microscope was very important in studying cells. Before the microscope, people used magnifying glasses to look at small things. Anton van Leeuwenhoek, a Dutch draper and scientist, was the first to create and use a real microscope. He drew inspiration from the drapers' spectacles used to assess fabric quality. He experimented with new techniques for refining small lenses, which at the time provided the highest quality magnifications. His microscopes, recognised as the first practical ones, became possible due to these lenses. In Leeuwenhoek's microscope, the object was attached to a needle-like screw on the other side of the lens, with the eye positioned near the lens. Each of his microscopes consisted of a single biconvex lens with a significant magnification capacity.

THE FUNDAMENTAL UNIT OF LIFE

Lens Sample holder Focus knob

Screw

Fig. 1.1 Microscope used by Leeuwenhoek

1.3.1 Types of microscopes Microscopes are of two types: ordinary microscopes and electron microscopes. Lens Observation tube Nose piece Neck Objective lens Stage Coarse focus Fine focus Light source Base

Ordinary microscope

Electron microscope Fig. 1.2 Types of microscope

Ordinary microscope: An ordinary compound microscope has two special lenses that can make small objects appear much bigger, up to 1000 times their actual size. It works by placing the object just beyond the focus of one lens, which creates a virtual, upside-down, and greatly enlarged image. This image is then seen clearly through the eyepiece. Electron microscope: An electron microscope is a different kind of microscope that uses beams of electrons to light up a sample and create a bigger image. It can magnify objects over 200,000 times more than what an ordinary compound microscope can do.

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1.4 CELL THEORY M.J. Schleiden (1838), a German botanist, and T. Schwann (1839), a German Zoologist, formulated the cell theory together, according to which the bodies of animals and plants are composed of cells. Schwann proposed that the presence of a cell wall is the unique character of plant cells. According to cell theory, the cell is a structural and functional unit of life. However, this theory did not explain how new cells were formed. Rudolf Virchow (1855) first explained that cells divide and give rise to new cells from pre-existing cells, known as 'cell lineage theory' or 'cell inheritance theory'. Virchow modified the cell theory as follows: (i) Cell is the structural unit of all living organisms. (ii) Cell is the functional unit of all living organisms. (iii) Cell is the hereditary unit of all living organisms. Cell theory applies to all living organisms except viruses, which are acellular entities and do not possess plasma membrane and metabolic machinery.

1.5 AN OVERVIEW OF CELL The morphology of a cell includes its size, shape, and structure. Different organisms have cells that vary in size and shape, depending on how complex the organism is. However, the basic structure of a typical cell is similar for all organisms. Cell number Organisms are divided into two categories based on the number of cells they have: unicellular and multicellular. Simple organisms are unicellular, meaning they are made up of only one cell. On the other hand, more complex organisms are multicellular, which means they are made up of many cells. Unicellular organism

Multicellular organism

It consists of only one cell.

It consists of more than one cell.

All life processes occur in one cell.

Division of labour among different cells is seen.

They are generally microscopic and cannot be seen. Prokaryotes have no membrane-bound organelles.

They maybe microscopic or visible to the naked eye. Eukaryotes have a distinct nucleus and cell organelles.

THE FUNDAMENTAL UNIT OF LIFE

Unicellular organism They can be either prokaryotes or eukaryotes. Examples: Bacteria, Amoeba, Paramecium, yeast

Multicellular organism These organisms are typically eukaryotes. Examples: Plants, animals, human

Table 1.1 Difference between unicellular and multicellular organisms

Cell size Cells are generally tiny and can only be observed under a microscope. The small size of cells has two significant advantages. Firstly, it enables fast and efficient communication and substance transfer between different parts of the cell. Secondly, the small size provides cells with a larger surface area in proportion to their volume, which is important for them to carry out their functions effectively. Cell shape Different types of cells have diverse shapes, which are important for carrying out specific functions within living organisms. Red blood cells (RBCs): RBCs have a bi-concave shape, resembling a hollow disk with a concave centre on both sides. This shape increases their surface area, allowing for the efficient exchange of gases like oxygen and carbon dioxide. The bi-concave shape also helps RBCs to pass through narrow capillaries in the circulatory system easily. White blood cells (WBCs): WBCs do not have a specific shape and are irregular. They can change their form. This ability to change shape helps them to move through narrow spaces, like capillary walls, to reach sites of injury or infection. They act as scavengers, defending the body against harmful microorganisms. Nerve cells: Nerve cells, also known as neurons, are long and branched. Their elongated shape allows them to transmit electrical impulses or signals over long distances. The branching structure enables efficient communication between different regions of the body. Muscle cells: Muscle cells are elongated and have the ability to contract. This facilitates movement and contraction of muscles, enabling locomotion and various physiological processes. Conducting cells in plants: In plants, conducting cells, such as xylem and phloem cells, are elongated and tubular. This shape is adapted for their role in transporting water, nutrients, and sugars throughout the plant. Bacterial cells: Bacteria exhibit various shapes, including cocci (spherical or oval), bacilli (rodshaped), and spiral forms. The specific shapes of bacteria can vary within each group. Spiral-shaped bacteria may include vibrio (comma-shaped), spirillum (thick and rigid spiral), and spirochete (thin and flexible spiral) forms. 4

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Spherical

Rod-Shaped

Spiral

Cocci

Bacilli

Spirillum

Fig. 1.3 Shapes of bacterial cell

1.6 PROKARYOTIC CELL The cells which lack a distinct cell wall and membrane bound organelles are called prokaryotic cells. These cells are usually smaller than eukaryotic cells. Bacteria, actinomycetes, mycoplasma or PPLO (Pleuro Pneumonia like Organisms), spirochaetes, rickettsiae and blue-green algae come under the category of prokaryotes.

Pilus Ribosome Capsule

Flagellum

Cell wall Nucleoid (DNA) Cell membrane

Fig. 1.4 Prokaryotic cell

Prokaryotic cells differ in size. Most bacterial cells are 1-2 μm in size. Bacteria like spirochaetes are very long, up to 500μ in length. Epulopiscium, a huge bacterium discovered in the intestine of the brown surgeonfish, measures up to 600μ long and 80μ wide. A larger bacterium, Thiomargarita namibiensis, a spherical bacterium measuring about 700μ in diameter, was discovered recently. Most prokaryotic cells, i.e., bacterial cells, have a chemically complex cell envelope. The envelope is made up of three layers. They are glycocalyx, cell wall, and plasma membrane. 5

THE FUNDAMENTAL UNIT OF LIFE

Glycocalyx: Glycocalyx is a sticky gelatinous material found outside the cell wall to form an additional surface layer. If it is loosely distributed around the cell, it is called a slime layer, and when firmly attached to the cell's surface, it is called a capsule. The capsule is made up of polysaccharides and amino acids. The presence of the capsule is genetically controlled. It protects bacteria from host cells and also prevents its desiccation. Capsulated bacteria are highly virulent, whereas noncapsulated bacteria are generally avirulent. Cell wall: Bacteria have a rigid cell wall. Their cell wall material is called peptidoglycan or murein. Bacteria can be classified into two groups, gram-positive and gram-negative bacteria, based on the difference in the cell wall structure and manner in which they respond to the staining procedure developed by Christian Gram. Plasma membrane: The plasma membrane is selectively permeable and helps in osmoregulation. It also helps in facilitated diffusion and active transport of solutes. The infolding of plasma membranes present in some bacteria is called mesosomes. These infoldings are in the form of vesicles, tubules, and lamellae. Some mesosomes help in cell wall formation, DNA replication and distribution of DNA to daughter cells. Some mesosomes help in increasing the surface area of the plasma membrane and enzymatic content. In cyanobacteria, the plasma membrane extends into the cytoplasm and forms chromatin pores containing photosynthetic pigments. Flagella: Bacteria cells may be motile or non-motile. If motile, they have thin filamentous extensions from their cell wall called flagella. The flagella apparatus consists of three parts: a basal body, a hook and a flagellar filament. Pili or fimbriae: Pilli are short hair-like structures on the surface of bacteria. They are composed of protein called pilin. They are shorter and stiffer than flagella and slightly smaller in diameter. They do not help in bacterial movement. They help attach bacteria to the substratum and other host cells.

1.7 ULTRASTRUCTURE OF A EUKARYOTIC CELL Eukaryotic cells possess well-organised nuclei, membrane-bound cell organelles and cytoskeletal structures. They are found in protists, fungi, plants and animals. Eukaryote cell organelles are the nucleus, endoplasmic reticulum, Golgi complex, ribosomes, vacuoles, and plastids.

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Fig. 1.5 Eukaryotic cell

1.7.1 Plasma membrane The term 'plasmalemma' was coined by Plowe. The term cell membrane was coined by Nageli & Cramer (1855). Chemical studies on human red blood cells (RBC) enabled scientists to deduce the possible structure of the plasma membrane. It is thin, elastic and selectively or differentially permeable. It is found between protoplasm and cell wall. It can be seen under the microscope in a 0 plasmolysed cell. Its thickness is 75 A . It is made up of proteins, phospholipids and carbohydrates. In a human erythrocyte, the composition of the plasma membrane is: a) Proteins - 52%

b) Lipids - 40%

c) Carbohydrates - 2-5%

Phosphoric phospholipids are also called amphipathic, i.e., phospholipid molecules contain both hydrophilic and hydrophobic parts. The lipids are arranged within the membrane with the polar (hydrophilic) head towards the outer sides and the hydrophobic tails towards the inner part. This ensures that the nonpolar tail of saturated hydrocarbons is protected from the aqueous environment. Carbohydrates of the cell membrane are oligosaccharides, which are branched (or) unbranched. I. Based on position, membrane proteins are of two types. They are: 1. Peripheral proteins: Present superficially on the outer and inner surface of the membrane and can be easily removed. E.g. Spectrin and Cytochrome.

THE FUNDAMENTAL UNIT OF LIFE

2. Integral proteins: Provide channels for the passage of water and water-soluble products. And cannot be removed easily. E.g. Carrier proteins. II. Based on functions, proteins in the plasma membrane are of three types. 1. Structural proteins: They form the backbone of the cell membrane. 2. Carrier proteins: They help in the transport of materials. 3. Catalytic proteins: These are enzymes. Various models of cell membranes have been proposed by different scientists, but the most accepted model is the fluid mosaic model. Fluid mosaic model Sugar

Glycolipid

Lipid bilayer

Protein

Peripheral protein

Cholesterol Integral proteins

Phospholipid

Fig. 1.6 Fluid mosaic model

Fluid mosaic model is the most accepted model of the plasma membrane. It was proposed in 1972 by S.I. Singer and G. Nicholson. According to this model, the membrane does not have a uniform disposition of lipids and proteins but is instead a mosaic of the two. Further, the membrane is not solid but is quasifluid. It postulates that the lipid molecules are present in a viscous bilayer. Protein molecules occur at places both inside and on the other side of the lipid bilayer. . Transport across plasma membrane

It is selectively permeable to some molecules present on either side of it. Many molecules can move briefly across the membrane without any energy requirement, which is called passive transport. Neutral solutes may move across the membrane by the process of simple diffusion along the concentration gradient, i.e., from higher concentration to the lower. Water may also move across this membrane from higher to lower concentration. The movement of water by diffusion across the membrane is called osmosis. As the polar molecules cannot pass through the nonpolar lipid bilayer, they require a membrane carrier protein to facilitate their transport across the membrane. A few ions or molecules are transported across the membrane. A few ions or molecules are transported 8

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across the membrane through its carrier proteins against their concentration gradient, i.e., from lower to higher concentration. Such transport is an energy-dependent process in which ATP is utilised and is called active transport, e.g., Na-K pump. Functions of plasma membrane

1. It protects the animal cells from injury. 2. It plays an important role in osmoregulation. 3. It helps in the transportation of materials. 1.7.2 Cell wall It is the non-living outer protective covering of the plant cell, fungi. It was first observed by Robert Hooke (1665) in the cork tissue of the Oak (Quercus) plant. It is absent in animal cells, gametes and some zoospores. The fungal cell wall consists of polysaccharide fibres with either chitin or cellulose. The cell walls of algae contain cellulose, galactans, mannans and minerals like calcium carbonate. In higher plants, the cell wall fibres are composed of cellulose and embedded in a highly cross-linked matrix of polysaccharides like pectin, lignin and hemicellulose. The cell wall is usually permeable. But suberised cell walls are impermeable. The cell wall is secreted by protoplasm and consists of three layers: middle lamella, primary cell wall and secondary cell wall. Middle lamella

It is an intercellular matrix lying between adjacent plant cells. It is a thin, amorphous, cementing layer and is mainly made up of calcium pectates. The calcium and magnesium ions help in crosslinking the pectic compounds binding to the adjacent cells. It is developed from a cell plate, which is formed by vesicles of the Golgi complex during cytokinesis of the cell division. Primary cell wall

It is the first layer, which lies inside the middle lamella. It is thin and elastic and allows the elongation of cells. It consists of cellulose, hemicellulose, pectic substances and proteins. It is composed of cellulosic microfibrils and a gel-like pectinaceous matrix. Meristematic cells and parenchyma cells contain a primary cell wall only along with the middle lamella. Secondary cell wall

In plant cells, after the completion of cell expansion, a secondary cell wall is formed inside the primary wall. It is thick and rigid. It is impregnated by various types of cell wall materials in different types of tissues. Lignification is observed in some plant cells, whereas deposition of suberin at places in the cell wall makes the cells impermeable to water. Functions of cell wall

1. It provides a definite shape, protection and mechanical support to the cell. 9

THE FUNDAMENTAL UNIT OF LIFE

2. Being a part of the apoplast, the cell wall also helps in transportation. 3. It prevents the bursting of the cell due to endosmosis. 4. The cell wall acts as the structural skeleton of the plant. 1.7.3 Cytoplasm Protoplasm is a clear substance that makes up the inside of a cell. It contains important things like the nucleus and cytoplasm. Cytoplasm is the gel like substance that fills inside the cell membrane. There are also small organelles that float around in the cytoplasm. 1.7.4 Cell organelles All the higher organisms are involved in complex biochemical processes for a simple process of living. Cells in these organisms will have subcellular components designated to perform particular functions. These subcellular components are called cell organelles. Cell organelles include: nucleus, mitochondria, endoplasmic reticulum, ribosomes, Golgi complex, lysosomes, plastids, vacuoles, centrioles, peroxisomes, etc. Nucleus

The nucleus is a spherical structure which controls and coordinates various life activities of a cell. It is the largest and most dynamic cell organelle. It was discovered by Robert Brown in orchid root cells. Cells are of three types based on the number of nuclei present in them. a. Uninucleate or monokaryotic: These are the most common type of cells with a single nucleus. b. Binucleate or dikaryotic: Cells with two nuclei, Eg: Paramecium caudatum, members of ascomycotina and basidiomycotina, tapetal cells of another wall. c. Coenocytic or multinucleate or syncytium: Cells with more than two nuclei. E.g: Vaucheria (Algae); Mucor, Rhizopus (Fungi), and tapetal cells of angiosperms.

Nucleolus Nuclear pore Nucleoplasm

Nuclear envelope Fig. 1.7 Nucleus

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It is the largest cell organelle and occupies 15-20% of cell mass. Its size may vary from cell to cell. In meristematic cells, it is centrally located. In permanent plant cells, the nucleus lies peripherally in the cytoplasm due to the presence of a large central vacuole. The shape of the nucleus is related to the shape of the cell. In most of the cells, it is spherical. The nucleus has four parts. Nuclear envelope: It is a double membrane envelope covering the nucleus. It is also called 'Karyotheca' (or) Nucleolemma. Each unit membrane is 5-10nm in thickness. The outer layer is called ectokaryotheca or outer nuclear membrane, and the inner layer is called endokaryotheca or inner nuclear membrane. The two membranes are separated by perinuclear space 10-50nm. The outer nuclear membrane is continuous with the endoplasmic reticulum. The nuclear envelope bears a number of perforations called nuclear pores. These are circular with a diameter between 10-100 nm. The nuclear pore may be plugged by a large central cart wheel-like diaphragm known as an annulus. The total number of pores in the nuclear envelope may vary from 100 to 107. Various molecules and substances are exchanged between cytoplasm and nucleoplasm through nuclear pores. Nucleoplasm: The nucleus is filled with transparent, granular, homogenous fluid known as nucleoplasm or karyoplasm. It is slightly acidophilic in nature. It is also called nuclear sap or karyolymph. It is composed of mainly nucleic acids, ribonucleoproteins, glycoproteins, enzymes like DNA polymerase, RNA polymerase, NAD synthetase, and dipeptidase, and it contains nucleolus and chromatin. Chromatin: The nucleoplasm contains many thread-like coiled elongated structures called chromatin or chromatin reticulum. Generally, chromatin reticulum is observed only in the interphase nucleus. During cell division, chromatin condenses into thick rod-like structures called chromosomes. Chemically, chromatin consists of DNA, proteins and traces of RNA. Histone proteins are constituents of the chromatin of all eukaryotes. Chromatin devoid of histone proteins is found in prokaryotes. Histone proteins have a high content of amino acids like arginine and lysine. RNA polymerase is a major enzyme that is a non-histone protein. There are two types of chromatin: euchromatin and heterochromatin. Euchromatin

Heterochromatin

Lightly stained

Darkly stained

Fibrous part of chromatin

Granular part of chromatin

Forms the bulk of chromatin

Consists of highly coiled DNA strands

Contains active genes

Consists of inactive genes

Loose coiling of nucleosome strands

Highly coiled DNA strands

Table 1.2 Difference between euchromatin and heterochromatin

THE FUNDAMENTAL UNIT OF LIFE

The chromatin material undergoes condensation to form chromosomes during cell division. The chromatin contains DNA, some basic proteins called histones, non-histone proteins, and RNA. A single human cell has an approximately 2-metre-long thread of DNA distributed among its 46 chromosomes. Chromosomes are vehicles of heredity, known as the physical basis of heredity. Mostly, the number of chromosomes is constant for a particular species. The sporophytic cells contain two sets of chromosomes, which are homologous and are called diploids. But in gametophytic cells, only one set of chromosomes, called haploids, is observed. The size of the chromosomes is usually measured in mitotic metaphase. It is as short as 0.25µm in fungi and birds or as long as 30 µm in Trillium, a monocot. However, most metaphase chromosomes fall in a range of 3µm to 12µm in various organisms. Plant chromosomes are larger than animal chromosomes. The structure of chromosomes is studied in metaphase due to maximum condensation and has the following parts. a. Chromatid: The longitudinal half of the chromosome is called chromatid. Each chromatid consists of one DNA molecule. The metaphase chromosome contains two chromatids that are attached to the centromere. b. Chromonema: The filament chromosomal material seen during mitotic prophase is called chromonemata. A chromonema represents a chromatin in the early stages of condensation. Hence, chromatid and chromonema are two names for the same structure, i.e. a single linear DNA molecule associated with histone proteins. c. Centromere: Chromonemata of chromosomes are connected at the centromere region. The centromere is otherwise called the primary constriction region of the chromosome. The centromere divides the chromosome into arms. d. Kinetochore: Kinetochore are disc-shaped structures made up of protein and seen surrounding the centromere. During cell division, the spindle fibres are implanted into kinetochore discs. e. Telomere: The ends of chromosomes having polarity are called telomeres. It prevents the fusion between two chromosomes. They are responsible for maintaining the stability and individuality of chromosomes. Nucleolus: It is a membrane-less, darkly stained, rounded structure present in the nucleoplasm, also known as plasmosome. The nucleus may contain one or two or many nucleoli. The nucleolus was first observed by Fontana. The nucleolus develops from the nucleolar organiser, which is the secondary constriction of the nucleolar organising chromosomes. It contains RNA, proteins and DNA. They produce ribosomes. Hence, the nucleolus is considered a ribosomal factory. It is the site for active ribosomal RNA synthesis. Larger and more numerous nucleoli are present in cells actively carrying out protein synthesis. The nucleolus disappears during prophase and reappears during telophase during cell division.

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Mitochondria Intermembrane space

Inner membrane

Outer membrane Ribosomes

Matrix

DNA

Granules

Cristae

Fig. 1.8 Mitochondria

Mitochondria were first discovered by Kolliker (1850) in muscle cells. The term mitochondrion was coined by Benda (1857). It is surrounded by a double membrane envelope. The outer and inner membranes are separated by perimitochondrial space. Usually, the outer membrane is smooth, and the inner membrane forms tubular infoldings (or) invaginations into the matrix, known as cristae. It increases the surface area. The matrix of mitochondrion contains single, naked, double-stranded DNA, RNA, 70s ribosomes and respiratory enzymes. They are semi-autonomous cell organelles and are capable of self-duplication. Both transcription and translation take place in mitochondria. In eukaryotes, except glycolysis, the remaining steps of aerobic respiration occur in mitochondria. Light reaction and Krebs cycle take place in the matrix. Electron transport and oxidative phosphorylation take place on the inner membrane of mitochondria. They convert potential energy into kinetic energy and store the energy in the form of ATP (chemical energy). The mitochondria are called bio furnaces (or) powerhouses of the cell. ATP molecules are called the energy currency of the cell. Endoplasmic reticulum

Endoplasmic reticulum was first noticed by Porter, Claude and Fullam (1945). The term ER was coined by K.R Porter (1953). It is a lipoproteinaeous network that runs throughout the cytoplasm from the plasma membrane to the nuclear membrane. It is found in all eukaryotic cells except egg and early embryonic cells. It is a single membrane-bound structure that constitutes more than 50% of the total lipoprotein structures of the cell. ER divides the intracellular space into two distinct compartments, i.e., luminal (inside ER) and extraluminal (cytoplasm) compartments.

THE FUNDAMENTAL UNIT OF LIFE

ER is surrounded by a single unit membrane. It consists of three types of structural components: cisternae, vesicles and tubules There are two types of endoplasmic reticulum such as, 1. Smooth endoplasmic reticulum 2. Rough endoplasmic reticulum Nucleus

Cisternal space

Ribosomes Smooth Endoplasmic Reticulum (SER)

Rough Endoplasmic Reticulum (RER) Cisternae

Fig. 1.9 Endoplasmic reticulum

Smooth ER (SER)

Rough ER (RER)

Walls are smooth

Walls are rough

Ribosomes are not attached to the ER membranes Found in glycogen-storing cells, muscle cells, adipose cells, and leucocytes Develops spherosomes and Golgi complex Developed from RER

80S ribosomes are attached to the ER membranes Found more abundant nearer to the outer nuclear membrane of the cell Has more cisternae than vesicles and tubules Develops from the nuclear envelope

Table 1.3 Difference between smooth and rough endoplasmic reticulum

Functions of endoplasmic reticulum 1. To provide mechanical support to colloidal components of cytoplasmic matrix. 2. Intracellular transportation. 3. Formation of desmotubules. With the help of desmo tubules, the ER of one cell is connected with the ER of an adjacent cell. 4. Provide precursors to the Golgi apparatus. 5. Transmission of nerve impulses. 6. Localisation of cell organelles and keeping various cell organelles in specific positions. 14

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Functions of RER 1. Provides surface for protein synthesis. 2. Formation of the nuclear envelope Functions of SER 1. Provides surface for fat/lipid synthesis. 2. Glycogenolysis, i.e. enzymes of SER, are responsible for the breakdown of glycogen in liver cells. 3. It helps in the synthesis of steroid hormones like testosterone in the testis and estrogen in the ovaries. 4. Storage of glycogen. 5. Detoxification of foreign substances like pollutants, drugs, carcinogens, etc. Ribosomes

Ribosomes were discovered by George Paladae, so-called Paladae granules. These are the smallest and most membranous cell organelles. Ribosomes occur in both prokaryotic and eukaryotic cells. These are present on the surface of the outer nuclear membrane and ER. These are the most primitive cell organelles. Ribosomes are involved in the synthesis of proteins. Therefore, they are known as protein factories. Golgi complex

Camello Golgi (1873) was the first person to discover the Golgi apparatus in the nerve cells of an owl. It is also known as Lipochondria (or) Idiosome (or) Dalton complex (or) Baker's body. It is present in all eukaryotic cells except mature sieve elements in plants, mature sperm cells, and RBC in animals. In plants and lower invertebrates, it is also called the dictyosome. Golgi apparatus develops from invagination of the plasma membrane, evagination of the nuclear membrane, or ER. It has three parts as follows. a. Cisternae b. Tubules c. Vesicles Cisternae are flat, curved, parallelly arranged, smooth membranes with swollen ends. They have a definite polarity. The Golgi complex is a polarised cell organelle. Curvature gives polarity to the cisternae. Tubules are short, branched, and interconnected filamentous structures that develop on the sides and maturing faces of cisternae. Vesicles are small sacs that develop from tubules. The large vesicles are called Golgi vacuoles. They are rounded sacs produced by the concave surface. They are filled with amorphous or granular substances. They function as lysosomes.

THE FUNDAMENTAL UNIT OF LIFE

Functions of Golgi complex 1. In plants, the Golgi complex is mainly involved in the secretion of materials from primary and secondary cell walls and cell plates. 2. In animals, the Golgi apparatus is involved in the packaging and exporting of materials. These packed materials may be delivered within the cell or outside the cell. Materials to be packed as vesicles from the ER fuse with the cis face of the Golgi apparatus and move towards the trans face. That is why the Golgi is closer to the ER. 3. Secretion is the major function of the Golgi complex. 4. The Golgi complex produces a cell plate, which is further converted into the middle lamella. 5. Primary lysosomes arise from the Golgi complex. 6. The Golgi apparatus is an important site for the formation of glycoproteins and glycolipids. Lysosomes

Lysosomes are round, vacuolar structures filled with hydrolysing enzymes and surrounded by a single-unit membrane. They are 0.2-0.5µm in size. Lysosomes may contain all types of hydrolytic enzymes like lipases, phosphatases, sulphatases, nucleases, proteases and carbohydrases, which remain active under acidic conditions. These enzymes can digest carbohydrates, proteins, lipids and nucleic acids. Lysosomes may arise from the Golgi complex or SER. Lysosomes play a vital role in the intracellular digestion of food materials (autophagy). Under starvation conditions, they cause autolysis of cell contents and are hence known as 'suicidal bags of cells'. Plastids

Plastids are double membrane cell organelles with their own genetic material and are concerned with the storage and synthesis of organic compounds. The term plastid was used by Haeckel. They occur in plants and some protistans, like Euglena. Based on pigmentation, the plastids are further divided into three types. These are polymorphic cell organelles. Plastids are of three main types. Leucoplast: These are colourless plastids found in deeper tissues which are not exposed to sunlight. They help in the storage of food materials. Chromoplasts: These are non-photosynthetic and coloured plastids. They contain fats-soluble carotenoid pigments like carotenes and xanthophylls. Chlorophylls are not found in chromoplasts. These are found in aerial parts like petals, seed coats, pericarp of fruits and some underground roots (e.g. carrot). Carotenes impart orange (or) red, and xanthophylls impart yellow colour to the plant plants. Chromoplasts in petals help to attract insects for pollination. Chloroplasts: These are green-coloured plastids involved in photosynthesis. These are the second largest cell organelles of the cell with 5-10 μm in diameter and 2-4 μm in width. In higher plants, mesophyll cells contain 20 - 40 chloroplasts. But a single chloroplast is present in the cells of

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Chlamydomonas. They are generally disc-shaped in higher plants. It is a double membrane-bound cell organelle differentiated into envelope, stroma, matrix, and grana. Outer membrane Intermembrane space Inner membrane

Granum

Thylakoid membrane Thylakoid space (lumen)

Chloroplast DNA Thylakoids

Stroma

Ribosome

Fig. 1.10 Chloroplasts

1. Envelope: It is made up of two smooth unit membranes which are separated by periplastidial space. In the envelope, the outer membrane is freely permeable to small molecules, and the inner membrane is selectively permeable with carrier proteins. 2. Stroma (Matrix): The colourless, homogeneous granular matrix of the chloroplast is called stroma. It contains naked, circular, double-stranded DNA, all three types of RNA, 70S ribosomes, enzymes required for the dark reaction and the most abundant protein, RUBISCO. Starch grains occur temporarily in the stroma of chloroplasts in higher plants. 3. Grana: These lamellae are compact, flattened sac-like structures called thylakoids. There are two types: Grana thylakoids and Stroma thylakoids. Grana thylakoids are staked in piles, and each stack is called Granum. Grana are interconnected by thylakoids called fret membranes (or) stroma thylakoids and are always single. Generally, chloroplasts may contain 40-60 grana. The grana thylakoid is surrounded by a single-unit membrane known as a thylakoid membrane. The central, empty space of the thylakoid is known as the lumen. Lumen serves as a reservoir of protons (H+)and a site for the photolysis of water. Pigments like chlorophylls, carotenes, and xanthophyll molecules are bound to the proteins in the thylakoid membrane. Vacuoles

Vacuoles are membrane-bound spaces present in the cytoplasm. In plant cells, the vacuole can occupy up to 90% of the volume of the cell and play an important role in osmoregulation. Based on the contents and functions, they are of three types.

THE FUNDAMENTAL UNIT OF LIFE

Central vacuole: These vacuoles are filled with cell sap. Meristematic cells have a number of small vacuoles. A mature plant cell has a single large centrally located vacuole formed by the fusion of small vacuoles. The vacuole is covered by a unit membrane called a tonoplast. It is selectively permeable, has ion channels of carrier proteins, and helps transport materials against the concentration gradient. Therefore, the concentration of ions and other materials is higher in cell sap than in cytoplasm. The fluid content of vacuoles is called cell sap or tonoplasm. The sap contains a variety of minerals, proteins, esters, alkaloids, tannins, water-soluble pigments like anthocyanins (blue, pink, violet) and waste products. They play an important role in osmoregulation. They are known as the 'storehouse' of the cell or 'repository of the cell'. Contractile vacuole: These are the vacuoles concerned with the collection of extra fluid materials from the cytoplasm and their release to the outside of the cell. They occur in freshwater protistans (Paramecium, Amoeba) and simple algae (Chlamydomonas). Contractile vacuoles help in controlling the osmotic pressure of the cell. They also help with excretion. Food vacuoles: These are formed due to fusion of phagosomes with lysosomes. These are also called digestive vacuoles. They occur in protozoans, coelenterates and phagocytes of higher animals. Centrosomes or centrioles

Centrosome was discovered by Boveri. Centrioles, the two components of one centrosome, are arranged at right angles and surrounded by pericentriolar materials. Centrioles (centrumcentre) are non- membranous cell organelles which are seen in pair. A pair of centrioles is called a diplosome. Centrioles are seen in all animal cells except mammalian erythrocytes. Most of primitive fungi, protists, bryophytes and pteridophytes have centrioles. Multiple centrioles are seen in bone marrow cells. It is made up of the protein tubulin and a small amount of ATPase.. Peroxisomes

The term peroxisome was coined by Christian de Duve. They are spherical bodies bounded by a single membrane with 0.3 to 1.5μ in diameter. The matrix contains peroxidases, D-amino acid oxidase, urate oxidase and catalase enzymes. Peroxisomes are abundant in the mesophyll cells of plants. They originate from the ER. Peroxisomes perform photorespiration in association with chloroplast and mitochondria in C3 plants. They are also involved in β oxidation of fatty acids, synthesis of phospholipids and detoxification of H2O2.

1.8 COMPARISON OF PLANT CELLS AND ANIMAL CELLS Eukaryotic cells are further divided into plant cells and animal cells. Plant cells are characterised by cell walls and a large central vacuole. Animal cells lack cell walls and consist of small vacuoles and centrioles.

IL Foundation Series Class 9

Plant cell

Animal cell

Fig. 1.11 Comparison of plant cells and animal cells

Plant cell

Animal cell

Presence of cell wall

Absence of cell wall

Plastids are present

Plastids are absent

Presence of permanent vacuoles

Presence of small and temporary vacuoles

Golgi complexes are simple

Golgi complexes are highly complex

Absence of centrosomes and centrioles

Presence of centrosomes and centrioles

Table 1.4 Difference between plant cell and animal cell

QUICK REVIEW • Cells are the tiniest parts of living things that help them stay alive and function properly. • Robert Hooke named the small compartments in cork 'cells' because they looked like boxes. • A compound microscope is a tool with two small lenses that help us see small objects better. • According to the cell theory, cells come from existing cells. • Living things made of only one cell are called unicellular organisms, while others, like plants and animals, which are made of many cells and are called multicellular organisms. • The shape of a cell is connected to its function. • Animal cells have a special layer called a cell membrane, and plant cells have an extra outer layer called a cell wall. • Eukaryotic cells have different parts called organelles, each with a specific function. Cell organelles include the nucleus, endoplasmic reticulum, Golgi complex, ribosomes, mitochondria, plastids, peroxisomes, and centrosomes. • More complex structures and organisations are found in the cells of plants and animals.

THE FUNDAMENTAL UNIT OF LIFE

WORKSHEET - 1 MULTIPLE CHOICE QUESTIONS WITH SINGLE CORRECT ANSWER I. Introduction

1. Smallest cells are a. Bacteria

b. Cyanobacteria

c. Mycoplasma

d. RBC

2. The largest cell is a. Egg of Ostrich

b. RBC

c. WBC

d. Mesophyll cell

3. Arrange the following cells in an ascending order based on their size. i) Mycoplasma

ii) Ostrich egg

iii) Human RBC

a. i, iv, iii, ii

b. i, ii, iii, iv

c. ii, i, iii, v

d. iii, ii, i, v

4. The structural and functional unit of all living organisms is a. Nucleus

b. Protoplasm

c. Cell

d. Gene

II. Discovery of the cell

1. The living cell was first discovered by a. R. Hooke

b. A.V. Leeuwenhoek

c. N. Grew

d. R. Brown

2. Cell was first discovered by a. Robert Hooke

b. Leeuwenhoek

c. Dujardin

d. Janssen

3. Robert Hooke wrote a book entitled a. Enquiry into plants

b. Micrographia

c. Historia Plantarum

d. Cell

4. Bacteria were first discovered by

a. Robert Hooke

b. Janssen

c. Leeuwenhoek

d. Robert Brown

iv) Bacterium

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III. Microscopes & cell theory

1. All structural details of the cell were revealed through the following instrument a. Light microscope

b. Ultracentrifuge

c. Electron microscope

d. Phase contrast microscope

2. Cell lineage or cell inheritance theory was proposed by a. R. Virchow

b. R. Brown

c. Sutton & Boveri

d. Hanstein

3. Cell theory is not applicable to a. Viruses

b. Viroids

c. Prions

d. All the above

4. According to the cell theory, cells are: a. Non replicating unit b. Always multicellular c. Structural unit of life d. Both (a) and (b) 5. The scope of cell theory was extended by a. Schleiden & Schwann

b. R. Virchow

c. Robert Hooke

d. Corti

IV. Prokaryotic cell

1. Bacterial flagellum is composed of a. Basal body

b. Hook

c. Filament

d. All of the above

2. Match the following with reference to the shapes of different bacteria List - I

List - II

A. Coccus

1. Comma

B. Bacillus

2. Spiral

C. Vibrio

3. Spherical

D. Spirochaete

4. Rod/Column 21

THE FUNDAMENTAL UNIT OF LIFE

a. A-3, B-4, C-2, D-1 b. A-2, B-4, C-1, D-3 c. A-3, B-1, C-2, D-4 d. A-3, B-4, C-1, D-2 3. Prokaryotic cells are characterised by a. Having a nucleus b. Having membrane-bound organelles c. Being unicellular d. Being larger in size than eukaryotic cells 4. The cell wall of prokaryotic cells is primarily composed of: a. Cellulose

b. Chitin

c. Peptidoglycan

d. Lipids

5. Which of the following structures are not seen in prokaryotic cells? a. Cell membrane

b. Cell wall

c. Ribosomes

d. Nucleus

V. Ultrastructure of a eukaryotic cell

1. Common cell wall material in the primary wall and secondary wall is a. Cellulose

b. Suberin

c. Pectin

d. Lignin

2. Which of the following is not a function of nucleus? a. Regulation of gene expression

b. Storage of genetic material

c. Synthesis of ATP

d. Control of cellular activities

3. Living structures passing through the cell wall at the region of primary pit fields are called as a. Plasma membrane

b. Microtubules

c. Cytoskeleton

d. Plasmodesmata

4. Major cell wall material present in the cell wall of fungal cells is

a. Cellulose

b. Suberin

c. Chitin

d. Cutin

IL Foundation Series Class 9

5. The most widely accepted model for plasma membranes is a. Sandwich model

b. Fluid mosaic model

c. Unit membrane model

d. Trilamellar model

6. The following is common for both prokaryotic and eukaryotic cells a. Nucleus

b. DNA with histones

c. Cytoplasm

d. 80S Ribosomes

7. Which structure within the nucleus is responsible for storing and organising genetic material? a. Nucleolus

b. Nuclear envelope

c. Nucleoplasm

d. Chromatin

8. The site of a number of biological processes in a cell is a. Nucleolus

b. DNA

c. Protoplasm

d. Plasma membrane

9. The smooth ER is generally made up of: a. Cisternae

b. Tubules

c. Vesicle

d. All the above

10. Cell organelle rich in almost all types of hydrolytic enzymes in a cell is a. Mitochondria

b. Chloroplast

c. Lysosomes

d. Cytoplasm

WORKSHEET - 2 MULTIPLE CHOICE QUESTIONS WITH SINGLE CORRECT ANSWER 1. The plasma membrane mainly consists of: a. Phospholipids embedded in a protein bilayer b. Proteins embedded in a carbohydrate bilayer c. Proteins embedded in a polymer of glucose molecules d. Proteins embedded in a phospholipid bilayer

THE FUNDAMENTAL UNIT OF LIFE

2. Select the correct statement from the following regarding the cell membrane. a. Lipids are arranged in a bilayer with polar heads towards the inner part. b. The fluid mosaic model of the cell membrane was proposed by Singer and Nicolson. c. Na+ and K+ ions move across the cell membrane by passive transport. d. Proteins make up 60 to 70% of the cell membrane. 3. The primary function of the cell wall is to: a. Regulate the movement of molecules in and out of the cell b. Provide structural support and protection to the cell c. Store genetic information d. Participate in enzymatic activity 4. A polysaccharide NOT found in the cell wall of plants is: a. Cellulose

b. Lignin

c. Chitin

d. Pectin

5. The nuclear lamina is primarily composed of: a. DNA

b. RNA

c. Proteins

d. Lipids

6. Among the following components, which is not typically observed within the highly organised structure of a eukaryotic nucleus? a. Nucleosome

b. Nucleolus

c. Chromatin

d. Circular DNA molecule

7. The process of movement of molecules into or out of the nucleus is regulated by: a. Nuclear pores

b. Nuclear matrix

c. Nuclear lamina

d. Nucleolus

8. Which of the following statements are true? i. Smooth ER of liver cells detoxifies many drugs. ii. ER forms an intercellular transport system for the cell. iii. Rough ER is responsible for the synthesis and transport of lipids. iv. Smooth ER is responsible for the synthesis of proteins. a. i and iv

b. ii and iii

c. iii and iv

d. i and ii

IL Foundation Series Class 9

9. Which of the following statements about the rough endoplasmic reticulum (RER) is correct? a. RER is involved in lipid synthesis. b. RER is responsible for detoxification of drugs and toxins. c. RER possesses ribosomes on its surface that are involved in protein synthesis. d. RER plays a crucial role in calcium ion storage and release. 10. Identify the incorrect statement from the following options regarding chloroplasts and mitochondria: a. Both chloroplasts and mitochondria contain an inner and an outer membrane. b. Both chloroplasts and mitochondria have an internal compartment, the thylakoid space bounded by the thylakoid membrane. c. Both chloroplasts and mitochondria contain DNA. d. Chloroplasts are typically found in animal cells, while mitochondria are found in plants. cells.. 11. Assertion (A): Lysosomes are involved in intracellular digestion. Reason (R): Chromosomes are chiefly concerned with the transfer of genetic traits from one generation to the next generation. a. Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A). b. Both Assertion (A) and Reason (R) are true and Reason(R) is not the correct explanation of Assertion (A). c. Assertion (A) is true, but Reason (R) is false. d. Both Assertion (A) and Reason (R) are false. 12. Assertion (A): Mitochondria is often referred to as powerhouse of cell. Reason (R): Mitochondria is responsible for cellular respiration, producing ATP. a. Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A). b. Both Assertion (A) and Reason (R) are true and Reason(R) is not the correct explanation of Assertion (A). c. Assertion (A) is true, but Reason (R) is false. d. Both Assertion (A) and Reason (R) are false. 25

THE FUNDAMENTAL UNIT OF LIFE

13. Which of the following statements is incorrect for ribosomes? a. Synthesize protein in cytoplasm and nucleus b. Composed of ribonucleic acid and proteins c. Not surrounded by any membrane d. Organelle within organelle 14. Assertion (A): Presence of ribosomes is a must in all living cells. Reason (R): Mitochondria are responsible for energy production in the living cells. a. Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A). b. Both Assertion (A) and Reason (R) are true and Reason(R) is not the correct explanation of Assertion (A). c. Assertion (A) is true, but Reason (R) is false. d. Both Assertion (A) and Reason (R) are false. 15. Assertion (A): Cell wall is a non-living part of the cell. Reason (R): Many of the metabolic processes take place in the cell wall.. a. Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A). b. Both Assertion (A) and Reason (R) are true and Reason(R) is not the correct explanation of Assertion (A). c. Assertion (A) is true, but Reason (R) is false. d. Both Assertion (A) and Reason (R) are false. 16. Assertion (A): Glycoproteins are formed by conjugating proteins with carbohydrates. Reason (R): Most of the complex carbohydrates are synthesised by the Golgi complex. a. Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A). b. Both Assertion (A) and Reason (R) are true and Reason(R) is not the correct explanation of Assertion (A). c. Assertion (A) is true, but Reason (R) is false. d. Both Assertion (A) and Reason (R) are false. 26

IL Foundation Series Class 9

17. Assertion (A): Lysosomes are formed by the Golgi complex. Reason (R): The Golgi complex forms a cell wall. a. Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A). b. Both Assertion (A) and Reason (R) are true and Reason(R) is not the correct explanation of Assertion (A). c. Assertion (A) is true, but Reason (R) is false. d. Both Assertion (A) and Reason (R) are false. 18. Assertion (A): Lysosomes are formed by the Golgi complex. Reason (R): The Golgi complex is involved in the formation of secretory vesicles and other cell organelles. a. Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A). b. Both Assertion (A) and Reason (R) are true and Reason(R) is not the correct explanation of Assertion (A). c. Assertion (A) is true, but Reason (R) is false. d. Both Assertion (A) and Reason (R) are false. 19. Assertion (A): Chloroplasts produce both energy and food material. Reason (R): Mitochondria produce energy but not food material. a. Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A). b. Both Assertion (A) and Reason (R) are true and Reason(R) is not the correct explanation of Assertion (A). c. Assertion (A) is true, but Reason (R) is false. d. Both Assertion (A) and Reason (R) are false. 20. Assertion (A): Cell organelles like mitochondria and ribosomes are abundant in meristematic cells. Reason (R): Mitochondria have their own DNA which can replicate independently. a. Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A). b. Both Assertion (A) and Reason (R) are true and Reason(R) is not the correct explanation of Assertion (A). 27

THE FUNDAMENTAL UNIT OF LIFE

c. Assertion (A) is true, but Reason (R) is false. d. Both Assertion (A) and Reason (R) are false. 21. Site of aerobic respiration in a eukaryotic cell is a. Plasma membrane

b. Cytoplasm

c. Mitochondria

d. Peroxisome

22. Cell organelle which produces the glucose using sunlight a. Mitochondria

b. Chloroplast

c. Ribosome

d. Endoplasmic reticulum

23. The colourless (non-pigmented) plastids are a. Leucoplasts

b. Chloroplasts

c. Chromoplasts

d. Both (a) and (c)

24. Leucoplasts, which help in the storage of carbohydrates, are a. Elaioplasts

b. Aleuroplasts

c. Amyloplasts

d. Amorphoplasts

25. The cell organelle which principally performs the function of packaging materials in a cell is a. RER

b. SER

c. Golgi complex

d. Cell wall

26. The nucleus is often described as the 'cell brain' because a. It is located in the centre of the cell. b. It is shaped like that of a brain. c. It controls and coordinates various metabolic activities. d. It can divide and give rise to new nuclei. 27. Prokaryotic cells differs from eukaryotic cells in not having a. Nuclear membrane

b. Mitochondria

c. Plastids

d. All the above

28. Microfilaments perform all the following functions, except a. Provide support to the plasma membrane b. Involved in cyclosis

IL Foundation Series Class 9

c. Help in cell plate method during cell division d. Help in pseudopodia formation 29. What is the function of the mitochondria in a eukaryotic cell? a. Cellular respiration

b. Protein synthesis

c. Cell division

d. Lipid synthesis

30. What is the function of the lysosomes in a eukaryotic cell? a. Storage of water and nutrients

b. Synthesis of proteins

c. Breakdown of cellular waste and debris

d. Production of ATP

31. Which organelle contains DNA and controls cellular activities in a eukaryotic cell? a. Golgi apparatus

b. Nucleus

c. Peroxisomes

d. Vacuole

CELL CYCLE AND CELL DIVISION

2.1 INTRODUCTION The growth and development of multicellular organisms depend on the growth and generation of their cells. Nageli (1846) pointed out that new cells are always formed through the division of preexisting cells. Virchow (1859) supported the above concept and proposed the 'cell lineage' or 'cell inheritance' theory. According to this theory, the daughter cells always arise from pre-existing cells by division (Omnis cellula-e-cellula). Three types of cell division have been distinguished in living organisms: 1. Amitosis 2. Mitosis 3. Meiosis 2.1.1 Amitosis It is characterised by the splitting of the nucleus, followed by that of the cytoplasm. It is seen in unicellular organisms like primitive algae and protozoans. It does not involve the disappearance of the nuclear membrane or the formation of chromosomes and spindle, and is hence called direct cell division. It starts with the elongation of the nucleus, followed by its division. Amitosis does not involve nuclear events (Fig. 2.1). Cytoplasm Nucleus

Parent cell

Division of parent cell

Daughter cells

Fig. 2.1 Amitosis

2.2 CELL CYCLE The sequence of events by which a cell duplicates its genome, synthesises the other constituents of the cell, and eventually divides into daughter cells is termed the 'cell cycle'. Although cell growth

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(in terms of cytoplasmic increase) is a continuous process, DNA synthesis occurs only during one specific stage in the cell cycle. The replicated chromosomes (DNA) are then distributed to daughter nuclei by a complex series of events during cell division. These events are themselves under genetic control. 2.2.1 Phases of cell cycle Human cells divide once every 24 hours, and yeast cells in about 90 minutes. The life cycle (cell cycle) of a cell involves two distinct phases.

op ha

se ha se p a a et ph e M Ana phas lo Te sis kine o Cyt

Period of cell growth after the DNA is duplicated

sis ito M

Period when the DNA is duplicated

Period of cell growth before the DNA is duplicated

G0 Cell cycle arrest

Fig. 2.2 Cell cycle

1. Interphase (non-dividing phase) 2. Cell division or Mitosis (division phase) There is a long non-dividing growing I-phase and a short dividing M-phase. M-phase is the period of actual cell division. It is of short duration as compared to the I-phase. In the average duration of 24 hours in the cell cycle of dividing human cells, the M-phase lasts for a mere one hour (less than 5% of the total). 1. Interphase

Interphase is a series of changes that takes place in a newly formed cell and its nucleus before it becomes capable of cell division. It is the interval period between two successive cell divisions. Previously, it was called the resting stage because there is no apparent activity related to cell division. Though apparently inactive, the nucleus and cytoplasm are metabolically and synthetically active; hence, this phase is also called the preparatory phase. On the basis of synthetic activities, it is divided into three distinct periods: G1 (Gap1) period, S-period, and G2 (Gap2) period. • G1 period: It is also called the first growth period or the post-mitotic period. This G1 phase corresponds to the interval between the M-phase of the previous cell cycle and the initiation 31

CELL CYCLE AND CELL DIVISION

of DNA replication. During this period, the cell size increases. RNA and proteins required for DNA synthesis are synthesised. Since DNA synthesis does not occur, it is also called the first gap period. Tubulin and other mitotic apparatus proteins are also synthesised. The cell is metabolically active and grows in size. • Synthetic period (S period): It is characterised by the replication of the DNA. The number of chromosomes remains the same, but the DNA content is doubled. If the amount of DNA in the G1 Phase is 2C, it is doubled to 4C during the S-phase. In animal cells, centriole duplicates in the cytoplasm. If DNA replication doesn't take place within 24 - 28 hours after division, the cell does not divide further. • G2 period: It is also called the premitotic period or the second growth period. The volume of the nucleus increases. Protein synthesis and the synthesis of nucleolar RNA, r-RNA, m-RNA are synthesised. The number of cell organelles is doubled. Energy pools required for spindle formation and chromosomal movement are also synthesized. The cell is prepared for another division. Some cells in adult animals do not divide (e.g. heart cells). Some cells divide occasionally as needed to replace cells that have been lost because of injury or cell death. These cells exit from the G1 phase, and enter into an inactive stage called the quiescent stage or the G0 stage. They remain metabolically active, but divide again if required. 2. M-phase

The phase of actual cell division or mitosis, the M-phase starts with the nuclear division (karyokinesis) followed by the division of cytoplasm (cytokinesis). Mitosis involves the exact replication of the parent cell followed by its division into two identical daughter cells containing the same number of chromosomes as found in the parent cell. Hence, it is also called equational division. It was first observed by Strausburger (1870) in plant cells, and Walter Flemming (1882) in animal cells. Flemming used the term 'mitosis' due to the thread-like appearance of the chromosomes early in cell division. The two daughter cells formed are similar to the mother cell. Hence, it is called homotypic division. In plants, mitotic cell division is seen in haploid and diploid cells, whereas in animals, mitosis is only seen in diploid somatic cells. In some social insects, haploid cells are also divided by mitosis. In higher plants, the root apex is the best material to observe mitosis. Mitosis consists of two steps: 1. Karyokinesis 2. Cytokinesis Karyokinesis The division of the nucleus is called karyokinesis. Though karyokinesis is a continuous process, for the sake of convenience, it is divided into four stages: prophase, metaphase, anaphase, and telophase. 32

IL Foundation Series Class 9

1. P rophase: Karyokinesis begins with the prophase. The changes that occur during this stage are divided into two types as follows. • Nuclear changes: Chromosomal material undergoes condensation to form distinct chromosomes by losing water. These long thread-like chromosomes are called prochromosomes. In the mid-prophase, the chromosomal arms split longitudinally, except at the centromere (DNA already duplicated in S-phase) to form two chromatids for each chromosome. At the end of the prophase, the two chromatids of each chromosome become more distinct. The nucleolus, the nuclear membrane Golgi, and the endoplasmic reticulum disappear. It results in the scattering of chromosomes in the cytoplasm. • Cytoplasmic changes: In animal cells, the centriole divides into two and moves to opposite poles. Astral rays radiate from each daughter centriole. The initiation of the assembly of the mitotic spindle takes place with the help of microtubules. 2. M etaphase: The complete degradation of the nuclear envelope starts the second phase (metaphase). The chromosomal condensation is completed, and each chromosome with two chromatids is distinctly seen under a microscope. This is the best stage to study the morphology of chromosomes (Karyotype). Spindle fibres are connected to the kinetochores of each chromatid, and the chromosomes scattered in the cytoplasm migrate towards the equator of the spindle. These orient themselves on the equator so that their centromeres lie on the equator and arms are towards the poles. This plane of alignment of the chromosomes at the equator is called the metaphase plate. One chromatid of each chromosome is connected by its kinetochore to spindle fibres from one pole, and its sister chromatid is connected by its kinetochore to spindle fibres from the opposite pole. • Spindle apparatus: From the cytoplasm, special fibres called spindle fibres are developed from each pole of the cell. The entire structure with fibres looks like a spindle, also called the bipolar spindle apparatus. It was discovered by Fol. The fibres are made up of protein tubulin. Hence, the fibres can contract or relax. 3. Anaphase: Due to the contraction of the spindle fibres, the centromere of each chromosome splits, separating the two chromatids into daughter chromosomes and moving towards the poles. Each daughter chromosome has one chromatid with one DNA molecule. As the chromosomes move away from the equatorial plate, the centromeres move towards the poles, and their arms trail behind. Depending upon the position of the centromere, chromosomes form different shapes like 'V', 'L', 'J', and 'I'. 4. T elophase: The characters observed in telophase are the reverse of prophase. Daughter chromosomes that have reached their respective poles undergo decondensation and lose their visibility, ultimately to form a chromatin network. Nuclear membrane, nucleolus, Golgi complex and ER reappear. Two daughter nuclei are formed, one at each pole of the spindle.

CELL CYCLE AND CELL DIVISION

Cytokinesis Cytokinesis is the division of the cytoplasm of a cell into two daughter cells after the nuclear division. Cell organelles are also distributed between the two daughter cells. The process of cytokinesis differs in plant and animal cells. In animal cells, cytokinesis starts with the appearance of a shallow groove or constriction or furrow in the plasma membrane. The furrow gradually deepens and ultimately joins in the centre, dividing the cell cytoplasm into two. This is called the 'cell furrow' method. Sister chromatids Nucleolus Spindle Centromere

Chromatin

Spindle

Centrioles Nuclear pore

Nucleolus

Nuclear envelope

Later interphase

Nuclear envelope fragments Later prophase Metaphase

Nuclear envelope fragments

Chromosome Daughter cells Centromere

Early Interphase

Furrow

Telophase

Anaphase

Fig. 2.3 Different stages of mitosis in an animal cell

In plant cells, cytokinesis takes place using the cell plate method. At the end of the telophase, the remnants of spindle fibres form a barrel-shaped structure called the phragmoplast. The Golgi complex adds calcium and magnesium pectates to the phragmoplast and transforms it into a liquid cell plate. The cell plate is the precursor of the middle lamellum. The cell plate grows centrifugally and joins the parental cell wall on both sides. It then gradually solidifies and transforms into a solid middle lamellum, which separates the cell into two daughter cells. During cytokinesis, the cell organelles, mitochondria and plastids are distributed between the two daughter cells.

Interphase

Prophase

Metaphase

Anaphase

Telophase

Fig. 2.4 Different stages of mitosis in a plant cell

Multinucleate conditions arise due to free nuclear divisions leading to the formation of syncytium, multinucleate or coenocyte. E.g. Liquid endosperm in Cocos. 34

IL Foundation Series Class 9

Significance of mitosis Mitosis is a significant aspect of the growth of living matters. It serves the following purposes. • Equal distribution of chromosomes: The genetic integrity of an individual is maintained by equal distribution of chromosomes in daughter cells. All diploid cells of an individual (from zygote to meiocyte) contain the same number of chromosomes. • Restoration of surface-to-volume ratio: A smaller cell has a greater amount of surface available in relation to volume than a larger cell; hence, smaller cells are metabolically more active. As the cell increases in size, the available surface area in relation to the increased volume becomes less ,and affects oxygen diffusion, exchange of material, etc.; therefore, the cell divides. • Nucleoplasmic index (Nucleo-cytoplasmic ratio): The DNA content of a cell is constant, which can control the activities of the cell up to a specific size beyond which proper control is not possible. A cell cannot grow in size to a large extent without disturbing the ratio between the nucleus and the cytoplasm. When a cell grows to a particular size, it divides and restores the nucleoplasmic index. Hence, the growth of a multicellular organism takes place by an increase in the number of cells rather than by an increase in the size of cells. • Cell repair: Wounded and damaged or disturbed regions of the body are replaced by the addition of cells. Dead cells of the upper layer of the epidermis, cells of the gut lining and RBC are constantly being replaced. • In unicellular forms, mitosis helps in their reproduction. • The growth of multicellular organisms occurs due to mitosis. For example, mitotic divisions in the meristematic tissues, the apical and the lateral cambium, result in the continuous growth of plants throughout their life.

2.3 MEIOSIS Meiosis is a double division that occurs in a diploid cell and gives rise to four haploid cells, each having half the number of chromosomes compared to the parent cell. In sexually reproducing organisms, chromosome number remains constant from generation to generation, leading to genetic stability. The chromosome number, which is doubled during fertilisation, is reduced to half by meiosis during the formation of gametes. Thus, meiosis is also called reductional division or heterotypic division. Meiosis ensures the production of the haploid phase in the life cycle of sexually reproducing organisms, whereas fertilisation restores the diploid phase. August Weismann (1887) first observed the reduction of chromosomal numbers in animals. Meiosis was discovered by Strausburger (1888) in plants, and the name 'meiosis' was coined by Former and Moore (1905). The cell which undergoes meiosis is called a meiocyte. 35

CELL CYCLE AND CELL DIVISION

2.3.1 Stages of meiosis Interphase occurs prior to meiosis. Meiosis is divided into two major stages viz. meiosis-I and meiosis-II. 1. Meiosis-I

It is a complicated and lengthy phase and is further divided into karyokinesis-I and cytokinesis-I. Karyokinesis-I • It is the first nuclear division in the meiocyte. • The number of chromosomes present in the meiocyte is reduced by half. • It is divided into four phases: prophase-I, metaphase-I, anaphase-I, and telophase-I. • Prophase-I is the most important stage of meiosis, has a longer duration, and is more complex when compared to prophase of mitosis. It is further divided into sub-phases, i.e., leptotene, zygotene, pachytene, diplotene and diakinesis. • In leptotene, the size of the nucleus increases, and chromosomes become more distinct with their double strands. The chromosomes appear as slender threads bearing a series of granuleslike structures called chromomeres. • In zygotene, the chromosomes become shorter and thicker. Homologous chromosomes come together and pair lengthwise. This process of pairing is called synapsis. The nucleolus increases in size, and the centrioles move apart, initiating the spindle formation. • During the pachytene stage, the paired chromosomes of bivalent shorten and thicken to appear as tetrads. Each bivalent consists of four chromatids. • Diplotene is characterised by the beginning of separation and repulsion of paired homologous chromosomes. • Diakinesis is the final stage of meiotic prophase-I. The chromosomes are fully condensed. The nuclear membrane and nucleolus disappear, and bivalents are scattered in the cytoplasm.

Prophase I

Metaphase I

Anaphase I

Telophase I & Cytokinesis

Fig. 2.5 Different stages of meiosis-I

• In metaphase-I, bivalents move towards the equator. A bipolar spindle is formed. Spindle fibres are attached to the centromeres of the two homologous chromosomes.

IL Foundation Series Class 9

• During anaphase-I, the two chromosomes of the bivalent separate, and the tetrad separates into two dyads. The homologous chromosomes, each consisting of two chromatids united by a centromere, move towards the poles of the cells. • No division of centromere, unlike mitosis. The two genomes are separated, and the chromosome number is reduced to half at each pole. • At telophase-I, the chromosomes at the poles of the spindle undergo decondensation and become elongated. • The nuclear membrane and the nucleoli reappear. • At the end of the telophase-I, two daughter nuclei appear distinctly. Cytokinesis-I As the nuclear membrane and nucleolus reappear, cytokinesis follows. This is called a dyad of cells. Interphase is the stage between meiosis-I and meiosis-II. DNA duplication (S-phase) does not occur. 2. Meiosis-II (Homeotypic division) • The second meiotic division is a mitotic division. • It takes place independently in both the haploid daughter cells. • During this period, the DNA does not duplicate, but the centromere divides.

A new spindle forms around the chromosomes.

Metaphase II chromosomes line up at the equator.

Centromeres divide. Chromatids move to the opposite poles of the cells.

A nuclear envelope forms around each set of chromosomes. The cytoplasm divides.

Prophase II

Metaphase II

Anaphase II

Telophase II & Cytokinesis

Fig. 2.6 Different stages of meiosis-II

• Like mitosis, four haploid daughter cells are formed. Significance of meiosis • In sexually reproducing organisms, the constant number of chromosomes through generations is maintained by meiosis by producing haploid gametes. 37

CELL CYCLE AND CELL DIVISION

• Due to crossing over, the hereditary factors from the male and female parents get mixed, thus providing a new combination of genetic material. • Variations inherited lead to the evolution of species.

QUICK REVIEW • Multicellular organisms start their life from a single cell 'zygote'. • Amitosis does not involve the disappearance of the nuclear membrane and formation of chromosomes and spindle and is hence called direct cell division. • The sequence of events by which a cell duplicates its genome, synthesises the other constituents of the cell, and eventually divides into daughter cells is termed 'cell cycle'. • The cell cycle involves two distinct phases: interphase (non-dividing phase) and cell division or mitosis (division phase). • Mitosis is also called equational division or homotypic division. It involves the exact replication of the parent cell followed by its division into two daughter cells, which are identical and contain the same number of chromosomes found in the parent cell. • The division of the nucleus is called karyokinesis. Though karyokinesis is a continuous process, for convenience, it is divided into four stages: prophase, metaphase, anaphase, and telophase. • The division of cytoplasm into two daughter cells is called cytokinesis. • In animal cells, cytokinesis starts with the appearance of a shallow groove or a constriction or a furrow in the plasma membrane. • In plant cells, cytokinesis takes place using the cell plate method. • In sexually reproducing organisms, chromosome number remains constant from generation to generation and leads to genetic stability. The chromosome number, which is doubled during fertilisation, is reduced to half by meiosis during the formation of gametes. • Meiosis is divided into two major stages, viz. meiosis -I and meiosis -II. Meiosis-I is a disjunctional (or) heterotypic (or) reduction division, whereas meiosis-II is a normal (or) equational division (or) homotypic division. • Prophase-I is the most important stage of meiosis. It is further divided into sub-phases based on chromosomal behaviour, i.e. leptotene, zygotene, pachytene, diplotene, and diakinesis.

IL Foundation Series Class 9

WORKSHEET - 1 MULTIPLE CHOICE QUESTIONS WITH SINGLE CORRECT ANSWER I. Introduction to cell cycle and cell division 1. Human cells in culture divide approximately every a. 90 minutes

b. 19 minutes

c. 24 hours

d. 1 hour

2. The parental chromosomes produce two identical sister chromatids during the a. G1 phase

b. G2 phase

c. S phase

d. Prophase

3. During this phase of the cell cycle, the cell is metabolically active without duplication of DNA. a. M phase

b. S phase

c. G1 phase

d. G2 phase

4. In a meristematic cell, DNA quantity becomes double in a. G1 sub-phase

b. S sub-phase

c. G2 sub-phase

d. Prophase

5. Proteins and RNA synthesis occurs during the a. S phase and G1 phase

b. G1 and G2 phase

c. G1 and M phase

d. S and G2 phase

6. The number of chromatids in G1 and G2 respectively in a somatic cell with 2n =20 is a. 40, 20

b. 20, 40

c. 10, 20

d. 10, 40

7. Select the incorrect statement with respect to the cell cycle. a. Duplication of genes occurs twice in meiosis. b. Karyokinesis occurs twice during meiotic division. c. Cyclins are proteins that activate protein kinases to regulate the cell cycle. d. After telophase-I, the chromosome number is reduced to half.

CELL CYCLE AND CELL DIVISION

8. The correct sequence of phases of the cell cycle is a. M → G1 → G2 → S

c. S → G1 → G2 → M

[NEET - 2019]

b. G1 → G2 → S → M d. G1 → S → G2 → M

9. The shorter and longer arms of a sub metacentric chromosomes are referred to as

[NEET - 2019]

a. s-arm and 1-arm, respectively

b. p-arm and q-arm, respectively

c. q-arm and p-arm, respectively

d. m-arm and n-arm, respectively

10. In the prophase stage of mitotic cell division, how many chromatids are attached together at the centromere to compose the chromosomes? a. Two

b. Four

c. Three

d. Infinite

II. Cell cycle 1. Which of the following is not a feature of telophase? a. Chromosomes cluster at opposite spindle poles b. The centromere split and the chromatid separation c. The nuclear envelope assembles around the chromosome clusters d. Nucleolus, Golgi complex and ER reform 2. Identify the wrong statement regarding the metaphase of mitosis. a. Chromosomes can be observed clearly under the microscope once their condensation is completed. b. A chromosome is made up of two sister chromatids, which are held together by the chiasmata. c. Small disc-shaped structures at the surface of the centromeres are called kinetochores. d. Chromosomes are moved to the spindle equator, and get aligned along the metaphase plate through spindle fibres. 3. Which of the following options gives the correct sequence of events during mitosis?

[NEET - 2017]

a. Condensation → arrangement at equator → centromere division → segregation → telophase

IL Foundation Series Class 9

b. Condensation → nuclear membrane disassembly → crossing over → segregation → telophase

c. Condensation → nuclear membrane disassembly → arrangement at equator → centromere division → segregation → telophase

d. Condensation → crossing over → nuclear membrane disassembly → segregation → telophase 4. Which of the following points is not applicable for the prophase of mitosis? a. The initiation of assembly of mitotic spindle. b. Chromosomes are seen to be composed of two chromatids attached together at the centromere. c. Spindle fibre attaches to the kinetochores of the chromosomes. d. The centriole starts to move towards the opposite poles. 5. Select the incorrect match.

[NEET - 2018]

a. Sub-metacentric chromosomes

L-shaped chromosomes

b. Allosomes

Sex chromosomes

c. Lamp brush chromosomes

Diplotene bivalents

d. Polytene chromosomes

Oocytes of amphibians

6. Study the following lists. List - I

List - II

A. Prophase

I. Formation of spindle fibres

B. Metaphase

II. Nucleolus disappears

C. Anaphase

III. DNA replication

D. Telophase

IV. Centromere divides

The correct match is a. A-II, B-IV, C-III, D-V

b. A-II, B-IV, C-I, D-V

c. A-II, B-I, C-IV, D-V

d. A-IV, B-III, C-II, D-I

7. The longest and the shortest phases of mitosis are respectively a. Prophase and metaphase

b. Metaphase and anaphase

c. Anaphase and telophase

d. Prophase and anaphase

CELL CYCLE AND CELL DIVISION

8. Cells in this stage can enter into the G0 stage a. S phase

b. G2 phase

c. G1 phase

d. M phase

9. A bacterial cell divides every minute. It was found that it filled the petri plate in half an hour. In how much time will one-fourth of the plate be filled? a. 7.5 minutes

b. 15 minutes

c. 28 minutes

d. 29 minutes

10. Mitotic division is also called equational division because a. The chromosome number in daughter cells is the same b. The chromosome number in daughter cells and the parental cell is the same c. The amount of DNA is the same in both daughter cells d. The amount of DNA is the same in both the daughter and parental cell 11. Chromosomes are scattered in the cytoplasm during a. Early metaphase

b. Late metaphase

c. Early anaphase

d. Late anaphase

12. Chromosomes decondense and lose their individuality during a. Prophase

b. Metaphase

c. Anaphase

d. Telophase

13. Which among the following is reformed during telophase? a. Nucleolus

b. Golgi complex

c. ER

d. All of the above

14. An example of a coenocytic condition is the a. Liquid endosperm of coconut

b. Solid endosperm of coconut

c. Telophase-II

d. Both (a) and (b)

15. In animal cells, cytokinesis is achieved by

a. Cell furrow method

b. Cell plate method

c. Both (a) and (b)

d. None of the above

IL Foundation Series Class 9

III. Meiosis 1. The complex formed by a pair of synapsed homologous chromosomes is called a. Equatorial plate

b. Zygotene

c. Bivalent

d. Axoneme

2. Meiosis takes place in

a. Meiocyte

b. Conidia

c. Gemmule

d. Megaspore

[2013]

3. Assertion (A): Meiosis takes place in the pollen mother cells. Reason (R): Each pollen mother cell produces four haploid pollen grains. a. Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A). b. Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A) c. Assertion (A) is true, but Reason (R) is false. d. Assertion (A) is false, but Reason (R) is true. 4. Identify the labelled parts of the following diagram. A1

B1 C A2 B2

a. A1, A2 are sister chromatids; B1, B2 are non-sister chromatids; C = Chiasmata; D = centromere b. A1, A2 are sister chromatids of non-homologous chromosomes; B1, B2 are sister chromatids; C = Region of crossing over; D = Centromere c. A1, A2 are sister chromatids; B1, B2 are sister chromatids; C = crossing over; D = centromere d. A1, A2 are sister chromatids; B1, B2 are sister chromatids; C = Kinetochore; D = Centromere

CELL CYCLE AND CELL DIVISION

5. Arrange the various phenomena of meiosis in a correct sequence. A) Pairing of homologous chromosomes

B) Separation of genomes

C) Recombination between two chromosomes

D) Chiasmata

a. D, B, A, C

b. D, C, A, B

c. A, C, D, B

d. C, D, B, A

6. The following stage is incorrect with reference to meiosis a. Nucleus divides twice

b. Chromosomes divide twice

c. Chromosomes divide once

d. Centromere divides once

7. During the cell cycle, every chromosome contains two DNA molecules from the a. G1 sub-phase to anaphase

b. G2 sub-phase to anaphase

c. S sub-phase to metaphase

d. S sub-phase to anaphase

8. The ratio of chromosomes moving to each pole during anaphase-II to those moving to each pole during anaphase-I is a. 1: 1

b. 1: 2

c. 2: 1

d. 1: 4

9. Find out the correct sequence of events during meiosis I) Disjunction

II) Crossing over

III) Synapsis

IV) Terminalisation

a. III, II, I, IV

b. III, II, IV, I

c. II, III, I, IV

d. III, IV, II, II

10. Meiosis is characterised by a. Two successive divisions of cytoplasm nuclei and chromosomes b. Two successive divisions of cytoplasm and nuclei accompanied by one replication of chromosomes c. One division of cytoplasm and nuclei accompanied by replication of chromosomes twice d. One division of cytoplasm and nuclei accompanied by replication of chromosomes once 11. The daughter cells formed as a result of meiosis are not similar to that of parent cell because a. Meiosis is completed in two stages b. Prophase is the longest phase c. Nucleus size increases in daughter cells d. Crossing-over takes place, and the chromosome number is halved 44

IL Foundation Series Class 9

12. Genomes migrate to the opposite poles by the end of a. Anaphase-I

b. Telophase-I

c. Diakinesis

d. Cytokinesis

13. The number of meiotic divisions required to produce 100 seeds in an angiosperm plant is a. 25

b. 50

c. 100

d. 125

14. How many reductional divisions are required to form 400 synergids? a. 400

b. 300

c. 200

d. 100

15. Identify the correct statement with regard to the G1 phase (Gap 1) of interphase.[NEET 2020] a. The DNA synthesis or replication takes place. b. The reorganisation of all cell components takes place. c. The cell is metabolically active and grows, but does not replicate its DNA. d. Nuclear division takes place.

WORKSHEET - 2 I.

MULTIPLE CHOICE QUESTIONS WITH SINGLE CORRECT ANSWER

1. The growth of multicellular organisms is initiated by a. Cell division

b. Cell enlargement

c. Cell differentiation

d. Morphogenesis

2. Yeast cells can progress through the cell cycle in about a. 90 minutes

b. 19 minutes

c. 90 seconds

d. 19 seconds

3. The M-phase of the cell cycle starts with a. Duplication of DNA

b. Karyokinesis

c. Cytokinesis

d. Division of chromosomes

4. In animal cell cycle, the centriole duplicates during a. G1 phase

b. G2 phase

c. S phase

d. M phase 45

CELL CYCLE AND CELL DIVISION

5. The condensation of chromosomal material is initiated during a. Prophase

b. Metaphase

c. Anaphase

d. Telophase

6. Spindle fibres are chemically a. Carbohydrates

b. Proteins

c. Proteins and carbohydrates

d. Proteins and fats

7. The precursor of the cell plate is the a. Phragmoplast

b. Middle lamellum

c. Primary cell wall

d. Secondary cell wall

8. Diakinesis is mainly characterised by a. Synapsis

b. Crossing over

c. Segregation

d. Terminalisation

9. The longest phase of meiosis is a. Prophase-I

b. Prophase-II

c. Anaphase-I

d. Metaphase-I

10. Chromosomes are first visible under the light microscope during a. Leptotene

b. Zygotene

c. Pachytene

d. Diplotene

11. The amount of DNA per cell remains the same during a. S, G1, G2 and metaphase

b. G1, G2, M-phase

c. Anaphase, telophase, G1 phase

d. Both (a) and (c)

12. Two DNA molecules in a cell are observed, but they are not distinct in which of these phases? a. S and G2

b. G2, prophase

c. Metaphase and anaphase

d. G1 and G2 phases

13. When compared to the G1 phase of mitosis, the quantity of DNA in the nucleus of each daughter cell will be

a. Half as much as in the parent nucleus

b. Same as much as in the parent nucleus

c. Twice as much as the parent nucleus

d. Highly variable

IL Foundation Series Class 9

14. Identify the correct sequence of the following phases during the cell cycle. I) M-phase

II) S sub-phase

III) G2 sub-phase

IV) G1 sub-phase

a. IV, II, III, I

b. I, IV, II, III

c. IV, III, II, I

d. II, IV, III, I

15. Name the A, B, C, and D parts during the cell cycle.

a. A = G2 period

B = Mitosis

C = S phase

D = G1 period

b. A = S phase

B = G2 period

C = Mitosis

D = G1 period

c. A = G1 period

B = G2 period

C = S phase

D = Mitosis

d. A = Mitosis

B = S phase

C = G2 period

D = G1 period

16. Which among the following characters is not observed during anaphase? a. Centromere splits b. Chromatids moving towards the equator c. Chromatids moving towards poles d. Centromeres of chromatids getting oriented towards the poles 17. Cell division usually involves a. Karyokinesis followed by cytokinesis

b. Karyokinesis preceded by cytokinesis

c. Cytokinesis followed by karyokinesis

d. Both (a) and (c)

18. Condensation and decondensation of chromosomes occur, respectively, in a. Prophase and metaphase

b. Anaphase and metaphase

c. Prophase and anaphase

d. Prophase and telophase 47

CELL CYCLE AND CELL DIVISION

19. When 16 cells are formed from a single cell, how many times do the cells divide, and how many cells are formed in the third generation? a. 4 and 8

b. 4 and 7

c. 3 and 8

d. 4 and 16

20. If a bacterial cell divides once every minute, it takes one hour to fill a cup. How much time will it take to fill half of the cup? a. 30 minutes

b. 59 minutes

c. 58 minutes

d. 15 minutes

21. If each cell of the spore tetrad contains four chromosomes, how many pachytene tetrads are found in the meiocyte of that plant? a. 2

b. 8

c. 4

d. 16

22. What is the ratio of the number of chromatids, chromosomes, bivalents and centromeres in a cell during metaphase-I? a. 1: 2: 2: 1

b. 4: 2: 2: 1

c. 4: 2: 1: 2

d. 2: 1: 2: 1

23. The movement of bivalents towards the periphery of the nucleus, and their movement towards the equator of the meiocyte occur, respectively, during a. Diakinesis and anaphase-I

b. Diplotene and diakinesis

c. Leptotene and diakinesis

d. Diakinesis and metaphase

24. During meiosis, when are the paternal and maternal chromosomes brought together and separated, respectively? a. Zygotene and anaphase-II

b. Prophase-II and anaphase-I

c. Zygotene and anaphase-I

d. Leptotene and telophase-I

25. Identify the correct ascending sequence of the following aspects of meiosis.

A) Number of spindle apparatus formed

B) Number of chromosomal divisions

C) Number of cells formed

D) Number of nuclear generations

a. B, C, A, D

b. B, D, C, A

c. D, C, A, B

d. B, D, A, C

IL Foundation Series Class 9

26. Find the correct statement with respect to the replication of the DNA in cell division. a. It occurs during the G1 phase of the interphase. b. New strands complementary to old strands are synthesised with the help of endonucleases. c. Two strands of DNA unwind from each other due to DNA polymerase. d. It occurs by the semi-conservative method. 27. Mark the correct statements. A) In the 24-hour average duration of the cell cycle of a human cell, cell division properly lasts for only about an hour. B) Interphase lasts more than 95% of the duration of the cell cycle. C) The DNA content gets half at the S-phase of the interphase. D) The G2 phase is also called the post-mitotic phase. a. A and B

b. B and C

c. A, B and D

d. C and D

28. Identify the incorrect statement from the following. a. The M-phase represents the phase when the actual cell division or mitosis occurs, and the interphase represents the phase between two successive M-phases. b. The division phase lasts more than 95% of the duration of the cell cycle. c. Yeast can progress through the cell cycle in only about 90 minutes. d. The interphase is the time during which the cell is preparing for division by undergoing both cell growth and DNA replication in an orderly manner. 29. S-phase is not characterised by a. DNA duplication b. No increase in chromosome number c. DNA replication d. Duplication of centriole in the nucleus of eukaryotic animal cell 30. Which one is the false statement about the G2 phase? a. It is a post-S phase and pre-M phase. b. In this phase, the cell quantity of DNA in each cell is (4C). If the DNA is in the G1 phase, the cell quantity is (2C). 49

CELL CYCLE AND CELL DIVISION

c. G0 resides in this phase. d. Proteins like tubulin are formed for mitosis as well as cell growth continues. 31. Select the incorrect statement. I. Cell-plate formation occurs in plant cells during cytokinesis. II. During cytokinesis, mitochondria and plastids get distributed between two daughter cells in mitosis. III. Liquid endosperm in coconut is syncytium. IV. Furrow formation occurs in plant cells during cytokinesis. a. I

b. II

c. III

d. IV

32. Metaphase is not characterised by the a. Complete condensation of chromosome c. Attachment of spindle fibre to kinetochore

b. Alignment of chromosomes of metaphase plants d. Splitting of chromosome

33. Which of the following does not occur during mitotic prophase? a. Disappearance of the nuclear envelope c. Migration of centriole towards the cell poles

b. Chromosome condensation d. Synapsis of homologous chromosomes

34. Identify the phases A and B.

a. A = Metaphase

B = Early prophase

b. A = Early anaphase B = Late prophase

c. A = Anaphase

B = Early prophase

d. A = Metaphase

35. Identify the correct statement. a. Each metaphase chromosome shows four DNA molecules. b. Each metaphase chromatid shows one DNA molecule. 50

B = Pachytene

IL Foundation Series Class 9

c. Each chromatid shows two DNA molecules in all stages of meiosis. d. Early anaphasic chromosomes show one DNA but two kinetochore discs. 36. Meiosis in a plant occurs when there is a change from a. Gametophyte to sporophyte

b. Sporophyte to sporophyte

c. Sporophyte to gametophyte

d. Gametophyte to gametophyte

37. A somatic cell that has just completed the S-phase of its cell, as compared to a gamete of the same species, has:

[NEET - 2015]

a. Four times the number of chromosomes and twice the amount of DNA b. Twice the number of chromosomes and twice the amount of DNA c. Same number of chromosomes but twice the amount of DNA d. Twice the number of chromosomes and four times the amount of DNA 38. Which among the following is incorrect with regard to meiosis? a. The nuclear envelope disappears twice. b. The nuclear envelope reappears twice. c. The DNA content of daughter cells is reduced to 1/4th of the parental cell. d. The DNA duplicates once. 39. Assertion (A): Chromosomal congression leads to the equatorial arrangement of chromosomes during metaphase. Reason (R): The force responsible for the equatorial arrangement of chromosomes is the equal pull of chromosomal fibres. a. Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A). b. Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A). c. Assertion (A) is true, but Reason (R) is false. d. Assertion (A) is false, but Reason (R) is true.

CELL CYCLE AND CELL DIVISION

40. Identify the sub-phases A and B.

a. A = Late prophase B = Metaphase

b. A = Diplotene

B = Diakinesis

c. A = Metaphase

d. A = Pachytene

B = Diplotene

B = Diakinesis

TISSUES

3.1 INTRODUCTION TO TISSUES Cells are the basic building blocks of all living organisms. All metabolic activities take place in the cells. In unicellular organisms, all activities are performed by a single cell. In multicellular organisms, all the cells are not alike. The specific tasks are performed by groups of similar cells. Such groups of cells are termed tissues. The term 'tissue' originates from the French word 'Tisser', which means 'something woven'. The study of tissues is known as histology.

3.2 ARE PLANTS AND ANIMALS MADE OF THE SAME TYPES OF TISSUES? Plants and animals are made up of different kinds of tissues that serve different functions. There are noticeable differences between the two types of tissues. Sr No.

Plant Tissues

Animal Tissues

Tissue organisation is targeted towards the stationary habit of plants.

Tissue organisation is targeted towards the mobility of animals.

Organisation is simple.

Organisation is complex.

Many of the tissues are dead. For example, cork.

Most of the tissues are living.

Growth is confined to certain areas.

Growth is not limited to areas.

Less maintenance energy is required.

More maintenance energy is required.

Plants grow continuously throughout life.

After reaching the maturity stage, animals do not show further growth.

Table 3.1 Difference between plant tissues and animal tissues

3.3 PLANT TISSUES 3.3.1 Introduction to plant tissues Plant tissues are grouped into two groups: meristematic tissue and permanent tissue 53

TISSUES

Plant tissues

Meristematic Tissues

Permanent Tissues

Simple permanent tissues

Apical meristem

Intercalary meristem

Lateral meristem

Complex permanent tissues

Parenchyma

Xylem

Collenchyma

Phloem

Sclerenchyma

Fig. 3.1 Different types of plant tissue

3.3.2 Meristematic tissue The term 'meristem' was given by C. Nageli. The meristematic tissue, or meristem, is defined as the tissue in a mature plant body, the cells of which continuously divide to add new cells to the plant body. The meristem is of embryonic origin and remains active throughout the life of the plant. Characteristics of meristematic tissue

• The cells of this tissue are round, oval, polygonal, or rectangular. • They are compactly arranged without intercellular spaces. • They have thin cellulosic walls, dense cytoplasm, and prominent nuclei. • Vacuoles are almost absent in such cells. • The cells actively undergo cell division and form new cells. Types of meristem

Based on the location in the plant body, meristems are of three types: 1. Apical meristem 2. Intercalary meristem 3. Lateral meristem 54

IL Foundation Series Class 9

Apical meristem

Intercalary meristem

Lateral meristem

Fig. 3.2 Types of meristems Type of Meristems Location

Function

Apical Meristem

Intercalary Meristem

Lateral Meristem

At the apices (growing At the base of the leaves and tips) of the root, stem, and the nodal region of twigs branches

Present at the lateral axis parallel to the periphery of the stem or root (below the outer layers of stems and roots).

Increase in height of the plant (length of roots and stems) by the active division of cells.

Increase in girth or width (diameter) of the plant by active division.

Remain active only for a short period. Rapid stem elongation; tissue at the base of leaves allows the regrowth of the leaves when damaged. Table 3.2 Types of meristem

3.3.3 Permanent tissue The meristematic tissue, after differentiation, gives rise to permanent tissues. These constitute a major portion of the plant body. Characteristics of permanent tissue

• Permanent tissues are composed of mature cells that, after complete growth, have assumed a definite shape, size, and function and have temporarily or permanently lost the power of division. • Permanent tissues may have thin walls, or walls with thickening of various degrees and types. • Permanent tissues with thin wall are generally living, whereas the thick-walled tissues may be living or dead. 55

TISSUES

• They develop from the meristems and may be the primary permanent tissues if derived from apical and intercalary meristems or secondary permanent tissues if derived from the lateral meristems. They can be classified into two main types: 1. Simple permanent tissues 2. Complex permanent tissues Simple permanent tissue

A simple permanent tissue is a group of permanent cells that are structurally and functionally similar (i.e., perform a common function). A simple permanent tissue is further differentiated into three types: parenchyma, collenchyma, and sclerenchyma. 1. Parenchyma Structure: This tissue is made up of large and unspecialised living cells. Cells may be oval, rounded, or a polygonal peripheral protoplasm containing a prominent nucleus. Intercellular spaces are present. It forms the basic packing tissue of the plant body. Location: It is widely found in various plant organs such as roots, stems, leaves, flowers and fruits. Functions • The main function of the parenchymatous tissue is storage of food, e.g., starch in potato tuber. • In fleshy stems and leaves, the parenchyma cells serve as the water storage tissue, e.g., Euphorbia and Opuntia. • It forms the framework of all the plant organs and tissues. • It stores plant waste materials, such as gum, crystals, resins, tannins, etc. • The intercellular air spaces of the parenchyma cells allow gaseous exchange.

Fig. 3.3 Structure of parenchyma

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2. Collenchyma Structure: Schleiden discovered and coined the term 'collenchyma'. It is a living tissue of the primary body. The cells are thin-walled but possess thickenings of cellulose and pectin substances at the corners where the number of cells joins together. Cells are compact, and the intercellular spaces are absent. Location: It is found in the petioles, leaves, and stems of the herbaceous dicots. Functions • It provides mechanical support, protection, and elasticity to the plant organs. • Due to its peripheral position, it helps leaves in the bending and pulling action of wind. • Chloroplast containing collenchyma cells are responsible for photosynthesis.

Fig. 3.4 Structure of collenchyma

3. Sclerenchyma Structure: It is a simple, dead mechanical tissue with usually lignified cell walls and simple or slightly bordered pits. Cells may be short or elongated and single or in groups. If these cells are in groups, intercellular spaces are absent. Protoplast is absent at maturity, and the cell has an empty central region known as a lumen. Lignification of the cell wall helps with overcoming various strains caused by stretching, bending, weight, and pressure.

Fig. 3.5 Structure of sclerenchyma

TISSUES

Although sclerenchyma shows great variations and transitional forms, they are categorised into two types: sclerenchyma fibres and sclereids. i. Sclerenchyma fibres: They are highly elongated, narrow, thick-walled cells with pointed or oblique end walls. Fibres are usually clustered into strands that interlock to form tissue that is strengthening. ii. S clereids: They are highly thickened, irregularly shaped cells that are broader than fibres. They may occur singly or in groups. Lumen Thick cell wall

Pits Lumen Thick cell wall

A ﬁbre

A sclereid Fig. 3.6 Sclerenchyma fibre and sclereid

Location: This tissue is found in the hard grit of a pear fruit, the hard walls of nuts and the brittle coats of seeds, veins of leaves, husk of coconut, etc. They form the major part of walnut shells and of other nuts. They form an important part of the bark of trees. Functions • Sclerenchyma acts as a mechanical tissue, giving support and strength to various parts of the plant body. • They protect the plant from environmental forces like strong winds. • They make the plant hard and stiff. Complex permanent tissue

These tissues are made up of more than one type of cells. All these cells work together to perform a common function. The complex tissue carries out the function of conduction of substances through the plants. Hence, this tissue is also called vascular tissue or conducting tissue. The tissue which is concerned with the conduction of water and minerals from the roots to the other parts of the plant is called the xylem. The tissue which is concerned with the conduction of food materials from the leaves to the other parts of the plant is called phloem. Usually, in higher plants, the xylem and phloem occur together in the roots, stems and leaves. These are called vascular bundles. 58

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1. Xylem Structure: Their cells are thick-walled. The xylem tissue consists of four types of cells. They are tracheids, vessels, xylem parenchyma, and xylem fibres. Fibre

Tracheids Perforation plates

Vessel members

Fig. 3.7 Xylem and its components

i. Tracheids • They are non-living, elongated cells with tapering ends. • Their cell wall is highly thickened with lignin. • These are networks of hollow connected cells through which water can pass. ii. Xylem vessels • They are non-living cylindrical tube-like cells. • They are placed one above another. • Vessels are made up of lignin. • Lignin makes the cell walls rigid and long-lasting. • Vessels are interconnected through the perforations in their common walls. iii. Xylem parenchyma • They contain living cells. • Their cell walls are made up of cellulose. iv. Xylem fibres • They are non-living, thick-walled cells.

TISSUES

• They provide mechanical energy. Functions • The living parenchyma cells of xylem parenchyma help in the sideways conduction of water and dissolved minerals. • They also helps in the storage of starch and other materials. • The lignin in xylem vessels helps in holding the trees up. • Tracheids help to transport water and minerals from the soil to the leaves for the manufacture of food. • Xylem tissue carries out the upward conduction of water and minerals from the roots to the other parts of the plant. • Older xylem forms the wood and gradually loses the ability to transport. 2. Phloem Structure: The phloem tissue consists of four types of cells. They are the sieve tubes, companion cells, phloem parenchyma, and phloem fibres. All the phloem cells are living cells except those that form the phloem fibre. i. Sieve tubes • They are elongated cylindrical, thin-walled cells with perforated ends. • Matured sieve tubes lose nuclei and other cell organelles, except the vacuoles. • They are considered living cells without nuclei. • The nuclei of companion cells control the functional activities of the sieve tubes. • Perforations (or pores) help in the easy transportation of substances from one cell to the adjacent cells. Fibre Sieve plates Companion cell Sieve areas

Sieve elements

Fig. 3.8 Phloem and its components

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ii. Companion cells • They are living cells, smaller in size. • They contain dense cytoplasm and prominent nuclei. • These cells help the sieve cells control the transportation through sieve tubes. iii. Phloem parenchyma • Contains living cells with thin cell walls made up of cellulose. • Forms packing tissue in connecting different cells. • Helps in the storage of starch and other organic substances, such as latex, resins, etc. • Helps in the sideways conduction of water. iv. Phloem fibres • Elongated tapering dead cells are found in the stem. • The cell walls are thickened and give mechanical support. Function • Phloem tissue provides for the downward transportation of prepared food material (starch) from leaves to various parts of the plant. • This process of transporting food in plants is called translocation. Sr. No.

Xylem

Phloem

(i)

It conducts water and inorganic solutes in vascular plants.

It conducts organic solutes in vascular plants.

(ii)

Conduction mostly occurs in one direction (i.e., upward).

Conduction may occur in both directions, i.e., upward and downward.

(iii)

Conduction channels (tracheary elements) are tracheids and vessels.

Conducting channels are sieve tubes.

(iv)

Its components include tracheid, vessels, xylem parenchyma and xylem fibres.

Its components include sieve tubes, companion cells, phloem parenchyma and phloem fibres.

(v)

Tracheid, vessels and xylem fibres are dead, and only xylem parenchyma is living.

Sieve tubes, companion cells, and phloem parenchyma are living, and only phloem fibres are dead.

(vi)

Xylem provides mechanical strength also.

Phloem does not provide mechanical strength.

Table 3.3 Difference between xylem and phloem

TISSUES

3.3.4 Tissue systems in plants A tissue or a group of tissues that performs a similar function, irrespective of its position in the plant body, is called a tissue system. Based on the structures and functions, various types of tissues (both meristematic and permanent) are found in the internal structure of a plant. Introduction to tissue system in plants

Based on the morphological characters, development, and function, Sachs distinguished three tissue systems in plants: 1. Epidermal (or tegumentary) system 2. Ground (or fundamental) system 3. Vascular (or fascicular) system 1. Epidermal tissue system The epidermis is the outermost protective layer of plant organs. It is usually single-layered, but in the leaves of some plants growing in dry habitats, it is multi-layered and thick. This is to protect the plant from water loss. The epidermis protects all the parts of the plant. Cells of the epidermis form a continuous layer without intercellular spaces to protect the plant tissues. Epidermal cells of aerial parts of the plant secrete a waxy, water-resistant layer on their outer surface. It protects them against loss of water, mechanical injury and any attack by pathogenic fungi.

Epidermis

Fig. 3.9 Epidermis

In desert plants, the outer walls of the epidermis are usually thick and covered with organic substances like cutin. The thick cutinised wall of the epidermis greatly reduces the loss of water by transpiration. The epidermal cells of the roots contain long hair-like structures called root hairs. The root hairs increase surface area for absorption of water and nutrients from soil. The epidermis of the leaf contains small pores called stomata. The stomata help in the exchange of gases with the atmosphere. They also help in the loss of water in the form of water vapour known as transpiration. 62

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Cork: As plants grow older with time, protective tissues at the periphery undergo some changes. In them, a strip of secondary lateral meristem (cork cambium) originates below the epidermal layer of the stem. The cork cambium gives off new cells on both sides, forming a cork on the outer side and a secondary cortex on the inner side. Cork in mature woody stem is made up of dead, thick-walled cells compactly arranged without any intercellular spaces. The walls of the cork cells also contain suberin (a chemical substance), which is impervious to gases and water. The secondary cortex is composed of parenchymatous cells. Cork performs protective functions in the following ways: • Cork cells, being highly suberised and thick-walled, protect the inner tissues. • It provides insulation from freezing temperatures. • It protects the inner tissues from the attacks of microorganisms and prevents water loss.

Vascular cambium Living phloem cork Cambium Periderm Cork

Bark

Fig. 3.10 Cork cambium and cork

2. Ground tissue system This tissue system is located below the epidermal tissue. This tissue system forms the bulk of the plant body. The composition of ground tissue is variable as it depends on the parts of the plant in which it is located.

Vascular tissues

Xylem

Dermal tissue (epidermis)

Phloem

Ground tissue

Fig. 3.11 Ground tissue system

TISSUES

In leaves, the ground tissue is located between the upper epidermis and lower epidermis. It is called mesophyll and is composed of parenchyma tissue, which is rich in chloroplasts. It is mainly concerned with the manufacture of food (photosynthesis) and its storage. In stems and roots, the region beneath the epidermis is occupied by the tissues of the ground tissue system. The ground tissue in stems and roots is usually heterogeneous, as it is made up of all three types of simple permanent tissues: parenchyma, collenchyma, and sclerenchyma. It performs variable functions of all three types of tissues. In roots, it is mostly supportive in function. 3. Vascular tissue system The vascular tissue system is present below the ground tissue system. It lies towards the central region of all the parts of the plant. This is composed of the conducting tissues, namely, the xylem and the phloem. The xylem and the phloem together constitute a vascular bundle. In the stems and roots of most plants, a layer of lateral meristematic tissue is present between the xylem and phloem. This layer is called the vascular cambium. The vascular cambium undergoes repeated mitotic divisions and forms a secondary xylem to the inside and a secondary phloem to the outside. This results in the growth in the girth (diameter) of the stems and roots. In woody plants, the growth of secondary xylem in stems is enormous and forms wood. As the wood grows older, the tissue loses the capacity to conduct water. The formation of wood is a significant event in the growth of the plant. It is because of the high commercial value attributed to wood that the term xylem originated from the word 'xylo', which means wood. This means xylem tissue is the woodforming tissue. The nature and quality of wood depend on the age of the plant. The older the tree, the greater the quality of the wood.

Xylem vessel Cambium

Phloem vessel

Fig. 3.12 Vascular tissue system Secondary Growth in Plants

The formation of wood depends on environmental factors and varies from one season to the other. The spring season is the favourable season for the growth of the plants. Therefore, during this 64

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season, the plant needs a large amount of water and minerals. Hence, the xylem vessels possess large cavities. This wood is called spring wood. It is light in colour. The autumn season is generally less favourable for the growth of plants. Therefore, during this season, the plant requires a lesser amount of water and minerals. Hence, the xylem vessels possess small cavities. This wood is called autumn wood. It is dark in colour. The two types of wood are formed every year, and they appear as concentric rings of light and dark circles when the horizontal cross-section of the stem is observed. These concentric rings are called annual rings. The age of the plant can be determined by the number of annual rings that appear.

Fig. 3.13 Annual rings

3.4

ANIMAL TISSUES

3.4.1 Introduction to animal tissues The human body is composed of billions of cells. The structure of the cells varies according to their function. Therefore, the tissues are different and are broadly classified into four types: 1. Epithelial tissue 2. Connective tissue 3. Muscular tissue 4. Neural tissues

Epithelial tissue

Nervous tissue

Muscle tissue

Connective tissue

Fig. 3.14 Types of animal tissues

TISSUES

3.4.2 Epithelial tissue Epithelial tissue is the simplest type of tissue, which forms the outer protective covering all over the animal body and lines the inside of all cavities, such as those of the mouth, throat, stomach, and more. The epithelial cells are tightly packed with little or no intercellular substance or matrix between them. The epithelial tissue rests on a thin, non-cellular basement membrane, which is made of a network of glycoproteins and collagen fibres. Functions of epithelial tissue i. P rotection: Most epithelia protect the underlying tissues against mechanical injury such as abrasion. Some epithelia protect against water loss, dehydration, and infection by microorganisms. ii. R ole in physiological processes: Some epithelia are involved in physiological processes such as respiratory gas exchange and elimination of waste products, and some cells become glandular in nature and perform secretory functions. iii. Sensory role is performed by sensory epithelium. iv. Transport of materials is accomplished by ciliated epithelium. Epithelium may be one-cell thick, that is, single-layered (simple epithelium), or it may be severalcell thick, that is, many-layered (compound or stratified epithelium). Simple epithelium

It has a single layer of cells resting on a basement membrane. It covers moist surfaces where there is little wear and tear due to friction. They are further of five types according to the form and structure of their cells: squamous, cuboidal, columnar, ciliated, and pseudostratified. 1. Simple squamous epithelium

It consists of thin, flat, disc-like cells closely fitted like the tiles on a floor. Hence, it is also called pavement epithelium. They function in the exchange of material by diffusion. These epithelia line blood vessels and the air sacs of the lungs, where diffusion of nutrients and gases is critical. 2. Simple cuboidal epithelium

It consists of cells that are about as tall as wide. The nucleus is rounded and lies at the centre of the cell. This makes up the epithelia of kidney tubules and many glands. 3. Simple columnar epithelium

It consists of cells that are much taller than wide. The nucleus is elongated along the long axis of the cell and may have a variable position. It lines the intestines. This epithelium secretes digestive juices and absorbs nutrients. 66

IL Foundation Series Class 9

4. Simple ciliated epithelium

It consists of cells that bear fine, vibratile cytoplasmic processes, the cilia, on the free surface. It is of two types: i. Cuboidal ciliated epithelium: It lines certain parts of the urinary tubules of the kidney. ii. Columnar ciliated epithelium: It lines the nasal passages, oviducts, terminal bronchioles, ventricles of the brain, and central canal of the spinal cord of the embryo. 5. Pseudostratified epithelium

It is of two types: columnar and ciliated. Pseudostratified columnar cells line the large ducts of certain glands, such as the parotid salivary gland. They are also a component of olfactory mucosa. Pseudostratified columnar ciliated epithelium lines the trachea and large bronchi.

Simple squamous epithelium

Simple columnar epithelium

Simple cuboidal epithelium

Simple ciliated epithelium

Pseudostratified epithelium

Fig. 3.15 Types of simple epithelium Compound epithelium

The compound epithelium is also known as the stratified epithelium. In this, the cells are arranged in many layers, one above the other. It is found in places where there is much wear and tear, such as the epidermis of the skin, the lining of the mouth cavity, etc. 1. Stratified squamous epithelium

Stratified squamous epithelium regenerates rapidly by cell division near the basement membrane. The new cells are pushed to the free surface as replacements for cells that are continually sloughed

TISSUES

off. This type of epithelium is commonly found on surfaces subject to abrasion, such as the outer skin and linings of the oesophagus. The stratified squamous epithelium is of two types: i. K eratinised stratified squamous epithelium: The outer few layers contain a hard waterproof protein, keratin, in the cytoplasm. These cells are helpful in protecting against abrasion and infection (e.g., skin epidermis, hair, and nails) and also prevent drying or desiccation. ii. N on-keratinised stratified squamous epithelium: Cells do not have keratin in their upper layers. Thus, they cannot check the water loss. The non-keratinised stratified squamous epithelium is found in the cornea, oral cavity, oesophagus, rectum, internal portion of lips, etc. 2. Stratified cuboidal epithelium

It lines the sweat gland ducts and larger salivary and pancreatic ducts. It forms the epidermis of fish and many urodeles. 3. Stratified columnar epithelium

It consists of the outer layer of ciliated columnar cells and the basal layer of columnar cells. It lines the larynx and upper part of the soft palate. 4. Transitional epithelium

This epithelium is present only in the urinary system. The transitional epithelium of the undistended urinary bladder has about four or five layers of cells. The superficial cells are rounded. When the urinary bladder is full of urine, the superficial cells become squamous, and the epithelium appears to be two or three cells thick.

Stratified squamous non-keratinised

Stratified squamous keratinised

Stratified cuboidal

Stratified columnar

Transitional (urothelium) in relaxed state

Transitional (urothelium) in distended state

Fig. 3.16 Types of stratified epithelium

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3.4.3 Connective tissue Introduction to connective tissue

The connective tissue is the most abundant and widely distributed tissue in the body. It is responsible for providing and maintaining form (shape) in the body. They are named connective tissues because of their special function of linking and supporting other tissues or organs of the body. It also protects and insulates internal organs and serves as the major transport system (blood). The major constituent of connective tissue is the extracellular matrix, in which the cells are scattered. The matrix consists of different combinations of protein fibres (collagen, reticular, and elastic) and ground substance. The ground substance consists of water and combinations of polysaccharides and proteins. 1. Cells of connective tissue The different types of cells found in the connective tissue are fibroblasts, mast cells, macrophages, plasma cells and adipocytes. 2. Fibres of connective tissue The connective tissue fibres are formed of proteins. The three main types of connective tissue fibres are collagen, reticular, and elastic fibres. Collagen (white) fibres are composed of collagen. They are strong and stretch-resistant. Elastic (yellow) fibres are composed mainly of elastin. These form a kind of lattice (network) by joining their branches. They are strong but can be stretched. They can return to their original shape after being stretched. Reticular fibres are extremely thin collagen fibres and form an extensive network in certain organs. They provide support and strength.

Fig. 3.17 Types of connective tissue Loose connective tissue

This has cells and fibres loosely arranged in a semi-fluid ground substance. Loose connective tissue includes areolar connective tissue and adipose tissue. 69

TISSUES

1. Areolar tissue

It is one of the most widely distributed connective tissues in the body. It contains all the three types of fibres and cells typically found in a connective tissue. It often serves as a support framework for epithelium. It occurs beneath the skin and is found beneath the epithelia of many visceral organs like the stomach and trachea and in the walls of arteries and veins. The areolar tissue joins different tissues, forms the packing between them and helps to keep the organs in place and in normal shape.

Macrophage Fibroblast Collagen ﬁbres

Mast cells

Fig. 3.18 Areolar tissue 2. Adipose tissue

It is another type of loose connective tissue located mainly beneath the skin. The adipose tissue synthesises, stores, and metabolises fat. The excess nutrients that are not used are converted into fats and are stored in cells called adipocytes. It contributes to the thermal insulation of the body. It forms shock-absorbing cushions around the kidneys and eyeballs and in the soles and palms. Subcutaneous adipose tissue is responsible for the body contour. Fat vacuole Cytoplasmic rim of a fat cell Nucleus of a fat cell Capillary

Arteriole

Fig. 3.19 Adipose tissue Dense connective tissue

This tissue contains numerous compactly packed fibres and fibroblasts. There are three types of dense connective tissue: the dense regular connective tissue, the dense irregular connective tissue, and the elastic connective tissue. 70

IL Foundation Series Class 9

1. Dense regular connective tissue

The fibroblasts are present in rows between many parallel bundles of fibres. This tissue has bundles of collagen fibres arranged parallel to one another. Examples include tendons (connect muscles to bones) and ligaments (connect one bone to another bone).

Fibroblast nuclei

Collagen ﬁbres

Collagen ﬁbres bundles Fibroblast nuclei

Dense regular connective tissue

Dense irregular connective tissue Fig. 3.20 Dense connective tissue

2. Dense irregular connective tissue

This tissue has fibroblasts and bundles of collagen fibres that are oriented irregularly. It occurs in the periosteum, perichondrium, pericardium, heart valves, joint capsules, and the deeper region of the dermis of the skin. 3. Elastic connective tissue

In this tissue, the elastic fibres predominate, giving a yellowish colour to the tissue. This tissue can recoil to its original shape after being stretched and released. For example, the wall of elastic arteries, vocal cords, trachea, bronchi, etc. Specialised connective tissue

Cartilage, bone, blood, and lymph are the types of specialised connective tissue. Cartilage and bone constitute skeletal tissue. They have a rigid matrix and form the endoskeleton. Blood and lymph constitute fluid connective tissue. They have a liquid matrix. 1. Skeletal connective tissue

This tissue forms the internal framework of the body,provides for muscle attachment, and defines the place of various organs. This tissue can be categorised into cartilage and bone. i. Cartilage

Cartilage is also called gristle. It is a solid but semi-rigid and flexible (pliable) connective tissue that imparts support and flexibility to the organs. There are three types of cartilage in the human body: hyaline, fibrous, and elastic. 71

TISSUES

Parameter

Hyaline

Fibrous

Elastic

Appearance

Bluish, transparent

Whitish, opaque

Yellowish, opaque

Flexibility

Flexible

Firm

Highly flexible

Perichondrium

Present

Absent

Present

Fibres

Fewer, thin white

Abundant, white

Abundant, yellow

Location

End of the ribs, nose, larynx, trachea, and bronchi

Intervertebral disks and at the intersections of ligaments and tendons

External ear, the auditory tube of the middle ear, and the epiglottis

Diagram

Table. 3.4 Difference between the different types of cartilage

Cartilage is surrounded by a tough fibrous membrane called perichondrium. Matrix is dense and rubbery and composed of proteins and calcium salts. The cells of the cartilage called chondroblasts are embedded in the matrix in groups of two, four or more in fluid-filled spaces called lacunae. It is avascular and is nourished by the diffusion of nutrients from capillaries in the perichondrium. It is rich in collagen and fibroblasts. ii. Bone

It is the main tissue of the adult endoskeleton that provides the structural frame of the body. Bones support and protect softer tissues and organs. They also interact with skeletal muscles attached to them to bring about movements. Long bones serve a weight-bearing function. The bones form a reservoir for the homeostatic control of calcium and phosphorous. Bone tissue is vascular. The ground substance of bone tissue is hard and non-pliable, rich in calcium salts and collagen fibres, which give bone its strength. There are three types of bone cells. • Osteoblasts (bone-forming cells) synthesise the organic components of the matrix and play a role in the mineralisation of bone. • An osteoblast is gradually surrounded by a newly formed matrix and becomes an osteocyte, enclosed in a space called a lacuna. • Osteoclasts are involved in the resorption and remodelling of bone tissue. They are a type of macrophage in bone.

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Structure of compact bone tissue: A compact bone is lined by an endosteum on the internal surface and a periosteum on the external surface. In the matrix, collagen fibres are arranged in lamellae. It has many Haversian systems. Osteocyte

Haversian canal

Lamellae

Osteon

Volkmann’s canal

Canaliculi

Periosteum Spongy bone

Fig. 3.21 Structure of compact bone

Each Haversian system consists of a Haversian canal parallel to the marrow cavity. It contains blood vessels and nerves. It is surrounded by concentric layers of bone lamellae. Lacunae containing osteocytes are found between the lamellae. Each lacuna encloses an osteocyte. An osteocyte has an irregular shape and long cytoplasmic processes. The cytoplasmic processes of osteocytes extend into minute canals called canaliculi that radiate from the lacuna. Canaliculi connect lacunae and with the Haversian canal. A Haversian canal and the surrounding concentric lamellae and lacunae are collectively called a Haversian system or osteon. The Haversian canals communicate with the marrow cavity, the periosteum, and one another through transverse or oblique Volkmann's canals. Fluid connective tissue

The tissue consists of a fluid matrix. The fibres are absent in the matrix. The matrix is in the form of liquid, which is called plasma. The cells are found floating in the plasma and are called corpuscles. The material of the matrix is not secreted by the cells present in the tissue. Depending on the composition, this tissue is classified into two types: blood and lymph. 1. Blood

Blood is a special connective tissue consisting of a fluid matrix (plasma) and formed elements. It is a red, opaque, slightly alkaline fluid. The study of blood is termed haematology. Blood has two components: 1. Formed elements, or blood cells that account for 45% of blood volume. 2. Plasma that accounts for 55% of blood volume. 73

TISSUES

Whole Blood

Fig. 3.22 Composition of blood i. Formed Elements

These are the cells and cell fragments suspended in plasma. These include erythrocytes (red blood cells), leucocytes (white blood cells), and platelets. a. Erythrocytes

These are the most abundant of all the formed elements in the blood. The number of RBCs per mm3 or μL of blood is about 5 to 5.5 million in men and 4.5 to 5 million in women. The production of RBCs is called erythropoiesis. Most mammalian erythrocytes are enucleated (devoid of nucleus) and biconcave. The biconcave shape provides a large surface-to-volume ratio, thus facilitating gas exchange. Erythrocytes are surrounded by a flexible plasma membrane (Donnan's membrane). Nucleus and other organelles are absent. The cytoplasm of RBC contains a red-coloured, iron-containing complex protein called haemoglobin, hence the colour and name of these cells. A healthy individual has 12-16g of haemoglobin in every 100 mL of blood. The average life span of human erythrocytes is about 120 days. Old RBCs are phagocytosed by macrophages in the spleen or liver or the red bone marrow. The spleen is often described as the graveyard of RBC. b. Leucocytes

They are colourless and nucleated spherical or irregular cells. The number of leucocytes is roughly 6,000-8,000 per mm3 of blood. The production of WBC is called leucopoiesis. Generally, they are

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short-lived. According to the presence or absence of specific granules in their cytoplasm, leucocytes are divided into two groups: granulocytes and agranulocytes. •

Granulocytes

Granulocytes possess specific granules that are stainable in different dyes. Granulocytes have lobed nuclei that may assume different shapes. Hence, they are called polymorphonuclear leucocytes. They are of three types: neutrophils, eosinophils, and basophils. i . Neutrophils: Neutrophils constitute about 60-65% of circulating leucocytes. Their nucleus consists of two to five (usually three) lobes linked by fine threads of chromatin. Cytoplasm has small specific granules that are stained by neutral dyes. They are the most abundant cells. They are active phagocytes. i i. Eosinophils: Eosinophils or acidophils constitute about 2-3% of leucocytes. They have a characteristic bilobed nucleus. Cytoplasm has many large specific granules that are stained by acidic dyes, such as eosin. Eosinophils phagocytose antigen-antibody complexes. An increase in the number of eosinophils in blood during allergic reactions and helminthic infections is termed eosinophilia. iii. Basophils: Basophils constitute about 0.5-1% of leucocytes. The nucleus is S-shaped or irregularly lobed. The specific granules are stainable with basic dyes. They are the least in number. Basophils secrete heparin, histamine and serotonin and are involved in inflammatory reactions. •

Agranulocytes

Agranulocytes do not have specific granules. The nucleus is unlobed and includes lymphocytes and monocytes. i. Lymphocytes: They constitute about 20-25% of leucocytes. They are spherical cells. They have a spherical nucleus and scanty peripheral cytoplasm. The two major types are the B-cells and the T-cells. They play an important role in immune reactions. Some lymphocytes (E.g. plasma cells) live only a few days, while others (memory cells) survive for many years. Lymphocytes are the only leucocytes that return from the tissues back to the blood after diapedesis via the lymphatic system. ii. Monocytes: They constitute about 6-8% of leucocytes. Monocytes are the largest leucocytes (12-15 m). Their nucleus is kidney shaped. After entering connective tissues, monocytes differentiate into macrophages. These are highly mobile and phagocytic and engulf the bacteria or other microbes. These are also called internal scavengers because they remove dead cells from the sites of injury. c. Platelets

Platelets are also known as thrombocytes. They are round or oval biconvex disc-shaped cell fragments. In healthy humans, the ratio of platelets to RBCs ranges from 1:10 to 1:20. Normal platelet count ranges from 150,000 to 350,000 per cubic mm of blood. They are anucleated and the 75

TISSUES

smallest of the formed elements. They are formed by the fragmentation of giant megakaryocytes in the red bone marrow and have a life span of about 8-10 days. The development of platelets is called thrombopoiesis. They release a variety of substances (e.g. thromboplastin), most of which are involved in the coagulation or clotting of blood (haemostasis). They help in preventing excessive blood loss during an injury.

RBC/Erythrocyte

Neutrophil

Lymphocyte

Basophil

Monocyte

Eosinophil

Platelet

Fig. 3.23 Formed elements ii. Plasma

Plasma is a straw-coloured, slightly alkaline (pH 7.4) liquid matrix in which the formed elements are suspended. It consists of about 90-92% water and 8-10% of solutes. The solutes include inorganic and organic substances. Organic substances include plasma proteins, glucose, amino acids, cholesterol, fatty acids, vitamins, enzymes, hormones, gases, and wastes such as urea, uric acid, creatinine, ammonia and bilirubin. Plasma proteins such as albumins, globulins and fibrinogen are the major plasma proteins. Albumin is the most abundant plasma protein. It is responsible for the blood's colloidal osmotic pressure. Globulins include α, β and γ globulins. γ globulins are the immunoglobulins or antibodies. Fibrinogen is needed for blood coagulation (clotting). Some other factors for coagulation or clotting of blood are also present in the plasma in an inactive form. 2. Lymph

The plasma that has oozed out of the blood vessels is called the lymph. It is colourless. It has RBCs and platelets but contains WBCs. The type of WBCs that are commonly present in lymph are called lymphocytes. It is present in the nodes, spleen, tonsils, adenoids and thymus. They transport nutrients to the heart from blood capillaries that may have been filtered out. It carries nitrogenous waste products and carbon dioxide from the tissue fluid back to the blood. It forms the body's immune system and shields it against infections. 76

IL Foundation Series Class 9

3.4.4 Muscular tissue Introduction to muscular tissue

The muscle tissue is composed of cells called myocytes (also known as muscle cells) and forms muscles in the body. Myocytes are long and tubular. The muscle cells are formed from the cells called myoblasts. The cytoplasm of the cells of the muscular tissue contains elongated fibrils called myofibrils. The cytoplasm of the cells is called sarcoplasm. Sometimes, the muscle fibre is externally covered by a membrane called sarcolemma. The muscle cells contain a special protein called contractile protein. This protein is responsible for the ability of this tissue to contract and relax. Contractility is the special feature of this tissue. Hence, this tissue is also called contractile tissue. The muscle tissues are held together by connective tissues. Based on their structure, location, and function, muscles are of three types. They are listed as follows. 1. Striated muscles 2. Non-striated muscles 3. Cardiac muscles 1. Striated muscle: It is closely attached to the skeletal bones; hence, it is also known as skeletal muscle. It rounds in the muscles of the limbs, the body walls, the tongue, the pharynx, and the beginning of the oesophagus and is under the control of the animal's will. Each skeletal muscle consists of numerous muscle fibres. Each muscle fibre is an elongated cell, which is syncytial (multinucleate). Its membrane is called sarcolemma. Each muscle fibre contains many myofibrils. A myofibril has dark and light bands. The dark bands are also called A-bands. The light bands are also called I-bands. Each I-band has at its centre a dark membrane called a Z-line. The part of the myofibril between two Z-lines is called sarcomere. Thus, each sarcomere is a bundle of thick and thin myofilaments. The thick filament consists mainly of myosin protein. The thin filament is composed of three different proteins: actin, tropomyosin, and troponin.

Fig. 3.24 Skeletal muscle tissue

TISSUES

2. Non-striated muscle: Due to lack of striations, this muscle is also called the smooth muscle. It is found in the oesophagus (posterior part), stomach, intestine, lungs, urinogenital tract, urinary bladder, blood vessels, the iris of the eye, the dermis of the skin, and the arrector pili muscle of hair. It is involuntary in function. Functionally, the smooth muscle is of two types: i. Single-unit smooth muscle is found in the walls of hollow visceral organs like the gastrointestinal tract and the urinary bladder. ii. Multi-unit smooth muscles are found in the arrector pili muscles of the skin dermis, ciliary and iris muscles in the eyes, and muscles of the walls of the large blood vessels.

Fig. 3.25 Smooth muscle tissue

3. Cardiac muscle: It is found in the walls of the heart and has a very rich supply of blood. It is uninucleated, involuntary, and divided at places by intercalated discs. The fibres have some lateral branches, known as cross bridges. It is supplied with both central and autonomic nervous systems and is not under the control of the will of the animal. However, this muscle never gets fatigued. It has the property of contraction, even when it is isolated from the body temporarily. The human heart is myogenic. It means cardiac impulses originate from the Sino-atrial node or SA mode (a node of specialised cardiac muscle fibres situated in the wall of the heart).

