Class 11-science NCERT Solutions Biology Chapter 7 - Structural Organisation In Animals

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122

Structural Organisation In Animals Exercise 121

Solution 1

i. American cockroach

ii. Four pairs of spermathecae are found in earthworm.

iii. Two large ovaries are found lying laterally in the 2nd to 6th abdominal segments.

iv. The abdomen of a cockroach consists of 10 segments.

v. Malpighian tubules are present at the junction of the mid gut and the hind gut of the alimentary canal of insects.

Structural Organisation In Animals Exercise 122

Solution 2

I. Nephridia are the excretory and osmoregulatory organs of earthworm.

II. There are three types of nephridia in earthworm:

i. Septal nephridia: It is present on both the sides of intersegmental septa of segment 15 to the last which opens into the intestine.

ii. Integumentary nephridia: It is attached to the lining of the body wall of segment 3 to the last which opens on the body surface.

iii. Pharyngeal nephridia: It is present as three paired tufts in the 4th, 5th and 6th segments.

Solution 3

Reproductive organs of an earthworm:

Solution 4

Alimentary canal of a cockroach:

Solution 5

(a) The prostomium is a small, fleshy lobe which serves as a covering for the mouth and as a wedge to force open cracks in the soil into which the earthworm may crawl, whereas the peristomium is the crescentic aperture at the anterior end of the first segment of the earthworm which contains the mouth.

(b)

Septal Nephridia

Pharyngeal Nephridia

i. These occur on the anterior and posterior surfaces of all the septa after segment 15 in an earthworm.

ii. They discharge excretory matter into the lumen of the alimentary canal.

i. These occur in three pairs of bunches in the 4^th, 5^th and 6^th segments lying on each side of the alimentary canal.

ii. They discharge excretory matter into the gut, i.e. the buccal cavity or pharynx.

Solution 6

Red blood cells, white blood cells and blood platelets are the cellular components of blood.

Solution 7

a) Chondrocytes are cells of cartilage. These are large, rounded, mature cells occurring in groups in the matrix of the cartilage. The cartilage is found in the pinna, tip of the nose, outer ear joints, limbs and hands and between adjacent bones of the vertebral column in adults.

b) The axon is the tail-like structure of a neuron. Each axon is a long, cylindrical process of the nerve cell. It arises from the cyton and conducts nerve impulses away from the cell body. It ends in a group of branches called terminal arborisations. These are present in the entire body.

c) The ciliated epithelium consists of cells which bear fine, vibratile cytoplasmic processes called cilia on its free surface. Cilia help to trap and clear dust and foreign particles. It is found in the inner lining of bronchioles, urinary tubules of kidneys, nasal passage, oviducts and ventricles of the brain.

Solution 8

Epithelial tissues: Epithelial tissues provide covering to the inner and outer lining of various organs. The cells of epithelial tissues are compactly packed with little intercellular matrix. There are two types of epithelial tissues:

I. Simple epithelium: Simple epithelium is composed of a single layer of cells and functions as a lining for body cavities, ducts and tubes.

i. On the basis of structural modification of cells, the simple epithelium is further divided into three types. These are

Squamous epithelium: The squamous epithelium is made of a single thin layer of flattened, disc-like cells such as the tiles of a floor. Hence, it is also called pavement epithelium. It is found in the walls of blood vessels, lining of Bowman's capsules of urinary tubules and air sacs of lungs.

Functions: It is involved in protection, excretion, gas exchange and secretion of coelomic fluid.

ii. Cuboidal epithelium: The cuboidal epithelium is composed of a single layer of cube-like cells. The cell outlines are polygonal in surface view. The nucleus is rounded and lies at the centre of the cell. It is found in the ducts of glands and tubular parts of nephrons in the kidneys.

Functions: Its main functions are protection, secretion and absorption and gamete formation.

iii. Columnar epithelium: The columnar epithelium is composed of a single layer of tall and slender cells. The nuclei of these cells are elongated and located at variable positions. The columnar epithelium is found in the lining of the stomach, intestines, gall bladder and bile duct. If the columnar or cuboidal cells bear cilia on their free surface, then it is called ciliated epithelium. Its function is to move particles or mucus in a specific direction over the epithelium. It is mainly present in the inner surface of hollow organs such as bronchioles and fallopian tubes.

Functions: It helps in secretion and absorption.

