CBSE Class 10 Science Important Questions Chapter 6 Life Processes Part 3 (For CBSE, ICSE, IAS, NET, NRA 2022)

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3 Marks Questions

1. What are the functions of lymph in our body?

Ans. Functions of lymph are-

a) It returns tissue fluid from interstitial space into the blood.

b) It collects carbon dioxide, waste products and metabolites from tissues via tissue fluid.

c) Lymph has lymphocytes (WBC՚s) , the lymph provides in immunity to the body and fight against the invading organisms.

2. How is haemoglobin associated with respiration explained?

Ans. Transportation of oxygen and carbon – dioxide occurs with the help of respiratory pigment haemoglobin. Haemoglobin is a red pigment having very high affinity for oxygen. Oxygen is transported from the lungs to the body cells in the form of oxyhemoglobin. Carbon – dioxide is transported from the body cells to the lungs in the form of carbamino – haemoglobin

3. What are the modes of excretion in plants?

Ans. Modes of excretion in plants are –

a) The plants get rid of excess water by transpiration.

b) The only major gases excretory product of plants in oxygen. It is released from plants into the environment by diffusion.

c) Organic wastes of plants are stored within dead permanent tissues such as wood or within leaves or bark which are periodically removed.

d) The plants also excrete some wastes substances into the soil around them.

e) Many wastes products of plants are stored in cellular vacuoles.

4. Give an experiment to prove the essentiality of light for photosynthesis

Ans. a) destarched the plant by leaving it in dart for 48 – 72 hours.

b) Now place strips of black paper or metal foil over destarched leaves and expose them to light for several hours.

5. What is β€œtranslocation” ? Why it is essential for plants.

Ans. Transportation of organic solutes in the plants is called translocation. It is necessary, because all the cells need food to carry out their vital functions. It occurs in upward as well as downward direction or to the storage organs of roots, fruits, seeds and to growing organs.

6. How respiration does takes place in plants?

Ans. There are three modes for the exchange of gases in plants –

a) Some small plants can carry out gaseous exchange by simple diffusion over their whole surfaces.

b) Large flowering plants exchange gases through stomata on their leaves and green stem.

c) In woody stems, exchange occurs through cracks in the bark or lenticels.

7. How is transpiration pull responsible for upward movement of water?

Ans. The leaves loose water in the form of water vapours through stomata by a process known as transpiration. Continuous transpiration creates as suction in the water column of the xylem elements and it reaches up to the roots. This pull is called transpiration pull. Due to transpiration, the water column of the plant is pulled up from below to the top of the plant.

8. Discuss the major steps involved in process of nutrition in human beings.

Ans. Major Steps involved in human nutrition are –

a) Ingestion – Intake of food through mouth. Humans have holozoic mode of nutrition. They engulf solid particles.

b) Digestion – The break down complex food material into simpler one in alimentary canal with the help of mechanical as well as chemical process.

c) Absorption – Digested food is absorbed by the small finger like projections, villi present in the small intestine.

d) Assimilation – Absorbed food reaches to all cells via blood, and utilized for energy, growth and development.

e) Excretion – Undigested food from small intestine passed into large intestine, and then it is thrown out by Anus.

9. Discuss the mode of nutrition in amoeba.

Ans. Steps of Nutrition in amoeba –

a) Formation of pseudopodia – When Amoeba comes in contact with a food particle, it forms pseudopodia which envelops food particles.

b) Ingestion – The tips of pseudopodia fuse with each other, together with variable amount of food particles and water, forms food vacuole, this process is known as ingestion.

c) Digestion – The vacuoles are surrounded by lysosomes which fuses with vacuole and digest the food particles present in vacuole.

d) Exocytosis – The soluble products of digestion are passed out into due cytoplasm from the food vacuole. And the remaining undigested materials are passed out of the body with the help of a process called exocytosis.

10. With the help of labelled diagram, discuss the structure of cross – section of leaf.

Ans. Leaf has two parts:

(i) Epidermis – Outermost layer of cell is called epidermis. Lower epidermis has small pores in between cells called stomata.

(ii) Mesophyll – Parenchymatons cells containing chloroplast is called mesophyll. It is two types – palisade and spongy parenchyma.

11. What do you mean by β€˜lymph’ ? Mention its function.

Ans. Lymph- The fluid present in the spaces between the cells in the tissues is called tissue fluid or lymph.

Functions of lymph:

(i) It returns tissue fluid from the interstitial spaces into the blood.

(ii) Lymph capillaries of intestinal villi called lacteals helps in absorption of fats.

(iii) It collects carbon dioxide, waste products and metabolites form tissues via tissue fluid.

12. How are lungs designed in human beings to maximize the area of exchange of gases?

Ans. Lungs have some adaptations in them so that efficient exchanges of gases take place. The adaptations are –

a) Increased surface area

b) Very fine and delicate surface for easy exchange of oxygen and carbon dioxide

c) Mechanism for moving the air in and out of respiratory surface where the oxygen is absorbed.

Lungs Designed in Human Beings

13. Dark reaction of photosynthesis does not need light. Do plants undergo dark reaction at night explain.

Ans. Dark reaction does not mean that it occurs in the absence of light i.e.. , at night. Infact these reactions do not depend on light energy and occur simultaneously with light reaction.

14. Differentiate inhalation and exhalation.


Inhalation and Exhalation
It is taking in of air from the atmosphereIt is expelling out of air from the lungs.
Diaphragm contract & flattens.Diaphragm relaxes and becomes dome shaped.
Ribs movement is forward & outward.Ribs movement is downward & inward
Volume of thoracic cavity increasesVolume of thoracic cavity decreases
Pressure of thoracic cavity decreasesPressure of thoracic cavity increases

15. With the help of diagram, show pulmonary circulation in man.

Ans. Diagram – Pulmonary circulation in man.

Pulmonary Circulation in Man

16. What are the functions of human respiratory system?

Ans. (i) Gaseous exchange for the cellular respiratory process.

(ii) Sound production by vocal cords

(iii) Abdominal compression which helps in urination, passing of faces and childbirth.

(iv) Laughing and sneezing for self-cleaning the respiratory surface.

17. What is role of skin, lungs and intestine in the process of excretion in man?

Ans. Skin – Skin excrete excess salts and water in the form of sweat.

Lungs – Lungs expel carbon – dioxide during exhalation.

Intestine – Intestine throw out undigested food in the form of faeces through anus

18. Explain the structure of chloroplast.

Ans. Fig – structure of chloroplast.

Structure of Chloroplast

19. Why and how does water enter continuously into the root xylem of plants?

Ans. Xylem transports water and minerals to the plant body. The roots of a plant have hair called root hairs. The root hairs are directly in contact with the film of water in between the soil particles. Water and minerals get into the root hair by the process of diffusion. The water and minerals absorbed by the root hair form the soil pass from cell to cell by osmosis through the epidermis root cortex, endodermis and reaches the root xylem. The xylem vessels of the root the plant are connected to the xylem vessels into stem.

Therefore, the water containing dissolved minerals enter the root xylem vessels into stem xylem vessels. The xylem vessels of the stem branch into the leaves of the plants. So the water & minerals carried by the xylem vessels in the stem reach the leaves through the branched xylem vessels which enter from the petiole into the each part of the leaf. Thus the water and minerals form the soil reach through the root and stem to the leaves of the plants.

Evaporation of water molecules from the cells of a leaf creates a suction which pulls water from the xylem cells of roots. The loss of water in the form of vapour from the aerial parts of the plants is known as transpiration.

20. What is the role of following in human digestive system –

a) Mucous

b) Bicarbonate

c) Trypsin

Ans. a) Mucus – It protects the inner living of stomach from HCl.

b) Bricarbonate – It makes the acidic food alkaline so that pancreatic enzymes act on it.

c) Trypsin – It digest proteins into amino acids.

21. What are outside raw materials used for by an organism?

Ans. Outside raw materials used for by an organism includes:

a. Food

b. Water

c. Oxygen

22. What processes would you consider essential for maintaining life?

Ans. The processes essential for maintaining life are

a. Nutrition

b. Respiration

c. Transportation

d. Excretion

23. What are difference between autotrophic and heterotrophic nutrition?

Ans. Distinction between autotrophic and heterotrophic nutrition:

Autotrophic and Heterotrophic
Autotrophic NutritionHeterotrophic Nutrition
The mode of nutrition in which an organism makes its own food the simple inorganic materials like carbon dioxide and water present in the surroundings with the help of sunlight energy. All green plants.The mode of nutrition in which an organism cannot makes its own food the simple inorganic materials like carbon dioxide and water present in the surroundings and depends on other organism for food. All non-green plants.