NCERT Class 11-Biology: Chapter –7 Structural Organization in Animals Part 7

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Question 20:

What is special about tissue present in the heart?

Answer:

Cardiac muscle tissue is an extremely specialized tissue which is only found in the heart and it has the following special features:

(i) It has similar characteristics of skeletal as well as smooth muscles. Like skeletal muscle tissue it is striated and like smooth muscle tissues it has cells connected together by intercalated discs.

(ii) It can sustain contraction and relaxation rapidly and in complete efficient coordination and synchronization.

(iii) The cardiac muscle tissue is involuntary and unlike other muscle tissues it doesn’t get tired.

Long Answer Type Questions

Question 1:

Classify and describe epithelial tissue on the basis of structural modifications of cells.

Answer:

Epithelial cells are divided into two broad categories on the basis of structural modification of the cells:

(A) Simple Epithelium and (B) Compound (Stratified) Epithelium

(A) Simple Epithelium: It is the epithelium tissue which has a single layer of cell. Thus, it is known as simple epithelium tissue. It is further divided into three types on the basis of the cell shape and structures:

(i) Squamous (flattened) cells: These are cells which flattened in shape and they allow materials and gases to pass through them by methods like diffusion and filtration. They can also secrete lubricating substances. They are found in the blood and lymphatic vessels, lining of the heart and air sacs of the lungs.

(ii) Cuboidal cells: These cells are shaped like cuboid and they help in the secretion and absorption of gases and other materials in the skin. They also have microvilli present. They are found in ducts like collecting tubule of the kidney.

(iii) Columnar epithelium: These cells are present in a tube or column-like shaped and they are used in absorption and secretion of certain enzymes and mucus. They can have microvilli, surface cilia, etc. They are present in the fallopian tube, small intestine, gall bladder, etc.

(B) Compound (stratified) Epithelium: It is the epithelium tissue which has two or more layers of cells lined together. It is also divided like simple epithelium on the basis of structure and it differs from simple epithelium because of the presence of more than one layer of cells.

Question 2:

Write down the common features of the connective tissue. On the basis of structure and function, differentiate between bones and cartilages.

Answer:

The common features of connective tissue are:

(i) They are involved in the binding and connection of different tissues and organs.

(ii) They help in providing structural rigidity, support and protection of the body.

(iii) They are involved in the transport and exchange of various enzymes, hormones, gases and molecules such as nitrogenous wastes, vitamins, etc.

(iv) They have good regeneration ability.

(v) All the connective tissues have fibers, cells and matrix present.

Difference between bones and cartilages is:

Bones and Cartilage
Bones and Cartilage

Bones

Cartilage

(i) They are firm and brittle

(i) They are soft and elastic

(ii) Ossein is the protein which is present its matrix

(ii) Aggregan is the protein which is present in its matrix.

(iii) It has bidirectional growth.

(iii) It has unidirectional growth

(v) Lamellae is present

(v) Lamellae is absent

(vi) It provides structural support to the body, helps in locomotion, used as a storage for minerals and it is used for the production of RBCs and WBCs.

(vi) It acts as a shock absorber and helps in reducing friction between the joints. It helps in maintain the structural shape and flexibility of appendages like ears and nose.

Question 3:

Comment upon the gametic exchange in earthworm during mating.

Answer:

The mating process in earthworms is referred to as copulation which occurs during the rainy season. The gamete exchange in the earthworms occur through the following sequential steps:

(i) Two earthworms come closer to each other and they get ventrally attached to each other in the opposite direction.

(ii) The copulation process begins and the male genital pore (i.e., papilla) of one earthworm is inserted into the spermathecal pore of the other earthworm.

(iii) The earthworm remains mutually close together by the penetration of setae in their bodies. Therefore,

(iv) Sperm and prostatic fluid of the earthworm are exchanged and the spermathecal pore stores the spermathecae.

(v) The earthworms remain attached for an hour and the sperm and egg are passed into cocoon which gets secreted by the clitellar gland present in the 14th to the 16th segment of the earthworm.

Therefore, gamete exchange of earthworms occur through cross-fertilization and external fertilization.

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