II. Compound epithelium: The compound epithelium consists of two or more layers of cells. Therefore, it is stronger and thicker than the simple epithelium. It serves the function of protection. Example: Skin. It covers the dry surface of the skin, the moist surface of the buccal cavity, pharynx and inner lining of ducts of salivary glands and pancreatic ducts.

Solution 9

a) Simple epithelium and compound epithelium

Simple Epithelium

Compound Epithelium

i. It is only one cell deep.

ii. All cells rest on the basement membrane.

iii. It provides poor protection to underlying tissues.

iv. It plays a role in absorption, secretion and excretion.

i. It is many cells deep.

ii. Only cells of the lowermost layer rest on the basement membrane.

iii. It provides much better protection to underlying tissues.

iv. It has little role in absorption, secretion and excretion.

b) Cardiac muscle and striated muscle

Cardiac Muscle

Striated Muscle

i. It occurs in the walls of the heart, pulmonary veins and superior vena cava.

ii. Fibres are branched.

iii. It is uninucleated.

iv. It never gets fatigued.

v. It is an involuntary muscle.

i. It occurs in the limbs, body walls, tongue, pharynx and beginning of oesophagus.

ii. Fibres are unbranched.

iii. It is multinucleated.

iv. It soon gets fatigued.

v. It is a voluntary muscle.

c) Dense regular connective tissue and dense irregular connective tissue

Dense regular connective tissue

Dense irregular connective tissue

i. It has a regular pattern of fibres.

ii. The collagen fibres are present in rows between many parallel bundles of fibres.

Examples: Tendon and ligament

i. It has an irregular pattern of fibres.

ii. It has fibroblasts and many fibres (mostly collagen) which are oriented differently. Example: Skin

d) Adipose and blood tissues

Adipose tissue

Blood tissue

i. Adipose tissue is a type of loose connective tissue located mainly beneath the skin.

ii. Its main function is to store fat. The excess of nutrients which are not used immediately are converted into fats and are stored in this tissue.

i. Blood is a fluid connective tissue.

ii. The main function of blood is to transport gases, nutrients and waste products in the body.

e) Simple gland and compound gland

Simple gland

Compound gland

i. It is composed of a single cell.

ii. Its secretory part opens into a single duct.

i. It is composed of multiple cells.

ii. It has many secretory parts, the ducts of which join to form ducts of higher order and finally a single duct.

Solution 10

a) Neuron. The neuron is not a connective tissue; all the others are examples of connective tissues.

b) Cartilage. The cartilage is not part of blood; all the others are components of blood.

c) Ligament. The ligament is a connective tissue; all the others are types of glands.

d) Antennae. The antennae are thread-like structures lying in the front of the eyes in a cockroach, whereas all the others are mouth parts of a cockroach.

e) Protonema. The protonema is a thread-like chain of cells found in the life cycle of moss; all the others are parts or segments present in the legs of a cockroach.

Solution 11

(a)-(iii); (b)-(iv); (c)-(v); (d)-(ii); (e)-(i); (f)-(vii); (g)-(vi)

Solution 12

Blood vascular system of earthworm: Earthworm (Pheretima) exhibits a closed type of blood vascular system. It consists of blood vessels, capillaries and heart. Due to a closed circulatory system, blood is confined to the heart and blood vessels. Contractions keep blood circulating in one direction. Smaller blood vessels supply the gut, nerve cord and body wall. Blood glands are present on the 4th, 5th and 6th segments. They produce blood cells and haemoglobin which is dissolved in blood plasma. Blood cells are phagocytic in nature. Earthworms lack specialised breathing devices, so respiratory exchange with their blood stream occurs through the moist body surface.

Solution 13

Digestive system of frog:

Solution 14

a) Ureters in frog: In male frog, the ureters conduct both urine and spermatozoa to the cloaca. Hence, it acts as a urinogenital duct in male frogs. In females, the ureters conduct only urine and the oviducts open separately in the cloaca.

b) Malpighian tubules: Malpighian tubules are the organs of excretion and osmoregulation in insects. Each tubule is lined by glandular and ciliated cells. They absorb nitrogenous waste products and convert them into uric acid, which is excreted out through the hindgut.

c) Body wall in earthworm: The body wall of the earthworm is covered externally by a thin non-cellular cuticle below which are the epidermis, two muscle layers (circular and longitudinal) and an innermost coelomic epithelium. The epidermis is made up of a single layer of columnar epithelial cells which contain secretory gland cells. It protects the delicate internal organs from injury. It also produces setae.