6. LIFE PROCESSES
Questions:
1. The first Step in photosynthesis is
(a) Photolysis of water
(b) Production of assimilatory pigments
(c) Excitation of chlorophyll
(d) Synthesis of ATP
Ans: (c) Excitation of chlorophyll
2. What is the role of saliva in the digestion of food?
Ans: Saliva moistens the ingested food with mucus, sterilises it with lysozyme and partially digests starch part of food into sugar with the help of salivary amylase or ptyalin.
3. State the function of digestive enzyme.
Ans: Digestive enzyme are hydrolytic proteinaceous substances which cause breakdown of complex insoluble components of food into simple, soluble and absorbable substances.
4. Draw the diagram of an open stomatal pore of a leaf and label on it chloroplast and guard cells.
Ans:
5. Mention the site of complete digestion in our body. Name the end products formed on complete digestion of carbohydrates, proteins and fats.
Ans: Site of Complete digestion: Small intestine in alimentary canal. End products formed are: Proteins → Amino acids Carbohydrates → Simple sugars Fats → Fatty acids + Glycerol.
6. Why does the medium become acidic in mouth? What is the ill effect of this acidic medium? How can this be prevented?
Ans: (i) Bacteria present in the mouth produce acids by degradation of sugar and food particles in the mouth that may bring down pH in the mouth below 5.5.
(ii) Tooth enamel get corroded by the action of acids and tooth decay occurs.
(iii) By cleaning the teeth with tooth paste which is basic in nature.
7. What is the function of digestive enzymes?
Ans: Digestive enzymes convert the large and insoluble food molecules into small water soluble molecules during the process of digestion.
8. Describe heterotrophic mode of nutrition and give its examples. Name the three types of
this nutrition.
Ans: It is the mode of nutrition in which an organism cannot make its own food and depends on other organisms for food. All the animals including man, most bacteria and some fungi have heterotrophic mode of nutrition and these organisms are called heterotrophs. Holozoic, Saprophytic and Parasitic.
9. Name three different glands associated with the digestive system in humans. Also name their secretions.
Ans: Difference between name of the glands and name of secretions.
10. List the role of each of the following in our digestive system:
(i) Muscles of stomach wall
(ii) Hydrochloric acid
(iii) Mucus.
Ans: (i) Help in mixing the food thoroughly with more digestive juice by peristalsis.
(ii) Creates an acidic medium which facilitates the action of the enzyme pepsin.
(iii) Protects the inner lining of the stomach from the action of the acid.
11. Mention the organ and site of photosynthesis in green plants. What are the raw materials essential for this process? How are they obtained? Write complete balanced chemical equation for the process. Name the byproducts.
Ans: (i) Photosynthesis takes place in the grana and stroma of the chloroplast (Plastid) in green plants.
(ii) The raw materials required for this process are carbon dioxide and water in the presence of sunlight and chlorophyll.
12. (a) Draw a well labelled diagram of human alimentary canal, and label the following parts:
(i) Liver
(ii) Pancreas
(iii) Small intestine
(iv) Large intestine.
(b) What is peristaltic movement?
(b) Peristaltic movement: The lining of alimentary canal has muscles that contract rhythmically in order to push the food forward. This is called are peristaltic movements.
13. Haemoglobin levels in the blood samples of two persons A and B are found to be 9 gm/dL and 13 gm/dL respectively. Which statement is true with respect to the amount of oxygen supply in their body? [SSLC, 2016 April]
(a) More in person B than in person A
(b) More in person A than in person B
(c) Equal in person A and person B
(d) No relation between oxygen supply and the level of haemoglobin.
Ans: (a) More in person B than in person A.
14. Name the respiratory pigment in human beings. Where is this pigment found?
Ans: The respiratory pigment in human being is haemoglobin. Haemoglobin is present in RBC’s of blood in humans.
15. How do guard cells regulate opening and closing of stomatal pores?
Ans: The swelling of guard cells due to absorption of water causes opening of stomatal pores while shrinking of guard cell closes the pores. Opening and closing of stomata occur due to turgor changes in guard cells. When guard cells are turgid, stomatal pores is open while in flaccid conditions the stomatal aperture doses.
16. “Respiration is an Exothermic Reaction.” Justify this statement giving the chemical equation for the reaction involved.
Ans: During respiration, the carbohydrates are broken down to form glucose. This glucose combine with oxygen in our cells and provide energy (heat). C6H12O6 + 6O2 → 6CO2+ 6H2O + Energy
17. Give reasons for: [SSLC July, 2018-19]
(i) Oxygenated and deoxygenated bloods are separate in the heart of mammals.
(ii) Ventricles are thick walled.
(iii) Herbivores have longer small intestine as compared to carnivores.
Ans: (i) This allows a highly efficient supply of oxygen, and meet their high energy needs (as they are warm—blooded animals).
(ii) Because they have to pump blood throughout the body or into various organs.
(iii) To allow cellulose to be digested.
18. Explain the activity with diagram to show that carbon dioxide is essential for photosynthesis.
Ans: (i) Take two healthy potted plants which are nearly the same size.
(ii) Keep them in a dark room for three days.
(iii) Now place each plant on separate glass plates. Place a watch glass containing potassium hydroxide by the side of one of the plants. The potassium hydroxide is used to absorb carbon dioxide.
(iv) Take two separate bell-jars and cover both plants with them.
(v) To seal the bottom of the jars to the glass plates use vaseline so that the setup is air tight.
(vi) Now place the plants in sunlight for about two hours.
(vii) Pluck a leaf from each plant and check for the presence of starch.
(viii) Leaf from plant A shows absence of starch whereas leaf from plant B tests positive for starch.
19. (i) Draw the human respiratory system and label the following— lung, bronchi and alveolar sac.
