CBSE Class 11 Biology Short 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: Short Answer Type Questions

Answer Length: 60–80 Words

Syllabus Compliance: 100% NCERT

Exam Relevance: CBSE Class 11 Annual & School Examinations

Section A: Animal Tissues (Questions 1–20)

Epithelial Tissue

Q1. Describe the general characteristics of epithelial tissue.
Ans: Epithelial tissue consists of closely packed cells with minimal intercellular space, forming protective coverings and linings of organs. It rests on a basement membrane, lacks blood vessels, and shows high regenerative capacity. These features make epithelial tissue suitable for protection, absorption, secretion, diffusion, and filtration in various body organs.

Q2. Explain the structural features of simple squamous epithelium and its functions.
Ans: Simple squamous epithelium is composed of thin, flat cells arranged in a single layer. This structure allows rapid diffusion and filtration. It is found in alveoli, blood capillaries, and Bowman’s capsule, where exchange of gases and substances occurs efficiently due to minimal thickness.

Q3. Why is cuboidal epithelium well suited for secretion and absorption?
Ans: Cuboidal epithelium consists of cube-shaped cells with centrally placed nuclei and ample cytoplasm. These structural features provide sufficient cellular machinery for metabolic activities, making it ideal for secretion and absorption. It commonly lines kidney tubules and ducts of glands.

Q4. Describe the structure and function of columnar epithelium.
Ans: Columnar epithelium is made of tall, cylindrical cells arranged in a single layer. The cells often bear microvilli, increasing surface area. This tissue is mainly involved in absorption and secretion and is found lining the stomach and intestines.

Q5. What is the significance of ciliated epithelium?
Ans: Ciliated epithelium has hair-like projections called cilia on its free surface. These cilia beat rhythmically to move materials like mucus or ova. It is found in respiratory passages and oviducts, where it helps clear dust particles or transport eggs.

Connective Tissue

Q6. Explain the basic components of connective tissue.
Ans: Connective tissue consists of cells embedded in an extracellular matrix made up of fibres and ground substance. The matrix may be solid, semi-solid, or fluid. These components provide strength, flexibility, support, and binding functions to different organs and tissues.

Q7. Describe areolar tissue and state its functions.
Ans: Areolar tissue is a loose connective tissue containing fibroblasts, collagen fibres, and elastic fibres. It acts as a packing tissue, fills spaces between organs, supports blood vessels and nerves, and helps in tissue repair by providing structural support.

Q8. How does adipose tissue help in maintaining body functions?
Ans: Adipose tissue stores fat beneath the skin and around organs. It acts as an energy reserve, provides insulation to prevent heat loss, and cushions internal organs against mechanical shock, thus maintaining overall body homeostasis.

Q9. Differentiate between tendons and ligaments based on structure and function.
Ans: Tendons are dense connective tissues composed mainly of collagen fibres and connect muscles to bones, transmitting muscular force. Ligaments contain more elastic fibres and connect bones to bones, providing stability while allowing limited movement at joints.

Q10. Explain why bone is considered a rigid connective tissue.
Ans: Bone contains a hard matrix rich in calcium salts and collagen fibres. This mineralized structure provides rigidity, strength, and support, protects vital organs, and serves as a site for muscle attachment and mineral storage.

Muscular and Nervous Tissue

Q11. Describe the structure and function of skeletal muscle tissue.
Ans: Skeletal muscle tissue consists of long, cylindrical, multinucleated fibres with striations. It is attached to bones and works under voluntary control. Its structure allows rapid contraction and relaxation, enabling body movements and posture maintenance.

Q12. Explain the role of smooth muscles in the human body.
Ans: Smooth muscles are non-striated, spindle-shaped cells found in internal organs like the stomach and intestines. They function involuntarily, producing slow and sustained contractions that help in peristalsis and regulation of internal movements.

