CBSE Class 11 Biology Long Answer Questions: Structural Organisation in Animals (NCERT-Based)

Course and Examination Framework

Course: CBSE Class 11 Biology

Board: Central Board of Secondary Education

Unit II: Structural Organisation in Animals and Plants

Chapter 7: Structural Organisation in Animals

Question Type: Long Answer Type Questions

Answer Length: 120–150 Words

Syllabus Compliance: 100% NCERT

Exam Relevance: CBSE Class 11 Annual & School Examinations

Section A: Animal Tissues (Questions 1–10)

Q1. Describe epithelial tissue, highlighting its structural features and functions.

Ans:
Epithelial tissue is composed of closely packed cells with minimal intercellular space, forming protective coverings and linings of body organs. These tissues rest on a basement membrane and lack blood vessels, but they receive nutrients through diffusion. Epithelial tissue shows high regenerative capacity, enabling rapid repair. Structurally, epithelial tissues may be simple or stratified, depending on function. Functionally, they play vital roles in protection, absorption, secretion, diffusion, and filtration. For example, simple squamous epithelium facilitates diffusion, while stratified epithelium protects against mechanical stress. Thus, the structure of epithelial tissue is closely related to its function.

Q2. Explain the different types of simple epithelial tissue with suitable functions.

Ans:
Simple epithelium consists of a single layer of cells and is mainly involved in absorption, secretion, and diffusion. Simple squamous epithelium has thin, flat cells that allow rapid diffusion and filtration, as seen in alveoli and capillaries. Cuboidal epithelium consists of cube-shaped cells with centrally placed nuclei, suited for secretion and absorption in kidney tubules and glands. Columnar epithelium is composed of tall cells that increase surface area for absorption, especially in the intestine. Ciliated epithelium bears cilia that help move substances like mucus or ova. Each type is structurally specialized for its specific function.

Q3. Describe connective tissue and its major components.

Ans:
Connective tissue functions to bind, support, and protect different organs of the body. It consists of cells embedded in an extracellular matrix composed of fibres and ground substance. The matrix may vary from fluid to rigid, depending on the tissue type. Cells such as fibroblasts, adipocytes, and macrophages perform various roles. Fibres include collagen for strength, elastic fibres for flexibility, and reticular fibres for support. Ground substance fills spaces and facilitates exchange of substances. This structural diversity allows connective tissues to perform functions such as support, protection, transport, and storage.

Q4. Explain the structure and functions of areolar and adipose tissue.

Ans:
Areolar tissue is a loose connective tissue composed of fibroblasts, collagen fibres, elastic fibres, and ground substance. It acts as a packing tissue, filling spaces between organs, supporting blood vessels and nerves, and aiding tissue repair. Adipose tissue contains adipocytes specialized for fat storage. It occurs beneath the skin and around internal organs. Adipose tissue acts as an energy reservoir, provides thermal insulation, and protects organs from mechanical shock. The loose arrangement of cells and fibres in both tissues allows flexibility and cushioning.

Q5. Differentiate between bone and cartilage based on structure and function.

Ans:
Bone is a rigid connective tissue with a hard matrix rich in calcium salts and collagen fibres. It provides support, protection to vital organs, attachment for muscles, and acts as a mineral reservoir. Bone contains living cells called osteocytes embedded in lacunae. Cartilage, in contrast, is a flexible connective tissue with a matrix called chondrin and cells called chondrocytes. It provides support with flexibility and reduces friction at joints. Cartilage lacks blood vessels, whereas bone is well vascularized.

Q6. Describe the three types of muscular tissue and their functions.

Ans:
Muscular tissue is specialized for contraction and movement. Skeletal muscles are long, cylindrical, multinucleated, and striated fibres attached to bones. They function voluntarily and enable locomotion and posture. Smooth muscles are spindle-shaped, non-striated, and involuntary, found in internal organs like the stomach and intestines, where they regulate movements such as peristalsis. Cardiac muscles are striated but involuntary, with branched fibres connected by intercalated discs. They form the heart muscle and ensure rhythmic contractions for blood circulation.

Q7. Explain the structure and functions of nervous tissue.

Ans:
Nervous tissue is specialized for receiving stimuli and transmitting nerve impulses. It consists of neurons and neuroglial cells. A neuron has a cell body, dendrites, and a long axon. Dendrites receive impulses, while the axon transmits them over long distances. Neuroglial cells provide support, nourishment, and protection to neurons. Nervous tissue forms the brain, spinal cord, and peripheral nerves. Its primary functions include coordination, control, and integration of body activities, enabling quick responses to internal and external stimuli.

Section B: Earthworm – Morphology and Anatomy (Questions 11–15)

Q11. Describe the external morphology of earthworm.

