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Short & Long Question Answers with Solution: Structural Organisation in Animals | Biology Class 11 - NEET PDF Download

Q1. Give a brief account of the circulatory system of earthworm.
Ans: The earthworm possesses a closed circulatory system, comprising capillaries, blood vessels, and a heart. In this closed system, the blood remains contained within the heart and vessels. Smaller blood vessels distribute blood to the gut, body wall, and nerve cord. Interestingly, the 4th, 5th, and 6th segments of the earthworm house not only blood but also glands responsible for producing blood cells and dissolvable hemoglobin that mixes with the plasma.

Q2. Name the tissue that forms the outermost exposed surface of the skin. Also, state any two advantages of this tissue being there.
Keratinized squamous epithelium is the tissue that forms the outermost exposed surface of the skin. It contains an insoluble protein known as keratin, which is impervious to water and prevents water loss. It also provides physical protection to the skin against mechanical injury, pressure, friction and water loss.

Q3. State the functions and types of nephridia in an earthworm.

  • It controls the content and quantity of bodily fluids.
  • Initially, it assumes the shape of a funnel to gather surplus fluid from the coelomic chamber.
  • This structure links with the tubular sections of the nephridium, facilitating waste elimination through an external pore.

Types of Nephridia:

  • Septal nephridia
  • Pharyngeal nephridia
  • Integumentary nephridia

Q4. What are the different cell junctions found in tissues?
Ans: Tissues exhibit various cell junctions, including:

  • Tight Junctions - These hold the plasma membranes of adjacent epithelial cells in close proximity.
  • Gap Junctions - They enable the exchange of molecules between neighboring cells.
  • Adhering Junctions - These aid in the connection of adjacent cells to one another.

Q5.  How is blood prevented from clotting in blood banks?
In the blood banks, there are various anticoagulants. Sodium oxalate, sodium citrate and EDTA, known as Ethylene diamine tetraacetic acid, are used which prevent the coagulation of blood by the removal of the calcium ions. Acid citrate dextrose is the most commonly used anticoagulant to store blood in the blood banks

Blood clotting can also be prevented by removing free calcium ions from the whole blood component, as this metallic ion is an important requirement in the coagulation mechanism process.

Q.6. Mention the functions of each of the following:

  • Ureters in frog
  • Malpighian tubules
  • Body wall in the earthworm


Ureters in Frogs

  • Ureters in frogs serve a multifunctional role.
  • They transport sperms, excretory waste, and ova to the cloaca.

Malpighian Tubules

  • Malpighian tubules, composed of glandular cells, are responsible for excretion.
  • These glandular cells absorb excretory substances and convert them into uric acid.
  • The resulting uric acid is then eliminated through the hindgut.

Body Wall in Earthworms

  • The earthworm's body wall comprises three key cell types: basal cells, receptor cells, and gland cells.
  • It offers structural support.
  • Gland cells secrete mucus, ensuring the skin remains moist.
  • Muscles embedded in the body wall provide strength and rigidity to the organism.

Q 7. How does saltatory conduction take place across a nerve fibre?
The conduction of impulse along with a myelinated nerve fibre is called saltatory conduction. This occurs because of the ionic changes and consequent depolarization that occur only at the Ranvier nodes, which are free from myelin sheath leading to the jumping of action.

Q8. Where are the following found in the animal body?

  • Chondrocytes
  • Axons
  • Ciliated epithelium


  • Chondrocytes: These specialized cells reside within the cartilage of connective tissue, where they actively produce and release the extracellular matrix.
  • Axons: Axons are elongated fibers with an extensive distal end, featuring a bulbous structure known as a synaptic knob. They function in transmitting nerve impulses away from nerve cells.
  • Ciliated Epithelium: This epithelial tissue is equipped with cilia, which play a crucial role in propelling particles or fluids across the epithelial surface. It is notably found in structures like the trachea, nasal cavities, and bronchial tubes.Q.16. What is connective tissue?

Q9. Classify the muscular tissue into three different types.
Ans:  Muscular tissues can be divided into three broad categories depending on their cytologic characteristics.
These are striated muscles, non-striated muscles, and smooth muscles.
Striated muscle cells are also classified as voluntary muscles, while the non-striated or unstriped plain or smooth are classified as involuntary muscle fibres.
Cardiac – are striated and involuntary muscle fibres.

