Assertion Reason Questions for Biology Chapter 7 Structural Organisation in Animals

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Directions: In the following questions, a statement of assertion is followed by a statement of reason.
Mark the correct choice as:
(a) If both Assertion and Reason are true and Reason is the correct explanation of Assertion.
(b) If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
(c) If Assertion is true but Reason is false.
(d) If both Assertion and Reason are false.

Q.1. Assertion : Specialization of cells is advantageous for the organisms.
Reason : It increases the operational efficiency of an organism.

Answer Answer: (a) Specialization of cells into tissue, organ and organ systems is advantageous for the organisms. It increases the operational efficiency through division of labour which avoids duplication of work.

Q.2. Assertion : The squamous epithelium is made of a single thin layer of flattened cells with irregular boundaries.
Reason : They are found in walls of blood vessels and air sacs of wings. [AIIMS 2017]

Answer Answer: (b) Squamous epithelium is a single layer of flattened cells in contact with basal lamina of the epithelium. This type of epithelium is often permeable and occurs where small molecules need to pass quickly through membranes.

Q.3. Assertion : Urinary bladder can considerably expand to accommodate urine.
Reason : It is lined by stretchable squamous epithelium.

Answer Answer: (c) Urinary bladder is not lined by squamous epithelium but by transitional epithelium which is a stretchable compound epithelium. It has a single layer of cuboidal cells at the base, 2-3 middle layers of large polygonal cells and a superficial layer of large, broad rectangular cells. Stretching considerably flattens and broadens the cells of superficial and middle layers, hence causing expansion of the urinary bladder.

Q.4. Assertion : Columnar epithelium lining the intestinal mucosa appears to have a brush like appearance.
Reason : A large number of microvilli are present on brush bordered columnar epithelium.

Answer Answer: (a) Columnar epithelium is a type of simple epithelium characterised by the presence of tall column like cells. Its major function is absorption or secretion. It covers the inner surface of the intestine, stomach and gall bladder. In the intestine, it appears to have a brush like appearance on the free surface, which is due to the presence of large number of microvilli. Function of microvilli is to enhance absorption. Due to the presence of microvilli, the epithelium is also called as brush bordered columnar epithelium.

Q.5. Assertion : Surface of skin is impervious to water.
Reason : Surface of skin is covered by stratified cuboidal epithelium.

Answer Answer: (c) Surface of skin is impervious to water because it is covered by stratified keratinised squamous epithelium. This epithelium has many superficial layers of horny, scale like remains of dead squamous cells and several deeper layer of living polygonal cells. Heavy deposits of the insoluble protein keratin are present in the dead superficial layers which makes this epithelium impervious to water. Stratified cuboidal epithelium, on the other hand, lines the inner surface of sweat gland, larger salivary and pancreatic ducts.

Q.6. Assertion: Stomach and intestine of our body has columnar epithelium.
Reason: Columnar epithelium helps in secretion and absorption.

Answer Answer: (a) The columnar epithelium is composed of a single layer of tall and slender cells. Their nuclei are located at the base. Free surface may have microvilli. They are found in the lining of stomach and intestine and help in secretion and absorption.

Q.7. Assertion: Cell junctions are present in the epithelium and other tissues.
Reason: Among cell junctions, adhering junctions help to stop substances from leaking across a tissue.

Answer Answer: (c) All cells in epithelium are held together with little intercellular material. In nearly all animal tissues, specialized junctions provide both structural and functional links between its individual cells. Three types of cell junctions are found in the epithelium and other tissues. These are called as tight, adhering and gap junctions. Adhering junctions perform cementing function to keep neighbouring cells together.

Q.8. Assertion: Simple epithelium covers surfaces exposed to mechanical or chemical abrasions.
Reason: Protection of underlying tissues is the major function of simple epithelium.

Answer Answer: (d) Simple epithelium does not cover surfaces exposed to mechanical or chemical abrasions because it is made up of a single layer of cells, hence it is not effective in protecting the underlying tissue. Simple epithelium occurs mainly on secretory and absorptive surfaces. There is another types of epithelial tissue called compound epithelium which being multilayered is effective in providing protection to underlying tissues, therefore, covers the surfaces exposed to mechanical and chemical abrasions.

Q.9. Assertion: Compound epithelium play important role in absorption, secretion and excretion.
Reason: Compound epithelium is found in the stomach lining.

Answer Answer: (d) Compound epithelium performs the function of providing protection against chemical and mechanical stress. Thus, it has limited role in absorption, secretion and excretion. This epithelium is found in the moist surface of buccal cavity, pharynx, inner lining of duct of salivary gland but not in stomach lining.

Q.10. Assertion : Cartilage (protein matrix) and bone (calcium matrix) are rigid connective tissue.
Reason : Blood is connective tissue in which plasma is the matrix.

Answer Answer: (b) Cartilage comprises of mucopolysaccharide called chondroitin sulphate. Bone is a hard connective tissue while blood is a fluid connective tissue.

Q.11. Assertion: Connective tissues are most abundant and widely distributed in the body of complex animals.
Reason: Connective tissues link and support other tissues or organs of the body.

Answer Answer: (b) Connective tissue is the most abundant and widely distributed tissue of the body. It connects different tissues or organs and provides support to various structures of animal body. The connective tissue consists of living cells and extra-cellular matrix. It includes soft connective tissues and specialised tissues like cartilage, bone, adipose and blood.

Q.12. Assertion: Tendons attach one bone to another bone.
Reason: Ligaments attach skeletal muscles to bones.

Answer Answer: (d) Tendon is made up of white fibrous tissue. Tendon connects a skeletal muscle to bone. It is tough and inelastic. Ligament is strong and elastic and made up of yellow elastic tissue with some collagen fibres. Ligament connects a bone to another bone.

Q.13. Assertion: The cells of connective tissues except blood secrete fibres.
Reason: Fibres provide strength, elasticity and flexibility to the tissue.

Answer Answer: (b) All cells of connective tissue except blood secrete fibres. Fibroblasts are the main cells of connective tissue, which secrete various types of fibres. There are three types of fibres secreted by connective tissue cells and each type is formed by proteins. These are collagen fibres (made up of collagen protein), elastic fibres (formed of elastin) and reticular fibres (made up of reticulin). All provide strength, elasticity and flexibility to the connective tissue.


Q.14. Assertion: Presence of connective tissue inside the brain is essential for conduction of nerve
impulse.
Reason: Connective tissue hold together the nerve cells of brain.

Answer Answer: (d) Ordinary connective tissue is absent inside the central nervous system. i.e. brain and spinal cord and has no function in the conduction of nerve impulse. The neurons of nerve tissue inside the brain and spinal cord are held together by supporting cells called neuroglia cells. Neuroglia cells resemble neurons and have long radiating processes but no nissl granules.

Q.15. Assertion: Tendon is present in all bone joints.
Reason: Tendon connects the bones together and holds them in position.

Answer Answer: (d) It is not tendon but another type of connective tissue called ligament which is present in most of the bone joints and connect the bones together. Ligament also helps in holding the bones in position. Tendon, on the the other hand, is a dense, strong, fibrous connective tissue which forms strong inextensible attachment of a skeletal muscle to a bone.

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