Q 1. Name the following:
(a) The process in plants that links light energy with chemical energy.
(b) Organism that can prepare their own food.
(c) The cell organelle where photosynthesis occurs.
(d) Cells that surround a stomatal pore.
(e) Organisms that cannot prepare their own food.
(f) An enzyme secreted from gastric glands in stomach thact acts on proteins.
Ans: (a) Photosynthesis
(d) Guard cells
Q 2. “All plants give out oxygen during day and carbon dioxide during night”. Do yo agree with this statement? Give reason.
Ans: Yes, respiration takes place throughout day and night but photosynthesis occurs only during the day. During daytime, plants give out oxygen which is a product of photosynthesis. Thus, during night when there is no photosynthesis, plants liberate carbon dioxide.
Q 3. Two green plants are kept separately in oxygen free containers. One in dark and other in continuous light which one will longer? Give reasons.
Ans: The plant which kept in continuous light will live longer because in light, the plant will be able to undergo photosynthesis and able to convert carbon dioxide into oxygen whereas the plant in dark cannot perform photosynthesis and lack of oxygen will kill the plant.
Q 4. Why do fishes die when taken out of water?
Ans: Fishes die when taken out of water because they cannot obtain gaseous oxygen.
They breath through gills, which are richly supplied with blood capillaries and can readily absorb oxygen dissolved in water.
Q 5. Is ‘nutrition’ a necessity for an organism? Discuss.
Ans. Yes, ‘nutrition’ is a necessity for an organism because:
Q 6. What would happen if green plants disappear from the earth?
Ans: If green plants disappear from the earth, then the herbivores will die of starvation followed by carnivores and then decomposers.
Q 7. Leaves of a healthy potted plant were coated with vaseline will this plant remain healthy for long? Give reasons for your answer.
Q 8. What are the adaptations of leaf for photosynthesis?
Ans: The adaptations of leaf for photosynthesis are as follows:
Q 9. Why do herbivores have longer, small intestines than carnivores?
Ans: Cellulose is difficult to digest and hence takes a long time for complete digestion which is why herbivores need a comparatively longer small intestine. Meat is easy to digest and hence carnivores like tigers have a comparatively shorter small intestine.
Q 10. Why is the small intestine in herbivores longer than in carnivores?
Ans: Herbivores eat grass and need a longer small intestine to allow complete digestion of cellulose. But carnivores cannot digest cellulose, and therefore they have a shorter intestine.
Q 11. What will happen if the mucus is not secreted by the gastric glands?
Ans: If the mucus is not secreted by the gastric glands, it will lead to corrosion of the inner lining of the stomach, causing excessive acidity, ulcers, and extreme discomfort as mucus protects the inner lining of the stomach from the action of hydrochloric add and enzyme pepsin.
Q 12. Why does absorption of digested food occur mainly in the small intestine?
Ans: Absorption of digested food occurs mainly in the small intestine because:
(i) Digestion of food is completed in the small intestine.
(ii) Inner lining of the small intestine bears a number of finger-like projections called villi, which increases the surface area for absorption.
(iii) Wall of the intestine has blood vessels for carrying the absorbed food to different parts of the body.
Q 13. Why is the rate of breathing in aquatic organisms much faster than in terrestrial organisms?
Ans: The rate of breathing in aquatic organisms is much faster than in terrestrial organisms because the amount of dissolved oxygen in water is low as compared to the amount of oxygen in the air. Aquatic animals take in water through their mouths and past it to the gills where the dissolved oxygen is taken up by the blood.
Q 14. What is the advantage of having a four-chambered heart?
Ans: The advantage of having a four-chambered heart is that it prevents oxygenated and deoxygenated blood from mixing, as the left half of the four-chambered heart is completely separated from the right half by septa. This mechanism is useful to animals with high energy needs such as birds and mammals. In this way, a highly efficient supply of oxygenated blood is passed to all parts of the body.
Q 15. In each of the following situations what happens to the rate of photosynthesis?
(a) Cloudy days
(b) No rainfall in the area
(c) Good manuring in the area
(d) Stomata gets blocked due to dust.
Ans: (a) On cloudy days, photosynthesis is reduced due to low light intensity.
(b) In case of no rainfall in the area, rate of photosynthesis decreases.
(c) With good manuring in the area, rate of photosynthesis increases, it increases soil fertility.
(d) When stomata gets blocked due to dust, photosynthesis decreases by reducing gaseous exchange.
Q 16. Name the energy currency in the living organisms. When and where is it produced?
Ans: Adenosine triphosphate (ATP) is the energy currency of the living organisms. It is produced during respiration in living organisms and also during photosynthesis in plants.
Q 17. What is common for cuscuta, ticks and leeches?
Ans: All are parasites and they derive their nutrition from their hosts directly without killing them.
Q 18. What are the functions of gastric glands present in the wall of the stomach?
Ans: Functions of the gastric glands present in the wall of the stomach are as follows:
(i) Secretion of mucus for protection of inner lining of stomach.
(ii) Secretion of HCI which makes the food soft and acidified for pepsin to act upon food.
(iii) Secretion of pepsin enzyme that digests proteins.
Q 19. Plants have low energy needs as compared to animals. Explain.
Ans: Plants have low energy needs as compared to animals because plants do not move and most of their body is made up of dead cells like sclerenchyma. But animals move about in search of food, mate and shelter.
Q 20. Why and how does water enter continuously into the root xylem?
Ans: Cells of root are in close contact with soil and so actively take up ions. Ions pass inward increasing osmotic concentration of xylem. Because of it water from the soil continuously pass into the root xylem.
Q 21. How do leaves of plants help in excretion?
Q 22. Explain the importance of soil for plant growth.
Ans: Importance of soil for plant growth:
23. Describe the alimentary canal of man.
Ans: Alimentary canal in man is 9 meters long and consists of the following parts: