Important Questions Class 11 Biology Chapter 7

CBSE Class 11 Biology Chapter 7 Question Answers: Structural Organisation in Animals

Biology is a subject that all of us should study to better understand the world we live in, and it is a key subject for careers in the life sciences and healthcare domain. Chapter 7 of CBSE Class 11 Biology deals with further classification within the animal kingdom and is named as the ‘Structural Organisation in Animals’. 

While each organism of the animal kingdom is multicellular, they do not show the same pattern of cell organisation. Based on the patterns of cellular organisation, levels of organisation in animals are classified as “The Cellular Level of Organisation”, “Tissue Level of Organisation”, “Organ Level of Organisation”, and “Organ System Level of Organisation”. This chapter describes animal structural organisation, and we will try to get a glimpse of a few of the Important Questions Class 11 Biology Chapter 7 in this article.

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Important Questions Class 11 Biology Chapter 7 Structural Organisation in Animals with Solutions

Solving important questions from our question bank of Important Questions Class 11 Biology Chapter 7 helps students in increasing knowledge by revising the key concepts of this topic. Our faculty experts at Extramarks understand this crucial method of imparting education which covers the entire chapter. Therefore, we focus on developing content that includes all the necessary questions and solutions for the topics studied in the chapter. The Class 11 Biology Chapter 7 Important Questions covers the concepts of the chapter “Structural Organisation in Animals”.

Given below are some of the questions and answers from our Important Questions Class 11 Biology Chapter 7.

Q1. What is the utility of the transitional epithelium constituting the surface layer of the urinary bladder?

Answer 1- 

Transitional epithelium is highly stretchable and does not allow the urinary bladder to break off when the urinary bladder is filled with urine. It undergoes considerable expansion, which accommodates the maximum quantity of urine.

Q2. Classify the muscular tissue into three different types.

Answer 2-

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.

Q3. What is the major function of haemoglobin? Explain briefly.

Answer 3 

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.

Q4. What are the main characteristics of epithelial tissue?

Answer 4- 

It classifies closely packed cells of various types and shapes, forming several organs’ inner lining membranes.

The cells of the epithelial membrane are formed in one or many layers that rest upon the thin non-cellular basement membrane. These cells are supported by intercellular substances and close vascular connective tissues.

The basement membrane is made of protein fibres which are interspersed in the matrix of the polysaccharide. The connective tissues secrete the matrix.

The cementing substance between these cells is formed of mucoprotein containing hyaluronic and calcium salts.

Q5. What is an oligodendrocyte? What are their main functions? 

Answer 5- 

Oligodendrocytes are classified as a type of neuroglial cells that helps to hold the neurons in position concerning the central nervous system. Their cells spiral around the nerve fibres to form a myelin sheath in the absence of Schwann cells in the central nervous system.

Q6. Why does oedema disease occur in persons suffering from a dietary deficiency of proteins? Explain  briefly.

Answer 6 – 

Albumin and globulin are proteins necessary for retaining water in the blood plasma by their osmotic effects. In the dietary deficiency of proteins, insufficient water is retained in the blood plasma; thus, it gets filtered out from the blood into the tissue. This can lead to swelling of the hands and feet.

Q7. Name the tissue that forms the outermost exposed surface of the skin. Also, state any two advantages of this tissue being there.

Answer 7:

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.

Q8. Explain in brief about erythropoiesis.

Answer 8 –

The formation of new erythrocyte cells is called erythropoiesis and occurs in the hematopoietic tissue. The hematopoietic tissue in the young foetus is the liver and spleen, whereas, in adults, it is the bone marrow of the long bones.

The hematopoietic tissue synthesis of millions of RBCs every minute. The RBC replaces the worn-out erythrocytes promoted by erythropoietin, a glycoprotein produced by the renal tissue in response to the liberation of ACTH. However, iron deficiency, folic acid and vitamin B lead to anaemia and megaloblastic anaemia.