Fig. 3.26 Cardiac muscle tissue

IL Foundation Series Class 9

3.4.5 Nervous tissue The nervous tissue is a special kind of tissue and is the main tissue component of the nervous system, which includes the brain, spinal cord, and nerves. The tissue comprises neurons and neuroglia or glial cells. Neurons are the functional units of the nervous system, as they receive and transmit nerve impulses. These cells are sensitive to stimuli. The neuroglia or glial cells help in the propagation of nerve impulses and provide nutrients for the neurons. Depending on the function associated with the neurons, they are categorised into three types. 1. Motor neurons: They are involved in movement and locomotion. 2. Sensory neurons: They are involved in the perception of sensations. 3. Interneurons: They form connections between neurons and help in the transmission of messages and conduction of nerve impulses. Though there is a slight variation in the structure of these different types of neurons, the basic structure of a typical neuron is almost the same. The junction where the dendrite terminal of one neuron is connected to the axon terminal of the other neuron is known as the synapse. Some nerve fibres are covered by a myelin sheath and are called the myelinated nerve fibres. These are generally present in the brain and spinal cord. The bundles of nerve fibres are called nerves. Structure of neuron

The neutron is composed of three parts, as mentioned: • The main body is called the cyton. It contains a nucleus. • Short hair-like processes called dendrons arise from the cell body. These dendrons further branch into many thin cytoplasmic processes called dendrites. • A long, cylindrical process arising from the cyton is called an axon. It forms branches at the other end. • Neurons are joined end-to-end to form nerve fibres. • The junction where the axon terminal of one neuron joins with the dendrite terminal of the adjacent neuron is called a synapse. Functions of neuron

The nerve fibres transmit messages received from the brain or spinal cord from one part of the body to the other. They receive stimuli from the outside environment and send messages to the brain and spinal cord, which in turn send impulses to various organs. Neurons work in coordination with the muscular system to cause various body movements and locomotion. They help the brain to carry out the important functions of memory and coordination. 79

TISSUES

Dendrite Nucleus Dendritic branches Nerve ending

Axon

Cell body

Schwann cell Myelin sheath

Node of Ranvier

Synaptic terminals

Fig. 3.27 Neuron

QUICK REVIEW • Tissues are groups of similar cells that perform specific tasks. • Several tissues performing a specific function together form an organ. • Plants and animals show large variation in the type of tissues and, hence, in the body organisation. • Plant tissues are of two types: meristematic and permanent tissues. • Meristematic tissues have cells which divide actively throughout the life of the plant. • Cells of permanent tissue take up a specific role and lose their ability to divide. • Based on the structures and functions, all the various types of tissues in the internal structure of a plant are categorised into dermal, ground, and vascular tissue systems. • Depending on the location and functions of the tissues in the human body, the tissues are categorised into four types: epithelial, connective, muscular and nervous tissue. • Epithelial tissue is a thin and protective sheet of continuous cells. • Connective tissue is specialised in connecting various tissues and organs. • Muscular tissue forms muscles in the body. • Nervous tissue is a special kind of tissue and is the main tissue component of the nervous system, which includes the brain, spinal cord, and nerves.

IL Foundation Series Class 9

WORKSHEET - 1 MULTIPLE CHOICE QUESTIONS WITH SINGLE CORRECT ANSWER I. Plant tissues and tissue systems

1. Meristems are: a. Mature cells

b. Well-differentiated cells

c. Undifferentiated cells

d. None of these

2. Meristematic activities are best seen in the a. Cambial meristem

b. Root and shoot apices

c. At leaf tips

d. All of these

3. Meristem, which produces vascular bundles, is a a. Procambium

b. Lateral meristem

c. Secondary meristem

d. Mass meristem

4. The apical, intercalary, and lateral meristems are recognised based on their: a. Specific function

b. Position

c. Mode of formation

d. None of these

5. The lateral meristem is a. Procambium and phelloderm

b. Interfascicular and phelloderm

c. Phellogen and phelloderm

d. Phellogen and fascicular cambium

6. Which one of the following is not a lateral meristem? a. Interfascicular cambium

b. Fascicular cambium

c. Phellogen

d. Intercalary meristem

7. Which among the following are cylindrical meristems? a. Apical meristems

b. Intercalary meristems

c. All primary meristems

d. Lateral meristems

TISSUES

8. Statement - I: Intercalary meristem increases the length of a plant, like apical meristems. Statement - II: Intercalary meristem originates from the apical meristems. a. Both statements are true. b. Both statements are false. c. Statement I is true, and Statement II is false. d. Statement I is false, and Statement II is true. 9. Which of the following types of tissue is usually absent in roots? a. Parenchyma

b. Meristem

c. Collenchyma

d. Sclerenchyma

10. Sclerenchyma is a mechanical tissue because it has: a. Thin cell walls

b. Lignified cell wall

d. Has bordered pits

Uneven thickening in specific areas

11. The companion cells are associated with a. Sieve tube elements

b. Vessel elements

c. Tracheids

d. Sieve cells

12. Enucleated living cells are seen in the cells of a. Xylem fibres

b. Tracheids

c. Vessels

d. Sieve cells

13. The pulp of some fleshy fruits is rich in a. Collenchyma

b. Xylem

c. Fibres

d. Sclereids

14. All types of tissue systems have

a. Collenchyma

b. Sclerenchyma

c. Meristems

d. Parenchyma

IL Foundation Series Class 9

15. The main elements for the conduction of water and mineral salts in pteridophytes and gymnosperms is/are a. Tracheae

b. Sieve cell

c. Tracheids

d. Sieve tube

16. Sieve cells are found in a. Gymnosperms and bryophytes

b. Thallophytes and bryophytes

c. Gymnosperms and pteridophytes

d. Algae and fungi

17. Collenchyma is capable of providing mechanical strength because of having a a. Thick lignification

b. Thick cuticularisation

c. Thick suberisation

d. More thickened corners

18. Impermeability is best seen in a. Cork cells

b. Sclerenchyma

c. Stone cells

d. Collocytes

19. Parenchyma cells are associated with activity like: a. Assimilation and storage

b. Conduction and secretion

c. Dedifferentiation

d. All of these

20. A living component of the xylem element is the a. Xylem tracheid

b. Xylem vessels

c. Xylem fibres

d. Wood parenchyma

21. Lignin is most abundant in a. Collenchyma

b. Xylem

c. Phloem

d. Chlorenchyma

22. At maturity, sieve tubes do not possess a. Cell wall

b. Cytoplasm

c. Nucleus

d. Vacuoles

TISSUES

23. During dedifferentiation, a. Parenchyma is converted into sclerenchyma b. Parenchyma forms meristem c. Derivatives of primary meristem form primary tissues d. Sclerenchyma becomes totipotent 24. Parenchyma is absent in a. Monocot leaf

b. Monocot stem

c. Dicot root

d. Dicot stem

25. Identify the incorrect statement regarding tracheary elements of xylem a. Protoplasts are absent b. Elongated cells with lignified secondary walls c. All groups of plants (vascular) contain both the tracheary elements d. Chiefly concerned with the conduction of water 26. Collenchyma differs from parenchyma in having: a.

Living protoplasm

b. Cellulose walls c.

Vacuoles

d. Pectin deposits at corners 27. Select the incorrect statement from the following. a.

Tracheids, vessel, xylem sclerenchyma and parenchyma are without protoplast.

b. The presence of vessels is a characteristic feature of angiosperms. c. Radial conduction of water takes place by the ray parenchymatous cells. d. Vessel members are interconnected through perforations in their common wall.

IL Foundation Series Class 9

28. Select the incorrect statement from the following: a. The end walls of the sieve tube have sieve plates. b. Sieve tube elements and companion cells are connected by a pit field present between their common longitudinal walls. c. Companion cells are specialised parenchymatous cells that have a nucleus that controls the function of sieve tubes. d. Phloem parenchyma is present in most of the monocots. 29. Which of the following statements is incorrect about sclereids (stone cells)? a. Variously shaped b. Highly thickened and lignified cell wall and lumen in narrow c. Commonly found in the fruits, walls of nuts, seed coats of legumes, and leaves d. Types of parenchyma 30. Choose the incorrect one a. The ground tissue may consist of simple tissues that lie in between the epidermis and vascular bundles. b. In leaves, the ground tissue consists of thin-walled chloroplast containing cells called mesophyll. c. The vascular system consists of complex tissue, the phloem and the xylem. d. Secondary growth/secondary tissues are formed in monocots due to the presence of cambium. 31. Identify the set of structures reported in the epidermal tissue system. a. Epidermal cells, stomata, trichomes and hairs b. Epidermal cells, stomata, vascular tissues c. Stomata, trichomes, stellar tissues d. Epidermal cells, stomata, trichomes, cortical cells [AIPMT 2014]

32. Tracheids differ from the tracheary elements in a. Being imperforate

b. Having Casparian strips

c. Lacking nucleus

d. Being lignified 85

TISSUES

33. Select the incorrect statement from the following: a. Trichomes help in preventing water loss due to transpiration. b. Cuticle prevents loss of water. c. Cuticle is absent in roots. d. The epidermis is made up of elongated, loosely arranged cells, which form a continuous layer. 34. Which of the following statements regarding a trichome is wrong? a. The trichomes in the shoot system are usually multicellular. b. They may be branched or unbranched. c. The trichomes help prevent water loss due to transpiration. d. On the roots, the epidermal hairs are called trichomes. [NEET 2013]

35. Age of a tree can be estimated by a. Its height and girth b. Biomass c. Diameter of its heartwood d. Number of annual rings II. Animal tissues

1. The ciliated columnar epithelial cells in humans are known to occur in a. Eustachian tube and stomach lining

b. Bronchioles and fallopian tube

c. Bile duct and oesophagus

d. Fallopian tube and urethra

2. The kind of epithelium which forms the inner walls of blood vessels is a. Cuboidal epithelium

b. Columnar epithelium

c. Ciliated columnar epithelium

d. Squamous epithelium

3. The kind of tissue that forms the supportive structure in our pinna (external ears) is also found in

a. Nails

b. Ear ossicles

c. Tip of the nose

d. Vertebrae

IL Foundation Series Class 9

4. The cell junctions called tight, adhering and gap junctions are found in a. Connective tissue

b. Epithelial tissue

c. Neural tissue

d. Muscular tissue

5. The epithelial tissue present on the inner surface of bronchioles and fallopian tubes is a. Glandular

b. Ciliated

c. Squamous

d. Cuboidal

6. Which one of the following is the correct pairing of a body part and the kind of muscle tissue that moves it? a. Biceps of the upper arm - Smooth muscle fibres b. Abdominal wall - Smooth muscle c. Iris - Involuntary smooth muscle d. Heart wall - Involuntary unstriated muscle 7. Which one of the following pairs of structures distinguishes a nerve cell from other types of cells? a. Vacuoles and fibres

b. Flagellum and medullary sheath

c. Nucleus and mitochondria

d. Perikaryon and dendrites

8. In which one of the following preparations are you likely to come across cell junctions most frequently? a. Thrombocytes

b. Tendon

c. Hyaline cartilage

d. Ciliated epithelium

9. Areolar connective tissue joins a. Bones with bones

b. Fat body with muscles

c. Integument with muscles

d. Bones with muscles

10. Four healthy people in their twenties got involved in injuries, resulting in the damage and death of a few cells. Which of the given cells are least likely to be replaced by new cells? a. Liver cells

b. Neurons

c. Malpighian layer of the skin

d. Osteocytes

TISSUES

11. Mast cells of connective tissue contain a. Vasopressin and relaxin

b. Heparin and histamine

c. Heparin and calcitonin

d. Serotonin and melanin

12. Which one of the following contains the largest quantity of extracellular material? a. Striated muscle

b. Areolar tissue

c. Stratified epithelium

d. Myelinated nerve fibres

13. Collagen is a. Fibrous protein

b. Globular protein

c. Lipid

d. Carbohydrate

14. Which of the following statements is correct for the node of Ranvier of the nerve fibre? a. Neurilemma is discontinuous. b. Myelin sheath is discontinuous. c. Both neurilemma and myelin sheaths are discontinuous. d. It is covered by a myelin sheath. 15. Which cartilage is present at the end of long bones? a. Calcified cartilage

b. Hyaline cartilage

c. Elastic cartilage

d. Fibrous cartilage

16. During an injury, the nasal septum gets damaged, and for its recovery, which cartilage is preferred? a. Elastic cartilage

b. Hyaline cartilage

c. Calcified cartilage

d. Fibrous cartilage

17. Tendon and ligament are examples of a. Dense regular connective tissue

b. Dense irregular connective tissue

c. Loose connective tissue

d. Specialised connective tissue

18. The type of epithelial cells which line the inner surface of the fallopian tubes, bronchioles and bronchi are known as: a. Squamous epithelium 88

b. Ciliated epithelium

IL Foundation Series Class 9

c. Columnar epithelium

d. Cubical epithelium

19. Symphysis contains a. Hyaline cartilage

b. Fibrous cartilage

c. Calcified cartilage

d. None of these

20. A polysaccharide constituent found in the matrix of cartilage is a. Ossein

b. Collagen

c. Chondroitin

d. Hyaline

21. Osteoblasts are found in a. Blood

b. Muscle

c. Bone

d. Cartilage

22. Cells that maintain marrow cells are called a. Osteocytes

b. Chondrocytes

c. Osteoclasts

d. None of these

23. The Volkmann’s canals connect the a. Haversian canal with matrix

b. Haversian canal with Haversian canal

c. Haversian canal with marrow cavity

d. Lacunae to lacunae

24. The Haversian canal is interconnected by a. Volkmann's canal

b. Neural canal

c. Lamellae

d. None of these

25. The protein that is present in the connective tissue is a. Keratin

b. Collagen

c. Chondrin

d. Melanin

26. Which of the following is the structural and functional unit of the nervous system? a. Neuron

b. Neuroglia

c. Axon

d. Osteocyte

27. Which type of white blood cells are concerned with the release of histamine and the natural anticoagulant heparin? 89

TISSUES

a. Neutrophils

b. Basophils

c. Eosinophils

d. Monocytes

28. The most active phagocytic white blood cells are a. Neutrophils and eosinophils

b. Neutrophils and monocytes

c. Eosinophils and lymphocytes

d. Lymphocytes and macrophages

29. Which of the following is a transparent tissue? a. Tendon

b. Fibrous cartilage

c. Hyaline cartilage

d. All of these

30. The leucocytes contain which of the following in large quantity? a. Basophils

b. Neutrophils

c. Eosinophils

d. Monocytes

31. The compound squamous epithelium is found in the a. Stomach

b. Intestine

c. Trachea

d. Pharynx

32. The ligament is mainly made up of a. Reticulin

b. Elastin

c. Myosin

d. Collagen

WORKSHEET - 2 MULTIPLE CHOICE QUESTIONS WITH SINGLE CORRECT ANSWER 1. The parts removed by herbivorous animals are regenerated by a. Apical meristems

b. Lateral meristems

c. Intercalary meristems

d. All of these

2. Meristematic cells do not show a. A large conspicuous nucleus b. Ergastic substances like tannins, resins, etc.

IL Foundation Series Class 9

c. Active metabolism d. Proplastids 3. The interfascicular cambium and the cork cambium belong to the a. Primary meristems

b. Secondary meristems

c. Apical meristems

d. Seasonal meristems

4. The apical meristems are absent at the tips of a. Root

b. Stem

c. Leaves

d. Branches

5. The linear growth in the stem of grasses is caused by a. Intercalary meristems

b. Apical meristems

c. Fascicular cambium

d. Both (a) and (b)

6. Companion cells are a. Sclerenchymatous in nature

b. Parenchymatous in nature

c. Meant for the conduction of food

d. None of these

7. The sieve tube is a a. Vessel-like structure b. Provided with oblique septa c. Main conducting element for the translocation of food d. All of these 8. The complex tissue comprises the a. Xylem and phloem

b. Heterogeneous tissue

c. Conductive tissue

d. All of these

9. Vessels are not found in: a. Pteridophytes

b. Gymnosperms

c. Bryophytes

d. All of these

10. The albuminous cells of gymnosperms are equivalent to: a. Sieve tubes

b. Sieve cells 91

TISSUES

c. Companion cells

d. Cork cambium

11. The cell wall is impermeable in a. Sclerenchyma

b. Xylem tracheids and vessels

c. Cork cells

d. Sieve elements

12. Living cells showing mechanical function is/are a. Sclerenchyma

b. Stone cells

c. Aerenchyma

d. Collenchyma

13. Match Column - I with Column - II and select the correct option Column - I

Column - II

A. Tracheids

i. Elongated and tube-like cells with a thick lignified wall and tapering ends

B. Vessels

ii. Tube-like structure made up of many cells, each cell with a lignified wall and a large central cavity

C. Xylem fibre

iii. Highly thickened walls and obliterated central lumen

D. Xylem parenchyma

iv. Living cell with a thin cell wall made up of cellulose

a. A - ii; B - i; C - iii; D - iv

b. A - iii; B - i; C - ii; D - iv

c. A - i; B - ii; C - iii; D - iv

d. A - iii; B - ii; C - i; D - iv

14. Sieve tubes are better suited for translocation because they a. Possess broader lumen and perforated cross walls b. Are broader than long c. Possess bordered pits d. Possess no end walls 15. Collenchyma generally occurs a. In scattered dicot roots b. In a ring in monocot roots

IL Foundation Series Class 9

c. In patches under the epidermis in the dicot stem d. All of these 16. A mature sieve tube differs from a vessel in a. Being nearly dead b. Lacking cytoplasm c. Lacking a functional nucleus d. Absence of lignified walls 17. Tracheids and vessel elements a. Die before they become functional b. Are important constituents of all plants c. Are found in the secondary plant body d. Lack lignified walls 18. In angiosperm phloem, a. Both the sieve tube elements and companion cells have nuclei b. Sieve tube elements have nuclei, but companion cells do not c. The companion cells have nuclei, but the sieve tube elements do not d. Neither the companion cells nor sieve tube elements have nuclei 19. The living and non-lignified components of the vascular bundle are a. Vessels and tracheids

b. Vessels and phloem

c. Wood fibre and phloem

d. Wood parenchyma and sieve tube

20. Collenchyma differs from sclerenchyma in: a.

Being meristematic

b. Having thick walls c. Having wide lumen d. Retaining cytoplasm at maturity

TISSUES

21. Striped muscles are characterised by a. Syncytial

b. Spindle-shape

c. Uninucleate

d. None of these

22. The inner lining of blood vessels is formed by a. Ciliated epithelium

b. Squamous epithelium

c. Cubical epithelium

d. Columnar epithelium

23. Nucleated RBC is present in a. Man

b. Rat

c. Frog

d. Rabbit

24. Schwann cell is found around a. Axon

b. Cyton

c. Dendrite

d. Dendron

25. Which of the following statements regarding the skeletal muscle fibres is true? a. They are found in the walls of internal organs.

b. They contain intercalated discs.

c. They are involuntary in nature.

d. They are multinucleated.

26. The ensheathing of muscles is called a. Tendon

b. Ligament

c. Peritoneum

d. Fascia

27. Brush-bordered epithelium is found in a. Fallopian tube

b. Small intestine

c. Stomach

d. Trachea

28. The pseudostratified epithelium is found in

a. Seminiferous tubule

b. Fallopian tube

c. Trachea

d. Kidney tubules

IL Foundation Series Class 9

29. Adult human RBCs are enucleated. Which of the following statement(s) is/are the most appropriate explanation for this feature? i. They do not need to reproduce. ii. They are somatic cells. iii. They do not metabolise. iv. All their internal space is available for oxygen transport. a. Only iv

b. Only i

c. i, iii and iv

d. ii and iii

30. The myelin sheath is produced by the a. Schwann cells and oligodendrocytes b. Astrocytes and Schwann cells c. Oligodendrocytes and osteoclasts d. Osteoclasts and astrocytes 31. The receptor sites for neurotransmitters are present in the a. Membranes of synaptic vesicles b. Pre-synaptic membrane c. Tips of axons d. Post-synaptic membrane 32. The smooth muscles are a. Involuntary, fusiform, non-striated

b. Voluntary, multinucleate, cylindrical

c. Involuntary, cylindrical, striated

d. Voluntary, spindle-shaped, uninucleate

33. Choose the correctly matched pair. a. Adipose tissue - Dense connective tissue b. Areolar tissue - Loose connective tissue c. Cartilage - Loose connective tissue d. Tendon - Specialised connective tissue

TISSUES

34. Dense regular connective tissue is present in a. Ligament and tendon b. The joint capsule and Wharton's jelly c. Periosteum and endosteum d. Pericardium and heart valves 35. Which of the following is/are false statements? a. The compound squamous epithelium lies in the pancreatic duct of humans. b. The stratified epithelial lining is found in the intestine. c. The plasma membrane of intestinal cells is modified into microvilli. d. Both (a) and (b) 36. Choose the correctly matched pair. a. Tubular parts of nephrons - Cuboidal epithelium b. Moist surface of buccal cavity - Glandular epithelium c. Inner surface of bronchioles - Squamous epithelium d. Inner lining of salivary ducts - Ciliated epithelium

DIVERSITY IN LIVING ORGANISMS

The Earth is inhabited by millions of wide varieties of living organisms. Living organisms are characterised by certain unique phenomena, such as growth, reproduction, responsiveness, etc., in contrast to non-living things which do not show these characteristic features. These features are common to all living organisms. However, the different living organisms show a wide range of variations in form, functioning and behaviour. This is known as biological diversity or biodiversity. This wide range of variations in external and internal features and also in their behaviour and functioning makes the task of identifying these organisms practically difficult, or rather impossible, without a systematic approach. A systematic approach to the study of living organisms involves the identification, naming and categorisation of living organisms. The systematic study of these organisms becomes easier only when the organisms are identified and grouped based on certain similarities and differences. This practice of identifying, naming, and grouping living organisms is known as classification. The study of principles and procedures of the classification of living organisms is called taxonomy.

4.1

BASIS OF CLASSIFICATION

A study of the living world shows that evolution has produced an immense diversity of forms. There are about several million different species of organisms that differ in their morphology, function and behaviour. Aristotle, a Greek philosopher, made the first recorded attempt to classify both plants and animals. He classified animals into two groups, namely Anaima, i.e., animals without red blood (invertebrates) and Enaima animals with red blood vertebrates. The grouping of organisms based on various common characters is called classification. It helps in understanding the interrelationships among the diversified groups of organisms.

4.2

NEED FOR BIOLOGICAL CLASSIFICATION

The following points help to understand the necessity of identifying and classifying living things. • Helps in the study of different organisms and their evolutionary relationships • Helps to analyse the sequence in which the various groups of organisms evolved • Useful for study, identification and taxonomy • Helps to understand the interdependence between various groups of organisms

DIVERSITY IN LIVING ORGANISMS

Modern classification requires knowledge of external and internal structures along with cytological details, developmental processes, and ecological knowledge. Therefore, identification, nomenclature, and classification of organisms became mandatory for taxonomy.

4.3

NOMENCLATURE

Plants and animals in an area are known by their local or vernacular names. These local names vary from place to place and create a lot of confusion. For e.g., Onion is called Ulli (Telugu), Ullagaddi (Kannada), Pyaaz (Hindi), and Vengayan (Tamil). Its scientific name is Allium cepa. Therefore, any biologist in any part of the world would identify Allium cepa. Hence, this method of standardising the naming of living organisms is called nomenclature. 4.3.1 Binomial nomenclature Carolus Linnaeus, a Swedish botanist and physician, introduced the binomial nomenclature and laid the ground rules which paved the way for modern taxonomy. Thus, Carolus Linnaeus is also called the Father of Modern Taxonomy. The word binomial refers to two; thus, in binomial nomenclature, an organism has a scientific name with two components, namely a generic name and a specific epithet. As for e.g. the binomial name of mango is Mangifera indica. 4.3.2 Rules of nomenclature The names of plants have been standardised through the International Code of Botanical Nomenclature (ICBN 1961), and those of animals through the International Code of Zoological Nomenclature (ICZN 1964), the International Code for Nomenclature of Bacteria (ICNB), the International Code for Nomenclature of Cultivated Plants (ICNCP), and International Committee for the Taxonomy of Viruses (ICTV). The rules of nomenclature are as follows:

• Each organism is given a scientific name that consists of two words. The first word, generic name, represents the genus, and the second word, specific epithet, denotes the species. • Genus name should start with a capital letter and species name with a small letter. The same generic name should not be given to organisms of different domains/kingdoms, such as plants and animals, but the same specific names can be used for organisms belonging to different genera. For e.g. Raphanus sativus, Lathyrus sativus • The generic name is written first, followed by the specific epithet, and then the name of the discoverer's name in full or in abbreviation. • Both the words in a biological name, when handwritten, are separately underlined or printed in italics to indicate their Latin origin.

IL Foundation Series Class 9

4.4

TAXONOMIC HIERARCHY

Taxonomy is the branch of science that deals with the classification of organisms. It involves a hierarchy of steps in which each step represents a rank or category called a taxon. The sequence of arrangement of taxa in descending order in classification is called taxonomic hierarchy or Linnaeus hierarchy. Organisms are arranged into different groups or levels according to their similarities. As we go up the hierarchy, the organisms have fewer similarities. • A kingdom is the highest level of classification, which consists of a number of phyla or divisions (in the case of plants) with similar characteristics. • Phylum/Division is a level of classification which consists of a number of classes with similar characteristics. • A class is the level of classification which consists of a number of orders with similar characteristics. • An order is the level of classification which consists of a number of families with similar characteristics. • A family is the level of classification which consists of a number of genera with similar characteristics. • Genus is the level of classification which consists of a number of species with similar characteristics. • Species is the level of classification which consists of a number of organisms with similar characteristics that can interbreed to give rise to fertile offspring.

Fig. 4.1 Taxonomic hierarchy

DIVERSITY IN LIVING ORGANISMS

4.5

SYSTEMS OF CLASSIFICATION

Several scientists have developed different systems for classifying living organisms throughout history. Contributions of Aristotle and Theophrastus • Aristotle was the first to attempt the task of classifying organisms. He focused primarily on animals. He categorised them based on their habitat, distinguishing between terrestrial, aquatic, and aerial species. He is thus known as the Father of Biology and Zoology. • Theophrastus, also regarded as the Father of Botany, extended this classification to plants, categorising them into herbs, shrubs, and trees. Other contributions • Carolus Linnaeus (1707 - 1778) proposed the two-kingdom classification, which included Plantae and Animalia. However, this system does not distinguish between prokaryotes and eukaryotes or unicellular and multicellular organisms. • Ernst Haeckel, in the 1860s, separated unicellular animals, algae and fungi from other organisms on the basis of lack of tissue differentiation in a new group and called it kingdom Protista. He proposed the three-kingdom classification, which included Plantae, Animalia and Protista. • Copeland (1902 - 1968) proposed the four kingdom classification. The four kingdoms were Monera, Protista, Plantae, and Animalia. With the advent of microscopes, it became clear that bacteria and related organisms have different cellular structures from other organisms. These are prokaryotes, in contrast to others that have true nuclei and are called eukaryotes. Hence, a new kingdom, Monera, was added. • Robert Whittaker (1969) developed the five kingdom classification based on the nutrition modes, cell structure, and cellular organisation. It was the most accepted system of classification that solved most of the issues in taxonomy related to the placement of bacteria and fungi. The five kingdoms included were Monera, Protista, Fungi, Plantae and Animalia.

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Animals Eukaryotic Multicellular Ingest Motile Sexual

Plants

Fungi

Eukaryotic Multicellular Photosynthesize Nonmotile Sexual

Eukaryotic Multicellular Absorb Nonmotile Sexual

Protists

Monera

Eukaryotic Unicellular or multicellular Absorb, ingest, or Photosynthesize Sexual and asexual

prokaryotic Absorb and photosynthesize Motile or Non-motile asexual

Fig. 4.2 Whittaker’s five kingdom classification Characters

Monera

Protista

Fungi

Plantae

Animalia

Cell type

Prokaryotic

Eukaryotic

Cell wall

✔

Chloroplast

✔

Mitochondria

✔

Motility

Flagella

Cilia & Flagella

Mode of nutrition

All types of nutrition

Photosynthetic & Heterotrophic

Heterotrophic, Saprophytic & Parasitic

Autotrophic & Photosynthetic

Heterotrophic

Sexual reproduction

Conjugation Transduction Transformation

Syngamy & Meiosis, Conjugation or none

Fertilisation & Meiosis

Nuclear membrane Tissue organisation

Table 4.1 Comparative study of five kingdoms

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4.6

KINGDOM MONERA

The kingdom includes all prokaryotic organisms such as mycoplasma, bacteria, actinomycetes and cyanobacteria or blue-green algae. General characteristics

• Unicellular prokaryotes lacking membrane-bound organelles. • Cell walls are generally present with a variation in their composition. • Varied modes of nutrition are seen, such as saprophytic, parasitic, chemoautotrophic, photoautotrophic and symbiotic. • Generally exhibit anaerobic respiration, but aerobic respiration may occur under suitable conditions. • Asexual mode of reproduction is predominant. • Monera is comprised of two major groups: archaebacteria and eubacteria. A. Archaebacteria

• They represent the most ancient and primitive group of bacteria that live under extremely harsh conditions. • Based on their habitat, they are categorised as halophiles (salt pans), methanogens (marshy areas) and thermoacidophiles (hot springs). • They are characterised by the absence of mucopeptide substances in their cell walls. • Their cell wall contains pseudomurein, which enables them to survive in extreme conditions. • Cell membrane is characterised by branched chain lipids. • They may survive as obligate anaerobes (methanogens and halophiles) or facultative anaerobes (thermoacidophiles). • Examples are Methanobacterium, Halobacterium, Thermoplasma, etc. B. Eubacteria

• They are true bacteria which are characterised by the presence of rigid cell walls. • They include bacteria, cyanobacteria and mycoplasmas. 1. Bacteria • They have the most primitive and simple cell structure. • Some are motile and possess flagella. Flagella are single-stranded and made up of a protein called flagellin.

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• They show extensive metabolic diversity. • While a majority of the bacteria are heterotrophs, some are autotrophs that include photosynthetic and chemosynthetic forms. • Based on the shape, the bacteria are classified into cocci (spherical), bacilli (rod), vibrio (comma) and spirilla (spiral). • These typical prokaryotic cells are surrounded by a cell wall, which encloses protoplasm. The cytoplasm contains ribosomes of 70S type (30S and 50S). • They contain a single circular DNA not enclosed by a nuclear membrane and are located in a distinct region of a cell called the nucleoid. • The DNA is circular and double-stranded. It lacks histones, hence called naked DNA. • Examples are Bacillus, Clostridium, Nitrosomonas, etc.

Ribosomes Food granule

Chromosome (nucleoid region) Pili

Prokaryotic flagellum Capsule or slim layer Cell wall Plasmid Cytoplasm Plasma membrane (DNA) Fig. 4.3 Bacterial cell

2. Cyanobacteria • They are also called blue-green algae, and they perform oxygenic photosynthesis. • They may be unicellular and filamentous (Spirulina), colonial (Microcystis) or multicellular filamentous (Nostoc, Anabaena), fresh water, marine (or) terrestrial algae. • The colonies are generally surrounded by a gelatinous sheath. • They often form blooms in polluted water bodies. • Examples are Nostoc, Anabaena, Spirulina, etc.

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Mucilage

Cell wall

Chromatin

Plasma membrane Ribosomes

Membrane with Hyaloplasm Chlorophyll

Fig. 4.4 Cyanobacteria

3. Mycoplasma • Smallest and simplest free-living, anaerobic organisms. The size ranges from 0.1-0.15 µm. • They are also called PPLO (Pleuropneumonia-like organisms) or MLO (Mycoplasma-like organisms). • Mode of nutrition is heterotrophic. Some of them live as saprophytic, and the majority are parasitic. • They are unicellular without cell walls; hence, they are not affected by penicillin and lysozyme. • The absence of cell walls enables them to change their shape (pleomorphic), hence called 'Jokers of the plant kingdom'.

Plasma membrane

Enzymes Ribosome

Protein particles

DNA

Fig. 4.5 Mycoplasma

4.7

KINGDOM PROTISTA

This kingdom includes all unicellular and colonial eukaryotes. They were the first eukaryotes to evolve about 1000 million years back phylogenetically. This kingdom acts as a connecting link 104

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between the prokaryotic kingdom Monera and the complex multicellular kingdoms - Fungi, Plantae, and Animalia. General characteristics

• Protista includes unicellular organisms with eukaryotic cell structures and a few multicellular organisms like algae, which can exist in both unicellular and multicellular forms. • The cells are characterised by advanced features, including a well-defined nucleus and membrane-bound organelles. • Diatoms and protozoans represent unicellular organisms within this kingdom. • They predominantly inhabit aquatic environments or moist soil. • Some protists exhibit both autotrophic and heterotrophic modes of nutrition, for e.g. Euglena, while many exhibit parasitic nutrition. • Aerobic respiration was observed due to the presence of mitochondria. However, in parasitic forms, anaerobic respiration may take place. • Reproduction takes place in both asexual and sexual modes. Binary fission is the most prevalent method of asexual reproduction. Flagellum

Stigma(eyespot) Contractile vacuole Mitochondria Golgi apparatus Ribosomes

Photoreceptor

Cilia

Anterior contractile vacuole

Food vacuoles

Cytoplasm Macronucleus Nucleolus Nucleus Micronucleus Endoplasmic reticulum

Chloroplast

Cytoplasm Pellicle

Euglena

Oral groove Cell mouth Food vacuole (forming) Posterior contractile vacuole

Cytoproct

Paramecium Fig. 4.6 Protists

4.8

KINGDOM FUNGI

It is a large group of eukaryotic organisms having a chitinous wall. They include yeast, moulds, and the more familiar mushrooms. The discipline of biology devoted to the study of fungi is known as Mycology. Micheli is considered the Father of Mycology. De Bary is considered the Father of modern mycology. General characteristics

• It comprises multicellular organisms.

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• A single filament of fungus is referred to as hypha, and the cluster of these filaments forms a structure known as mycelium. • The cells of fungi are encased in a sturdy cell wall composed of chitin, a complex carbohydrate and a distinctive feature of this kingdom. • They lack plastids (chlorophyll) and show a heterotrophic mode of nutrition. Predominantly, these organisms exhibit a saprophytic mode of nutrition, wherein they feed on decaying organic matter. Nutrients obtained are stored in the form of glycogen and oil globules. • Fungi typically follow an aerobic pathway facilitated by the presence of mitochondria where cellular respiration occurs. Unlike some living organisms, fungi do not display movement. • They show vegetative, asexual and sexual modes of reproduction.

Yeast

Aspergillus

Agaricus (mushroom)

Fig. 4.7 Fungi

4.9

KINGDOM PLANTAE

This kingdom includes plants that are multicellular, eukaryotic organisms with cell walls. They are autotrophs as they can synthesise their own food in the presence of sunlight. General characteristics

• The plant cells have plastids that contain the photosynthesising pigment chlorophyll. • A few members are partially heterotrophic, such as insectivorous plants or parasites. Pitcher plants and Venus fly traps are examples of insectivorous plants, and Cuscuta is a parasite.

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Venus fly trap (insectivorous)

Cuscuta (parasite)

Fig. 4.8 Heterotrophic plants

• All plant cells have a cell wall mainly made of cellulose. • Each plant cell has a nucleus and membrane-bound organelles like vacuoles, mitochondria, plastids, etc. • The reserve food material is starch and lipids (oils). • Plantae includes algae, bryophytes, pteridophytes, gymnosperms and angiosperms. • The life cycle of plants has two distinct phases - the diploid sporophytic and the haploid gametophytic, which alternate with each other. The lengths of the haploid and diploid phases, and whether these phases are free-living or dependent on others, vary among different groups in plants. This phenomenon is called the alternation of generation.

Moss (bryophyte)

Fern (pteridophyte)

Cycas (gymnosperm)

Paeonia (angiosperm)

Fig. 4.9 Plants

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4.10 KINGDOM ANIMALIA This kingdom is characterised by multicellular eukaryotic organisms that lack a cell wall and plastids in their cells. They directly or indirectly depend on plants for food. General characteristics

• Members of the animal kingdom include animals that occupy land and water. • They do not possess chloroplasts and primarily exhibit a heterotrophic mode of nutrition, meaning they obtain their nutrients by consuming other organisms. • Their mode of nutrition is the holozoic ingestion of food. • They digest their food in an internal cavity and store food reserves as glycogen or fat. • They follow a definite growth pattern and grow into adults that have a definite shape and size. • Higher forms show elaborate sensory and neuromotor mechanisms. • Most of them are capable of locomotion. • Sexual reproduction is by copulation of male and female followed by embryological development. • The kingdom is diverse, encompassing a wide range of organisms from simple invertebrates like sponges to complex vertebrates like mammals, birds, and reptiles.

Fish

Clam

Cow

Hen Fig. 4.10 Animals

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4.11

CLASSIFICATION OF PLANT KINGDOM

The plant kingdom is divided into two main groups based on the presence or absence of flowers. 1. Cryptogamae 2. Phanerogamae Kingdom Plantae Cryptogamae

Phanerogamae

•

Primitive plants lack flowers, fruits, and seeds and are characterised by hidden reproductive organs.

•

Flower-bearing and seedproducing plants characterised by visible reproductive organs.

•

Reproduce through spores

•

Reproduce through flowers

•

Include thallophytes, bryophytes & pteridophytes

•

Include gymnosperms & angiosperms

Table 4.2 Division based on the presence or absence of flowers

Cryptogams are further classified into three subdivisions based on the differentiation of the plant body into roots, stems, and leaves and the presence of vascular tissue for water and nutrient conduction. 4.11.1 Thallophyta Thallophytes are simple photoautotrophic, non-embryophytic, and avascular. They include algae, which means seaweed. Linnaeus gave the term 'algae'. They form the main autotrophs of our planet as they carry out 90% of global photosynthesis. The study of algae is called Phycology and F.E. Fritsch is known as the Father of Phycology. General characteristics

• The plant body ranges from a unicellular to a highly organised multicellular structure. • They are soft, nonvascular, thread-like water plants without roots, stems, or leaves. • Their plant body is called a thallus and lacks well-organised tissues. • They reproduce without seeds. • Minute, free-floating alga are called phytoplankton. Some are microscopic, and some are macroscopic. • Some algae live in close association with fungi and form a composite organisms called lichen. Algae contribute through photosynthesis, producing carbohydrates, and providing food to the fungi. On the other hand, fungi absorb moisture and nutrients from the atmosphere and provide them to the alga apart from anchorage and protection. 109

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• Examples of thallophytes include Spiyrogyra, Sargassum, Chlorella, Ulothrix, Oedogonium, kelps, etc.

