Short Answer Type Questions
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:
(i) It is required for the growth of new cells and repair of worn out cells.
(ii) It is required to develop resistance against various diseases.
(iii) It gives us energy for various metabolic activities of our body.
Q 6. What would happen if green plants disappear from earth?
Ans: If green plants disappear from earth, then the herbivores will die of starvation followed by carnivores and then decomposers.
Q 7. Leaves of a healthy plotted plant were coated with vaseline will this plant remain healthy for long? Give reasons for your answer.
Ans: (a) The plant will die soon because layer of vaseline will prevent the exchange of gases for respiration.
(b) It will also close the stomatal openings and plant won’t be able to get the necessary raw materials for photosynthesis.
Q 8. What are the adaptations of leaf for photosynthesis?
Ans: The adaptations of leaf for photosynthesis are as follows:
(i) Leaf has a large surface area to absorb maximum light.
(ii) Arrangement of leaves in order to absorb optimum amount of light.
(iii) The large number of veins provide mechanical strength and also take part in quick transport of substances to and from the mesophyll cells.
(iv) Leaf is the site of transpiration which cools the leaf surface for optimum photosynthesis.
(v) Leaf has numerous stomata for gaseous exchange.
(vi) Large number of chloroplasts are present on upper surface of leaves.
Q 9. Why do herbivores have longer, small intestine than carnivores?
Ans: Cellulose is difficult to digest and hence takes a longer 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 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 mucus is not secreted by the gastric glands?
Ans: If mucus is not secreted by the gastric glands, it will lead to corrosion of inner lining of stomach, causing excessive acidity, ulcers and extreme discomfort as mucus protects the inner lining of 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 occur mainly in the small intestine because:
(i) Digestion of food is completed in small intestine.
(ii) Inner lining of small intestine bears a number of finger-like projections called villi, which increases the surface area for absorption.
(iii) Wall of 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 blood.
Q 14. What is the advantage of having four chambered heart?
Ans: The advantage of having 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 right half by septa. This mechanism is useful to animals with high energy needs such as birds and mammals. In this way, 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) In 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?
Ans: (a) In leaves, the waste materials are stored in the vacuoles of mesophyll and epidermal cells. When old leaves fall, the waste materials are excreted along with the leaves.
(b) Transpiration of gases via stomata helps in removal of gaseous waste of respiration and photosynthesis.
Long Answer Type Questions
Q 22. Explain the importance of soil for plant growth.
Ans: Importance of soil for plant growth:
(i) It anchors the plant.
(ii) It is the source of water and minerals.
(iii) It helps in symbiotic association with microbes.
(iv) It helps for respiration of root cells due to availability of oxygen of food material.
23. Describe the alimentary canal of man.
Ans: Alimentary canal in man is 9 metres long and consists of the following parts :
(i) Mouth. It leads into buccal cavity.
• The floor of the buccal cavity has a tongue bearing taste buds. Man possess teeth on both the jaws. There are 32 teeth of four different : types, namely incisors, canines, premolars and molars.
(ii) Pharynx. It is a short, conical region that lies after the mouth cavity.
(iii) Oesophagus. It is a long, narrow, muscular tube which leads to the stomach.
(iv) Stomach. It lies below the diaphragm on the left side of abdominal cavity and is J-shaped. The food is stored and partly digested in the stomach.
(v) Small Intestine. It is a convoluted tube and differentiated into three regions, viz., duodenum, which is the first part of small intestine and is curved C-shaped; jejunum, comparatively longer and more coiled, and ileum, which is the last part of small intestine whose inner surface is folded to form villi, which absorbs the products of digestion.
(vi) Large Intestine. It is much shorter and wider than small intestine and is differentiated into three regions viz., caecum, which is small rounded blind sac from which vermiform appendix arises; colon is the inverted U-shaped tube and the rectum opens to exterior through anus.