Q9.  How is blood prevented from clotting in blood banks?

Answer 9-

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 10. How does saltatory conduction take place across a nerve fibre?

Answer 10-

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.

Q11. Describe in brief the blood-vascular system of the Cockroach.

Answer 11-

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.

Q12. Setae are not uniformly present in all the segments but help locomotion in earthworms. They are present in

1. 1st segment
2. Last segment
3. Clitellar segment
4. 20th – 22nd segment

Answer – Option (b) is the answer.

Explanation- The segment that helps in locomotion is the last segment.

Q13. Which one of the following statements listed below is correct for cockroaches?

An a. The number of ovarioles present in each ovary is ten.

1. The larval stage is called caterpillar
2. Anal styles are absent in female
3. They are ureotelic

Answer- Option (d) is the answer.

Explanation – cockroaches are ureotelic in nature as they secrete their waste from uric acid.

Q14. The following parts form the digestive system of a frog. Arrange them in an ascending order beginning from the mouth to the aperture. Mouth, stomach, intestine, cloaca, oesophagus, buccal cavity, rectum, and cloacal aperture

Solution 14:

The digestive system of a frog starts from the mouth, buccal cavity, oesophagus, stomach, intestine, rectum, cloaca and cloacal aperture in order.

Q15. What is the major difference between cutaneous and pulmonary respiration in the lungs?

Answer 15-

Cutaneous respiration refers to the interaction of gases through the  surface of the skin or by diffusion through the skin, while pulmonary respiration refers to the exchange of gases through the lungs.

Q16. Mention special features of an eye in cockroaches.

Answer 16- 

1. They have compound eyes for better night vision with numerous small visual units. 
2. The visual unit in their eye is known as  ommatidia
3. Their eyes have higher sensitivity but a lower reAnswer.

Q17. Explain the digestive system of cockroaches. 

Answer 17:

 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

1. 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.

Q18. Correct the wrong statements among the following:

1. In earthworms, a single male genital pore is present.
2. Setae help in the locomotion of earthworms.
3. Muscular layer in the body wall of an earthworm is made up of only circular muscles.
4. Typhlosole is the part of the intestine of earthworm.

Answer:

1. Wrong statement.

In earthworms, there is a pair of male genital pores.

1. Correct statement
2. Wrong statement

The muscular layer in the body wall of the earthworm is not only made up of circular muscles but also longitudinal muscles.

1. Correct statement.

Q19. Describe the three major types of cell junctions.

Answer 19-

1. Tight junctions: Plasma membranes of adjacent cells are fused at intervals. They help to stop substances from crossing or leaking across a tissue.
2. Adhering junctions: Perform cementing function to keep neighbouring cells together.
3. Gap junction: They facilitate the cells’ communication by connecting the cytoplasm of adjacent cells for rapid transfer of ions, small molecules, and sometimes big molecules.

Q20. What are Specialised Connective Tissues? Explain them in brief.

Answer 20-

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.

1. Cartilage: chondrocytes and collagen fibres; intercellular material is solid and resists compression. 
2. 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.
3. Blood: Fluid connective tissue consists of plasma and blood cells.

Q21. What is dense connective tissue? Explain briefly. 

Answer 21 –

Dense connective tissue includes fibres and fibroblasts, which are compactly packed.

1. Dense Regular: Collagen fibres present in rows. Tendons attach skeletal muscle to bone. Ligaments attach bone to bone.
2. Dense Irregular: Has collagen fibres and fibroblasts oriented differently. This tissue is present in the skin.

Q22. Which of the following types of cells listed below is involved in forming the inner walls of large blood vessels?

(a) Cells of cuboidal epithelium

(b) Cells of Columnar epithelium

(c) Cells of Squamous epithelium

(d) Cells of Stratified epithelium

Ans: option (c) is the right answer.

Explanation – The squamous epithelium, also known as pavement epithelium, comprises a single thin layer of flattened cells. These squamous cells are found in the walls of blood vessels and air sacs of the lungs and are involved in forming a diffusion boundary.

Q23. Why are blood, bone and cartilage classified under connective tissue?

Answer 23– 

Blood, bone, and cartilage are classified under connective tissue because of their special function of linking and supporting other tissues and organs of the body.

Q24. Why are neurons called excitable cells? Mention the special features of the neuron membrane.

Answer 24- 

Neurons are called excitable cells because they generate an electrical disturbance whenever a neuron is stimulated, swiftly travelling along its plasma membrane. The arrival of the disturbance at the neuron’s endings, or output zone, triggers events that may cause stimulation or inhibition of adjacent neurons and other cells.

Q25. Why is the earthworm called the friend of the farmer?

Answer 25- 

Earthworms are also known as ‘friends of farmers’ because they burrow in the soil and make it porous, which helps in the respiration and penetration of the developing plant roots. The process of increasing the fertility of the soil by the earthworms is called vermicomposting.

Q26. How do you distinguish between the dorsal and ventral surfaces of an earthworm’s body?

Answer 26- 

 The dorsal surface of the earthworm’s body is marked by a dark median mid-dorsal line known as a dorsal blood vessel along with the longitudinal axis of the body. At the same time, the ventral surface is distinguished by the presence of genital openings (pores).

Q27. Classify and describe in detail epithelial tissue based on structural modifications of cells.

Answer 27- 

There are two major types of epithelial tissues: simple epithelium tissue and compound epithelium tissue. Simple epithelium tissue is made of a single layer of cells. The simple epithelium tissue is a lining for body cavities, ducts, and tubes in the human body. On the other hand, the compound epithelium consists of two or more cell layers and functions as a protective layer on our skin. 

Based on the structural modification of the cells, simple epithelium tissue is further divided into three major types. These are (i) Squamous Epithelium, (ii) Cuboidal Epithelium and (iii) Columnar Epithelium.

• The squamous epithelium tissue comprises a single thin layer of flattened cells containing irregular boundaries. These cells are found in the walls covering blood vessels and air sacs of the lungs; these cells are also involved in functions like forming a diffusion boundary. The cuboidal epithelium is commonly composed of a single layer of cube-shaped cells. This is majorly found in ducts of glands and tubular parts of nephrons in kidneys, and its main functions are secretion and absorption. The epithelium of the proximal convoluted tubule, known as PCT of the nephron in the kidney, has microvilli. 
• The Columnar epithelium comprises a single layer of tall and slender cells. Their nuclei are located at the base. The free surface may have microvilli. They are found in the stomach and intestine lining and help in secretion and absorption.
• Cuboidal epithelium cells are cube-like in appearance, denoting they have equal width, height, and depth. Cuboidal epithelium is formed of more than one layer, called multi-layered, and thus has a limited role in secretion and absorption. Their main function is to protect against chemical and mechanical stresses. They cover the whole dry surface of the skin, the moist surface of the buccal cavity, the pharynx, the inner lining of ducts of salivary glands and pancreatic ducts.

Q28. Explain the gametic exchange in earthworms during mating.

Answer 28- 

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.

Q29. Write down the most common features of connective tissue.  On the basis of function and structure, differentiate between cartilage and bones.

Answer 29- 

Connective tissues are the most abundant and widely distributed tissue in the bodies of complex animals and humans. They are called connective tissues because they link and support other tissues and organs of the body. Connective tissue ranges from soft connective tissues to specialised types, including cartilage, bone, adipose, and blood.

 In all connective tissues except red blood cells, the cells secrete fibres of structural proteins called collagen or elastin. These fibres are responsible for the tissue’s strength, elasticity, and flexibility. These cells also secrete modified polysaccharides, which aggregate between cells and fibres and act as a matrix known as the ground substance.

• The intercellular material of cartilage is solid, pliable and resists compression. Cells of this tissue are called chondrocyte cells. These cells are enclosed in small cavities within the matrix secreted by them. Most of the cartilage present in vertebrate embryos is replaced by bones in adults. Cartilage is present at the tip of the nose, on outer ear joints called the pinna, and between the adjacent bones of the vertebral column, limbs, and hands in adults.
• While bones have a hard and non-pliable ground substance rich in calcium salts and collagen fibres that strengthen the bone. The main tissue provides a structural frame for the human body. Bones support, surround and protect softer tissues and organs. The bone cells called osteocytes are present in the spaces called lacunae. 

Limb bones consist of the long bones of the legs that serve weight-bearing functions. They also work with skeletal muscles attached to them to help in movements. The bone marrow in some bones is the primary site of the production of blood cells.

Q.30 

(a) Give the common name of Periplaneta Americana.

(b) How many spermathecae are found in cockroaches?

(c) What is the position of the ovaries present in cockroaches? 

(d) How many segments are found in the abdomen of a cockroach? 

(e) Where do you find Malpighian tubules? 

(f) What is the mosaic vision? 

Answer 30

 (a) American Cockroach. 

(b) One pair, is present in the 6th segment. 

(c) Between the 2nd and 6th abdominal terga.

 (d) Ten segments. 

(e) At the junction of midgut and hindgut in arthropods.

 (f) Mosaic vision is where a compound eye forms several images of an object arc. Mosaic vision helps detect the movement of objects very efficiently.

Q31. Describe the use of voluntary muscles.

Answer 31 –

 A voluntary muscle is classified as a bundle of numerous striated muscle fibres. Each fibre is long and unbranched, measuring around 40 mm in length & 20mm in thickness. Each fibre is found under a sarcolemma membrane, and its cytoplasm is called sarcoplasm. 

The sarcoplasm contains numerous long, thin, unbranched, and cross-striated myofibrils. Each myofibril consists of an alternating thick A band and a light I-band. The thick A band is formed from the protein myosin, and the thin I-band is formed from actin protein. 

The thick filament bands lie parallel to each other while the thin filament extends between them up to a considerable distance in an orderly manner. A fine, dense, dark Z-line is at the I-band’s centre. Each segment of the myofibril from one Z-band to the next functions as a contractile unit & is called a sarcomere. 

Q32.How does blood get coagulated when it’s coming out from an injured vessel? How coagulation normally prevents uninjured vessels. 

Answer 32. When a blood vessel is injured, blood comes out of it, and the thrombocytes clump together, break, and then release the coagulation-promoting substances called thromboplastin. This thromboplastin substance helps in the formation of the enzyme thrombokinase. The enzyme thrombokinase then hydrolyses prothrombin in the plasma into thrombin, and calcium ions are needed for both the activation and functioning of thrombin. Thrombin then catalyses the hydrolysis of soluble fibrinogen in the plasma into insoluble fibrin. This fibrin precipitates as a network of fibres and traps many blood cells to form a red solid mass called a blood clot. This blood clot seals the wound in the blood vessel to stop the bleeding. However, in uninjured tissues & blood vessels, thromboplastin is not released. That’s why coagulation does not take place in an uninjured vessel.

Q 33. Explain the cellular components of blood.

Answer 33. Erythrocytes (RBCs), leucocytes (WBCs), and thrombocytes (platelets) are the key cellular components of blood and constitute 45% of the blood. The remaining 55% of the fluid is called plasma.

In mammals, the erythrocytes are the biconcave-coloured cells, devoid of the nucleus, and thus, this creates space for carrying and transporting respiratory gases.

The leukocytes, also known as white blood cells, are nucleated cells. These are primarily divided into granulocytes (neutrophils, eosinophils, and basophils) and agranulocytes (lymphocytes and monocytes). Leukocytes mainly help destroy foreign particles, as they possess a phagocytic nature.

The megakaryocytes of the bone produce thrombocytes, the cell fragments, and help in clotting the blood.

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