Q13. What makes cardiac muscle unique in structure and function?
Ans: Cardiac muscle is striated like skeletal muscle but functions involuntarily like smooth muscle. The cells are branched and interconnected by intercalated discs, allowing coordinated rhythmic contractions essential for continuous heart pumping.

Q14. Describe the structure of a neuron.
Ans: A neuron consists of a cell body containing the nucleus, short dendrites for receiving impulses, and a long axon for transmitting impulses. This structure enables efficient communication within the nervous system.

Q15. State the functions of nervous tissue.
Ans: Nervous tissue receives stimuli, conducts nerve impulses, and coordinates body activities. It plays a vital role in control, regulation, and integration of functions, ensuring proper responses to internal and external environments.

Section B: Earthworm – Morphology and Anatomy (Questions 21–30)

Q21. Describe the external morphology of earthworm.
Ans: Earthworm has a long, cylindrical, segmented body showing metamerism. The body surface bears setae for locomotion. A distinct clitellum is present, which plays a role in reproduction. The body is moist, aiding respiration.

Q22. Explain the digestive system of earthworm.
Ans: The digestive system includes mouth, pharynx, oesophagus, gizzard, intestine, and anus. The gizzard grinds food mechanically, while the intestine absorbs digested nutrients, ensuring efficient digestion and absorption.

Q23. Describe the circulatory system of earthworm.
Ans: Earthworm possesses a closed circulatory system with blood flowing through dorsal, ventral, and lateral vessels. Haemoglobin dissolved in plasma transports oxygen, ensuring efficient internal circulation.

Q24. How does respiration occur in earthworm?
Ans: Respiration occurs through the moist skin by diffusion. Oxygen dissolves in the moisture on skin and diffuses into blood capillaries, while carbon dioxide diffuses out.

Q25. Explain the excretory system of earthworm.
Ans: Nephridia are the excretory organs of earthworm. They remove nitrogenous wastes and help maintain osmotic balance, playing a vital role in excretion and regulation.

Section C: Cockroach – Morphology and Anatomy (Questions 31–40)

Q31. Describe the external features of cockroach.
Ans: Cockroach body is divided into head, thorax, and abdomen. It has a hard chitinous exoskeleton, jointed appendages, compound eyes, and antennae, providing protection and sensory functions.

Q32. Explain the digestive system of cockroach.
Ans: The digestive system includes foregut, midgut, and hindgut. Gastric caeca secrete digestive enzymes, increasing digestion efficiency, while the hindgut absorbs water.

Q33. Describe the respiratory system of cockroach.
Ans: Cockroach respires through a tracheal system. Spiracles open into tracheae, which deliver oxygen directly to tissues, eliminating the need for blood in gas transport.

Q34. Explain the circulatory system of cockroach.
Ans: Cockroach has an open circulatory system. Haemolymph flows freely in the haemocoel and does not transport oxygen, mainly distributing nutrients and wastes.

Q35. Describe the excretory system of cockroach.
Ans: Malpighian tubules remove nitrogenous wastes from haemolymph and discharge them into the hindgut, helping in excretion and osmoregulation.

Section D: Frog – Morphology and Anatomy (Questions 41–50)

Q41. Describe the external morphology of frog.
Ans: Frog has a streamlined body with moist, glandular skin. It lacks scales and has webbed hind limbs for swimming. The skin aids in respiration and protection.

Q42. Explain the digestive system of frog.
Ans: The digestive system consists of mouth, oesophagus, stomach, intestine, and cloaca. Digestion begins in the stomach and is completed in the intestine.

Q43. Describe the respiratory organs of frog.
Ans: Frog respires through skin, lungs, and buccopharyngeal cavity. Skin respiration is important in water, while lungs function mainly on land.

Q44. Explain the circulatory system of frog.
Ans: Frog has a closed circulatory system with a three-chambered heart. It ensures partial separation of oxygenated and deoxygenated blood.

Q45. Describe the excretory system of frog.
Ans: Kidneys filter blood and remove nitrogenous wastes. Urine is stored in the urinary bladder and released through the cloaca.