Q.10. What is connective tissue?
The group of tissues composed of an extracellular matrix is collectively called the connective tissues. Blood, bones, tendon, adipose, ligaments and areolar tissues are examples of connective tissues. There are three different types of connective tissue:

  • Fluid Connective Tissue.
  • Fibrous Connective Tissue.
  • Skeletal Connective Tissue.

Q11. What is the major function of haemoglobin? Explain briefly.
Ans:  The functions of haemoglobin are as follows- 

Haeme means iron, and globin is the molecule that is essential for oxygen carriers. It carries dissolved oxygen from the lungs to the tissue in the form of an element called oxyhaemoglobin.  Each molecule of haemoglobin contains about 1.33 ml of oxygenated oxygen.

Haemoglobin plays an important part in transporting CO2 as Carbaminohemoglobin from tissue to the lungs. About 23 percent of Carbon dioxide is transported back to the lungs through the haemoglobin.

It also acts as a buffer and regulates blood reactions by maintaining a constant pH.

Q12. Describe in brief the blood-vascular system of the Cockroach.
Ans:  The Cockroach has an open circulatory system where its blood is colourless and contains plasma with colourless cells, the leukocytes. The blood does not contain haemoglobin and, thus, plays no major role in respiration.

A cockroach’s heart is thirteen-chambered, long, narrow, muscular, and tube-like. The three heart chambers lie in the thorax, whereas ten are in the abdomen. The posterior end of the heart is closed, while the anterior end is continued forwards and emerges as the anterior aorta. The anterior aorta opens into a haemocoel in the head.

There is a small hole called the Ostia at the posterior side of each chamber. Ostia is guided by valves that allow blood flow only in one direction, from the haemocoel to the heart’s inner chamber.

All visceral organs present in cockroaches are bathed in blood. It consists of a colourless liquid part known as plasma containing many corpuscles called haemocytes.

Q13. Explain the digestive system of cockroaches. 
Ans: A Cockroach’s alimentary canal comprises three major parts – foregut, midgut, and hind-gut.

(A) Foregut: The foregut consists of the mouth of cockroaches. It contains the oesophagus, a narrow tube-like structure that leads to an organ known as a crop. The crop stores the food materials. It consists of the tongue and hypopharynx

(B) Midgut: The midgut is a narrow and short tube-like structure. It has an organ known as a gizzard that grinds the food into simpler components.

(C) Hindgut: The hindgut contains three main parts: Ileum, Colon, and Rectum, which help eliminate the process. Malpighian tubules help eliminate nitrogenous wastes as they convert the waste to uric acid.
The last part of the digestive system consists of Anus.

Q14. What are Specialised Connective Tissues? Explain them in brief.
Ans:  Specialised connective tissues include tendons and ligaments, Bone and Cartilage, haemopoietic tissue, blood, and adipose tissues. Bone contains Osteocytes, and osteoblasts (osteo – bone) which secrete the type of extracellular matrix material (ECM) that makes up bone.

  • Cartilage: chondrocytes and collagen fibres; intercellular material is solid and resists compression. 
  • Bones: Ground substance is rich in calcium salts and collagen fibres. Osteocytes are present in lacunae. Bones support and protect the softer tissues and organs. They interact with skeletal muscles to bring about movements. Bone marrow in some bones is the major site of blood cell formation.
  • Blood: Fluid connective tissue consists of plasma and blood cells.

Q15. Explain the gametic exchange in earthworms during mating.
A mutual exchange of sperm occurs between two earthworms during mating season. One worm has to find another worm, and they mate, juxtaposing opposite gonadal openings through which packets of sperms called spermatophores are exchanged. Mature sperm fused with egg cells and nutritive fluid are deposited together in the cocoons produced by the gland cells of the clitellum. Fertilisation  and development occur simultaneously within the cocoons deposited in the soil. The ova or eggs are fertilised by the sperm cells within the cocoon. These eggs then slip off the worm and are deposited in or on the soil. The cocoon holds together the worm embryos. And then three weeks later, each cocoon produces two to twenty baby worms. The development of earthworms is direct, which means no larva is formed.

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