Spirogyra

Sargassum Fig. 4.11 Thallophytes

4.11.2 Bryophyta Bryophytes are the simplest and most primitive embryophytes. They are nonvascular, archegoniate, embryophytic and first terrestrial plants. Braun gave the term 'bryophyta'. Though they are land plants, they require water for the successful growth of gametophytes and fertilisation. Hence, bryophytes are also called the 'amphibians of the plant kingdom'. General characteristics

• Their body can be differentiated into rhizoids, stem-like axes and leaf-like structures. • Rhizoids may be unicellular or multicellular, branched or unbranched. • Atracheates as vascular tissues are absent in both gametophyte and sporophyte. • Plant body is parenchymatous. • Sex organs arise singly or in groups. These are always multicellular, jacketed and stalked. • Male sex organ is antheridium that forms biflagellate male gametes. • The female sex organ is a flask-shaped archegonium with a stalk, venter and neck. • Fertilisation takes place in the archegonial venter and is oogamous. • Zygote undergoes mitotic divisions and forms an embryo.

Marchantia

Sphagnum Fig. 4.12 Bryophytes

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4.11.3 Pteridophyta The term 'pteridophyta' comes from the Greek words 'pteron,' meaning 'feather,' and 'phyta,' meaning 'plant.' This group mainly consists of feather-like plants, primarily ferns. Pteridophyta represents the earliest fully terrestrial plants with a differentiated plant body, including true roots, stems, and leaves. General characteristics

• The life cycle of pteridophytes includes the dominant sporophyte and the independent gametophyte forms. • Sporophyte has a plant-like appearance with clear differentiation into roots, stems, and leaves. • They are characterised by the presence of vascular tissue, which includes the xylem and phloem in primitive forms. The xylem lacks vessels and relies on tracheids, while the phloem lacks companion cells and relies on sieve cells. • Reproduction occurs through both asexual and sexual modes. • Asexual reproduction involves apogamy and apospory. • Sexual reproduction occurs through spore formation in sporangia on leaves. • Gametes undergo fertilisation, resulting in the formation of a zygote. The zygote develops into an embryo and then into a young sporophyte. • This alternation of generations characterises the life cycle of pteridophytes. Examples include Selaginella, Lycopodium, Dryopteris, and Salvinia.

Selaginella

Lycopodium

Salvinia

Fern Fig. 4.13 Pteridophytes

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4.11.4 Gymnosperms The term 'gymnosperms' is derived from two Greek words, 'gymnos', meaning 'naked', and 'sperma,' meaning 'seeds.' This indicates that gymnosperms produce seeds without enclosing them in fruits. These plants are exclusively found on land and can thrive in cold climates with snowfall and arid conditions (xerophytes), while others are evergreen trees that form canopies in forests. General characteristics

• They are characterised as perennial, woody trees or bushy shrubs. • The plant body is divided into roots, stems, and leaves. • They possess a robust and well-developed root system. • They exhibit well-organised tissue systems with a clear division of labour within the plant body. • These plants have well-developed vascular tissues, i.e. xylem and phloem, to facilitate the transport of water, nutrients, and food throughout the plant. • The stems of gymnosperms are typically upright and can be either branched or unbranched. • Their leaves contain resin ducts or latex tubes, which are specialised structures. • Instead of flowers, they bear cones as their reproductive structures, which are easily visible. • They are generally unisexual, meaning that individual plants have either male or female cones, and these reproductive structures are distinct from each other. • They undergo secondary growth, resulting in the formation of wood, making them typically tall and woody trees. • They can reproduce through both vegetative propagation and sexual reproduction. • The primary mode of reproduction in gymnosperms is sexual, involving distinct male and female cones. • Pollen grains are transferred to the female cone for fertilisation. • Male and female cones produce microspores and megaspores, respectively, as part of their reproductive process. • Gymnosperms do not form fruits as the female cone lacks an ovary. • Ovules are not enclosed in an ovary, resulting in the production of naked seeds by gymnosperms. • Examples include Pine, Cycas, Cedrus, Ginkgo, etc.

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Pinus

Cycas

Ginkgo

Cedrus Fig. 4.14 Gymnosperms

4.11.5 Angiosperms The term 'angiosperms' originates from two Greek words, 'angion,' meaning 'vessel,' and 'sperma,' meaning 'seed.' This signifies that these plants bear flowers and produce seeds enclosed within fruits. Angiosperms represent the most prevalent group of plants in the entire plant kingdom. Predominantly terrestrial angiosperms are referred to as mesophytes. Some species exhibit resilience in arid environments and are called xerophytes. Additionally, certain angiosperms are adapted to aquatic habitats and are known as hydrophytes. General characteristics

• They are divided into two classes: the dicotyledons and the monocotyledons. • The dicotyledons are characterised by seeds having two cotyledons, reticulate venation in leaves, and tetramerous or pentamerous flowers, i.e., having four or five members in each floral whorl. • The monocotyledons are characterised by single cotyledon seeds, parallel venation in leaves, and trimerous flowers having three members in each floral whorl. • The male sex organ in a flower is the stamen. Each stamen consists of a slender filament with an anther at the tip. The anthers, following meiosis, produce pollen grains.

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• The female sex organs in a flower are the pistil or the carpel. The pistil consists of an ovary enclosing one to many ovules. • Pollination occurs when pollen grains are dispersed by wind or various other agencies to the stigma of a pistil. • The pollen grains germinate on the stigma and form pollen tubes to enter the embryo sac, where two male gametes are discharged. One of the male gametes fuses with the egg cell to form a zygote (syngamy). The other male gamete fuses with the diploid secondary nucleus to produce the triploid primary endosperm nucleus (PEN). • Double fertilisation is a unique characteristic of angiosperms as two fusions take place. • The zygote develops into an embryo (with one or two cotyledons), and the PEN develops into endosperm, which provides nourishment to the developing embryo. • After fertilisation, the ovules develop into seeds, and the ovaries develop into fruit.

Orchid

Hibiscus

Rafflesia

Water lily Fig. 4.15 Angiosperms

4.12 CLASSIFICATION OF ANIMAL KINGDOM All animals are members of the Kingdom Animalia, also called Metazoa. They are multicellular eukaryotes and are heterotrophs. Animals constitute the most diverse group of living organisms, occupying a wide array of habitats and adopting various lifestyles with distinct food habits. Similar to the plant kingdom, the animal kingdom has been systematically classified into various taxonomic 114

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units at different hierarchical levels. Animals are broadly divided into two groups based on the presence or absence of a vertebral column. Those having a vertebral column are called vertebrates, while those lacking one are called invertebrates. 4.12.1 Basis of classification of animal kingdom Despite vast differences in the structural complexity of organisms, all animals share an intrinsic structural design and common fundamental features such as the arrangement of cells, body symmetry, nature of coelom, and the type of digestive, circulatory, or reproductive systems. These features or parameters form the basis of animal classification. Level of organisation

The body of animals is composed of many kinds of cells specialised for performing different functions. They exhibit higher levels (grades) of organisation, such as cellular level, tissue level, organ level and organ system level. • Cellular level of organisation is the lowest level of organisation in animals and is exhibited by the sponges or porifers. The cells are arranged as loose cell aggregates, each specialised to perform a specific function. However, they do not form tissues. • Tissue level of organisation is exhibited by diploblastic animals such as coelenterates (cnidarians and ctenophores). The cells performing the same function are aggregated into tissues. The functioning of different tissues is also coordinated. However, they are not assembled into organs. • Organ level of organisation is found in triploblastic platyhelminths. In these animals, tissues are grouped together to form functional units called organs, each specialised for a particular function. • Organ system level of organisation is found in higher triploblastic animals, such as annelids, arthropods, molluscs, echinoderms, and chordates. In these animals, groups of organs that work together are associated to form organ systems. Each organ system is concerned with a specific physiological function. Symmetry

The regular arrangement of body structures in a geometrical design relative to the axis of the body is called symmetry. The symmetrical animal can be cut into two mirror-image halves or antimeres by one or more planes of symmetry. Most of the sponges are asymmetrical. Symmetry in animals is further classified into two main types: • Radial symmetry: Organisms with radial symmetry can be divided into two halves by any plane passing through the centre from top to bottom. For e.g., the members of Phylum Cnidaria demonstrate radial symmetry.

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• Bilateral symmetry: Organisms with bilateral symmetry can be divided into two halves by a single plane passing through the centre. Most phyla fall into this category, and it is considered a more advanced feature compared to radial symmetry.

Plane of symmetry

Planes of symmetry No Symmetry

Radial Symmetry

Bilateral symmetry

Fig. 4.16 Types of symmetry Metamerism

The serial repetition of certain organs along the anterior-posterior axis is termed metamerism. The body is externally and internally divided into segments with a serial repetition of at least some organs. The segments are also called metameres or somites. Metamerism is observed in annelids, arthropods, and chordates.

Annelida Segments are alike

Arthropoda Segments are differentiated

(Homonomous metamerism)

(Heteronomous metamerism)

Vertebrates Metamerism is internal

Fig. 4.17 Metamerism Germ layers

The fundamental cell layers formed in an early embryo are called primary germ layers. Sponges are the only metazoans that lack true primary germ layers.

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Ectoderm Endoderm Mesoderm

Ectoderm Nervous tissue Epidermis cells Pigment cell

Mesoderm Muscle cells Skeleton Heart, Kidney, Blood

Endoderm Endocrine glands Lungs Gastrointestinal tract

Fig. 4.18 Germ layers

Diploblastic animals are metazoans in which only two embryonic germ layers (an external ectoderm and an internal endoderm) are formed, e.g. coelenterates (cnidarians and ctenophores). Triploblastic animals are metazoans in which the embryo has three embryonic germ layers, i.e. ectoderm, endoderm and mesoderm, for e.g. platyhelminths and other higher metazoan phyla. Coelom or body cavity

The fluid-filled body cavity is known as coelom. It acts like a shock absorber and protects the visceral organs. It also provides space for the expansion of visceral organs. The presence and nature of a coelom play a pivotal role in categorising animals into three distinct groups. • Acoelomates: These animals lack a coelom entirely. Members of the phylum Porifera, Cnidaria and Platyhelminthes are acoelomates. • Pseudo coelomates: This group of animals possesses a false or pseudo coelom. The body cavity is not entirely lined by layers of epithelial cells (peritoneum) on both the inner and outer sides. For e.g. phylum Aschelminthes. • Coelomate animals: These animals have a true coelom, where the body cavity is completely lined by layers of epithelial cells (peritoneum) on both inner and outer sides. For e.g. annelids, molluscs, arthropods, echinoderms, hemichordates, and chordates demonstrate a coelom.

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Diploblastic

Triploblastic Mesentery

Ectoderm Mesoderm

Ectoderm Endoderm

Endoderm

Mesoderm

Digestive cavity

Pseudocoelom

a. Acoelomate

b. Pseudocoelomate

Coelom

c. Coelomate

Fig. 4.19 Types of coelom Notochord

Notochord is a mesodermal rod-like structure formed on the dorsal side during embryonic development in some animals. Notochord persists in some species while most lose in due course of development. Animals possessing a notochord at any stage of their life are called chordates and constitute the phylum Chordata. About 95% of animals (porifers to hemichordates) do not possess a notochord and are classified as nonchordates. 4.12.2 Phylum Porifera The phylum Porifera includes primitive multicellular animals that are commonly called sponges. Porifera is the only metazoan phylum that includes animals without true embryological germ layers, tissues, and nerve cells. General characteristics

• Aquatic, predominantly marine, though some freshwater forms exist. Solitary or colonial, sessile (attached to the substratum). • Asymmetrical with diverse body shapes, including cylindrical, vase-like, rounded, or branched. • Cellular level of body organisation. • The body possesses pores (ostia), and a single large opening (osculum) is found at the top. • Internal skeleton present in almost all the sponges. It may consist of calcareous or siliceous spicules of fine spongin fibres or of both. • Lacks an alimentary canal. Digestion is intracellular. • Water entering through the ostia helps in the circulation of food and oxygen. • Respiratory, excretory, and nervous systems are absent. 118

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• Presence of a canal system for nutrition, respiration, excretion, and reproduction. • Elimination of carbon dioxide and nitrogenous wastes (ammonia) occurs through the osculum via diffusion. • Reproduction occurs through both asexual and sexual modes. • Asexual reproduction includes budding and gemmule formation (internal buds). • Internal fertilisation is part of the sexual mode.

Sycon

Spongilla

Euspongia

Euplectella Fig. 4.20 Porifera

4.12.3 Phylum Cnidaria The name 'Cnidaria' originates from the Greek word 'knide', signifying stinging cells, reflecting the presence of specialised cells with stinging structures. General characteristics

• Exclusive to aquatic environments, mainly marine. Freshwater species include Hydra. • Can be either sedentary or free-swimming. • Radially symmetrical, with varied body shapes, including cylindrical, vase-like, or sac-like. 119

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• Presence of slender, flexible, finger-like processes called tentacles around the mouth. Tentacles help in capturing food and defence. • Exhibit polymorphism. Alternation of generation includes sedentary polyp and the free-living medusa. Tentacle

Mouth

Reproductive tissue Mesoglea

Ectoderm Endoderm

Coelenteron

Mesoglea Reproductive tissue

Bud Oral arm

Basal plate

Mouth

Tentacle

Polyp Fig. 4.21 Polymorphism in cnidarians Medusa • Incomplete digestive tract. Absence of respiratory and excretory organs. Respiration and excretion occur through the body's surface. • Primitive nervous system with nerve cells and processes. Presence of sensory cells. • Cnidoblasts are specialised stinging cells that aid in paralysing prey. • Food and oxygen are carried along with water entering through the ostia. • Elimination of carbon dioxide and nitrogenous wastes (ammonia) through the osculum via diffusion. • Reproduction occurs through both asexual and sexual modes. • Gonads (testes and ovaries) present without ducts. • Asexual reproduction occurs through budding in the polyp form. Sexual reproduction takes place in the medusa form. • Fertilisation can be external or internal. The zygote develops into a larva called planula.

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Physalia

Aurelia

Jellyfish

Gorgonia

Meandrina

Adamsia

Fig. 4.22 Cnidaria

4.12.4 Phylum Ctenophora Ctenophores (Greek: 'cten’ = comb; 'phero’ = to bear) are commonly called comb jellies, sea gooseberries, or sea walnuts. Most of them are planktonic. They differ from cnidarians in being monomorphic throughout their life. General characteristics

• These are solitary, free-swimming animals and exclusively marine. • They are diploblastic with tissue level of organisation and exhibit radial symmetry. • They are transparent, gelatinous, unsegmented animals. • Comb plates present for locomotion. • The gastrovascular cavity consists of a pharynx, stomach, and a system of gastrovascular canals. Digestion is partly extracellular and partly intracellular. • They have a nerve net system. The statocyst is present. • Only sexual reproduction occurs. All are monoecious (bisexual). • Fertilisation is external. Development is usually indirect and includes a cydippid larva. • Regeneration is common. • They exhibit bioluminescence. 121

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• Examples include Pleurobrachia, Ctenoplana, Beroe, etc.

Pleurobranchia

Beroe Fig. 4.23 Ctenophora

4.12.5 Phylum Platyhelminthes Platyhelminthes include the flatworms. The term Platyhelminthes (Greek 'platys’ = flat; 'helminths’ = worm) refers to the dorsoventrally flattened body. General characteristics

• These are mostly endoparasites. Some are free-living. • They are triploblastic, bilaterally symmetrical with cephalisation and exhibit an organ level of body organisation. • They are acoelomates and lack a large fluid-filled body cavity. The connective tissue compartment between the gut and the body wall is called the parenchyma. • The gut is a blind sac. The mouth is used for ingestion and egestion. Anus is absent. They absorb nutrients from the host directly through their body surface. • Flukes have suckers, and tapeworms have hooks and suckers for attachment to the host body. • Respiratory and circulatory systems are absent. • Some helminths reproduce asexually by fragmentation (Turbellaria). They have the remarkable power of regeneration. • They are mostly hermaphroditic. Fertilisation is internal. • Development is mostly indirect with parasitic forms. Polyembryony is common in flukes. • Examples include Dugesia (planarian), Fasciola (liver fluke), Schistosoma (liver fluke), Taenia (tapeworm); and Echinococcus (dog tapeworm).

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Tapeworm

Liverfluke Fig. 4.24 Platyhelminthes

4.12.6 Phylum Aschelminthes Aschelminthes refers to roundworms that are characterised by a pseudocoelom. General characteristics

• Mostly free-living, with the ability to exist in terrestrial, marine, or freshwater environments. • Thin, thread-like cylindrical body with tapering ends. • Body unsegmented with distinguishable anterior and posterior ends and bilaterally symmetrical. • Head at the anterior end and anus at the posterior end. • Locomotion by ciliated body surface. • The fluid in the pseudocoelom (hydroskeleton) maintains body shape. • Complete digestive tract with a mouth bordered with lips containing sensory papillae. • Muscular pharynx for sucking in food. Extracellular digestion. • Respiration occurs through the body surface. Respiratory organs and the circulatory system are absent. • A pair of glandular cells or intracellular canals for excretion (ammonia waste). • The nervous system includes a nerve ring around the pharynx and dorsal and ventral longitudinal nerve cords. • Primitive sense organs, such as a pair of eye spots on the dorsal side in free-living forms. • Osmoregulation is essential. • The presence of gonads (testes and ovary) with ducts leads to copulatory organs. • Unisexual with sexual dimorphism. 123

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• Only sexual reproduction occurs; fertilisation is internal. • Indirect development often involves more than one host for the completion of the life cycle in parasitic forms like Ascaris (roundworm) and Wuchereria (Filarial worm).

Ascaris

Wuchereria Fig. 4.25 Aschelminthes

4.12.7 Phylum Annelida Phylum Annelida includes segmented worms. They are triploblastic bilaterally symmetrical, schizocoelomate protostomes. General characteristics

• Mostly free-living, found in terrestrial and aquatic environments (marine or freshwater). Few can be parasitic (leeches). • Body is cylindrical with tapering ends. Exhibit bilateral symmetry and organ system level of organisation. • Segmented body (metamerism) with distinguishable anterior and posterior ends. Each ringlike segment is called a metamere. • Head at the anterior end and anus at the posterior end. • Locomotory organs include setae or parapodia, made up of chitin. • The coelomic fluid maintains the body shape (hydroskeleton). • Complete digestive tract with a mouth bordered with lips containing sensory papillae. Extracellular digestion process. • Respiration can occur through the body surface or gills in some forms. • Closed circulatory system. Blood contains haemoglobin in plasma. • Coiled tubular structures called nephridia for excretion. • Nervous system with a nerve ring and a solid ventral nerve cord with ganglia (aggregations of nerve cells). 124

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• Primitive sense organs, like a pair of eye spots on the dorsal side in free-living forms. • Presence of gonads with ducts leading to copulatory organs. • Bisexual or unisexual with sexual dimorphism. • Fertilisation is internal, oviparous, where eggs are laid outside the body and develop externally. • Indirect development is a characteristic feature. • Asexual reproduction by regeneration is seen in some annelids • Examples of annelids are Pheretima (Earthworm), Nereis (ragworm), Hirudinaria (leech), etc.

Nereis

Hirudinaria

Pheretima

Fig. 4.26 Annelida

4.12.8 Phylum Arthropoda Arthropods have conquered land, sea, and air. With more than one million described species, it is the largest metazoan phylum. Over two-thirds of all named species on Earth are arthropods. Arthropoda is an incredibly diverse group of taxa and shows a great variety of adaptations. General characteristics

• Includes various species, with some being parasitic, like lice. • Body segmented into head, thorax, and abdomen. The head and thorax together form the cephalothorax. • Characterised by jointed legs and compound eyes with many lenses (mosaic vision). • Body covered by a hard exoskeleton made up of chitin. • Periodic shedding of the exoskeleton occurs and is known as ecdysis or moulting. • Body cavity is reduced and filled with blood (haemocoel). • Distinct digestive system with movable mouthparts. 125

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• Respiratory organs include gills, trachea, and book lungs. • Open circulatory system. • Excretory organs are green glands or Malpighian tubules. • Nervous system with a nerve ring and a solid ventral nerve cord with ganglia. A pair of antennae is sensory in function. • First animals to have an endocrine system, that releases hormones. • Gonads with ducts leading to copulatory organs are present. • Usually unisexual with sexual dimorphism in some animals. • Fertilisation is internal. Oviparity is observed in certain arthropods, such as insects. Development is indirect and involves the metamorphosis of distinct larval stages before reaching adulthood. • Some arthropods are viviparous, like aphids, as they give birth to live young ones. • Scorpions are ovoviviparous, where eggs develop and hatch internally, and the young are born alive.

Limulus

Penaeus

Bombyx

Locusta Fig. 4.27 Arthropoda

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4.12.9 Phylum Mollusca Mollusca (L. Mollusca =a soft nut) includes the familiar soft-bodied animals such as snails, slugs, mussels, oysters, octopuses, etc. Phylum Mollusca is the second largest animal phylum. General characteristics

• Primarily aquatic, most live in marine habitats, while some live in freshwater, e.g. octopuses and snails. • Body is soft and unsegmented. It is divided into an anterior head, a ventral muscular foot, and a dorsal visceral mass or hump. • Soft, muscular foot on the ventral side serves as a locomotory organ. • The exoskeleton is hard and made up of calcium carbonate, often in the form of a shell. • Visceral hump is on the dorsal side of the foot. • A thin fleshy fold called the mantle or pallium secretes the shell. The space enclosed between the mantle and the body is called the mantle cavity. • Reduced body cavity filled with blood (haemocoel). • Complete digestive tract with a radula as a rasping organ and chitinous teeth; anus opens into the mantle cavity. • Respiratory organs are gills or ctenidia located in the mantle cavity. • Open circulatory system with a dorsal heart and a few arteries that open into sinuses. • One or two pairs of kidneys (organs of Bojanus) that open into the mantle cavity serve as excretory organs. • Nervous system with a few pairs of ganglia joined by nerve connections. • Sense organs include eyes, tentacles, and statocysts. • Usually unisexual with sexual dimorphism in some animals. • Fertilisation can be internal or external. Generally, oviparous, fertilised eggs develop into larvae. • Some animals undergo direct development, while others exhibit indirect development.

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Octopus

Sepia

Pinctada

Pila

Chiton Fig. 4.28 Mollusca

4.12.10 Phylum Echinodermata The term 'Echinodermata' indeed originates from the Greek words 'echinos,' meaning spines, and 'derma,' meaning skin. Echinoderms exhibit radial symmetry, and they are triploblastic, meaning their bodies are composed of three germ layers during embryonic development. This phylum includes well-known marine animals such as starfish, sea urchins, and sea cucumbers, all of which feature distinctive spiny or textured skin. General characteristics

• Exclusively live in marine habitat. • Exhibits a star, disc or flower-like body with pentamerous symmetry. • Body is unsegmented and lacks a distinct head or tail. • Mouth is on the lower surface and anus on the upper surface. • Utilises soft and retractable tube feet as locomotory organs. • Possesses a hard exoskeleton with spines or projections. • Features a complete and simple digestive system. 128

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• The body cavity is modified into a water vascular system with tube feet. • Respiratory organs are gills; terrestrial forms may have lungs or air sacs. • Has a reduced circulatory system without a heart. • Lacks excretory organs. • Exhibits a primitive nervous system with a nerve ring and radial nerve cords. The brain is absent. • Unisexual without sexual dimorphism. • Asexual reproduction is possible through regeneration. • External fertilisation takes place. • Development is indirect, involving a larval stage.

Asterias

Echinus

Cucumaria

Antedon

Ophiura Fig. 4.29 Echinodermata

4.12.11 Phylum Hemichordata It was considered a subphylum under Chordata earlier. But now, it is treated as a separate phylum under nonchordates. General characteristics

• Exclusively marine, solitary, or colonial, mostly tubicolous. 129

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• The body is soft, wormlike, unsegmented, and bilaterally symmetrical. The body is divided into three regions: anterior proboscis, middle collar, and posterior long trunk. • They are triploblastic with the organ-system level of the organisation. • Coelom is enterocoelom. • They are ciliary filter-feeders. The digestive tube is complete, straight, or V-shaped. Foregut gives out a hollow buccal diverticulum that extends into the proboscis, which was earlier considered homologous to 'notochord'. • Respiratory System includes one to several pairs of dorsolateral pharyngeal gill slits. • The circulatory system is simple and is of open type. • Excretion occurs by a single proboscis gland or glomerulus. • The nervous system is primitive and consists mainly of two nerve cords: dorsal and ventral. • Sexes usually separate. Fertilisation is external and takes place in seawater. • Development is direct or indirect with a free-swimming tornaria larva. • Examples include Balanoglossus, Saccoglossus, Rhabodpleura (colonial), and Cephalodiscus.

Proboscis Collar

Trunk

Fig. 4.30 Hemichordata (Balanoglossus)

4.12.12 Phylum Chordata The name 'Chordata' refers to a rod-like structure called the notochord. Phylum Chordata includes all the animals that possess a notochord, at least at some stage of their life history. Animals belonging to the phylum Chordata are characterised by the presence of a dorsal hollow nerve cord, paired pharyngeal slits, and a post-anal tail apart from a notochord.

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Notochord

Muscle segments

Tail

Hollow nerve cord

Anus

Mouth Pharyngeal pouches

Fig. 4.31 Illustration of chordate characters General characteristics

• Notochord, a flexible rod made of cells, provides support and space for muscle attachment in the body. Notochord persists throughout life in some fishes, while in chordates like humans, it's replaced by the vertebral column as they grow. • The nerve cord lying along the back later develops into a brain and spinal cord during embryonic development or growth. • The pharyngeal gill slits, and openings in the throat, connect to the outside and aid in breathing, especially in aquatic species. • They have a tail located behind the anus, which is flexible, muscular and helps in movement. • They are triploblastic, bilaterally symmetrical, metamerically segmented coelomates. • They have a closed blood vascular system, with a heart that pumps blood. Classification of phylum chordata

Chordates are further classified into three subphyla. Phylum Chordata

Subphylum Urochordata

Subphylum Cephalochordata

Subphylum Vertebrata

Fig. 4.32 Classification of chordates

Subphylum Urochordata • Urochordates, also known as tunicates, are marine animals. • Their body is unsegmented and enveloped in a tunic or test. • The notochord is only present in the larval tail.

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• The dorsal nerve cord in the larval stage later reduces to a solid dorsal ganglion in the adult form. • The active, free-swimming ascidian larva transforms into a simple adult after metamorphosis. • Examples of Urochordates include Ascidia, Herdmania, Pyrosoma, and Salpa.

Fig. 4.33 Urochordata - Ascidia

Subphylum Cephalochordata • Cephalochordates, derived from the Greek kephale, meaning 'head', and Latin khorde, meaning 'cord', include lancelets. • These are marine organisms with small, fish-like translucent bodies. • All fundamental chordate characteristics persist throughout their entire life. • The notochord extends from the anterior to the posterior end and provides structural support. • Unlike some other chordates, cephalochordates lack a heart. • Examples include Branchiostoma (Amphioxus or lancelet). • Often, urochordates and cephalochordates are collectively termed protochordates. • They are also called acraniates because they lack a cranium or skull.

Fig. 4.34 Cephalochordata - Lancelet

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Subphylum Vertebrata • Vertebrates possess a notochord during the embryonic period, which is later replaced, either partly or wholly, by a cartilaginous or bony vertebral column in the adult, leading to the name Vertebrata. • Their bodies are covered with protective cellular skin and bear paired appendages. • The endoskeleton is made up of bone and/or cartilage. • The brain is protected by the cranium, giving rise to the name Craniata. • Exchange of respiratory gases occurs through gills or lungs. • The circulatory system-closed type includes a ventral muscular heart having 2, 3, or 4 chambers. • Presence of hepatic portal system and renal portal system (absent in cyclostomes & mammals). • Haemoglobin is present in erythrocytes. • A pair of kidneys perform excretion and osmoregulation. • Vertebrates like reptiles, birds, and mammals possess amnion, sac-like membranes are amniotes. Amnion encases the embryo in a protective fluid-filled compartment. • Vertebrates lacking amnion are termed amniotes and include fishes and amphibians. Vertebrata

Division Agnatha (Jaws absent)

Class Cyclostomata

Division Gnathostomata (Jaws present)

Superclass Pisces (Bear fins)

Superclass Tetrapoda (Bear limbs)

Class Chondrichthyes Osteichthyes

• Amphibia • Aves • Mammalia • Reptilia

Class

Fig. 4.35 Classification of subphylum vertebrata Division Agnatha

The term Agnatha is derived from the Greek word 'a' meaning 'without', and gnathos, meaning 'jaw', refers to jawless vertebrates. They lack paired fins and have a single nostril. 133

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Cyclostomata

• Cyclostomata, from the Greek cyklos meaning 'circular' and stoma meaning 'mouth', comprises extant jawless vertebrates. • This class includes hagfishes and lampreys. • Their body is elongated eel-like, with naked and slimy skin devoid of scales. • They lack paired fins. Their mouth is circular and sucker-like without jaws. • Both the cranium and vertebral column are cartilaginous. • They have a 2-chambered heart with one atrium and one ventricle. • Renal portal system is absent. • Cyclostomes exhibit anadromous migration, migrating to spawn in freshwater, after which they die. Their larvae, known as ammocoetes, return to the ocean after metamorphosis. • Examples include Petromyzon (lamprey) and Myxine (hagfish).

Petromyzon

Myxine Fig. 4.36 Cyclostomata

Division Gnathostomata

Gnathostomata, originating from the Greek gnathos, meaning 'jaw', and stoma, meaning 'mouth', encompasses vertebrates possessing a pair of jaws around the mouth. They typically have paired appendages, such as fins or limbs, and each internal ear contains three semi-circular canals. A. Superclass Pisces • This class comprises all types of fish, and members are exclusively aquatic, dwelling in either freshwater or marine environments. • Fish typically exhibit a streamlined body without limbs, and their exoskeleton is commonly composed of scales. • Fins and a muscular tail aid in locomotion, while respiration is performed by gills. • Fish generally have a two-chambered heart, and their brain features olfactory lobes and cerebellum, along with ten cranial nerves. 134

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• A pair of eyes and nostrils are present, but only internal ears are found. • A distinctive characteristic of this class is the presence of the lateral line sense organ. • Fish are unisexual and often display sexual dimorphism. 1. Class Chondrichthyes • Chondrichthyes, meaning 'cartilage fish', refers to a group of marine animals known as cartilaginous fishes. General characteristics

• These creatures have a streamlined body shape, and tough scales called dermal denticles, made of cartilage instead of bone. • The entire internal skeleton of cartilaginous fishes is made of cartilage, and their notochord, a flexible rod-like structure, stays present throughout their life. • Their mouths are located on the underside, and their teeth, which are modified placoid scales, point backwards. With powerful jaws, they are skilled predators. • Examples of sharks are the Indian dogfish (Scoliodon sorrakowah), the whale shark (Rhincodon typus), the hammer-headed shark (Sphyrna zygaena), the Great white shark (Carcharodon), the sawfish (Pristis), etc. • Examples of Rays and Skates are eagle ray (Myliobatis), electric ray (Torpedo), sting ray (Trygon), skate (Raja), etc.

Sphyrna

Shark

Sting ray

Electric ray Fig. 4.37 Cartilaginous fishes

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2. Class Osteichthyes Osteichthyes, which means 'bonefish,' includes a diverse group of aquatic animals known as bony fishes. General characteristics

• Bony fishes can be found in freshwater, brackish water, and marine environments, showing various shapes and sizes. • Their skin is covered with different types of scales, like cycloid, ctenoid, or ganoid scales. • The bony skeleton of these fishes is mostly made of bone, and their mouths are usually located at the front (terminal). • Examples of bony fishes include marine species like the flying fish (Exocoetus), sea horse (Hippocampus), tuna (Thunnus) and sucker fish (Echeneis). In freshwater, examples include rohu (Labeo rohita), katla (Catla), magur (Clarias), and eel (Anguilla). Some popular aquarium species are the Siamese Fighting fish (Betta splendens), Angelfish (Pterophyllum), and goldfish (Carassius auratus).

Tuna

Flying fish

Sea horse

Electric eel Fig. 4.38 Bony fishes

B. Superclass Tetrapoda Amphibians, reptiles, birds, and mammals are collectively termed tetrapods (four-footed).

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1. Class Amphibia Amphibians, the first land vertebrates, get their name from the Greek words 'amphi,' meaning both, and 'bios,' meaning life. This reflects their unique ability to live both in water and on land. General characteristics

• Smooth or rough, moist skin equipped with mucous glands and pigment cells (chromatophores). Lack of scales on the body. • Presence of a distinct head and trunk, with a few having tails. • Eyes have movable eyelids. • A lateral line system is present. • Four limbs, with five fingers each, display a pentadactyl structure. • Feet are webbed with toes lacking claws and nails. • Endoskeleton mostly bony. • Respiration through lungs or skin in the adult stage and gills in the larval stage. • Heart is 3-chambered, consisting of two auricles and one ventricle. • Blood is characterised by biconvex, oval, and nucleated red blood cells (RBC). • Presence of a pair of kidneys and a urinary bladder. Brain is underdeveloped. • External fertilisation occurs in a water medium. • Indirect development featuring metamorphosis, a distinctive trait of this class. • Life cycle includes a fish-like aquatic larva known as a tadpole. • Reproduction is oviparous, with eggs laid in masses. • Some species exhibit a primitive form of parental care. • Examples include frogs, toads, salamanders, and more.

Frog

Toad

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Hyla

Salamander Fig. 4.39 Amphibians

2. Class Reptilia The name Reptilia (L. repere or reptum = creep or crawl) refers to the creeping or crawling mode of locomotion. They are poikilothermic. General characteristics

• They are mostly terrestrial and are generally creeping or burrowing. • Body is distinguished into head, neck, trunk and tail. • Limbs are pentadactyl, each with five digits. Digits are clawed. Limbs are absent in snakes and some lizards. • Skin is dry and cornified with epidermal scales or shields or scutes. Some lizards, such as chameleons, change their colour for camouflage. • Gas exchange is primarily pulmonary. Intercostal muscles assist in ventilation. • Heart is usually three-chambered with an incompletely divided ventricle (interventricular septum is incomplete). In crocodiles, the ventricle is completely divided, and hence, the heart is four-chambered. • Kidneys excrete uric acid. • Digestive, excretory and reproductive systems open into the cloaca. • A tympanic membrane is typically found. Ear openings are absent in snakes. • Fertilisation is internal in all amniotes. • Reptiles are mostly oviparous. Eggs are cleidoic (shelled) and megalecithal (large amount of yolk). • Examples include Chelone (turtle), Testudo (tortoise), Chameleon (tree lizard), Calotes (garden lizard), Crocodilus (crocodile), Alligator, Hemidactylus (wall lizard), poisonous snakes like Naja (cobra), Bungarus (krait), Vipera (viper).

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Turtle

Tortoise

Chameleon

Alligator

Snake Fig. 4.40 Reptiles

Class Aves The class Aves includes birds and feathered bipedal vertebrates. Ornithology is the study of birds. Dr. Salim Abdul Ali (1896-1987) is an Indian ornithologist popularly known as the 'Birdman of India'.

General characteristics

• Presence of feathers and the power of flight. • They are warm-blooded and maintain a constant temperature (homoithermous). • The body is distinguished into the head, long neck, trunk and short tail. • The body is boat-shaped and streamlined, and it is well adapted for flight. • They are bipedal. Forelimbs are modified into wings. Hind limbs bear the whole weight of the animal and are modified for walking, swimming or clasping the tree branches (perching). • Skin is dry and without glands, except the oil gland (uropygial gland or preen gland) present at the base of the tail. • Exoskeleton consists of epidermal feathers, scales on legs, claws on toes and a horny covering on the beak. • Endoskeleton is fully ossified. Long bones are pneumatic. 139

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• Birds have no teeth; beak helps in feeding in many ways. • The digestive system starts with the mouth and ends in a 3-chambered cloaca. • The oesophagus is dilated into a crop. The muscular gizzard helps crush and churn the food. The lungs are inelastic and connected to air sacs. • They lack vocal cords in the pharynx, but a unique sound-producing organ called syrinx is present at the base of the trachea. • They have a pair of kidneys, and the urinary bladder is absent. • The heart is 4-chambered with two auricles and two ventricles.

Penguin

Peacock

Toucan

Hawk

Hummingbird

Crane

Fig. 4.41 Birds

4. Class Mammalia Mammals are the animals in which the young are nourished with milk from the mammary glands of the mother. They thrive in a variety of habitats - polar ice caps, deserts, mountains, forests, grasslands, dark caves, etc. Some of them have adapted to fly or live on land and in water. Three major types of living mammals are monotremes, marsupials and eutherians. The most advanced mammals are primates. General characteristics

• Mammals are warm-blooded or homoeotherms. • They have two pairs of limbs adapted for various activities such as walking, running, climbing, burrowing, swimming, or flying. • The skin contains different glands like sweat glands (excretion and temperature regulation) and sebaceous glands (secrete oily sebum for lubrication). • The mammary glands (modified sweat glands) secrete milk to nourish the young. 140

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• The body is covered in hair, which serves as an insulator. Claws, nails, and hooves are made of keratin and protect the tips of digits. • A muscular diaphragm separates the thorax and abdomen, playing a crucial role in breathing. • Dentition includes four types of teeth such as incisors, canines, premolars, and molars. Two sets of teeth present during their lifetime where deciduous/milk teeth are replaced by permanent teeth. • Respiration is pulmonary. The diaphragm and intercostal muscles assist in ventilation. • The larynx is the sound-producing organ. • Four-chambered heart with two atria and two ventricles. • The main excretory product is urea, and the kidneys have a loop of Henle for forming concentrated urine. A urinary bladder is present. • An external ear lobe or pinna is present. The middle ear contains three ear ossicles: malleus (hammer), incus (anvil), and stapes (stirrup). The cochlea in the internal ear is coiled. • Eyes have movable eyelids and eyelashes. • Testes are usually located outside the abdomen in scrotal sacs. • Most mammals are viviparous except egg-laying monotremes. Fertilisation is internal and development intrauterine. The foetus is connected to the mother through a placenta. • Examples include Platypus (egg laying), kangaroo, flying fox, camel, monkey, rat, dog, cat, elephant, horse, dolphin, blue whale, tiger, lion, etc.

