Chapter 7 Structural Organisation in Animals

In the previous chapter we have discussed plant tissue but animals have varieties of tissue that provides them a typical structure and enables them to perform various functions. In this chapter we understand the animals tissues it type and their function and morphological anatomical structure including alimentary canal, nervous system, reproductive structure and excretory structure of earthworm, cockroach and frog. This helps to provide knowledge about various animals, what are the physiological functions that help to survive.

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Exercise 1

  • Q1 Answer in one word or one line. (i) Give the common name of Periplaneta americana. (ii) How many spermathecae are found in earthworm? (iii) What is the position of ovaries in the cockroach? (iv) How many segments are present in the abdomen of cockroach? (v) Where do you find malphigian tubules?

    (i) The common name of Periplaneta americana is the American cockroach.

    (ii) Four pairs of spermathecae are present between sixth and the ninth segments. They help in receiving and storing the spermatozoa during copulation.

    (iii) In a cockroach, the pair of ovaries is located between 12th and 13th abdominal segments.

    (iv) In both sexes, the abdomen of a cockroach consists of ten segments.

    (v) Malphigian tubules are excretory organs of cockroaches. They form a part of the alimentary canal.

    Q2 Answer the following: (i) What is the function of nephridia? (ii) How many types of nephridia are found in earthworm based on their location?

    (i) Nephridia are segmentally arranged excretory organs present in earthworms.

    (ii) On the basis of their location, three types of nephridia are found in earthworms. They are:

    (a) Septal nephridia: These are present on both sides of the inter-segmental septa behind the 15th segment and they open into the intestine.

    (b) Integumentary nephridia: These lie attached to the body wall from the third segment to the last segment, which opens on the body surface.

    (c) Pharyngeal nephridia: These are present as three paired tufts in fourth, fifth, and sixth segments.

    Q3 Draw a labelled diagram of the reproductive organs of an earthworm.

                                         reproductive organs of an earthworm

    Q4 Draw a labelled diagram of alimentary canal of a cockroach.

                                         alimentary canal of a cockroach

    Q5 Distinguish between the following (a) Prostomium and peristomium (b) Septal nephridium and pharyngeal nephridium




    Prostomium is a small fleshy lobe, which overhangs the mouth of an earthworm. It helps the organism push into the soil and is sensory in function.

    The first body segment in the earthworm is called the peristomium. It surrounds the mouth opening.


    Septal nephridium

    Pharyngeal nephridium

    They are present on both sides of inter-segmental septa behind the 15thsegment and they open into the intestine.

    They are present as three paired tufts in the fourth, fifth, and sixth segments.


    Q6 What are the cellular components of blood?

    Components of blood include erythrocytes (RBCs), leucocytes (WBCs), and thrombocytes (platelets). These components form 45% of blood. They are suspended in the remaining fluid portion, called plasma.

    Mammalian erythrocytes are biconcave, coloured cells devoid of a nucleus. They help in transporting respiratory gases.

    Leucocytes or white blood cells are nucleated cells. They can be divided into two types, granulocytes (neutrophils, eosinophils, and basophils) and agranulocytes (lymphocytes and monocytes). They help fight against various disease-causing agents entering the body.

    Thrombocytes are cell fragments produced from megarkaryocytes of the bone. They play a major role during blood coagulation.

    Q7 What are the following and where do you find them in animal body (a) Chondriocytes (b) Axons (c) Ciliated epithelium


    They are cells of cartilages, and are present in small cavities within the matrix secreted by them.


    They are long, slender projections of neurons that help in carrying nerve impulses away from the neuron body. Axons aggregate in bundles which make up the nerves.

    Ciliated epithelium:

    It consists of simple columnar or cuboidal epithelium with cilia on their free surfaces. It is present on the inner surface of the oviducts and bronchioles. Where it helps in the movement of eggs or mucus in specific directions.

    Q8 Describe various types of epithelial tissues with the help of labelled diagrams.

    Epithelial tissue lines the surface of a body and forms a protective covering. Epithelium cells are packed tightly together with little intercellular matrix.

    Epithelial tissue in the body is of two types.

    (a) Simple epithelium: It consists of a single layer of cells where cells are in direct contact with the basement membrane. It is further sub-divided into the following types:

    (i) Simple squamous epithelium: It consists of a single layer of flat cells with irregular boundaries. It is found in the walls of the blood vessels and in the lining of alveoli.

    (ii) Simple cuboidal epithelium: It consists of a single layer of cube-like cells. It is present in regions where secretion and absorption of substances takes place such as the proximal convoluted tubule region of the nephron.

    (iii) Simple columnar epithelium: It consists of a single layer of tall, slender cells with their nuclei present at the base of the cells. They may bear micro-villi on the free surfaces. Columnar epithelium forms the lining of the stomach and intestines, and is involved in the function of secretion and absorption.

    (iv) Ciliated epithelium: It consists of columnar or cuboidal cells with cilia on their free surfaces. They are present in bronchioles and oviducts from where they direct mucus and eggs in specific directions.