Ans:
Earthworm has a long, cylindrical, bilaterally symmetrical body divided into numerous segments, showing metamerism. The body surface is moist and covered with a thin cuticle. Each segment bears setae, which help in locomotion. A distinct thickened region called the clitellum is present in mature earthworms and is involved in reproduction. The anterior end bears the mouth, while the posterior end has the anus. The segmented body structure increases flexibility and efficiency of movement in soil.

Q12. Explain the digestive system of earthworm.

Ans:
The digestive system of earthworm is a straight tube extending from mouth to anus. It includes mouth, pharynx, oesophagus, gizzard, intestine, and anus. Food is ingested through the mouth and ground mechanically in the gizzard. Digestion occurs mainly in the intestine with the help of enzymes, and nutrients are absorbed through the intestinal wall. Undigested matter is eliminated through the anus. This system ensures efficient digestion of organic matter present in soil.

Q13. Describe the circulatory system of earthworm.

Ans:
Earthworm possesses a closed circulatory system in which blood flows through a network of blood vessels. It includes dorsal, ventral, and lateral vessels connected by capillaries. Blood contains haemoglobin dissolved in plasma, which transports oxygen. The dorsal vessel pumps blood anteriorly, while the ventral vessel distributes blood to different body parts. This system ensures efficient transport of nutrients, gases, and wastes throughout the body.

Q14. Explain respiration and excretion in earthworm.

Ans:
Earthworm respires through its moist skin by diffusion. Oxygen diffuses into blood capillaries, while carbon dioxide diffuses out. Excretion is carried out by nephridia, which remove nitrogenous wastes and excess salts from the body. Nephridia also help maintain osmotic balance. Thus, respiration and excretion are efficiently adapted to a soil-dwelling lifestyle.

Q15. Describe the nervous system of earthworm.

Ans:
The nervous system of earthworm consists of a nerve ring formed by a pair of cerebral ganglia and circumpharyngeal connectives. From the nerve ring arises a double ventral nerve cord with segmentally arranged ganglia. This system controls movement, feeding, and responses to stimuli. Segmental ganglia allow localized control of body segments, aiding coordinated movement.

Section C: Cockroach – Morphology and Anatomy (Questions 16–20)

Q16. Describe the external morphology of cockroach.

Ans:
Cockroach has a dorsoventrally flattened body divided into head, thorax, and abdomen. The body is covered by a hard chitinous exoskeleton that provides protection and prevents water loss. The head bears compound eyes and antennae for sensory functions. Thorax has three pairs of jointed legs and two pairs of wings. The segmented abdomen houses various internal organs. This structural organization supports terrestrial adaptation.

Q17. Explain the digestive system of cockroach.

Ans:
The digestive system of cockroach consists of foregut, midgut, and hindgut. The foregut includes mouth, pharynx, oesophagus, crop, and gizzard. The midgut contains gastric caeca that secrete digestive enzymes. The hindgut absorbs water and salts. This system enables efficient digestion and absorption of food.

Q18. Describe the respiratory system of cockroach.

Ans:
Cockroach respires through a tracheal system. Air enters the body through spiracles and is distributed directly to tissues via tracheae and tracheoles. This system allows oxygen to reach cells directly without involvement of blood, ensuring efficient respiration.

Q19. Explain the circulatory and excretory systems of cockroach.

Ans:
Cockroach has an open circulatory system with haemolymph flowing freely in the haemocoel. The heart pumps haemolymph, which transports nutrients and wastes. Excretion occurs through Malpighian tubules that remove nitrogenous wastes and help maintain osmotic balance.

Q20. Describe the nervous system of cockroach.

Ans:
The nervous system consists of a brain, circumoesophageal connectives, and a ventral nerve cord with segmental ganglia. It controls movement, sensory perception, and coordination of body activities.

Section D: Frog – Morphology and Anatomy (Questions 21–25)

Q21. Describe the external morphology of frog.

Ans:
Frog has a streamlined body divided into head and trunk. The skin is moist, glandular, and scaleless, aiding respiration. Hind limbs are long and muscular with webbed feet for swimming. The eyes have a nictitating membrane for protection. These features help frog adapt to both aquatic and terrestrial environments.

Q22. Explain the digestive system of frog.

Ans:
The digestive system includes mouth, oesophagus, stomach, intestine, and cloaca. Digestion begins in the stomach and is completed in the intestine. Nutrients are absorbed in the intestine, while undigested matter is eliminated through the cloaca.

Q23. Describe respiration in frog.

Ans:
Frog respires through skin, lungs, and buccopharyngeal cavity. Skin respiration is important in water, while lungs function on land. This dual mode supports amphibious life.

Q24. Explain the circulatory system of frog.

Ans:
Frog has a closed circulatory system with a three-chambered heart consisting of two atria and one ventricle. This arrangement allows partial separation of oxygenated and deoxygenated blood.

Q25. Describe the excretory system of frog.

Ans:
The excretory system consists of kidneys, ureters, urinary bladder, and cloaca. Kidneys filter blood and remove nitrogenous wastes, maintaining internal balance.