Armadillo

Kangaroo

Lion

Bat

Elephant

Dolphin

Fig. 4.42 Mammals

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QUICK REVIEW • There are about several million different species of organisms that differ in their morphology, function and behaviour. • The need for classification arises from the vast array of living beings on Earth, making systematic study and understanding nearly impossible without a structured approach. • Aristotle, a Greek philosopher, made the first recorded attempt to classify both plants and animals. • Modern classification requires the knowledge of external and internal structures along with the cytological details, developmental process, and ecological knowledge. • The method of standardising the naming of living organisms is called nomenclature. • The system of binomial nomenclature, introduced by Carolus Linnaeus, involves naming organisms using a two-term structure: the genus name (capitalised) and the species name (lowercase). • Biological names are generally in Latin and written in italics. • The sequence of arrangement of taxa in descending order in classification is called taxonomic hierarchy or Linnaeus hierarchy. • The widely accepted five kingdom classification by Robert Whittaker (1959) categorises living beings into Monera, Protista, Fungi, Plantae, and Animalia. • He classified 5 kingdoms based on nutrition modes, cell structure, and cellular organisation. • Each kingdom exhibits unique characteristics, contributing to a comprehensive understanding of the diversity of life forms. • Within the Plantae kingdom, further divisions like Thallophyta, Bryophyta, Pteridophyta, Gymnosperms, and Angiosperms highlight the diverse characteristics of plant life. • Similarly, Kingdom Animalia is divided into phyla such as Porifera, Coelenterata, Platyhelminthes, Aschelminthes, Annelida, Arthropoda, Mollusca, Echinodermata, Protochordata, and Chordata. • Chordata, in turn, is classified into vertebrates and includes two superclasses: Pisces (fish) and Tetrapoda (four-limbed animals). • Vertebrates possess a notochord during the embryonic period, which is later replaced, either partly or wholly, by a cartilaginous or bony vertebral column in the adult, leading to the name Vertebrata.

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• Superclass Pisces comprises all types of fish, and members are exclusively aquatic, dwelling in either freshwater or marine environments. • Superclass Tetrapoda is further divided into Amphibia, Reptilia, Aves, and Mammalia, each class is characterised by specific features that adapt them to their environments.

WORKSHEET - 1 MULTIPLE CHOICE QUESTIONS WITH SINGLE CORRECT ANSWER I. Classification and nomenclature

1. Identify the correct sequence of taxonomic categories a. Species → order → phylum → kingdom c. Species→ Genus → order → class

b. Genus → species → order → kingdom d. Division → Family → order → Genus

2. The study of all living organisms is made possible by this aspect of taxonomy a. Identification

b. Systematics

c. Classification

d. Nomenclature

3. Choose the correct expression a. A group of related genera - Family

b. A group of related species - Order

A group of related families - Class

d. A group of related orders - Genus

4. Taxonomy comprises a. Identification

b. Classification

c. Nomenclature

d. All of these

5. The study of principles and procedures of classification of organisms is a. Classification

b. Taxonomy

c. Nomenclature

d. Grouping

6. Scientific names for the plants are given based on the principles provided by a. ICZN

b. BSI

c. ICBN

d. IUB

7. According to binomial nomenclature, two words used for naming a plant or animal are a. Family and genus

b. Species and family

c. Class and family

d. Genus and species

8. The fundamental taxonomic category is (basic unit is) a. Family

b. Class

c. Genus

d. Species

9. Which of the following statements is wrong w.r.t the rules of nomenclature? a. The first word denoting the genus starts with a capital letter b. The specific epithet starts with a small letter 143

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c. Biological names are printed in italics to indicate their Latin origin d. In the biological name - Mangifera indica L., 'L' denotes the word 'Latin'. 10. The processes that are basic to taxonomy include: a. Characterisation

b. Identification

c. Classification and nomenclature

d. All of the above

11. Each genus a. Always has one specific epithet

b. May have one or more specific epithets

c. Is a group of many families

d. Is always monotypic

12. In Whittaker's five-kingdom classification, eukaryotes were assigned to a. All the five kingdoms

b. Two of the five kingdoms

c. Four of the five kingdoms

d. Only one of the five kingdoms

13. In Whittaker's classification, Archaebacteria and nitrogen-fixing algae are placed under a. Plantae

b. Fungi

c. Monera

d. Protista

14. Two kingdoms that are common to all biological classifications a. Monera and Plantae

b. Plantae and Animalia

c. Protista and Monera

d. Animalia and Fungi

II. Kingdom Monera

1. The smallest living moneran cells that lack a cell wall are a. Cyanobacteria

b. Protozoa

Mycoplasma

d. Bacteria

b. Nostoc

Chlorella

d. Methanogens

b. Decomposers

c. Consumers

d. All the above

2. Nitrogen fixing cyanobacterium is a.

Rhizobium

3. Cyanobacteria are a. Producers 4. Bacteria closely resemble: a. Protista

b. Cyanobacteria

d. Fungi

Plantae

5. Monera includes a. Unicellular eukaryotes

144

b. Saprophytic eukaryotes

IL Foundation Series Class 9

c. Prokaryotes

d. All of these

III. Kingdom Protista

1. The photosynthetic protists are a. Euglenoids, diatoms, and dinoflagellates b. Ciliates, zooflagellates, and dinoflagellates c. Sarcodines, dinoflagellates, and slime moulds d. Sarcodines, dinoflagellates, and Euglenoids 2. Mixotrophic nutrition occurs in a. Diatoms

b. Paramoecium

Euglena

d. Amoeba

c. Green algae

d. Diatoms

3. Chief producers in the ocean are a. Slime moulds

b. Bacteria

4. Diatomaceous earth is indestructible due to cell walls embedded by a. Calcium

b. Silica

c. Zinc

d. Phosphorus

c. Monera

d. Plantae

IV. Kingdom Fungi

1. The plant body is mycelium in this kingdom a. Protista

b. Fungi

2. Chitinous cell wall and glycogen as reserve food are characteristic of this kingdom a. Plantae

b. Eubacteria

c. Monera

d. Fungi

d. Albugo

3. One of the following is a deuteromycetes fungus a.

Aspergillus

b. Agaricus

Alternaria

4. Puccinia is a. A fungus that produces antibiotics

b. A fungus of class Phycomycetes

c. A fungus that causes rust disease

d. An imperfect fungus

5. Fungus that is extensively used in biochemical & genetic work a.

Neurospora

b. Ustilago

Colletotrichum

d. Saccharomyces

6. What is the structural unit of a fungal mycelium that consists of a network of filamentous structures involved in nutrient absorption and growth? a. Budding

b. Hypha

c. Binary fission

d. Fragmentation 145

DIVERSITY IN LIVING ORGANISMS

V. Kingdom Plantae

Identify the correct sequence of taxonomic categories. a. Species → Order → Phylum → Kingdom c. Species → Genus → Order → Class

b. Genus → Species → Order → Kingdom d. Division → Family → Order → Genus

2. The plant that is responsible for the formation of peat is: a.

Anthoceros

b. Sphagnum

Riccia

d. Funaria

Cycas

d. Selaginella

b. Sargassum

Sphagnum

d. Polytrichum

b. Bryophyta

c. Pteridophyta

d. Gymnosperms

c. Pteridophyte

d. Gymnosperms

3. The plant categorised under living fossil is: a.

Marchantia

b. Pinus

4. Identify the algae rich in protein. a.

Spirulina

5. Liverworts belong to: a. Thallophyte

6. Moss plants belong to which category of plants? a. Thallophyte

b. Bryophyta

7. Floridean starch is the reserve food material in which of the following organisms? a.

Gelidium

b. Sargassum

Spirogyra

d. All of these

8. The development of haploid cells of gametophyte into a haploid sporophyte is called: a. Apogamy

b. Apospory

c. Budding

d. Binary fission

9. Which of the following pteridophyte plants is known for replenishing soils? a.

Azolla

b. Lycopodium

c. Fern

d. Marsilea

d. Hevea

10. Which of the following is used as green manure? a.

Azadirachta

b. Azolla

Crotalaria

11. Trimerous condition of floral whorls is present in: a. fern

b. dicots

c. gymnosperms

d. monocots

12. Which of the following groups of plants possesses cones as reproductive structures? a. Gymnosperms

b. Pteridophytes

c. Bryophytes

d. Thallophytes

13. Which of the following is absent in the life cycle of gymnosperms? a. Ovules 146

b. Ovary

c. Microspores

d. Megaspores

IL Foundation Series Class 9

14. Name the part of the plant cell which traps solar energy. a. Grana

b. Stroma

c. Cuticle

d. Mesosomes

c. Calyx

d. Pedicel

15. Sessile flowers lack which structure in the flower? a. Thalamus

b. Anther

16. Which part of the cactus plant is modified into a spine? a. Stem

b. Roots

c. Leaves

d. Branches

c. Simple

d. Compound

17. Name the venation in which veins form a network. a. Reticulate

b. Parallel

18. Underground stem modification is observed in which plant? a. Ginger

b. Sweet potato

c. Carrot

d. Beetroot

19. The plants that grow in nitrogen-deficient soil are: a.

Opuntia

c. Neem

b. Vallisneria d. Venus fly trap

20. Assertion (A): In ferns, the diploid cells of the sporophyte directly give rise to the diploid gametophyte Reason (R): Ferns reproduce by spore formation and gametic fusion a. Both A and R are true, and R is the correct explanation for A. b. Both A and R are true, but R is not the correct explanation for A. c. A is true, and R is false. d. A is false, and R is true. 21. Assertion (A): A thick waxy coating is found covering the shoot system of cactus Reason (R): Cactus is generally found in desert areas. a. Both A and R are true, and R is the correct explanation for A. b. Both A and R are true, but R is not the correct explanation for A. c. A is true, and R is false. d. A is false, and R is true.

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DIVERSITY IN LIVING ORGANISMS

22. Assertion (A): Gymnosperms do not produce fruits Reason (R): Gymnosperms are nonflowering plants. a. Both A and R are true, and R is the correct explanation for A. b. Both A and R are true, but R is not the correct explanation for A. c. A is true, and R is false. d. A is false, and R is true. 23. Assertion (A): Cycas bear reproductive structures on the leaves Reason (R): Pteridophytes possess sporangia on leaves a. Both A and R are true, and R is the correct explanation for A. b. Both A and R are true, but R is not the correct explanation for A. c. A is true, and R is false. d. A is false, and R is true. 24. Assertion (A): Tap root system is seen in monocotyledons. Reason (R): The fibrous root system anchors the plant firmly into the ground. a. Both A and R are true, and R is the correct explanation for A. b. Both A and R are true, but R is not the correct explanation for A. c. A is true, and R is false. d. A is false, and R is true. 25. Assertion (A): The dominant phase of the life cycle in angiosperms is the sporophyte Reason (R): Sporophyte in angiosperm is developed from diploid zygote a. Both A and R are true, and R is the correct explanation for A. b. Both A and R are true, but R is not the correct explanation for A. c. A is true, and R is false. d. A is false, and R is true. 26. Assertion (A): Dicotyledons undergo an epigeal type of germination. Reason (R): Endosperm forms nutritive tissue. a. Both A and R are true, and R is the correct explanation for A. b. Both A and R are true, but R is not the correct explanation for A. 148

IL Foundation Series Class 9

c. A is true, and R is false. d. A is false, and R is true. VI. Kingdom Animalia

1. Triploblastic animals show a. Asymmetry

b. Radial symmetry

c. Bilateral symmetry

d. Spherical symmetry

2. All the members of Animalia are a. Eumetazoans

b. Unicellular

c. Multicellular

d. With tissues

3. Cellular level of organisation is shown by a. Sponges

b. Coelenterates

c. Protozoans

d. Triploblasticans

4. Tissue level of organisation is shown by a. Sponges

b. Coelenterates

c. Both (a) and (b)

d. Triploblasticans

5. Organ-system level of the organisation is shown by a. Sponges

b. Coelenterates

c. Diploblasticans

d. Triploblasticans

6. A complete digestive system is seen in a. Coelenterates

b. Platyhelminths

c. Ctenophores

d. Annelids

7. The type of symmetry with only one central axis but many planes is a.

Bilateral symmetry

c. Asymmetry

b. Radial symmetry d. Spherical symmetry

8. Peristalsis of the alimentary canal occurs independent of the contraction and relaxation of the body wall in a. Acoelomates

b. Pseudocoelomates

c. Eucoelomates

d. Both (b) and (c)

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DIVERSITY IN LIVING ORGANISMS

9. The double-fold peritoneum that joins organs in eucoelom is a. Mesentery

b. Retroperitoneum

c. Perimysium

d. Ligament

10. Animals developing from three cell layers are called triploblastic animals. Identify the animal i) Annelida

ii) Cnidaria

a. i, ii and iii

b. i and ii

iii) Mollusca

iv) Porifera

c. ii and iv

d. i and iii

11. The body of an individual can be divided into equal halves by any plane passing through the centre from top to bottom. This type of symmetry is found in i) Cnidaria

ii) Echinodermata

iii) Coelenterata

a. i, ii and iii

b. i and ii

c. ii and iv

d. i and iii

iv) Mammals

12. Diploblastic organisms among the following is a. An echinoderm

b. A cephalochordate

c. A cnidarian

d. A fish

13. The alimentary canal has a single opening in a. Echinoderms

b. Platyhelminths

c. Nematodes

d. Annelids

14. Blood pumped out of the heart bathes the tissues directly, in_______type of the circulatory system. a. Closed

b. Open

c. Both (a) and (b)

d. None of these

15. The circulatory system, for the first time, developed in a. Platyhelminths

b. Aschelminths

c. Arthropoda

d. Annelida

16. The body forms left and right antimeres in only one plane in a. Mollusca

b. Echinodermata

c. Ctenophora

d. Cnidaria

17. Which group differs from the rest of the three regarding symmetry? a. Echinoderms

150

b. Annelids

c. Coelenterates

d. Ctenophores

IL Foundation Series Class 9

18. The body can be divided into identical halves in many planes, passing through the central axis in a.

An arthropod

b. A fish

c. A coelenterate

d. A mollusc

19. Most sponges exhibit a. Bilateral symmetry

b. Radial symmetry

c. Asymmetry

d. Spherical symmetry

20. Sponges are a. Generally marine

b. Generally freshwater

c. Mostly radial symmetrical

d. Tissue grade animals

21. Water enters into spongocoel through a. Osculum

b. Choanocytes

c. Ostia

d. Madreporite

22. Annelida is characterised by a. Pseudocoelom

b. Metamerism

c. Non-muscular pharynx

d. Renette gland

23. In Latin, 'annulus' means a. Little worm

b. Little ring

c. Jointed appendage

d. Spiny bodied

24. Locomotory organs of Nereis are a. Suckers

b. Setae

c. Parapodia

d. Jointed legs

25. A characteristic feature of birds is a. Homeothermy

b. Feathers

c. 4-chambered heart

d. Scales on legs

26. Structures that supplement respiration in birds are a. Lungs

b. Air bladders

c. Air sacs

d. Tracheae

d. Pavo

27. A flightless bird among the following is a.

Nephron

b. Struthio

Psittacula

28. The most unique mammalian feature is a. Homeothermy

b. Bony skeleton

c. 4-chambered heart

d. Mammary glands

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DIVERSITY IN LIVING ORGANISMS

29. The skin of mammals is unique in having a. Hair

b. No glands

c. Oil glands

d. Scales

c. Acrodont

d. Polyphyodont

30. Mammals have teeth of this type a. Homodont

b. Heterodont

WORKSHEET - 2 MULTIPLE CHOICE QUESTIONS WITH SINGLE CORRECT ANSWER 1.

In Whittaker's five-kingdom classification, eukaryotes were assigned to a. All the five kingdoms

b. Two of the five kingdoms

c. Four of the five kingdoms

d. Only one of the five kingdoms

2. Two kingdoms that are common to all biological classifications a. Monera and Plantae

b. Plantae and Animalia

c. Protista and Monera

d. Animalia and Fungi

3. Heterocysts are specialised in a. Nitrogen fixation under aerobic conditions b. Formation of internal hormones c. Nitrogen fixation under anaerobic conditions d. Saprotrophism 4. A pure (axenic) culture is a. A culture of microbe having multiple copies of a single kind of microbe b. A culture without any contamination c. Both (a) and (b) d. None 5. Cyanobacteria are characterised by a. Ability to perform oxygenic photosynthesis and absence of nitrogenase b. Ability to perform oxygenic photosynthesis and the presence of nitrogenase c. Have chlorophyll in chloroplast d. Ability to perform anoxygenic photosynthesis and the presence of nitrogenase

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IL Foundation Series Class 9

6. Seed-producing plants are called: a. spermatophytes

b. pteridophytes

c. bryophytes

d. embryophytes

7. Gametophytic and sporophytic generations are seen in the life history of: a. fungi

b. algae

c. ferns

d. diatoms

8. Identify the process in which both organisms benefit from their close association. a. Saprophytic

b. Saprozoic

c. Zinc

d. Symbiosis

9. Which of the following kingdoms do not have well-defined boundaries? a. Plantae

b. Monera

c. Protista

d. Algae

b. Mycoplasma

c. Diatoms

d. Euglena

10. Silica gel is obtained by a. Red algae

11. Sycon belongs to a group of animals which are best described as

[AIPMT-2003]

a. Unicellular or acellular b. Multicellular without any tissue organisation c. Multicellular with a gastrovascular system d. Multicellular having tissue organisation but no body cavity 12. Which of the following have porous bodies and are diploblastic?

[AIIMS-2010]

Aurelia and Obelia

b. Adamsia and Euplectella

Leucosolenia and Spongilla

d. Sycon and Hydra [AFMC-2005]

13. The canal system in Porifera is not concerned with a. Repiration

b. Nutrition

c. Locomotion

d. Sexual reproduction [JIPMER-2010]

14. During unfavourable conditions, the sponge's form a. Cyst

b. Encyst

c. Spicule

d. Gemmule 153

DIVERSITY IN LIVING ORGANISMS

15. Which of the following cell types is capable of giving rise to other cell types in sponges? [JIPMER-2009]

a. Thesocytes

b. Pinacocytes

c. Cnidocytes

d. Archaeocytes [JIPMER-2005]

16. Which cells are found only in sponges? a. Amoeboid cells

b. Choanocytes

c. Pigment cells

d. Gland cells [AIPMT-2006]

17. Metameric segmentation is the characteristic of a. Mollusca and Chordata

b. Platyhelminthes and Arthropoda

c. Echinodermata and Annelida

d. Annelida and Arthropoda

18. Two common characteristics found in centipedes, cockroaches, and crabs are [AIPMT-2006] a. Book lungs and antennae

b. Compound eyes and cerci

c. Jointed legs and chitinous exoskeleton

d. Green gland and tracheae [AIPMT-2005]

19. From the following statements, select the wrong one. a. Prawn has two pairs of antennae b. Nematocysts are characteristic of the phylum Cnidaria c. Millipedes have two pairs of appendages in each segment of the body d. Animals belonging to the phylum Porifera are freshwater and marine

20. Which one of the following is a matching pair of an animal and a certain phenomenon it [AIPMT-2003]

exhibits? a. Pheretima-Sexual dimorphism

b. Musca-Complete metamorphosis

c. Chameleon-Mimicry

d. Taenia-Polymorphism

21. Given below are four matchings of an animal and its kind of respiratory organ [AIPMT-2003] (A) Silverfish - Trachea

(B) Scorpion - Book lung

(D) Dolphin - Skin

The correct matchings are a. A and B 154

b. A, B and C

c. B and D

d. C and D

IL Foundation Series Class 9

22. Similarity in Ascaris lumbricoides and Anopheles stephensi is a. Sexual dimorphism

b. Metamerism

c. Anaerobic respiration

d. Endoparasitism

23. The animals with bilateral symmetry in the young stage and radial pentamerous symmetry in the adult stage belong to the Phylum a. Annelida

b. Mollusca

c. Cnidaria

d. Echinodermata [AFMC-2011]

24. Coelom in Echinodermata is a. Pseudocoelic

b. Haemocoelic

c. Schizocoelic

d. Enterocoelic

25. The echinoderms are

[JIPMER-2010]

a. Arboreal insects

b. Marine animals

c. Terrestrial insects

d. Freshwater forms

26. Tube feet are the locomotory organ in a. Starfish

b. Jellyfish

c. Silverfish

d. Scoliodon

27. The body is covered by dry and cornified skin and epidermal scales in a. Mammals

b. Reptiles

c. Amphibians

d. Fish

28. Crocodiles show a. External ear openings

b. Limbless condition

c. External fertilisation

d. Four-chambered heart

29. Which of the following animals casts skin in one piece? a.

Hemidactylus

b. Alligator

Testudo

d. Naja

Vipera

d. Macaca

30. Poikilotherm of the following is a.

Nephron

b. Aptenodytes

31. The first vertebrates which attempted the transition from water to land were a. Reptiles

b. Aves

c. Amphibians

d. Insects

c. Larynx

d. Teeth

32. Features that appeared even before amphibians are a. Limbs

b. True sternum

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DIVERSITY IN LIVING ORGANISMS

33. Among vertebrates, all of the following features are seen first in reptiles except a. True terrestrial nature

b. Amniotes

c. Cleidoic eggs

d. Viviparous

34. Correct one of the following is a.

Calotes - tree lizard

b. Chameleon - garden lizard

Chelone - tortoise

d. Bungarus - krait

35. Which of the following pairs of animals has non-glandular skin? a. Snake and frog

b. Chameleon and turtle

c. Frog and pigeon

d. Crocodile and tiger

36. All amniotes a. Have scales on the body

b. Are unmodified tetrapods

c. Lay down cleidoic eggs

d. Show internal fertilisation

37. The glands present at the base of the tail in birds are a. Sebaceous gland

b. Sweat gland

c. Oil gland

d. Femoral gland

38. Long bones of birds are a. Not ossified

b. Pneumatic

c. Cartilaginous

d. Solid

39. The additional chambers in the digestive tract of birds are a. Crop, cloaca

b. Gizzard, cloaca

c. Crop, gizzard

d. Intestine, crop

40. Long bones with air cavities occur in a.

Aptenodytes

b. Corvus

Pteropus

d. Bungarus

c. Flying fox

d. Blue whale

41. An oviparous mammal in the following is a.

Platypus

b. Kangaroo

42. Pinnae is present in a.

Aptenodytes

b. Chameleon

Ornithorhynchus

d. Macropus

43. The only gland present in the skin of birds is

156

a. Femoral gland

b. Musk gland

c. Uropygial gland

d. Sebaceous gland

IL Foundation Series Class 9

44. A special sound-producing organ in birds is a. Furcula

b. Larynx

c. Syrinx

d. Keel

45. Mammary glands are modified a. Sebaceous glands

b. Sweat glands

c. Preen glands

d. Femoral glands

46. The function of hair in mammals is that it a. Enhance beauty

b. Attract opposite sex

c. Acts as insulator

d. Makes body lightweight

47. Oviparous mammals are included in a. Theria

b. Metatheria

c. Prototheria

d. Eutheria

48. Thermoregulatory glands present in the skin of mammals are a. Sebaceous

b. Sudoriferous

c. Mammary glands

d. Uropygial glands

49. Whales have no limbs, bats have wings, yet both of them are included in Mammalia. The reason is they have a. Teeth

b. 12 pairs of cranial nerves

c. Mammary glands

d. Vertebrae

50. Which one of the following is not a mammalian character? a. Presence of milk-producing glands

b. Skin is unique in possessing hair

c. Presence of external ears called pinnae

d. Homodont type of dentition

51. The characteristic features of class - Aves are I) They are warm-blooded and oviparous

II) They have pneumatic bones

III) Syrinx is not present

IV) Fertilisation is external

Choose the correct option a. I, II and III

b. I and II

c. II and IV

d. I and III

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DIVERSITY IN LIVING ORGANISMS

52. What is true about mammals? I) Skin is covered by epidermal hair II) Evolved during the Triassic period of the Cenozoic era III) Kidneys are metanephric IV) Fertilisation is external Choose the correct option

158

a. I, II and III

b. I and II

c. II and IV

d. I and III

5.1

WHY DO WE FALL ILL?

INTRODUCTION

A cell is the basic building block of life. Subcellular entities known as organelles within a cell participate in the operation of the cells and perform distinct tasks. Organs and tissues carry out specialised functions to keep life going. For instance, the kidneys filter out toxic waste from our bodies, the heart beats constantly to pump blood, the lungs facilitate breathing to provide oxygen to the body’s cells, and the intestinal tract absorbs nutrients to provide essential raw materials to the cells for various metabolic processes. All of these tasks are related to one another, and maintaining life depends on their correct execution. Anything that prevents organs, tissues, or cells from operating properly can result in the ineffective functioning of our body.

5.2

HEALTH AND ITS FAILURE

"A state of complete physical, mental, and social well-being and not merely the absence of disease or infirmity" is how the World Health Organisation (WHO) in 1948 defined health. 5.2.1 The significance of health Physical health includes anything concerned with our bodies. It ensures the performance of many activities, such as walking, running, and exercising. Mental health includes the ability to express emotions appropriately, to learn, to make the right decisions, etc. Social wellness includes social networks, level of interdependence, care, safety, acceptance of diversity, etc. 5.2.2 Personal and community issues both matter for health The health of all living beings is influenced by their physical surroundings, social environment, personal hygiene, and economic status, among other factors. • Taking a bath every day, changing into clean clothes, washing dirty hands, regular dental checkups, eye care, and vaccinations help an individual maintain proper personal hygiene. • The health of every organism is influenced by its surroundings, including factors like rainfall, soil type, temperature, and light, which collectively form its physical environment. • Our social surroundings have a significant impact on our health. Thus, an individual’s health may suffer if public or community health services are inadequate. For e.g., trash on the road, open clogged drains and standing water in streets or public areas increase the likelihood of bad health. • A healthy economy and employment are essential to personal well-being. • Social harmony also contributes to an individual’s well-being as it involves sharing in one other’s happiness and sorrows. We cannot be content or healthy if we treat one another badly and are terrified of one another. Consequently, a person’s health is greatly influenced by both personal and social factors. 159

WHY DO WE FALL ILL?

5.2.3 Distinctions between healthy and disease-free Healthy and disease-free do not have the same meanings. If a person does not experience any discomfort with his body’s normal functioning, he is considered disease-free. A person is not necessarily healthy if he is free of any illnesses. He might be in poor health even if there isn’t a specific illness. For instance, a person can be considered disease-free but not healthy if he is experiencing any form of emotional stress. A person who can function normally in his social and community settings is considered healthy. S.No

Parameters

Healthy

Disease-free

Definition

State of physical, social and mental State of absence of discomfort in the well-being body

Inclusions

Comprises the individual, his society and surrounding

Comprises the individual only

Factors

Good economic conditions, social harmony and proper sanitation

Hygienic surroundings and protection against infections and diseases

Table 5.1 Difference between healthy and disease-free states

5.3 DISEASE AND ITS CAUSES A shift from the normal functioning of a person’s body and mind results in disease. It is characterised by the improper functioning of one or more organs in the body. While many of these abnormalities are curable, few may become life-threatening. 5.3.1 What does disease look like? A disease can be identified with distinct signs and symptoms. The symptoms are visible indicators of a disease. For example, a headache may indicate the presence of malaria, dengue, jaundice, vision problems, high blood pressure, etc. As a result, symptoms cannot pinpoint the precise cause of an illness. On the other hand, signs give a more definite indication of an illness. Based on the symptoms, a doctor looks for signs of a disease. 5.3.2 Acute and chronic diseases Based on how long a disease lasts, diseases are classified into two groups: acute diseases and chronic diseases. 1. Acute diseases

Acute diseases are short-duration diseases. There is a temporary impairment to normal activities. The patient makes a full recovery and starts living an ordinary, active life. Short-lived acute diseases, such as the common cold, malaria, typhoid, diarrhoea, dengue, etc., do not have a significant impact on health.

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IL Foundation Series Class 9

2. Chronic diseases

The conditions persist for an extended period, sometimes even a lifetime. The long-term consequences of chronic diseases on a patient’s health are severe. Diabetes, TB, elephantiasis, cardiovascular disorders, arthritis, cancer, and other conditions are examples of chronic diseases. Acute diseases

Chronic diseases

They may last for a few days.

They last for a longer period.

They do not have a major effect on the body.

They affect the body badly.

There is a short-duration loss of work and efficiency.

There is a prolonged loss of work and efficiency.

The patient recovers completely after the cure. E.g. Cough, cold, etc.

The patient may not recover completely. E.g. Elephantiasis.

Table 5.2 Difference between acute and chronic diseases

5.3.3 Chronic diseases and poor health The impact of acute and chronic diseases on our health is not the same. Any disease that impairs the proper functioning of a body part will have an impact on our health. Thus, for good health, all parts of the body should be able to function properly. However, chronic disease will take a longer time to significantly impact overall health than acute disease, which ends quickly. For instance, consider the common cold and cough that we all experience occasionally. Most people recover and get well in about one week. Also, there are no long-term consequences on our health. On the other hand, if we have a persistent disease like pulmonary tuberculosis, we will eventually lose weight and experience constant fatigue. Therefore, compared to acute diseases, chronic diseases have far more significant long-term consequences on people’s health. 5.3.4 Causes of diseases A person’s physical well-being can be influenced by various factors. These factors could belong to one of the two categories. 1. Immediate causes 2. Contributory factors 1. Immediate causes

When a person has a sickness, the immediate cause is the first thing identified. For instance, if someone has a cold, we can tell that a viral infection is the cause of the illness. Therefore, a virus is the primary cause of the disease. There are two categories of immediate causes: 161

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1. E xternal variables: These are the extrinsic or external elements that have an impact on the functioning of an illness under normal conditions. These include medications, pollution, poor food, and infections. 2. Internal factors: The human body has these elements. These may include immune system malfunctions, malfunctions of any organ, hereditary diseases, etc. 2. Contributory factors

Contributory factors are the second-level causes of any illness. They do not produce an illness on their own. For instance, a baby may be more susceptible to cold symptoms when exposed to a virus due to a genetic predisposition. The genetic condition alone could not induce any disease without the infection (virus). It does, however, start to contribute to the illness’s development. 5.3.5 Infectious and non-infectious causes Infectious diseases, also known as communicable diseases, are passed on from one person to another in various ways through air, water, food, physical contact and insects. These diseases are caused by microorganisms (bacteria, viruses, fungi, protozoa) and worms. Non-infectious diseases, also known as non-communicable diseases, are those that cannot be spread from person to person, i.e., these diseases remain confined to the diseased person and do not infect others by contact or by carriers. These diseases are not due to an external infection. For e.g. Diabetes, arthritis, cancer, heart diseases, haemophilia, etc. Many non-infectious diseases are caused due to nutritional deficiencies, e.g. obesity, marasmus, kwashiorkor, etc.

5.4 INFECTIOUS DISEASES 5.4.1 Infectious agents S. No.

Agent

Diseases caused

Bacteria

Tuberculosis, Diphtheria, Typhoid, Pertussis, Cholera, Leprosy, Gonorrhoea, Syphilis, Diarrhoeal diseases

Virus

Mumps, AIDS, Influenza, Measles, Chickenpox, Poliomyelitis, Rabies, Common cold, Influenza, Dengue, Hepatitis-B

Fungi

Ringworm, Athlete's foot

Protozoa

Malaria, Amoebiasis, Kala-azar, Sleeping sickness

Parasitic worms Filariasis, Ascariasis, Taeniasis Table 5.3 Agents of infectious/communicable diseases

5.4.2 Means of spread Infectious diseases can spread from one person to another. There are two ways through which the transfer can happen. 1. Direct transmission 162

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2. Indirect transmission 1. Direct transmission

Direct contact with an infected individual may result in the direct transmission of the infection. These diseases do not need any media or agents for transmission. Infections or diseases that spread through direct contact are contagious. The modes and examples of direct transmission of infectious diseases are shown in the following table. S.No

Modes of Transmission

Diseases caused

Contact with infected person

Chicken pox, Smallpox, Ringworm

Droplet infection, sneezing, coughing, spitting

Common cold, Influenza, Tuberculosis

From mother to foetus through placenta

Rubella (German measles), AIDS, Syphilis

Body fluids - blood & semen

AIDS, Hepatitis B, Gonorrhoea

Table 5.4 Modes of direct transmission of infectious diseases 2. Indirect transmission

This type of transmission of pathogens from an infected person requires a media/medium for spreading and causing an infection. The modes and examples of indirect transmission of infectious diseases are shown in the following table. S.No

Modes of Transmission

Diseases caused

Vector

Malaria by Anopheles mosquito, Cholera, Dysentery, Typhoid by houseflies

Air

Epidemic Typhus

Dirty hands

Ascariasis

Used belongings of an infected person Diphtheria, Hepatitis A, Eye and skin infections

Animal bite

Rabies

Table 5.5 Modes of indirect transmission of infectious diseases

5.4.3 Organ-specific and tissue-specific manifestations Pathogens are very small microorganisms that invade the body through various routes and cause infections. They could possibly travel to different organs or tissues. However, different species of microorganisms have adapted to infect a particular organ, tissue or organ system. This often depends on their point of entry into the body. They might travel to the lungs if they enter through the nose from the air, as observed in tuberculosis-causing bacteria. They can remain in the stomach lining like typhoid-causing bacteria if they enter through the mouth. Similarly, viruses that cause jaundice go to the liver. However, this isn’t always the case. Microbes that cause malaria enter the body through a mosquito bite, first travelling to the liver and subsequently to the red blood cells. The virus that causes brain 163

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fever, also known as Japanese encephalitis, also enters the body through a mosquito bite but travels to the brain to cause infection. When a bacterium infects a specific tissue or organ in the body, it can lead to signs and symptoms that are characteristic of the affected area. For example, breathlessness and coughing will be the symptoms if the lungs are the target. Jaundice is the manifestation if the target is the liver. We will notice headaches, vomiting, fits, or unconsciousness if the brain is the target. Knowing the target tissue or organ and its functions will help us anticipate the symptoms and signs of an infection. There will also be other common consequences of infectious diseases in addition to these tissuespecific ones. The severity of a disease’s manifestations corresponds to the number of microorganisms in the body. The disease’s symptoms could be mild or invisible if there are extremely few microorganisms. However, the sickness may become severe and life-threatening if there is a high concentration of the same microorganism. The quantity of bacteria that survive in the body is mostly determined by the immune system. 5.4.4 Inflammation The most typical side effects result from the immune system of the body being triggered in reaction to an infection. A functioning immune system draws a large number of cells to the afflicted area in order to eliminate the pathogens. We refer to this recruitment process as inflammation. This procedure involves both general side effects like fever and local side effects like redness, swelling or edema, pain, and discomfort. 5.4.5 Principles of treatment Generally, there are two approaches to treating an infectious disease. 1. Minimise the disease’s consequences

Symptoms are typically caused by inflammation. Medications can lower the temperature, ease discomfort, or stop diarrhoea. Bed rest can help to conserve energy and concentrate on healing. 2. Eradicate the disease’s cause

Pathogens can be killed by using antimicrobial medicines. Microorganisms such as bacteria, fungi, viruses, or protozoa have unique biochemical life processes that set them apart from each other. For instance, the process by which our cells synthesise new materials may differ from that of bacteria. Therefore, a specialised drug can inhibit the bacterial synthesis pathway without harming us. E.g. antibiotics. iruses lack their own biochemical pathways, which makes it difficult to develop antiviral drugs. V They invade the body's cells and exploit them to carry out their biological functions. This indicates that there are not many targets that are unique to viruses. Regardless of such limitations, antiviral medications, such as those that suppress HIV infection, are now available.

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5.4.6 Principles of prevention So far, we have discussed how to eliminate an infection in a diseased person. However, this strategy for managing infectious diseases has three drawbacks. • First, a person’s body functions are compromised due to disease and may never fully recover. • Second, proper treatment will not cure a sickness instantly; rather, the patient might remain bedridden for some time during the treatment. • Third, the individual afflicted with an infectious disease may become a point of source and spread the infection to other individuals. This can cause the problems mentioned above to multiply. There are two approaches to avoiding disease. 1. General approach

• Avoiding crowded places can prevent exposure to air-borne infections. • Drinking clean water can prevent water-borne diseases. • Maintaining clean and hygienic surroundings can keep away vectors of diseases. • Proper and adequate food and nutrients can strengthen our immune system. 2. Specific ways of preventing infectious diseases

This is based on a typical characteristic of the immune system, which generally wards off microbial infections. When an infectious microorganism enters the body for the first time, the body’s immune system reacts by fighting it off. The immune system then retains a distinct memory of it and defends the body vigorously the next time it encounters the same microorganism. This is the fundamental concept of immunisation. 5.4.7 Antibiotics An antibiotic is a chemical that has the ability to both kill and stop the growth of microorganisms. Most antibiotics are made by fungi or bacteria. Alexander Fleming discovered the first antibiotic in 1929. Penicillin is the name of the antibiotic isolated from the mould, Penicillium notatum. Large-scale production of penicillin is also possible from a different mould known as Penicillium chrysogenum. Another popular and efficient antibiotic is streptomycin. It is extracted from the Streptomyces bacterium. Clindamycin and ampicillin are examples of a few other antibiotics. 1. Applications of antibiotics

The following applications of antibiotics are possible : • Treating infections in humans by killing microbes-(microbiocidal) • Infection prevention by prohibiting microbial growth-(microbiostatic) • Food preservation, particularly for meat and fish • Plant pathogen growth inhibition

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2. Sulphownamide

Another class of drugs that combats infections, mostly bacterial and fungal, is sulphonamide. This drug is made synthetically and is used to treat pneumonia, bowel and urinary infections, etc. In addition to the types of drugs listed above, there are several other drugs that can be used to combat certain pathogenic microorganisms. 5.4.8 Bacterial diseases 1. Typhoid

Pathogen: Salmonella typhi

Fig. 5.1 Salmonella typhi

Mode of infection: Contaminated food and water. Symptoms: It lives in small intestines and enters other organs through blood. Sustained high fever (39o C to 40o C), weakness, stomach pain, constipation, headache, loss of appetite, intestinal perforation and death may occur in severe cases. Confirmatory test: Typhoid fever is confirmed by the Widal Test. A classic case in medicine: Mary Mallon nicknamed, 'Typhoid Mary', was a cook and typhoid carrier who could spread this disease through the food she prepared. Prevention: Eradication of breeding places of flies with insecticides. Administration of TAB vaccine or live oral vaccine. Treatment: Antibiotics, fluids and oral rehydration therapy. 2. Pneumonia

Pathogen: Streptococcus pneumoniae and Haemophilus influenzae

Fig. 5.2 Streptococcus pneumoniae

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Mode of infection: Contamination by inhaling droplets/aerosols released by an infected person or utensils used by the patient. Symptoms: It infects the alveoli of the lungs. Alveoli get filled with fluid, leading to severe problems in respiration. Fever, chills, cough, and headache are symptoms. In severe cases, the lips and fingernails turn grey to a bluish colour. Prevention: Some forms of pneumonia can be prevented by the vaccine, PCV13 (Pneumococcal conjugate vaccine) and PPSV23. Follow good oral hygiene and a healthy diet for immunity. Treatment: Antibiotics/Sulphonamides can treat many forms of pneumonia. 3. Peptic Ulcers

Pathogen: Helicobacter pylori Mode of infection: It infects the stomach lining through oral ingestion, often during childhood. Symptoms: Acidity-related pain and bleeding in the stomach and duodenum. Prevention: Maintaining a healthy lifestyle. Treatment: Can be cured by using antibiotics for a short period of treatment. 5.4.9 Fungal diseases 1. Ringworm

It is one of the most common infectious diseases in man. Pathogen: Many fungi belong to the genera Microsporum, Trichophyton, and Epidermophyton. Mode of infection: Contamination by using towels, clothes or combs of the infected persons or even from soil. Symptoms: Appearance of ring-like dry, scaly lesions accompanied by intense itching on various parts such as skin, nails, and scalp. Heat and moisture help these fungi to grow in skin folds such as the groin or between toes.