(ii) During breathing cycle, what is the advantage of residual volume of air in lungs? Explain.
20. Why do veins have thin walls as compared to arteries?
Ans: Veins have thin walls because the blood flowing through them is no longer under pressure, instead they have valves that ensure the blood flows in one direction only.
21. Explain how water and minerals are transported in plants?
Ans: Transport of materials in Xylem: The movement of water and minerals absorbed by the plant’s root from the soil through xylem elements – tracheids and vessels are transported to other plant parts. Transpiration helps in upward conduction.
Transport of materials in Phloem: Food synthesized in the leaves is transported through sieve tubes of phloem tissues to other parts both upwards and downwards.
22. (a) What is lymph? [SSLC April, 2016]
(b) How is composition of lymph different from blood plasma?
(c) List two functions of lymphatic system.
Ans: (a) Lymph is a tissue fluid, that contain plasma, proteins and blood cells which escapes into intercellular spaces.
(b) Lymph is colourless and contains less protein than plasma.
(c) Functions: (i) Carries digested food 34 (ii)Drains excess fluid from extracellular space back into the blood.
23. Write three points of differences between artery and vein.
Ans: Difference between Artery and Vein
24. Plants absorb water from the soil. Explain how does the water reach the tree top?
Ans: Xylem (vessels) of roots, stems and leaves are interconnected to form a continuous column. Roots also take up mineral salts actively, water moves in and as a result, it creates pressure which pushes the water up. Transpiration pull creates a suction force puffing up water.
25. (a) Draw a diagram of cross-section of the human heart and label the following parts:
(i) Right ventricle (ii) Aorta (iii) Left atrium (iv) Pulmonary arteries
(b) Give reasons for the following: (i) The muscular walls of ventricles are thicker than the walls of atria. (ii) Arteries have thick elastic walls.
26. Why is nitrogen considered an essential element? How do plants acquire nitrogen?
Ans: Nitrogen is an essential element used in the synthesis of proteins and other compounds. is taken up in the form of inorganic nitrates (or nitrites) or as organic compounds prepared by bacteria from atmospheric nitrogen.
27. List any four strategies used by the plants for excretion.
Ans: Strategies used by plants for excretion are:
(i) Many plant waste products are stored in cellular vacuoles.
(ii) Waste products may be stored in leaves that fall off.
(iii) Waste products are stored as resin and gums, especially in old xylem.
(iv) They can get rid of excess water and oxygen through stomata.
28. (i) Draw a diagram of an excretory unit of a human kidney and label the following: Bowman’s capsule, Glomerulus, Collecting duct, Renal artery.
(ii) Write the important function of the structural and functional unit of kidney.
(iii) Write any one function of an Artificial Kidney. [SSLC 2018-19, July]
Ans: (i)
(ii) Function of nephron is filtration, reabsorption and secretion.
(iii) Function of Artificial Kidney: Helps to remove harmful wastes, extra salts and water, control blood pressure. Maintain the balance of sodium potassium salts in a patient whose kidneys have failed.
Textbook Exercises
1. The kidneys in human beings are a part of the system for
(a) nutrition (b) respiration (c) excretion (d) transportation.
Ans: (c) excretion
2. The xylem in plants are responsible for
(a) transport of water (b) transport of food
(c) transport of amino acids (d) transport of oxygen
Ans: (a) transport of water
3. The autotrophic mode of nutrition requires
(a) carbon dioxide and water (b) chlorophyll (c) sunlight (d) all of the above
Ans: (d) all of the above
4. The breakdown of pyruvate to give carbon dioxide, water and energy takes place in
(a) cytoplasm (b) mitochondria (c) chloroplast (d) nucleus
Ans: (b) mitochondria
5. How are fats digested in our bodies? Where does the process take place?
Ans: Fats are digested with the help of pancreatic juices which contains an enzyme lipase which brings about the digestion of fat. Bile contains certain salts which bring about the emulsification of fat molecules into small globules. It takes place in small intestine.
6. What is the role of saliva in the digestion of food?
Ans: The enzyme ptyalin present in saliva splits starch and glycogen into maltose.
7. What are necessary conditions for autotrophic nutrition and what are its by product?
Ans: Light, appropriate temperature, CO2 chlorophyll and water are conditions necessary for autotrophic nutrition. Molecular oxygen is the by product.
8. What are the differences between aerobic respiration and anaerobic respiration. Name some organism that use anaerobic mode of respiration.
Ans: Difference between Aerobic Respiration and Anaerobic Respiration:
Organism that use the anaerobic mode of respiration are yeast, some bacteria and some parasite.
9. How are alveoli designed to maximise exchange of gases?
Ans: Alveoli contain an extensive network of blood vessels which provides a large surface area of exchange of gases.
10. What are the consequences of deficiency of haemoglobin in our bodies?
Ans: The deficiency of haemoglobin causes anaemia. The symptoms of anaemia are breathlessness, tiredness pale skin, palpitations and poor resistance to infection.
11. Describe double circulation in human beings, Why is it necessary?
Ans: The human heart consists of two sides: right and left. The right side of the heart receives deoxygenated blood and sends it further for purification to lungs. The left side of heart receives oxygenated blood from the lungs which is pumped further and sent to all the parts of the body through blood vessels. This is called double circulation. The energy demands for human beings is too large and hence it is necessary for the separation of oxygenated and deoxygenated blood to meet this energy demand.
12. What are the differences between the transport of materials in xylem and phloem.
Ans: (a) Xylem:
(i) It transports water and mineral.
(ii) It involves upward movement. (Unidirectional)
(b) Phloem:
(i) It transports food and hormones.
(ii) It involves upward and downward movements (bidirectional).
13. Compare the functioning of alveoli in lungs and nephron in the kidneys with respect to their structure and functioning.
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