Class 10 science ch 1 life Processes
Q. 1. Name the following :
(a) The process in plants that links light energy with chemical energy.
(b) Organisms that can prepare their food.
(c) The cell organelle where photosynthesis occurs.
(d) Cells that surround a stomatal pore.
(e) Organisms that cannot prepare their food.
(f) An enzyme secreted from gastric glands in the stomach that acts on proteins.
Answers:-
(a) Photosynthesis ;
(b) Autotrophs ;
(c) Chloroplast ;
(d) Guard cells ;
(e) Heterotrophs ;
(f) Pepsin.
Q. 2. “All plants give out oxygen during the day and carbon dioxide during night.” Do you agree with this statement? Give reason.
Answer: Plants undertake both photosynthesis and respiration during the day and as the rate of photosynthesis is faster than respiration so oxygen is evolved during the daytime. During the night, plants undertake only respiration but no photosynthesis so carbon dioxide is evolved during the night.
Q. 3. How do the guard cells regulate the opening and closing of stomatal pores?
Answer: Opening and closing of stomatal pores depend upon the guard cells’ turgor pressure, which depends upon the amount of water in the guard cells. Endosmosis increases the turgor pressure in the guard cells which opens the stomatal pore, while exosmosis decreases the turgor pressure in the guard cells which closes the stomatal pore.
Q. 4. Two green plants are kept separately in oxygen-free containers, one in the dark and the other in continuous light. Which one will live longer? Give reasons.
Answer: A plant kept in continuous light will live longer as it will be capable of photosynthesis in which oxygen will be produced for its respiration and energy production for its metabolic functions.
Q. 5. If a plant releases carbon dioxide and takes in oxygen during the day, does it mean that there is no photosynthesis occurring? Justify your answer.
Answer: It indicates either there is no photosynthesis or the rate of photosynthesis is very low than that of respiration. The carbon dioxide produced in respiration is not completely consumed in photosynthesis so CO2 is released.
Q. 6. Why do fishes die when taking out of water?
Answer: Fishes show branchial respiration in which oxygen is derived from water. The fishes cannot use gaseous oxygen so they die when taking out of water.
Q. 7. Differentiate between an autotroph and a heterotroph.
Answer: See table 1 of the chapter.
Q. 8. Is ‘nutrition’ a necessity for an organism? Discuss. (CBSE Sample papers-I: 2 marks)
Answer: Nutrition is essential because the food helps in:
- Providing raw materials for the growth and repair of body tissues.
- Providing energy for various metabolic functions.
- Provides resistance against various diseases.
Q. 9. What would happen if green plants disappear from the earth?
Answer: Green plants are autotrophic in nutrition. All the animals derive their nutrition directly or indirectly from the green plants. So the absence of green plants will cause the death of herbivores as well as carnivores.
Class 10 science ch 1 life Processes
Q. 10. Leaves of a healthy potted plant were coated with vaseline. Will this plant remain healthy for long? Give reasons for your answer.
Answer: This plant will not remain healthy for a long time because:
- it will not get oxygen for respiration.
- it will not get carbon dioxide for photosynthesis.
- Upward movement of water and minerals would be hampered due to lack of transpiration.
Q. 11. How does aerobic respiration differ from anaerobic respiration?
Answer: See table 9 of the chapter.
Q. 12. Match the words of column (A) with that of column (B):-
| Column A | Column B |
| (a) Phloem | (1.) Excretion |
| (b) Nephron | (2.) Translocation of food |
| (c) Veins | (3.) Clotting of blood |
| (d) Platelets | (4.) Deoxygenated blood |
Answer: (a) (2.)
(b) (1.)
(c) (4.)
(d) (3.)
Q. 14. What are the adaptions of leaves for photosynthesis?
Answer: 1. Leaves provide a large surface area for maximum light absorption.
2. Leaves are arranged at right angles to the light source in a way that causes overlapping.
3. The extensive network of veins enables quick transport of substances to and from the mesophyll cells.
4. Presence of numerous stomata for gaseous exchange.
5. The chloroplasts are more in number on the upper surface of leaves.
Class 10 science ch 1 life Processes
Q. 15. Why is the small intestine in herbivores longer than in carnivores?
Answer: Small intestine is longer in herbivores like rabbits, cows, etc. than in the carnivores like lions, tigers, etc. because cellulose takes a longer period to be digested completely.