Fig. 5.3 Ring-like scaly lesion on skin

Prevention: Avoid contact with an infected person. Treatment: Antifungal medication like griseofulvin and miconazole.

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5.4.10 Worm diseases They include filariasis, ascariasis, taeniasis, etc. 1. Ascariasis

Pathogen: Ascaris lumbricoides, commonly called roundworm, is a nematode parasite. It is the most common parasite in the small intestine. It completes its life cycle in humans. i = Infected stage d = Diagnostic stage

dd Hatched larvae enter circulation and migrate to lungs.

2 Fertilised

Unfertilised egg (will not undergo further devolopment) 2

Fig. 5.4 Life cycle of Ascaris

Mode of infection: Contaminated food and water containing eggs of the parasite that come out of the host through faeces. Symptoms: Intestinal bleeding, muscular pain, fever, anaemia due to nutritional deficiency, blockage of intestinal passage and stunted growth in children. Prevention: Proper disposal of sewage and following good personal hygiene. Treatment: Administration of albendazole and mebendazole. 2. Filariasis or Elephantiasis

Pathogen: Wuchereria bancrofti and W. malayi, commonly called filarial worm (a nematode parasite), which completes its life cycle in the human and female Culex mosquito.

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Mosquito Stages

Mosquito takes a blood meal (L3 larvae enter skin)

Human Stages

Migrate to head and mosquito's proboscis

L3 larvae

Adults in lymphatics

L1 larvae Mosquito takes a blood meal (ingests microfilariae

Adults produce sheathed microfilariae that migrate into lymph and blood channels

Microfilariae shed sheaths, penetrate mosquito's midgut, and migrate to thoracic muscles i = Infected stage d = Diagnostic stage

Fig. 5.5 Life cycle of Wuchereria

Mode of infection: Bite of an infected female Culex mosquito transmits the pathogens. Symptoms: Adult filarial worms live in lymphatic vessels, preferably in the lower limbs. They live for many years and cause chronic inflammation of the organs. In case of heavy infection, there is immense swelling (elephantiasis). The genital organs are affected, resulting in gross deformities. Prevention: Protection from mosquito bites by using mosquito repellant, eradication of vector Culex mosquito. Treatment: Administration of the drug diethylcarbamazine. 5.4.11 Viral diseases 1. Common cold

It is so common among people in various parts of the world that everybody experiences it at least once in their lifetime. It is a viral infection of the upper respiratory tract but not the lungs. Pathogen: Rhinovirus

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Fig. 5.6 Rhinovirus

Mode of infection: It spreads through tiny air droplets from a sick person or by direct contact with contaminated objects. Symptoms: Nasal congestion and discharge, sneezing, sore throat, cough, watery eyes, headache, muscular aches, fatigue, etc. It is contagious in the first 2-3 days of cold. Prevention: Avoid overcrowded places. Treatment: It generally subsides automatically in a week (3-7 days). 2. Chikungunya

Pathogen: Alphavirus

Fig. 5.7 Alphavirus

Mode of infection: The disease is spread by the vector Aedes mosquitoes. Symptoms: Rashes, arthritis of multiple joints, fever, conjunctivitis, photophobia. Characters: Arthritic symptoms can result in changes in the posture of patients, leading to stiffness and reduced mobility. Prevention: Vaccine is available. Treatment: Antiviral drugs. 3. Dengue fever

Pathogen: DEN-1, DEN-2, DEN-3, DEN-4

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Mode of infection: The disease is spread by the vector Aedes aegypti, tiger mosquito. Symptoms: Clinical dengue fever can occur in a mild form (Break bone fever) with high fever, painful bones, and a fall in blood platelet count. Dengue haemorrhagic fever (DHF), the fatal form, shows haemorrhagic spots, internal bleeding and a fall in blood platelet count. Prevention: Avoid mosquito bites. Treatment: Medical care and rest. 5.4.12 Protozoan diseases 1. Amoebiasis

Pathogen: Entamoeba histolytica 1

Mature cysts

Ingested 2

Excystation Trophozoite

Multiplication 4

Cysts

C 3

Trophozoite

B 4

Faeces

Fig. 5.8 Life cycle of E. histolytica

Mode of infection: Contaminated food and water. House flies act as mechanical carriers of parasites from faeces to food. Symptoms: It completes its life cycle in humans. The parasite feeds on tissues of large intestinal walls and causes ulcers. Symptoms of amoebiasis include constipation, abdominal pain and cramps, stools with excess mucous and blood clots. Sometimes, the pathogens travel to other organs, such as the liver, brain, etc., and cause extra-intestinal amoebiasis. Prevention: Living in good hygienic conditions and keeping food and water covered. Treatment: Use of metronidazole.

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2. Malaria

Pathogen: Different species of Plasmodium cause malaria in humans. • Plasmodium vivax - Benign tertian malaria • P. falciparum - Malignant tertian malaria/cerebral malaria/black water fever • P. ovale - Mild tertian malaria • P. malariae - Quartan malaria Mosquito Stages Ruptured oocyst

i Mosquito takes a blood meal. (injects sporozoites).

Human Liver Stages Liver cell

Exo-erythrocytic cycle Ruptured schizont

Oocyst

Schizont

Release of

i sporozoites

Human Blood Stages Immature trophozoite (ring stage) d

Sporogonic cycle Ookinete Macrogametocyte

Erythrocytic cycle

Mosquito takes a blood meal (ingests gametocytes).

Mature trophozoite d

Ruptured schizont P. falciparum

Microgamete entering macrogamete Exflagellated microgametocyte

d Gametocytes

i = Infective stage d = Diagnostic stage

d Gametocytes

P. vivax P. ovale P. malaria

Fig. 5.9 Life cycle of Plasmodium

Mode of infection: Bite of infected Anopheles mosquito. Life history: Plasmodium completes its life cycle in two hosts, namely human and female Anopheles mosquitoes. It reproduces asexually by multiple fission in humans and sexually in mosquitoes.

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Human phase When a mosquito bites a healthy person, sporozoites are injected with the bite

The mature infective stage escapes from the mosquito’s gut and reach its salivary glands

Parasites reach the liver through blood Parasites reproduce asexually in liver cells, bursting the cell and releasing it into the blood Parasites reproduce asexually in RBCs, bursting RBCs, and causing cycles of fever

Fertilisation and development occur in the gut of mosquitoes Mosquito phase Female mosquitoes take up gametocytes with blood meals

Sexual stages (gametocytes) develop in RBCs Fig. 5.10 Representation of infective stages in humans and mosquitoes

Symptoms: Recurring fever on every 3rd or 4th day. The bouts of fever are expressed in 3 stages. Cold stage (chills, shivering), hot stage (high temperature) and sweating stage (sweating followed by lowering of body temperature to normal). Prevention: Eradication of mosquitoes and their breeding places, like stagnant water. Treatment: Use of Chloroquine drug.

5.5

IMMUNISATION

5.5.1 Introduction to immune system •

The branch of biology that deals with immunity or the study of the immune system is called Immunology. Edward Jenner is acknowledged as the Father of Immunology.

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• The function of the immune system is to differentiate between self and non-self and to protect the body from harmful foreign substances, microorganisms, toxins and, malignant cells, etc. Lines of immunity or Lines of defence in the body: Lines of immunity or Lines of defence

Second line of defence

First line of defence

Third line of defence

•

Lysozyme of saliva

•

Phagocytes

•

Lymphocytes

•

Skin

•

Natural killer cells

•

Antibodies

Fig. 5.11 Lines of immunity

• Whenever bacteria, viruses, fungi and parasites try to enter the body of an organism, skin, mucous membranes and the lysozyme an enzyme present in saliva, tears etc., prevent their entry. This is called the First line of defence. • If the microorganisms cross the first line of defense line and enter the body, the phagocytes, natural killer cells, antimicrobial substances, inflammation, fever, etc., destroy them. This is called the Second line of defence. These two lines of defence are fast, but they are not specific. • If the microbes cross even the second line, the lymphocytes and antibodies fight against them. It is called the Third line of defence. It is highly specific but takes several days to become fully functional. If all the three lines of defence fail, it results in diseases. Types of immunity Types of Immunity

Innate immunity

Acquired immunity

Active acquired immunity Natural active immunity

Passive acquired immunity

Artificial active immunity Natural passive immunity

Artificial passive immunity

E.g. Transfer of antibodies through placenta or colostrum

E.g. Injection Antitetanus serum (ATS)

Fig. 5.12 Types of immunity

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Based on the nature of the response, immunity is mainly of two types, namely 1. Innate immunity 2. Acquired immunity 1. Innate immunity (Innate-inborn or present at the time of birth) The inborn resistance to diseases possessed by all living organisms is called innate immunity. It is a non-specific type of defence and does not depend on prior contact with the microorganisms. This is executed by providing different types of barriers like: • Physical barriers: Skin and mucous membranes are the main physical barriers. The Skin prevents the entry of microorganisms, whereas the mucus membranes help in trapping the microbes entering our body. • Physiological barriers: Secretions of the body like HCl in the stomach, saliva in the mouth, and tears from the eyes are the main physiological barriers against microbes. • Cellular barriers: Certain types of cells, like polymorpho-nuclear leukocytes (PMN-neutrophils), monocytes and natural killer cells in the blood, as well as macrophages in the tissues, are the main cellular barriers. They phagocytose and destroy the microbes. • Cytokine barriers: The cytokines secreted by the immune cells are involved in the differentiation of the cells of the immune system and protect the non-infected cells from further infection. 2. Acquired Immunity or Adaptive immunity The immunological resistance developed by an individual throughout life after birth is known as acquired immunity or adaptive immunity. It is pathogen specific and depends on prior contact with the infectious micro-organisms. Hence, it is characterised by immunological memory. It varies from person to person. It is again of two types, namely a. Active acquired immunity b. Passive acquired immunity a. Active acquired immunity The immunological resistance developed by the organisms through the production of antibodies in their body is called active immunity. It is a lifetime immunity (long-lasting immunity). But it is slow and takes time to show its fully effective response. It is again of two types, namely (i) Natural active acquired immunity (ii) Artificial active acquired immunity (i) Natural active acquired immunity: The resistance developed by an individual in response to natural infection, from which a person recovers, is called natural active acquired immunity, e.g., the lifetime immunity acquired by an individual after recovering immunity from infections such as smallpox, chickenpox, etc.

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(ii) Artificial active acquired immunity: The immunity developed by an individual due to the inoculation of weakened antigens into the body is called artificial active acquired immunity, e.g. immunity that develops due to vaccination. b. Passive acquired immunity The immunological resistance developed by an organism due to the transfer of ready-made (preformed) antibodies is called passive acquired immunity. It is again of two types, namely (i) Natural passive immunity (ii) Artificial passive immunity (i) Natural passive immunity: If the preformed antibodies are transferred from a mother to child, it is called natural passive acquired immunity, e.g. transfer of antibodies from mother to foetus across the placenta or from mother to child through colostrum. (ii) Artificial passive immunity: If the preformed antibodies are transferred from an immunised donor to a non-immunised individual, it is called artificial passive acquired immunity, e.g. injection of anti-tetanus serum (ATS), anti-rabies serum and serum containing antivenin against the venom of a snake, etc. These antibodies are generally produced in the body of an immunised horse or sheep. 5.5.2 Types of vaccines Immunisation is the process through which our body develops immunity to fight against infections when exposed to dead and weakened antigens. One method is vaccination. Vaccine is a suspension of killed/inactivated or attenuated/weakened or antigenic components of the pathogen (toxoids), which, when injected, provides immunity against the pathogen. The process of administration of vaccines is called vaccination. Antigen Vaccine

Antibody

Antigen produces antibody Fig. 5.13 Effect of vaccination

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Edward Jenner created the first vaccine, which was for smallpox. There are two methods for administering vaccines: either orally or by injection. Inoculation is the process of administering a vaccine by injection. Vaccines can be classified according to their contents. Listed below are a few of them. S.No

Content of vaccine

Vaccine name

Disease

Dead microbes

TAB vaccine

Typhoid

Living weakened microbes

CG (Bacillus CalmetteB Guerin

Tuberculosis

Living microbes

Smallpox vaccine

Smallpox

oxoids (Inactive toxic T substances that activate antibodies)

DPT vaccine

iphtheria, Pertussis D (whooping cough), Tetanus

Table 5.6 Different types of vaccines

QUICK REVIEW • "A state of complete physical, mental, and social well-being and not merely the absence of disease or infirmity" is how the World Health Organisation (WHO) in 1948 defined health. • Disease is "a condition of the body or some part of organ of the body in which its functions are disrupted." • All living beings are influenced by their physical surroundings, social environment, personal hygiene, and economic status, among other factors. • A disease can be identified with distinct signs and symptoms. • The human body’s physical well-being can be influenced by both immediate and secondary influences. • Diseases are classified into acute or chronic, depending on their duration. • Infectious diseases, also known as communicable diseases, are passed on from one person to another in various ways - through air, water, food, physical contact and insects. • Non-infectious diseases, also known as non-communicable diseases, are those which cannot be spread from person to person. • There are two ways through which the transfer can happen: direct transmission and indirect transmission. • Congenital diseases are those that affect a person from the moment of birth and are inherited. • Acquired diseases do not run in the family and can emerge at any age after birth. • The overall ability of an individual to fight against disease-causing organisms is called immunity. • The branch of biology that deals with immunity or the study of the immune system is called Immunology. 177

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• The inborn resistance to diseases possessed by all living organisms is called innate immunity. • The immunological resistance developed by an individual throughout life after birth is known as acquired immunity or adaptive immunity. It is pathogen specific. • The immunological resistance developed by the organisms through the production of antibodies in their body, is called active immunity. • Vaccine is a suspension of killed/inactivated or attenuated/weakened or antigenic components of the pathogen (toxoids), which, when injected, provides immunity against the pathogen.

WORKSHEET - 1 MULTIPLE CHOICE QUESTIONS WITH SINGLE CORRECT ANSWER I.

Health and its failure

Cancer is an example of a. Infectious disease

b. Contagious disease

c. Deficiency disease

d. Non-infectious disease

Identify the non-infectious disease from the following a. Typhoid

b. Pneumonia

c. Common cold d. Glomerulonephritis Diseases that are spread through insect vectors are a. Malaria, filariasis

b. Ringworms, cold

c. Typhoid, flu

d. Flu, rhinitis

Health is affected by A. Genetic disorders

B. Infections

C. Lifestyle

D. Regular exercise

a. A, B, D

c. A, B, C

b. B, C, D

d. A, B, C, D

Identify the incorrect statement a. Female Anopheles mosquito is the vector of Plasmodium. b. Pathogens temporarily stay in carriers until they infect other individuals. c. Disease-causing substances are called agents. d. Non-communicable diseases are caused by the contamination of food and water.

6. When a healthy person is diagnosed as unhealthy by a psychiatrist, the reason could be that a. The patient was not efficient at his work b. The patient was not economically prosperous c. The patient shows behavioural and social maladjustment d. He does not take interest in sports 178

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7. Which statement correctly reflects the relationship between personal and community issues for health? a. Personal issues have a more significant impact on health outcomes than community issues. b. Community issues are solely responsible for health disparities among individuals. c. Personal and community issues are interdependent, and both play crucial roles in determining health outcomes. d. Community issues are negligible and do not affect individual health in any way. II.

Disease and its causes

Stools with mucus and blood clots are characteristic symptoms of a. Malaria

c. Typhoid

d. Amoebiasis

c. Yellow fever

d. Measles

Which of the following is bacterial disease? a. Tuberculosis

b. Diarrhoea b. Rabies

What is the primary purpose of laboratory tests in diagnosing diseases? a. Validation of symptom accuracy

b. Identification of potential diseases

c. Alternative to physical examinations

d. Confirmation of specific disease

4. Which of the following diseases is an example of a condition that can switch between acute and chronic phases? a. Malaria 5.

b. Diabetes

c. Tuberculosis

d. Influenza

Which of the following factors can be classified as an immediate cause of disease? a. Unclean drinking water containing disease-causing pathogens. b. Genetic differences leading to increased susceptibility to pathogens. c. Poor nourishment and lack of adequate food intake. d. Poverty and inadequate public services.

Study the following and choose the correct: Disease

Causative pathogen

Mode of infection/symptoms

Typhoid fever Trichophyton

Pneumonia

Haemophilus influenza

Inhalation of droplets of infected person

Common cold

Rhinovirus

Skin rashes

Ringworm

Microsporum

Inoculation by mosquito bite

a. C

b. B

Intestinal perforations

c. A

d. D

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III. Infectious diseases

In human beings, Plasmodium undergoes a. Asexual multiplication

b. Sexual reproduction

c. Both asexual and sexual reproduction

d. No multiplication

Which of the following diseases is spread by droplets? a. Rabies, dengue fever

b. Malaria, Pneumonia

c. Chikungunya, typhoid

d. Pneumonia, common cold

3. Which of the following is the primary purpose of symptom-directed treatment for infectious diseases? a. To kill the cause of the disease

b. To reduce the symptoms of the disease

c. To promote inflammation and healing

d. To enhance the body’s immune response

What is the primary goal of preventing exposure to infectious agents? a. To ensure infected individuals receive proper treatment. b. To reduce the severity of symptoms in infected individuals. c. To reduce the chances of disease transmission from infected individuals to others. d. To eliminate the disease-causing microbes from the environment permanently.

Toxic substance, responsible for the symptoms of malaria is a. Haemolysin

b. Hystolysin

c. Hypnotoxin

d. Haemozoin

Common cold is not cured by antibiotics because it is a. Caused by a virus

b. Caused by a Gram-positive bacterium

c. Caused by a Gram-negative bacterium

d. Not an infectious disease

Assertion (A): Antibiotics are effective against bacteria but not against viruses.

Reason (R): Viruses have very few biochemical pathways of their own that are different from bacteria (viruses do not use these pathways). a. Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A). b. Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A). c. Assertion (A) is true, but Reason (R) is false. d. Assertion (A) is false, but Reason (R) is true. 8.

Typhoid is caused by a pathogen that belongs to genus a. Shigella

c. Salmonella

d. Corynebacterium

Pneumonia causing bacterium belongs to the genus a. Salmonella

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b. Haemophilus b. Streptococcus

c. Shigella

d. Pasteurella

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10. Which of the following is not a bacterial disease? a. Smallpox

b. Typhoid

c. Syphilis

d. Cholera

11. Which is not a mode of infection of 'Microsporum' a. Contaminated by using towels

b. Mosquito bite

c. Clothes & combs of infected person

d. Contact with soil

12. Identify the number of diseases caused by parasitic worms. Ringworm, Amoebiasis, Taeniasis, Ascariasis, Malaria, Filariasis a. 4

b. 6

c. 5

d. 3

13. Which is incorrect about helminthic diseases? a. Pigs act as intermediate hosts for Taeniasis b. The adult filarial worms live in the intestine for many years c. Female Culex mosquito transfer the microfilarial larvae d. Ascaris is a long cylindrical helminthic worm 14. Common cold is caused by a. Rhabdo viruses b. Rhinoviruses c. Alphavirus

d. Variola virus

15. Which of the following diseases is not transmitted through tiny air droplets? a. Common cold

b. Mumps

c. Measles

d. Rabies

16. Which of the following is a pair of viral diseases? a. Common cold, AIDS

b. Dysentery, common cold

c. Typhoid, tuberculosis

d. Ringworm, AIDS

17. Enteric protozoan in man is a. Entamoeba histolytica

b. Ascaris

c. Enterobius

d. Ancylostoma

18. Sexual stage of Plasmodium occurs in a. Salivary glands of mosquito

b. Human RBC

c. Intestine of mosquito

d. Human liver

19. The stages of Plasmodium, which are resistant to digestive enzymes of female Anopheles mosquito a. Gametocytes

b. Trophozoites

c. Merozoites

d. Sporozoites

20. Most fatal type of malaria is a. Mild tertian malaria

b. Benign tertian malaria

c. Quartan malaria

d. Malignant malaria

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21. Assertion (A): Houseflies act as mechanical carriers in amoebic dysentery. Reason (R): Dengue, malaria, filaria and chikungunya are vector-borne diseases. a. Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A). b. Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A). c. Assertion (A) is true, but Reason (R) is false. d. Assertion (A) is false, but Reason (R) is true. IV. Immunisation

Second line of defence is formed by a. WBC

b. Antibodies

c. Liver

d. Blood

Assertion (A): Tears and saliva act as physiological barriers Reason (R): Lysozyme of tears and saliva digests the bacterial cell walls and kills them. a. Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A). b. Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A). c. Assertion (A) is true, but Reason (R) is false. d. Assertion (A) is false, but Reason (R) is true.

3. The immunity that one receives from their mother, both pre-natal and post-natal, is referred to as

a. Passive natural

b. Passive artificial

c. Active natural

d. Active artificial

What is the basis of the principle of immunization? a. Inducing a mild form of a disease to create resistance against it. b. Providing nursing care to victims of infectious diseases. c. Making the immune system respond patiently to a particular microbe. d. Ensuring proper and sufficient food for the pathogen during multiplication.

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B.C.G. vaccine is used against a. T.B.

b. Leprosy

c. Food poisoning

d. None of these

What does 'T' stand for in the DPT vaccine? a. Tuberculosis

b. Typhoid

c. Trachoma

d. Tetanus

IL Foundation Series Class 9

Which of the following is used to make vaccines? a. Activated pathogen

b. Attenuated pathogen

c. Pathogen blocked by antibody

d. None of the above

WORKSHEET - 2 MULTIPLE CHOICE QUESTIONS WITH SINGLE CORRECT ANSWER 1.

AIDS is a. A metabolic disease

b. An infectious disease

c. Non-infectious disease

d. An allergic reaction

Airborne diseases are a. Typhoid, Ascariasis

b. Pneumonia, Common cold

c. Amoebiasis, Malaria

d. Pneumonia, Filariasis

Diseases which are transmitted from person to person are called a. infectious disease

b. Non-communicable

c. Genetic

d. Deadly

Disease-causing organisms are known as a. Vectors

d. Parasites

b. Haemophilia

c. Rabies

d. Pertussis

Helminth parasite, which lives in the lymphatic vessels of man a. Ascaris

c. Carriers

Which of the following diseases is not caused by external infection? a. Syphilis

b. Pathogens

b. Enterobius

c. Wuchereria

d. Ancylostoma

Identify the number of indirect transmission diseases Rabies, Tetanus, Amoebiasis, Malaria, Hepatitis, Tuberculosis a. 4

c. 5

d. 2

Generally, malaria is characterised by the recurrence of fever every a. Day

b. 3 b. Ten days

c. Three to four days

d. Fifteen days

Wuchereria causes a. Acute inflammation

b. Chronic inflammation

c. Bacterial inflammation

d. Viral inflammation

10. Typhoid infection spreads through the a. Droplet method

b. Vectors

c. Contaminated food and water

d. Air

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11. What is the significance of mental health in overall well-being? a. Mental health has no impact on physical health. b. Good mental health can improve physical health, relationships, and quality of life. c. Mental health is solely determined by genetic factors. d. Mental health is irrelevant to a person’s overall happiness 12. One of the following is a symptom of amoebic dysentery a. Presence of uninucleate metacystic forms in faeces b. Blood and mucous in faeces c. Sporozoites in the faeces d. Presence of octa nucleated cysts in faeces 13. The mature infective stages of the malarial parasite, which are transferred from mosquito to man, are a. Sporozoites

b. Merozoites

c. Trophozoites

d. Gametocytes

14. Fertilization of Plasmodium takes place in a. Liver cells of man

b. RBC of man

c. Gut of mosquito

d. Haemocoel of mosquito

15. A certain patient is suspected to be suffering from typhoid fever. This was further confirmed by a. Widal test

b. ELISA test

c. Schick test

d. Western blot

16. Pneumonia infection spreads by a. Droplet method

b. Contaminated food

c. Fungal disease

d. Animal bites

17. Most common infectious disease-ringworm is caused by a. Fungi

b. Bacteria

c. Virus

d. Protozoans

18. Life cycle of Wuchereria is completed in a. Man and mosquito

b. Man and housefly

c. Man and tsetse fly

d. Man only

19. Which of the following is caused by a virus? a. Diphtheria

b. Typhoid

c. Tuberculosis

20. Viral diseases have no cure because a. Viruses have no cell wall b. Viruses can multiply repeatedly within the host cell

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c. Presence of capsid d. Virus possesses no cytoplasm 21. Immunity due to injection of diphtheria toxoid is an example of a. Naturally acquired active immunity

b. Naturally acquired passive immunity

c. Artificially acquired active immunity

d. Artificially acquired passive immunity

22. Entamoeba histolytica is a parasite in the a. Small intestine of man

b. Large intestine of man

c. Stomach of man

d. Salivary glands of man

23. Cerebral malignant malaria is caused by a. Plasmodium falciparum

b. Plasmodium malariae

c. Plasmodium vivax

d. Plasmodium ovale

24. BCG vaccine provides protection from a. Polio

b. Typhoid

c. Cholera

d. Tuberculosis

25. Characters of acquired immunity are a. Specificity

b. Difference between self and non-self

c. Retains memory

d. All of these

26. Which of the following components is a key factor in determining the specific disease during medical diagnosis? a. Symptoms and patient history

b. Doctor’s intuition

c. Weather conditions

d. Number of medical tests performed

27. How do acute diseases differ from chronic diseases in terms of their impact on individuals? a. Acute diseases have a gradual onset, while chronic diseases have a sudden onset. b. Acute diseases often require lifelong management, while chronic diseases are usually selflimiting. c. Acute diseases are more common among the elderly, while chronic diseases affect individuals of all age groups. d. Acute diseases have a quick resolution, while chronic diseases have a prolonged course. 28. How does poverty contribute to disease development? a. Poverty has no direct impact on disease development. b. Poverty causes direct exposure to disease-causing pathogens. c. Poverty leads to genetic differences that increase disease susceptibility. d. Poverty results in inadequate nutrition and living conditions, weakening immunity.

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29. Which of the following examples best illustrates the impact of community issues on individual health? a. An individual’s genetic predisposition to certain diseases. b. A person’s personal preference for unhealthy eating habits. c. Limited access to healthcare services in a particular neighbourhood. d. Lack of personal motivation to exercise regularly. 30. Which of the following scenarios exemplifies the complex interplay between physical and mental health in distinguishing health from disease? a. A person experiences mild physical discomfort but maintains a positive attitude and social connections. b. A person diagnosed with a communicable disease follows a strict treatment plan for full recovery. c. A person exhibits severe physical symptoms, leading to anxiety and depression. d. A person recovers from an injury but experiences lingering psychological trauma. 31. Aedes mosquito is the vector for pathogens of a. Malaria, filariasis

b. Chikungunya, dengue fever

c. Yellow fever, malaria

d. Cholera, typhoid

32. The severity of disease manifestations primarily depends on which of the following factors? a. The type of microbe causing the infection b. The age of the individual affected by the infection c. The number of microbes in the body d. The point of entry of the microbe into the body 33. Which of the following principles of treatment involves reducing the symptoms of an infectious disease? a. Taking treatment of intravenous saline drip b. Being active and engaging in outdoor activities c. Drinking ice-cold water 2-3 times a day d. Providing treatment to bring down fever 34. Assertion (A): Sporozoites of malarial parasites enter the human body by biting off newborn female Anopheles, whose mother was a carrier. Reason (R): Male and gametocytes of the malaria parasite develop in the human intestine. a. Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A). b. Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).

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c. Assertion (A) is true, but Reason (R) is false. d. Assertion (A) is false, but Reason (R) is false. 35. Internal bleeding, blockage of intestinal passage, and anaemia are the symptoms of a. Filariasis

b. Amoebiasis

c. Ascariasis

d. Leishmaniasis

36. W. bancrofti infects which part of the human body? a. Blood vessels of upper limbs

b. Lymph vessels of lower limb

c. Blood vessels of lower limb

d. Lymph vessels of upper limb

37. The active form of Entamoeba histolytica feeds upon a. Food in the intestine

b. Blood only

c. Erythrocytes; mucosa and submucosa of colon

d. Mucosa and submucosa of colon only

38. Sexual stages of Plasmodium which develop in man are a. Microgametes

b. Gametocytes

c. Zygote

d. Macrogametes

39. Plasmodium causes hypertrophy to a. Erythrocytes in man

b. Hepatic cells in man

c. Bile duct in liver fluke

d. Reticuloendothelial cells in man

40. Assertion (A): Acquired immunity constitutes third line of defence Reason (R): Acquired immunity is characterised by diversity and memory a. Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A). b. Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A). c. Assertion (A) is true, but Reason (R) is false. d. Assertion (A) is false, but Reason (R) is true.

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6.1 INTRODUCTION Food is the basic requirement for all living beings. Simply put, life cannot exist without food. Food is essential for all living beings to carry out various functions of the body. It provides the energy needed for activities, helps in the growth and repair of tissues, maintains body temperature, and supports overall health and well-being. Without food, organisms would not have the necessary nutrients to sustain life. Food supplies proteins, carbohydrates, fats, vitamins and minerals. • Carbohydrates (glucose) and fats in the food serve as a respiratory fuel and, when oxidised, provide energy for temperature regulation and metabolic processes in the body. • Proteins in food are building blocks of the body and aid in the regeneration of damaged or worn-out body tissues. • Vitamins and minerals containing food provide protection against infections and diseases. The main food sources for humans include both plants and animals. This is why humans raise animals and grow plants according to their preferences and demands. Agriculture is the practice of cultivating land for crops and raising livestock for food, wool and other products. The green revolution in India during 1960's was a profound shift in the agricultural sector that significantly improved food grain production. Similarly, the white revolution launched by the National Dairy Development Board made India the world's greatest milk producer. However, the widespread use of chemical pesticides and fertilisers created environmental risks. Therefore, to reduce environmental pollution and preserve the ecological balance, sustainable techniques in agriculture and animal husbandry must be implemented. Name of Revolution

Significance

Green revolution

Food grain production

White revolution

Milk production

Blue revolution

Fish production

Yellow revolution

Oil seed production

Silver revolution

Poultry production

Red revolution

Meat/tomato production

Table 6.1 List of revolutions in agriculture (in India)

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6.1.1 Crops Crops are the same type of plants that are cultivated, harvested, and grown on a large scale for profit or sustenance in the agricultural field. Crops in India can be divided into three types based on the seasons. The primary types are Rabi, Kharif, and Zaid crops. Type of Crop

Season

Duration

Type of Crop

Rabi

Winter

October/November to March/April

Mustard, linseed, wheat, gram, and peas

Kharif

Rainy

June/July to September/October

Rice, soybeans, pigeon peas, maize, cotton, green and black grams

Zaid

Summer

April to June

Melon, cucumber, etc.

Table 6.2 Types of crops based on seasons

6.2 IMPROVEMENT IN CROP YIELDS Crop yields are increased when sustainable farming methods are used. There are three stages to this. a. Crop variety improvement b. Crop production improvement c. Crop protection management 6.2.1 Crop variety improvement Crop variety improvement refers to the techniques used to genetically alter the plants in order to increase production. Therefore, putting these strategies into practice can satisfy the need for food. One method for creating these kinds of crop varieties is plant breeding. Plant breeding produces new strains of crops that possess the following desirable characteristics. • Increased quantity and quality of production • Resistance to diseases • Improved response to fertilisers Methods of crop variety improvement

Crop variety improvement is possible by two methods: hybridisation and genetic engineering. A. Hybridisation The practice of crossing two genetically distinct parents, resulting in a new crop variety, is called hybridisation. There are three methods of hybridisation: 189

IMPROVEMENT IN FOOD RESOURCES

1. Intervarietal hybridisation, where plants of two distinct types are crossed. 2. Interspecific hybridisation, where plants of two different species within the same genus are crossed. 3. Intergeneric hybridisation, where the cross is done between two genera of plants. B. Genetic engineering This is a modern approach in the field of improving crop varieties. This method involves introducing a desired gene with a superior characteristic into a plant, which leads to the production of genetically engineered or modified crops. Examples of genetically modified crops or GM crops are Bt cotton, Bt brinjal, golden rice, etc.

Fig. 6.1 Genetic engineering in crops

Several tests are conducted on this enhanced crop type to ascertain factors like high yield, resistance to disease, pest tolerance to the environment, etc. The resulting seeds can be planted in any type of soil and are tolerant to a wide range of weather conditions. Primary objectives of crop variety improvement

• A surplus increase in the yield of plant products • Improvement in food crop quality • Developing biotic-resistant crop cultivars • Developing abiotic-resistant crop cultivars • Modifying the maturity period • Inducing desirable characteristics in crop plants

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6.2.2 Crop production management To obtain the optimal yield, crop production management controls several factors associated with crop production. Different agricultural approaches are used due to varying topographical and climatic conditions along with the economic conditions of farmers across the country. In order to regulate crop production and control these factors, the following three practices are used. • Nutrient management • Irrigation • Cropping patterns Nutrient management

Specific nutrients are necessary for the growth and development of plants. Of these nutrients, seventeen are considered essential. A plant cannot complete its life cycle if any of these nutrients are unavailable for its proper growth and metabolism. Three things provide nutrients to plants: soil, water, and air. Based on their requirements, the nutrients are divided into two groups, which are mentioned below. • Macronutrients: Nutrients that plants need in significant proportions are called macronutrients. Out of the seventeen nutrients, nine are classified as macronutrients. These are carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium and sulphur. • Micronutrients: Nutrients that plants need in relatively tiny amounts are called micronutrients. Although needed less, these nutrients are crucial for plant growth. Iron, manganese, boron, zinc, copper, molybdenum, chlorine, and nickel are the eight micronutrients. Source

Plant Nutrients

Air

Carbon, oxygen

Water

Hydrogen, oxygen

Soil

Nitrogen, phosphorus, potassium, calcium, magnesium, sulphur, iron, manganese, boron, zinc, copper, molybdenum, chlorine, and nickel Table 6.3 Plant nutrients and their different sources

To enhance crop yield, soil fertility can be improved by providing essential nutrients through the application of manure and fertilisers. This replenishes the soil with the necessary elements needed for plant growth, ensuring optimal conditions for healthy crop development and increased productivity.

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Manure: The organic substance obtained from biological wastes, such as plant and animal waste, is called manure. They make the soil fertile by replenishing its nutrients and are beneficial to the environment as they reduce the need for chemical fertilisers. The organic content in the manure prevents water logging in clayey soil and increases the water-holding capacity of sandy soil. • Compost: The substance that remains after the decomposition of biological wastes like vegetable waste, crop waste, animal excreta, domestic waste, etc., is called compost. It is rich in nutrients and organic matter. Vermicompost is the term for the compost obtained when earthworms are used to hasten the decomposition of waste matter. • Green manure: Plants like sun hemp and guar cultivated in agriculture fields are turned over to combine with the soil. This is done before the seeds are sown. As a result of their breakdown, these plants become green manure, which nourishes the soil with organic matter, nitrogen, and phosphorus.

Fig. 6.2 Vermicompost

Manure contains more humus content, which improves the soil texture by increasing its waterholding capacity and aeration. However, the addition of manure to the soil is required in bulk as its nutrient percentage is very low. Chemical fertilisers: These are inorganic substances that are added to the soil to restore essential nutrients such as potassium, phosphorus, and nitrogen. They release nutrients constantly, which raises crop productivity. They are required in low quantities, contain specific nutrients, and are less expensive. Category

Nutrient

Examples

Nitrogenous fertilisers

Nitrogen

Ammonium sulphate

Phosphatic fertilisers

Phosphate

Single Superphosphate

Potassic fertilisers

Potassium

Muriate of Potash

Complex fertilisers

Two or more elements

Urea ammonium phosphate

Table 6.4 Categories of chemical fertilisers based on nutrient content

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Organic farming The process of using organic resources in the cultivation of food crops is known as organic farming. It does not employ the usage of chemical fertilisers but relies on organic manure, biofertilisers, biopesticides, and different cropping patterns. • Organic manure is the compost obtained from farm waste. • Biofertilisers are soil-enriching organisms such as blue-green algae or nitrogen-fixing organisms. • Biopesticides are made by using turmeric or leaf extracts. These repel pests in granaries and storage houses. Irrigation

Water helps the plant roots extract nutrients from the soil and helps in the plant’s growth. The process of providing plants with a regulated amount of water is known as irrigation. Indian agriculture relies heavily on the monsoons. If the monsoon arrives late, it leads to the failure of crops. Therefore, appropriate irrigation techniques have been implemented to solve these issues. Depending on the climate and availability of water in an area, different irrigation techniques are used. The irrigation system uses the four main techniques listed below. 1. Wells: Wells are built to access groundwater. Generally, there are two types of wells. • Dug wells: These are simple and most common wells. Farmers can access water from the water-containing strata. These have a shorter lifespan as they quickly dry up when the water table drops. • Tube wells: The tube wells are powered by diesel or electricity-driven pumps or by bullockoperated devices. They receive water from the porous soil strata. However, deep-bore tube wells have a longer lifespan of many years and draw water from deeper layers.

(a)

Dug well

(b)

Tube well Fig. 6.3 Types of wells

2. Canals: Canals are vast irrigation systems that collect water from rivers, lakes, reservoirs, and tanks. They provide water to agricultural lands with the help of numerous branching distributaries. 193

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Fig. 6.4 Canal system

3. River lift systems: In areas where there is a river nearby, the water for irrigation is directly lifted from the river with the help of a pump. This is prevalent in those areas where the canal system is inefficient. 4. Tanks: The runoff from smaller catchment areas is collected and stored in small reservoirs called tanks. Small dams are constructed to control the tank outflow and ensure the availability of water for irrigation to every area. Rainwater harvesting is another method to replenish the natural reservoirs and increase the groundwater level. Farmers use different irrigation methods to keep their individual fields hydrated. Some of these artificial methods are sprinkler irrigation, drip irrigation and surface irrigation. Cropping patterns

Cropping pattern is the process of choosing the type of crop and estimating the area needed to grow them based on local climate, water availability, and soil nutrient levels. 1. Mixed cropping: The process of cultivating two or more crops on the same land is called mixed cropping. The chosen crops should not share similar characteristics. • Root growth: One crop should have deep roots and other shallow roots. • Water requirements: Both crops should have different water requirements. For e.g. one crop should need frequent irrigation while the other should need less irrigation. • Nutrient intake: The nutrient intake should also differ to avoid competition between both plant groups. • Crop maturity: It is intended that one crop reach maturity first and the other later.