    (v) Glandular epithelium:It consists of columnar or cuboidal cells involved in the secretion of substances. Glands are of two types, unicellular glands (goblet cells of the alimentary canal) and multicellular glands (salivary glands). They can be classified as exocrine (ductless glands) and endocrine glands (duct glands) by the method through which they release enzymes.

                                         epithelial tissues


    epithelial tissues

    Compound epithelium: It consists of many layers of cells. It is involved mainly in the function of providing protection and has a limited role in secretion and absorption.

    Dry surface of the skin or moist inner lining of the buccal cavity, pharynx, pancreatic ducts, and the inner lining of ducts of salivary glands are some of the examples of compound epithelium

    Q9 Distinguish between (a) Simple epithelium and compound epithelium. (b) Cardiac muscle and striated muscle (c) Dense regular and dense irregular connective tissues (d) Adipose and blood tissue (e) Simple gland and compound gland


    Simple epithelium

    Compound epithelium

    1. It is composed of only one layer of cells.

    2. It is mainly involved in the function of absorption and secretion.

    3. It is present in the lining of the stomach, intestine.

    1. It is composed of many layers of cells.

    2. It is mainly involved in the function of protection

    3. It is present in the lining of the pharynx and buccal cavity.


    Cardiac muscles

    Striated muscles

    1. They are involuntary in function.

    2. They are multi-nucleated and branched.

    3. They are found only in the heart.

    1. They are voluntary in function.

    2. They are multi-nucleated and un branched.

    3. They are found in triceps, biceps, and limbs.


    Dense regular connective tissues

    Dense irregular connective tissues

    1. In dense regular connective tissues, collagen fibres are present in rows between parallel bundles of fibres.

    2. They are present in tendons and ligaments.

    1. In dense irregular connective tissues, fibres are arranged irregularly.

    2. They are present in the skin.


    Adipose tissue

    Blood tissue

    1. It is composed of collagen fibres, elastin fibres, fibroblasts, macrophages, and adipociytes.

    2. It helps in the synthesis, storage, and metabolism of fats.

    3. It is present beneath the skin.

    1. It is composed of RBCs, WBCs, platelets, and plasma.

    2. It helps in the transportation of food, wastes, gases, and hormones.

    3. It is present in the blood vessels.


    Simple glands

    Compound glands

    1. They contain isolated glandular cells.

    2. They are unicellular.

    3. Examples include goblet cells of the alimentary canal.

    1. They contain a cluster of secretory cells.

    2. They are multicellular.

    3. Examples include salivary glands.


    Q10 Mark the odd one in each series: (a) Areolar tissue; blood; neuron; tendon (b) RBC; WBC; platelets; cartilage (c) Exocrine; endocrine; salivary gland; ligament (d) Maxilla; mandible; labrum; antennae (e) Prothorax; mesothorax; metathorax; coxa

    (a) Areolar tissue, blood, and tendons are examples of connective tissues. Neuron is an example of neural tissue.

    (b) RBCs, WBCs, and platelets are the three most important components of blood (fluid connective tissue) while Cartilage is skeletal connective tissue.

    (c) Exocrine, endocrine, and salivary glands are examples of simple glandular epithelium. Ligament is a connective tissue.

    (d) Maxilla, mandible, and labrum are mouthparts of a cockroach; white antennae are present in the head constituent of region of cockroaches.

    (e) Prothorax, Mesothorax and metathorax are parts of thorax of cockroach and present in the legs of a cockroach.

    Q11 Match the terms in column I with those in column II:Column I Column II(a) Compound epithelium (i) Alimentry canal (b) Compound eye (ii) Cockroach (c) Septal nephridia (iii) Skin (d) Open circulatory system (iv) Mosaic vision (e) Typhlosole (v) Earthworm (f) Osteocytes (vi) Phallomere (g) Genitalia (vii) Bone

    Column I

    Column II

    (a) Compound epithelium

    (b) Compound eye

    (c) Septal nephridia

    (d) Open circulatory system

    (e) Typhlosole

    (f) Osteocytes

    (g) Genitalia

    (iii) Skin

    (iv) Mosaic vision

    (v) Earthworm

    (ii) Cockroach

    (i) Alimentary canal

    (vii) Bone

    (vi) Phallomere


    Q12 Mention briefly about the circulatory system of earthworm

    Earthworm (Pheretima) have closed blood vascular systems, which consists of the heart, blood vessels, and capillaries. The heart pumps blood for circulating it in one direction. Blood is supplied by smaller blood cells to the gut, nerve cord and the body wall. Blood glands are present in the 4th, 5th, and 6th segments, which produce blood cells and haemoglobin dissolved in blood plasma. Blood cells in earthworms are phagocytic in nature.

    Q13 Draw a neat diagram of digestive system of frog.

                                         digestive system of frog

    Q14 Mention the function of the following (a) Ureters in frog (b) Malpighian tubules (c) Body wall in earthworm

    (a) Ureters in frogs: A ureter acts as a urinogenital duct, which carries sperms along with urine in male frogs.

    (b) Malphigian tubules: Malphigian tubules are excretory organs in cockroaches.

    (c) Body wall in earthworms: In earthworms, the body wall consists of muscle layers. It helps in movement and burrowing.