Q. 16. What will happen if the mucus is not secreted by the gastric glands?
Answer: Mucus is secreted by the goblet cells of the gastric glands. Mucus forms a protective lining on the inner surface of the stomach and protects it forms the action of hydrochloric acid and enzyme pepsin on it. The absence of mucus will lead to acidity and peptic ulcers.
Q. 17. What is the significance of emulsification of fats?
Answer: Emulsification involves breaking down large-sized fat droplets in the presence of the salts. This increases the efficiency of the lipolytic lipase enzyme on fat.
Q. 18. What causes the movement of food inside the alimentary canal?
Answer: The smooth muscles present in the wall of the alimentary canal undergo involuntary contraction and relaxation called peristalsis, which move the food downward inside the alimentary canal.
Q. 19. Why does absorption of digested food occur mainly in the small intestine?
Answer: Small intestine has the following structural adaptations to increase the surface area of absorption:-
- It is very long sized.
- Inner surface is raised into finger-like folds called villi.
- Each cell of villus has electron-microscopic folds called microvilli.
- Each villus is richly supplied by blood capillaries and lymph capillaries.
iMPORTANT QUESTIONS WITH ANSWERS OF NCERT Exemplar
Q. 20. Match group (a) and group (b):-
| Group (a) | Group (b) |
| (a) Autotrophic nutrition | (i) Leech |
| (b) Heterotrophic nutrition | (ii) Paramecium |
| (c) Parasitic nutrition | (iii) Deer |
| (d) Digestion in food vacuoles | (iv) Green plant |
Answer: (a) (iv)
(b) (iii)
(c) (i)
(d) (ii)
Q. 21. Why is the rate of breathing in aquatic organisms much faster than in terrestrial organisms?
Answer: Aquatic organisms like fishes obtain oxygen from water present in a dissolved state through their gills. Since the amount of dissolved oxygen is fairly low compared to the amount of oxygen in the air, the rate of breathing in aquatic organisms is much faster than that seen in terrestrial organisms.
Q. 22. Why is blood circulation in the human heart called double circulation?
Answer: Human heart is four-chambered and there is complete separation of oxygenated and deoxygenated blood. So the blood passes twice through the heart to supply once to the body. It occurs once in the left half of the heart and once through the right half to the heart.
Q. 23. What is the advantage of having four chambered hearts?
Answer: 1. There is complete separation of oxygenated and deoxygenated blood.
2. As oxygenated blood is supplied to body organs which increases their efficiency.
3. It supplies more oxygen to meet the high energy needs of birds and mammals.
Q. 24. Mention the major events during photosynthesis.
Answer: The major events during photosynthesis are:
- absorption of light energy by chlorophyll.
- conversion of light energy to chemical energy.
- splitting of H2O, O2 and e-.
- reduction of CO2 to carbohydrates.
Q. 25. In each of the following situations what happens to the rate of photosynthesis?
(a) Cloudy days
(b) No rainfall in the area
(c) Good maturing in the area
(d) Stomata get blocked due to dust
Answer: (a) Decreases;
(b) Decreases;
(c) Increases;
(d) Decrases.
Q. 26. Name the energy currency in the living organisms. When and where is it produced?
Answer: The energy currency of the living organisms is Adenosine Triphosphate (ATP). It is produced during respiration in all the organisms and photosynthesis in the plants.
Q. 27. What is common for Cusculta, ticks, and leeches?
Answer: All the parasitic in their nutrition and derive their food from other living organisms without killing them.
Q. 28. Explain the role of the mouth in the digestion of food?
Answer: 1. Food is crushed into small pieces by the teeth.
2. It mixes food with saliva and the enzyme amylase (found in saliva) breaks down starch into sugars.
3. Tongue helps through mixing of food with saliva and swallowing of the food bolus.
Q. 29. What are the functions of gastric glands present in the wall of the stomach?
Answer: 1. Secretion of pepsin enzyme which digests proteins.
2. Secretion of rennin enzyme which coagulates the milk proteins.
3. Secretion of mucus which protects the wall of the stomach from the action of enzymes.
4. Secretion of HCl acid which kills bacteria and provides an acidic medium.
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