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Fig. 6.5 Mixed cropping

The combination of crops grown together includes groundnut and mung bean or cotton, groundnut and sunflower or gram, cotton and mustard or gram, ragi and gram, wheat and gram or mustard and many more. Thus, mixed cropping ensures a better yield per piece of land with a variety of produce and no risk of failure. 2. Intercropping: In this system of cropping, different crops are cultivated on the same piece of land in specified rows. The patterns of rows may contain a row of primary crops alternating with one or more rows of intercrops. This is helpful as various crops require various amounts of nutrients and have different harvesting periods. As a result, this cropping method stops the spread of diseases among the crops grown on a single field, thereby increasing the yield.

Fig. 6.6 Intercropping

The choice of crops grown by intercropping is similar to those in mixed cropping. Some examples include cultivating finger millet with cowpea and soybean with maize.

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3. Crop rotation: Crop rotation is a methodical process of cultivating different crops on the same land in successive seasons. This method keeps a check on the soil nutrient levels, like the availability of nitrogen, thereby boosting the output and preventing pests and disease.

Fig. 6.7 Crop rotation

Crop rotation is applied for various crop combinations depending on the length of time. For instance, cereal crops and legume crops are cultivated alternately. Leguminous plants harbour nitrogenfixing bacteria in their root nodules, which fix atmospheric nitrogen into nitrates and make them available for plant intake. This increases nitrogen levels in the soil and makes it more fertile. 6.2.3 Crop protection management Crops benefit us in a number of ways. They provide us with food, fibre, medicine, etc. A wide range of weeds, insect pests, and diseases can damage standing crops. Thus, crop protection management takes care of the aspects that can hinder crop productivity. Weeds and their control

Unwanted plants like Parthenium and Xanthium are called weeds. These grow in croplands on their own and compete with crops for nutrients and other resources, thereby affecting their growth. Weed eradication is called weeding. This is primarily done in the early stages of crop growth.

Xanthium

Parthenium Fig. 6.8 Weeds

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Farmers use different methods like mechanical, chemical, biological and cultural methods to get rid of weeds. • Mechanical method: Farmers use their hands or a trowel to uproot weeds from the field. • Chemical method: Weeds-killing chemicals called weedicides are sprayed to eradicate weeds from the fields. E.g. atrazine, 2, 4-D (2, 4-dichlorophenoxy acetic acid), etc. • Biological method: Some natural enemies of weeds, like insects or organisms, are intentionally introduced in croplands that destroy weeds, e.g., cochineal insects for Opuntia. Crop plants like barley, millets and soybeans inhibit the growth of weeds and are thus known as smoother crops. • Cultural methods: Methods like intercropping, crop rotation, and timely sowing of crops are helpful in prohibiting the growth of weeds. Insect pests and their control

There are three ways that insects damage plants. • Chewing pests: Certain insects have chewing mouth parts that are used to severe and eat plant parts like the roots, stems, and leaves. E.g. grasshoppers, locusts, caterpillars, sawflies, etc. • Sucking pests: Insects with needle-like mouth parts puncture and feed on the cell sap of various plant parts. E.g. aphids, bugs, leafhoppers, etc. • Internal feeder: A few insects penetrate the fruit and stem. They live inside and consume the tissues, thereby harming the produce. E.g. weevil, stem borers, fruit borers like bollworms, etc.

Caterpillar

Stem borer

Leaf beetle

Fruit borer

Fig. 6.9 Common insect pests

Insect pests can be controlled by the use of natural insecticides like neem, nicotine, and pyrethrum or by using chemical pesticides. Nowadays, biological pest control methods are used to keep a check on pests. It employs the deliberate introduction of natural enemies of pests in croplands, like some insects, birds, or animals that feed on the target pests. Disease-causing agents and their control

Numerous pathogens, including bacteria, fungi, viruses, and nematode worms, can cause diseases in plants and can be found in the soil, water, and air. Using resistant varieties for cropping, timely 197

IMPROVEMENT IN FOOD RESOURCES

sowing, intercropping, and crop rotation can prevent diseases in crop plants. The soil should be properly ploughed, tilled, and exposed to the sun to eradicate the growth of pathogens in it.

White rust in Brassica

Powdery mildew in mung bean

Brown rust of wheat

Fig. 6.10 Common plant diseases Proper storage of grains

Safe storage of harvested grains and other agricultural products is one of the essential parts of agriculture. To obtain a constant supply of seasonal foods throughout the year, proper storage is required. Improper storage of food grains can cause spoilage and incur heavy losses to the farmers. Two factors cause losses during the storage of grains. They are abiotic and biotic factors. • Abiotic factors: This includes non-living environmental factors like temperature and moisture in the air. • Biotic factors: This includes the impact of living organisms like rodents, insects, bacteria or fungi on stored grains. Measures to prevent food grain damage

Granaries and storage houses should be properly cleaned and dried before storing food grains. Also, the grains should be properly sun-dried before storing them to inhibit the growth of microbial agents. Fumigation with EDCT or methyl bromide can be done to kill insect pests.

Traditional

Modern (silos) Fig. 6.11 Types of granaries

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6.3 ANIMAL HUSBANDRY Enhancement of food is a major necessity due to the increasing population. Biological principles applied to animal husbandry play a major role in our efforts to increase food production. Animal husbandry is the science of rearing, caring, feeding, breeding, improving, and utilising domesticated animals such as buffaloes, cows, pigs, horses, sheep, camels, goats, etc. In addition, animal husbandry also deals with poultry farming, fisheries and beekeeping. All these animals are used by humans for various products like milk, eggs, meat, wool, wax, honey, etc. 6.3.1 Cattle farming Cattle are reared to serve two main purposes. 1. To provide milk 2. To do labour • Cattle reared specifically for producing milk are called milch cattle and are considered dairy animals. Some commonly reared milch cattle include yaks, cows, buffalo, goats, and camels. These animals are taken proper care , provided nutrient food and kept in proper shelters. • The other group of cattle is used for labour in agricultural fields and is called draught cattle. These include bullocks, horses, elephants, mules, etc. These cattle being strong and sturdy are used to draw carts, plough land and transportation. Approximately 84 million cattle in India are draught cattle. Breeds of cow

• Indigenous breed: Sahiwal, Red Sindhi, Ongole, etc. • Exotic breeds: Brown Swiss, Jersey, Holstein, etc.

Red Sindhi

Jersey 6.12 Breeds of cow

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Breeds of buffalo

• There are seven breeds of buffalo in India. • Some of them are Mehsana, Surti, and Murrah.

Fig. 6.13 Breed of buffalo - Murrah Production of milk

The following aspects drive high-quality milk production. • Breed: Milk is obtained during the lactation period of the cattle, which is after the birth of a calf. Milk yield and quality both depend on the breed of cattle. Exotic cows yield more milk and have longer lactation periods, whereas native or local breeds yield less milk per day. Milk productivity can be increased by increasing the lactation period using the technique of cross-breeding. In this method, a local breed like Sahiwal or Red Sindhi is cross-bred with an exotic/foreign breed, such as Jersey or Brown Swiss. • Season: More milk is produced in winter than in summer. • Health: Both the quality and quantity of milk produced can be affected when cattle are sick or diseased. • Feed: Changes in the cattle's diets can have a momentary impact on the milk's quality. Food for cattle

Feed is the food provided to cattle for their nourishment. Proper, balanced feed is important for the growth and health of cattle so they can produce good quality milk in ample amounts. Cattle feed usually comprises roughage and concentrates. • Roughage: It is fibre-rich and includes hay, green fodder and silage. • Concentrate: It is rich in nutrients like carbohydrates, proteins, fat, vitamins and minerals. Shelter for cattle

• Good housing for dairy cattle has a significant impact on milk production. • Properly roofed sheds protect them from rain, heat, and cold. 200

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• Sufficient ventilation and a well-sloped floor connected to a drainage system help keep the shed dry and clean.

Fig. 6.14 Roofed shed for dairy cattle Cattle diseases and their prevention

Diseases in cattle not only impact their health but also reduce milk production. Some severe diseases, if not properly managed, lead to the death of animals. Nowadays, vaccines are available to protect cattle from bacterial and viral diseases. Also, treatment in the early stages of the disease is more effective. A few infectious diseases affecting the cattle are listed below. Disease Anthrax Haemorrhagic septicemia Foot and mouth disease

Cause and Characteristic Features Contagious bacterial disease. Causes death after a few days of infection. Serious bacterial disease. The disease is characterised by sudden onset fever, depression, difficulty breathing, and rapid death. Viral disease characterised by blisters on the mouth and foot. Affects milk production.

Rinderpest (cattle plague)

Viral disease, highly contagious and fatal. Causes fever and mouth ulcers.

Tuberculosis

Chronic infectious bacterial disease. Infected meat or milk may infect humans. Table 6.5 Common diseases in cattle

Preventive measures

• Cattle shelters should be spacious and well-ventilated. • The sheds should be clean and dry. • Cattle should be regularly bathed and maintained to prevent hair parasites • They should be given healthy and nutritive feed. • Regular vaccination keeps pathogens away. • It's essential to isolate sick animals.

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6.3.2 Poultry farming Raising domesticated birds, such as chickens, turkeys, ducks, and geese, for meat and eggs is known as poultry farming. Crossbreeding methods are used to create new breeds with enhanced traits. In many countries, poultry products are the preferred choice for staple foods for a majority of people. Layers and broilers

There are two main purposes of poultry farming. 1. Raising fowls called layers for laying eggs, e.g. White Leghorn. 2. Raising fowls called broilers for their meat, e.g. Vencobb, Plymouth Rock.

Layer - White Leghorn

Broiler - Vencobb

Fig. 6.15 Layers and Broilers Criteria

Layers

Broilers

Objective

Reared for eggs

Reared for meat

Shelter

Proper light and space

Proper conditions for fast growth & low mortality rate

Diet Rearing time

Restricted feed rich in vitamins and micronutrients Start laying at 20 weeks, reared for longer time

Feed rich in protein, fats, vitamin A & K Reared for 6-7 weeks and thereafter sent to market

Table 6.6 Characteristics/features of layers and broilers Important poultry breeds

• Indigenous poultry breeds in India include Aseel, Chittagong, Kadaknath, Brahma, and Busra. • Exotic breeds include white Leghorn, Australorp, Minorca, Plymouth Rock, Sussex, and Rhode Island Red. Diseases of poultry

Poultry birds are vulnerable to parasites, bacteria, fungi, and viruses. Preventive measures for infectious diseases include proper vaccination, regular spray of disinfectants, clean housing, and proper sanitation. 202

IL Foundation Series Class 9

6.3.3 Fish production Humans consume fish as they are readily digestible and high in protein. The process in which fish are caught from natural resources is called capture fishery, whereas the rearing of fish in small ponds and tanks for consumption is called culture fishery. The fishery is an industry devoted to the catching, processing or selling of fish. It also includes catching shellfish and molluscs for food, e.g. shrimp, prawn, crab, lobster, edible oyster, etc. • Aquaculture: It is the rearing of aquatic edible organisms such as fishes, prawns, crabs, mussels, oysters, etc. in freshwater bodies. • Pisciculture: It is the scientific rearing and management of fish in water bodies under controlled conditions. Fishery is of two types 1. Marine fishery (saltwater fishery) 2. Inland fishery (freshwater fishery) Marine fishery

The deep seas and 7500 km of shoreline are the resources for marine fishery in India. The fish varieties captured include tuna, sardines, Bombay duck, pomphret, salmon, mackerel and Hilsa. Well-equipped fishing vessels and boats containing different types of fishing nets and gear are used for capturing fish. Modern techniques like echo sounders and satellites are used to locate large schools of fish. Fish culture in marine water is of high economic value. This includes • Fin fish culture (e.g. bhetki, pearl spots and mullets) • Shellfish culture (e.g. oysters, mussels, lobsters, crabs and prawns)

Salmon

Bhetki

Tuna

Mackerel

Hilsa

Bombay duck

Fig. 6.16 Common marine fin fishes

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IMPROVEMENT IN FOOD RESOURCES

Prawn

Mussel

Lobster

Crab Fig. 6.17 Common shellfishes

Inland fishery

Inland fishery includes both freshwater and brackish water bodies. Rivers, canals, ponds and reservoirs are important freshwater resources. Estuaries and lagoons are brackish water resources that are more saline than freshwater but less saline than seawater. Since the fish harvested by the capture fishery in freshwater resources is insufficient, culture fishery is the main method used in the production of freshwater fish. Some common freshwater fishes include rohu, Catla, common carp, grass carp, etc.

Catla

Rohu

Grass carp

Common carp

Fig. 6.18 Common freshwater fishes Composite fish culture

The technique in which fish of different types that are compatible and have varying eating habits are reared in the same pond is called composite fish culture. The productivity of fish aquaculture is increased by this method. The same pond is used to raise a variety of five or six species, including common carp, grass carp, mrigala, rohu, and Catla. Since they get their nutrition from different

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areas of the pond, they do not compete for food. The following list includes fish species that are commonly used in composite fish culture. •

Surface feeder: Catla

•

Mid-zone feeder: Rohu

•

Bottom feeders: Common carp and mrigals

•

Weed feeders: Grass carps

Since most fish breed only during the monsoon season, composite fish culture faces challenges due to the scarcity of pure fish seed for culture. However, this has been resolved by using hormone stimulation to breed fish in ponds, thereby ensuring the supply of pure fish seed. 6.3.4 Beekeeping Beekeeping or apiculture is the maintenance of honeybee hives for the production of honey. It has been an age-old cottage industry. For apiculture, large places called apiaries or bee farms are established scientifically.

Fig. 6.19 Apiary (beekeeping)

It can be practised in any area that has sufficient bee pastures of wild shrubs, fruits, orchards, and cultivated crops. Bees are the pollinators of many of our crop species, such as sunflower, Brassica, apple and pear. The Khadi and Village Industries Commission (KVIC) and the Indian Council of Agricultural Research (ICAR) are making efforts to raise the commercial production of honeybee products. Species of honeybees

Four species of honeybees are reported in different parts of India, which are as follows: • Apis florea (Little bee) • Apis indica (Indian bee) - Common domesticated species in India • Apis dorsata (Rock bee) • Apis mellifera (European/Italian bee) - Commercial bee Products of bees

Bees are raised to obtain the following products:

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IMPROVEMENT IN FOOD RESOURCES

• Honey: It is a highly nutritive food and is used in indigenous medicine (ayurvedic medicine). Honey is sugary syrup with nearly neutral 6.8 pH, having 17-25% water, 3.3 % minerals, abundant vitamins (B1, B6, C, D), L-fructose (Levulose 41%), glucose (35%), sucrose (1.9%) and dextrin (1.5%). It is a tonic, laxative and sweetening agent. • Beeswax: Beeswax is secreted by the abdominal wax glands of the worker bees. It possesses a hardening substance from the cephalic gland and a resin called propolis from pollen grains. It is used in many industries in the preparation of cosmetics, paints, candles, and polishes. • Bee Venom: It is used in the treatment of arthritis. Beekeeping, though relatively easy, does require some specialised knowledge, and there are several organisations that teach beekeeping. Social organisation (caste system) of honeybee

The nest of the honeybee is known as the beehive. The hive consists of 32 to 60 thousand individuals, showing a highly organised division of labour in the colony. Bees are polymorphic, and consist of three types of individuals (castes) viz, queen, drone and worker.

Queen

Drone

Worker

Fig. 6.20 Social organisation of honeybee Queen

Drone

Large size, generally one queen per hive

Smaller than the queen, larger than workers. 200-300 per hive Haploid, fertile males

Diploid, fertile female Strong legs for walking on the comb. Feeds on royal jelly

Live in drone cells

The sting is curved, modified as egg laying organ called an ovipositor Lays both fertilised and unfertilised eggs, about 15002000 per day

Sting and wax glands are absent

Develop from fertilised eggs

Develop parthenogenetically from unfertilised egg

Life span 2-5 years

Die soon after fertilising the queen. Life span 57 days

Main function is to fertilise the queen bee

Worker Smallest in size. Majority in numbers Diploid sterile females, do not lay eggs Live in worker cell. Pollen grains adhere to branched hair on the body. Pollen basket on hind legs Have a sting with a poison sac at the tip of the abdomen Collect honey, look after young-ones, clean comb, defend the hive, and maintain temperature of the hive Develop from a fertilised egg Life span 4-5 months

Table 6.7 Different castes in a beehive

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QUICK REVIEW • Crop variety improvement refers to the techniques used to genetically alter the plants in order to increase crop production. • To achieve the highest yield, crop production management regulates crop production by following three practices: nutrient management, irrigation, and cropping patterns. • The organic matter that comes from biological wastes, such as plant and animal waste, is called manure. • The process of giving plants a regulated amount of water is called irrigation. • Cropping pattern is the process of choosing crop varieties and calculating the amount of land needed to cultivate them based on factors such as climate, availability of water, and soil nutrient levels. • Crop rotation refers to the methodical process of cultivating distinct crops on the same land in successive seasons, following a correct pattern. • Crop protection management takes care of the aspects that can hinder crop productivity. • Using resistant varieties for cropping, timely sowing, intercropping, and crop rotation can prevent diseases in crop plants. • Appropriate care, raising, and breeding of livestock are all included in animal husbandry. • Beekeeping, fish farming, poultry farming, and cattle rearing are all considered components of animal husbandry.

WORKSHEET - 1 MULTIPLE CHOICE QUESTIONS WITH SINGLE CORRECT ANSWER I. Introduction to improvement in food resources

1. ___________ crop is an example of Rabi crops. a. Paddy

b. Soybean

c. Wheat

d. Cotton

2. To get a full yield of crop plants, they should be protected from a. Pests

b. Pathogens

c. Weeds

d. All of these

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IMPROVEMENT IN FOOD RESOURCES

3. Assertion (A): Paddy is grown in the rainy season. Reason (R): Paddy is a Kharif crop. a. Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A). b. Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A). c. Assertion (A) is true, but Reason (R) is false. d. Assertion (A) is false, but Reason (R) is true. 4. Livestock includes a. Pigs and horses

b. Sheep and goats

c. Cows and buffaloes

d. All of these

5. The fertile female honeybee is called a. Queen

b. Drone

c. Worker

d. None of these

6. Shellfish is a member of which taxa a. Mollusca

b. Crustacea

c. Fishes

d. Insecta

7. An exotic breed of poultry is a. Assel

b. Busra

c. Brahma

d. White leghorn

8. It is the agricultural practice of breeding and raising livestock. a. Animal husbandry

b. Bioinformatics

c. Pharmacology

d. Biotechnology

9. The Green revolution in India occurred during a. 1960’s

b. 1970’s

c. 1980’s

d. 1950’s

10. The animals should be protected against anthrax with

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a. Vaccines

b. Proper medicines

c. Suitable antibiotics

d. Both (a) and (b)

IL Foundation Series Class 9

II. Improvement in crop yields

1. The method of producing a variety of crops by cross-breeding two species of the same genus is known as a. Inter varietal hybridisation

b. Interspecific hybridisation

c. Inter generic hybridisation

d. Genetic engineering

2. What are the basic objectives behind the crop variety improvement? a. To increase the yield of plant products b. To produce biotic and abiotic resistance to the plants c. To improve the quality of food crops d. All of these 3. Identify the micronutrients among the following. a. Nitrogen

b. Potassium

c. Calcium

d. Iron

4. The prevention of water logging in the clayey soil is due to the presence of a. Organic matter

b. Nitrogen

c. Oxygen

d. Phosphorus

5. Match the entries of Column 1 with those of Column 2. Column 1

Column 2

A. Crop variety improvement

i. Intercropping

B. Crop production management

ii. River lift system

C. Crop protection management

iii. Control of weeds, insects, etc.

D. Irrigation

iv. Crop rotation

E. Cropping pattern

v. Hybridisation

a. A → (v), B → (iv), C → (iii), D → (ii), E → (i) b. A → (iv), B → (v), C → (ii), D → (iii), E → (i) c. A → (v), B → (iv), C → (i), D → (iii), E → (ii) d. A → (i), B → (iv), C → (iii), D → (ii), E → (v)

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IMPROVEMENT IN FOOD RESOURCES

6. Which of the following are used to hasten the process of decomposition of organic matter for producing vermicompost? a. Rats

b. Earthworms

c. Rodents

d. Pigs

7. ____________and ____________ are the plants which are grown to produce green manure. a. Sun hemp and guar

b. Wheat and soybean

d. Cyperus and Rotundus

Xanthium and Parthenium

8. Nitrogen, phosphorus, and potassium are examples of a. Micronutrients

b. Macronutrients

c. Fertilisers

d. Both (a) and (b)

9. Assertion (A): Crop rotation is a part of sustainable agricultural practice. Reason (R): Crop rotation helps maintain soil fertility. a. Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A). b. Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A). c. Assertion (A) is true, but Reason (R) is false. d. Assertion (A) is false, but Reason (R) is true. 10. Xanthium, Parthenium and Cyperus are examples of a. Diseases

b. Pesticides

c. Weeds

d. Pathogens

11. Assertion (A): The river lift system is more economical than the canal system for irrigation. Reason (R): In the river lift system, a pump is used to lift the water from the river. a. Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A). b. Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A). c. Assertion (A) is true, but Reason (R) is false. d. Assertion (A) is false, but Reason (R) is true.

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IL Foundation Series Class 9

12. Assertion (A): Integrated farming is a part of sustainable agricultural practices. Reason (R): Sometimes fish is cultured in the paddy field along with the cultivation of rice crops. a. Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A). b. Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A). c. Assertion (A) is true, but Reason (R) is false. d. Assertion (A) is false, but Reason (R) is true. 13. Which combination of qualities is the first priority of a plant breeder? a. Increased yield b. Increased quality of food c. Increased resistance to pathogens d. Increased tolerance to environmental stresses 14. Which of the following is not a characteristic of the Green revolution? a. Use of modern agricultural methods

b. High-yielding crop varieties

c. Independent of chemical fertilisers

d. Increase in agricultural productivity

15. Which of the following statements about tanks used for irrigation is accurate? a. Tanks are large reservoirs used to store water for drinking purposes. b. Tanks are primarily employed for fish farming in agricultural areas. c. Tanks intercept and store runoff to supplement irrigation in smaller catchment areas. d. Tanks are an integral part of river lift systems for supplementary water supply. III. Animal husbandry

1. The saltwater fishery is known as a. Inland fishery

b. Marine fishery

c. River water fishery

d. None of these

2. The external parasites such as ____________ affect the stomach of animals. a. Worms

b. Flukes

c. Virus

d. Bacteria

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IMPROVEMENT IN FOOD RESOURCES

3. _____________ are used to protect the cattle from rain, heat and cold. a. Roofed sheds

b. Open places with no shelter

c. Sheds without roofs

d. Places near the sea

4. Match the entries of Column 1 with those of Column 2. Column 1

Column 2

A. Finned fish

i. Estuaries

B. Shellfish

ii. Canals

C. Freshwater resources

iii. Prawns

D. Brackish water resources

iv. Bhetki

a. A → (iv), B → (iii), C → (ii), D → (i)

b. A → (iv), B → (iii), C → (i), D → (ii) c. A → (iv), B → (i), C → (ii), D → (iii) d. A → (i), B → (iii), C → (ii), D → (iv)

5. ____________ is a source of wax and is used in the preparation of medicines, polish, etc. a. Manure

b. Beehives

c. Honey

d. Green manure

6. ____________ and are examples of shelled fish which come under fish production. a. Prawn and mollusc

b. Mullets and bhetki

d. Pearl spots and mullets

Catla and rohu

7. Which among the following is a local Indian breed of cattle? a. Jersey

b. Brown Swiss

c. Red Sindhi

d. None of these

8. Which of the following bee varieties yield maximum honey? a.

Apis indica

b. Apis dorsata

Apis mellifera

d. Apis florae

9. The Hilsa fish is found in

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a. Land

b. Pond

c. Freshwater

d. Marine water

IL Foundation Series Class 9

10. Identify the false statement regarding poultry. a. Cross-breeding techniques in poultry help produce new varieties with improved qualities. b. Vaccination can prevent the occurrence of infectious diseases. c. Poultry feed should be rich in vitamins K and E. d. Proper sanitation and maintenance are not so much required for poultry. 11. Identify the correct statement(s) regarding the cross-breed of Aseel and Leghorn. i. It has the greatest capability of egg production. ii. It cannot sustain high temperatures. iii. Low maintenance is required. iv. The name of this breed is broiler chicken. a. Only (i)

b. Both (i) and (iii)

c. Only (ii)

d. Both (ii) and (iv)

12. The production and management of fish are called a. Pisciculture

b. Apiculture

c. Sericulture

d. Aquaculture

13. Assertion (A): Composite fish culture involves the cultivation of different varieties of fish having the same feeding habits. Reason (R): Different varieties of fish utilise different areas of the same pond for their feed. a. Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A). b. Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A). c. Assertion (A) is true, but Reason (R) is false. d. Assertion (A) is false, but Reason (R) is true. 14. Select the correct match. Column 1

Column 2

A. Indian bee

i. Apis dorsata

B. Rock bee

ii. Apis florea

C. Little bee

iii. Apis mellifera

D. European bee

iv. Apis indica

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IMPROVEMENT IN FOOD RESOURCES

a. A → (iv), B → (i), C → (ii), D → (iii) b. A → (iii), B → (i), C → (ii), D → (iv)

c. A → (ii), B → (i), C → (iv), D → (iii) d. A → (i) B → (iv) C → (iii) D → (ii)

15. Estuarian fish culture is a culture of fish in a. Marine water

b. Freshwater of river

c. Freshwater of pond

d. Brackish water

WORKSHEET - 2 MULTIPLE CHOICE QUESTIONS WITH SINGLE CORRECT ANSWER 1. The major group of activities for improving crop yield can be classified as a. Crop variety improvement

b. Crop production improvement

c. Crop protection management

d. All of these

2. Apis cerana indica is commonly known as a. Indian cow

b. Indian buffalo

c. Indian bee

d. None of these

3. Catla and rohu are examples of a. Freshwater fish

b. Marine water fish

c. Both (a) and (b)

d. None of the above

4. Leghorn and Aseel are related to a. Apiculture

b. Dairy farming

c. Pisciculture

d. Poultry

5. Chemical fertilisers are a. Are non-biodegradable

b. Can cause water pollution

c. Can change the chemical nature of soil

d. All of these

6. The most common viral disease of cattle is a. Cowpox

b. Tuberculosis

c. Rinderpest

d. Foot and mouth disease

7. Which of the following is a high milk-yielding crossbreed?

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a. Karan Swiss

b. Murrah

c. Tharparkar

d. Red Sindhi

IL Foundation Series Class 9

8. The shelter provided for livestock depends on a. The location of the shelter

b. Number of animals to be sheltered

c. Type of animals to be sheltered

d. All of these

9. Catla, rohu and mrigals constitute a. Marine fish

b. Brackish water fish

c. Freshwater fish

d. Both (a) and (b)

10. Pigeon pea is a pulse commonly known as a. Chana

b. Matar

c. Arhar

d. Moong

11. Desirable agronomic characteristics like tallness and profuse branching are characteristic features of which crop? a. Cereal

b. Pulses

c. Fodder

d. Oil

12. Which of the following is known as a rock bee? a.

Apis cerana

b. Apis dorsata

Apis florae

d. Apis mellifera

13. Apiaries are established for a. Flower production

b. Apple production

c. Honey production

d. Fish production

14. Which of the following characteristics of crop plants cannot be considered desirable for crop improvement a. High yielding

b. Disease resistance

c. Late maturity

d. Wide adaptability

15. An improved variety is a. Always superior to the other existing varieties b. Always inferior to the other existing varieties c. May be superior to the other existing varieties d. More than one answer is correct 16. Select the marine edible fishes from the following i) Sardines

ii) Common carp

iii) Rohu iv) Hilsa v) Pomfrets

a. i, ii, iii, v and vi

b. ii, iii and vii

c. ii, iii, iv, vi and vii

d. i, iv, v and vi

vi) Mackerel

vii) Catla

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IMPROVEMENT IN FOOD RESOURCES

17. Fish used in the biological control of mosquitoes is a.

Gambusia

b. Hilsa ilisha

Scalophagus

d. Goldfish

18. Inland fisheries are a. Deep sea fishing

b. Capturing fishes from seacoast

c. Raising and capturing fishes in fresh

d. Oil extraction from fish

water 19. Fishes reared in culture fishery in India are a.

Salmon and rohu

b. Salmon and Catla

Catla and Hilsa

d. Rohu and Catla

20. Which of the following is a freshwater edible fish? a. Tuna

b. Rohu

d. Sardine

Hilsa

21. Edible marine fishes are a. Shark

b. Hilsa

c. Pomfret

d. Both (b) and (c)

22. Which of the following is a marine fish a.

Catla catla

b. Labeo rohita

Hilsa ilisha

d. Common carp

23. Fish introduced in India by foreigners is a.

Labeo rohita

c. Pomfret

b. Mystus seenghala d. Clarius batrachus

24. The aquaculture involves the production of useful a. Aquatic plants

b. Shrimps and prawns

c. Fishes and oysters

d. All of these

25. If more than a single species of fish is cultured at a time, then it is called a. Monoculture

b. Aquaculture

c. Polyculture

d. Sericulture

26. Identify the edible freshwater teleost. a.

Catla catla

c. Rays and skates 216

b. Hilsa ilisha d. Sharks

IL Foundation Series Class 9

27. Which one is not a marine fish? a. Pomfret

b. Sardine

c. Rohu

d. Mackerel

28. Fisheries include rearing, catching and selling of a. Fish

b. Shellfish

c. Crustaceans (prawns, crabs)

d. All of the above

29. Worker bees are a. Fertile males

b. Fertile females

c. Sterile females

d. Sterile males

30. The first & foremost aim of plant breeding is a. Transfer of disease resistance

b. Production of early maturing varieties

c. Breeding high-yielding varieties

d. Improvement of the quality

31. Assertion (A): Protein and fat-rich food should be provided to broiler chicken. Reason (R): Broiler chicken is grown to provide eggs of good quality. a. Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A). b. Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A). c. Assertion (A) is true, but Reason (R) is false. d. Assertion (A) is false, but Reason (R) is true. 32. What is the complex method that involves the intricate crossing of genetically distinct plants, aiming to incorporate a diverse array of desirable traits into crop varieties to enhance their overall productivity and adaptability? a. Interspecific breeding

b. Hybridisation

c. Intervarietal crossing

d. Intergeneric breeding

33. What primary characteristic sets organic farming practices apart from conventional agricultural methods? a. Use of synthetic fertilisers b. Genetically modified organisms (GMOs) in crop cultivation c. Minimisation of chemical fertiliser d. Use of chemical pesticides 217

IMPROVEMENT IN FOOD RESOURCES

34. In the poultry industry, the production of hatching eggs is more expensive than the production of market eggs mainly because: a. Cost of males and their depreciation is high b. Mortality of females is usually lower when they are mated with males c. Number of eggs produced by hatched flock are to be sold only as market eggs d. Some of the eggs produced by hatchery flocks are not acceptable for incubation 35. The milch breed is known for producing: a. High-yielding dairy breeds

b. High-yielding cattle breeds

c. Efficient working bullocks

d. Low-yielding dairy breeds

36. Assertion (A): Intercropping increases the productivity of agricultural land. Reason (R): Same fertilisers and pesticides can be used for different varieties of crops. a. Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A). b. Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A). c. Assertion (A) is true, but Reason (R) is false. d. Assertion (A) is false, but Reason (R) is true. 37. A queen honeybee lays eggs of a. One type from which all castes develop b. Two types, one forming queen and workers and the second forming drones c. Three types forming queen, drone and workers d. Unfertillised eggs die while fertilised ones from all castes. 38. Which are the primary and secondary products of apiculture? a. Wax is the primary product, but honey is the secondary product b. Honey is the primary product, but wax is the secondary product c. Both wax and Honey are considered secondary products, as some nutritive substances are also obtained from honeybees, which are primary products. d. No criteria are set to differentiate the primary and secondary products in apiculture.

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39. Assertion (A): Cross-breeding of dairy animals increases the productivity of milk. Reason (R): The lactation period of dairy animals can be increased by cross-breeding. a. Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A). b. Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A). c. Assertion (A) is true, but Reason (R) is false. d. Assertion (A) is false, but Reason (R) is true. 40. Which of the important components of poultry farm management? i. Selection of disease-free and suitable breeds

ii. Proper and safe farm conditions

iii. Proper feed and water

iv. Hygiene and health care

a. ii, iii, iv

b. i, ii, iv

c. i, iii, iv

d. i, ii, iii, iv

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ANSWER KEY 1: THE FUNDAMENTAL UNIT OF LIFE Worksheet 1 I. Introduction 1. c 2. a 3. a 4. c II. Discovery of the cell 1. b 2. a 3. b 4. c III. Microscopes & cell theory 1. c 2. a 3. d 4. c 5. b IV. Prokaryotic cell 1. d 2. d 3. c 4. c 5. d V. Ultrastructure of a eukaryotic cell 1. a 2. c 3. d 4. c 5. b 6. c 7. d 8. c 9. d 10. c Worksheet 2 1. d 2. b 6. d 7. a 11. b 12. a 16. a 17. c 21. c 22. b 26. c 27. d 31. b

3. b 8. d 13. a 18. b 23. a 28. c

4. c 9. c 14. b 19. b 24. c 29. a

5. c 10. d 15. c 20. b 25. c 30. c

2: CELL CYCLE AND CELL DIVISION Worksheet 1 I. Introduction to cell cycle and cell division 1. c 2. c 3. c 4. b 5. b 6. b 7. a 8. d 9. b 10. a II. Cell cycle 1. b 2. b 3. c 4. c 5. c 6. c 7. d 8. c 9. c 10. b 11. a 12. d 13. d 14. a 15. a III. Meiosis 1. c 2. a 3. a 4. c 5. c 6. b 7. c 8. a 9. b 10. b 11. d 12. a 13. d 14. c 15. c Worksheet 2 1. a 2. a 6. b 7. a 11. d 12. a 16. b 17. a 21. c 22. c

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3. b 8. d 13. b 18. d 23. d

4. c 9. a 14. a 19. a 24. c

5. a 10. a 15. b 20. b 25. d

26. d 27. a 28. b 29. d 30. c 31. d 32. d 33. d 34. c 35. b 36. c 37. d 38. c 39. a 40. b 3: TISSUES Worksheet 1 I. Plant tissues and tissue systems 1. c 2. b 3. a 4. b 5. d 6. d 7. d 8. a 9. c 10. b 11. a 12. d 13. d 14. d 15. c 16. c 17. d 18. a 19. d 20. d 21. b 22. c 23. b 24. a 25. c 26. a 27. a 28. d 29. d 30. d 31. a 32. a 33. d 34. d 35. d II. Animal tissues 1. b 2. d 3. c 4. b 5. b 6. c 7. d 8. d 9. c 10. b 11. b 12. b 13. a 14. b 15. b 16. b 17. a 18. b 19. b 20. c 21. c 22. a 23. c 24. a 25. b 26. a 27. b 28. b 29. c 30. b 31. d 32. d Worksheet 2 1. c 2. b 6. b 7. d 11. c 12. d 16. d 17. a 21. a 22. b 26. d 27. b 31. d 32. a 36. a

3. b 8. d 13. c 18. c 23. c 28. c 33. b

4. c 9. d 14. a 19. d 24. a 29. a 34. a

5. a 10. c 15. c 20. d 25. d 30. a 35. d

4: DIVERSITY IN LIVING ORGANISMS Worksheet 1 I. Classification and Nomenclature 1. c 2. b 3. a 4. d 5. b 6. c 7. d 8. d 9. d 10. d 11. b 12. c 13. c 14. b II. Kingdom Monera 1. c 2. b 3. a 4. b 5. c

ANSWER KEY III. Kingdom Protista 1. a 2. c 3. d 4. b IV. Kingdom Fungi 1. b 2. d 3. c 4. c 6. b V. Kingdom Plantae 1. c 2. b 3. c 4. a 6. b 7. a 8. a 9. a 11. d 12. a 13. b 14. a 16. c 17. a 18. a 19. d 21. b 22. a 23. d 24. d 26. b VI. Kingdom Animalia 1. c 2. c 3. a 4. b 6. d 7. b 8. c 9. a 11. a 12. c 13. b 14. b 16. a 17. b 18. c 19. c 21. c 22. b 23. b 24. c 26. c 27. b 28. d 29. a Worksheet 2 1. c 2. b 6. a 7. c 11. b 12. c 16. b 17. d 21. b 22. a 26. a 27. b 31. c 32. d 36. d 37. c 41. a 42. d 46. c 47.c 51. b 52. a

3. c 8. d 13. c 18. c 23. d 28. d 33. d 38. b 43. c 48. b

4. c 9. c 14. d 19. a 24. d 29. d 34. d 39. c 44. c 49. d

5: WHY DO WE FALL ILL? Worksheet 1 I. Health and its failure 1. d 2. d 3. a 4. d 6. c 7. c II. Disease and its causes 1. d 2. a 3. d 4. c 6. b

5. a

5. b 10. b 15. d 20. d 25. b

5. d 10. d 15. d 20. a 25. b 30. b 5. b 10. c 15. d 20. b 25. b 30. c 35. b 40. b 45. b 50. d

5. d

5. a

III. Infectious diseases 1. a 2. d 3. b 4. c 5. d 6. a 7. a 8. c 9. b 10. a 11. b 12. d 13. b 14. b 15. d 16. a 17. a 18. b 19. a 20. d 21. b IV. Immunisation 1. b 2. a 3. a 4. a 5. a 6. d 7. b Worksheet 2 1. b 2. b 6. c 7. b 11. b 12. b 16. a 17. a 21. c 22. b 26. a 27. d 31. b 32. c 36. b 37. c

3. a 4. b 8. c 9. b 13. a 14. c 18. a 19. d 23. a 24. d 28. d 29. c 33. d 34. d 38. b 39. a

5. b 10. c 15. a 20. b 25. d 30. d 35. c 40. a

6: IMPROVEMENT IN FOOD RESOURCES Worksheet 1 I. Introduction to improvement in food resources 1. c 2. d 3. a 4. d 5. a 6. d 7. d 8. a 9. a 10. a II. Improvement in crop yields 1. b 2. d 3. d 4. a 5. a 6. b 7. a 8. b 9. a 10. c 11. d 12. b 13. a 14. c 15. c III. Animal Husbandry 1. b 2. a 3. a 4. a 5. b 6. a 7. c 8. c 9. d 10. d 11. b 12. a 13. d 14. a 15. d Worksheet 2 1. d 2. c 6. d 7. a 11. c 12. b 16. d 17. a

3. a 8. d 13. c 18. c

4. d 9. c 14. c 19. d

5. d 10. c 15. a 20. b

221

ANSWER KEY 21. d 26. a 31. c 36. c

222

22. c 27. c 32. b 37. b

23. c 28. d 33. c 38. b

24. d 29. c 34. d 39. a

25. c 30. c 35. a 40. d