Life processes(Question Answer)

QUESTIONS

1. Why is diffusion insufficient to meet the oxygen requirements of multicellular organisms like humans? 

Answer: The body structure of multicellular organisms is very complex and they have some special cells and tissues for each function in the body. Therefore, multicellular organisms need more oxygen. Therefore, it is not enough to obtain the required oxygen through the diffusion process alone.

2. What criteria do we use to decide whether something is alive? 

Answer:  An organism can be identified as living or dead by observing its various movements. 

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

Answer: An organism needs a variety of raw materials to survive. Some of these substances are food for heterotrops and carbon dioxide (CO2), water, oxygen (O2), various minerals for autotrophs.

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

Answer: The most important processes for maintaining life are-

                        1. Nutrition

                        2. Respiration

                        3. Transportation

                        4. Excretion etc.

5. What are the differences between autotrophic nutrition and heterotrophic nutrition? 

Answer: 

Autotrophic Nutrition	Heterotrophic Nutrition
1. Autotrophic organisms prepare their own food.	1. Organisms cannot prepare their own food and take it from outside sources.
2. Food is prepared from simple organic compounds like carbon dioxide (CO2), water, etc.	2. Obtain food from autotrophic organisms.
3. Chlorophyll is required	3. Chlorophyll is not required
4. Food is generally prepared during day time	4. Food can be obtained at any time
5. Such mood of nutrition is found in all green plants and some bacteria.	5. This type of nutrition is found in all animals and reptiles.

6. Where do plants get each of the raw materials required for photosynthesis? 

Answer: The photosynthesis process requires carbon dioxide (CO2), water, and sunlight. Carbon dioxide is absorbed by plants from the atmosphere through the stomata in leaves, water is absorbed from the soil by the plant's roots and carried to the leaves through xylem. and chlorophyll absorbs sunlight. 

7. What is the role of the acid in our stomach? 

Answer: The hydrochloric acid creates an acidic medium which facilitates the action of the enzyme pepsin. It also kills the germs present in food. 

8. What is the function of digestive enzymes? 

Answer: The molecules in the food we eat are complex in nature. They cannot be absorbed by our body in this complex form. Digestive enzymes convert these complex food molecules into the simplest molecules so that they can be easily absorbed by our body.

9. How is the small intestine designed to absorb digested food?

Answer: From the stomach, the partially digested food enters the small intestine. This is the longest part of the alimentary canal which is fitted into a compact space because of extensive coiling. The length of the small intestine differs in various animals depending on the food they eat. The small intestine is the site of the complete digestion of carbohydrates, proteins and fats. It receives the secretions of the liver and pancreas for this purpose. The food coming from the stomach is acidic and has to be made alkaline for the pancreatic enzymes to act. Bile juice from the liver accomplishes this in addition to acting on fats. Fats are present in the intestine in the form of large globules which makes it difficult for enzymes to act on them. Bile salts break them down into smaller globules increasing the efficiency of enzyme action. The pancreas secretes pancreatic juice which contains enzymes like trypsin for digesting proteins and lipase for breaking down emulsified fats. The walls of the small intestine contain glands which secrete intestinal juice. The enzymes present in it finally convert the proteins to amino acids, complex carbohydrates into glucose and fats into fatty acids and glycerol. The digested food is taken up by the walls of the intestine. The inner lining of the small intestine has numerous finger-like projections called villi which increase the surface area for absorption. The villi are richly supplied with blood vessels which take the absorbed food to each and every cell of the body, where it is utilised for obtaining energy, building up new tissues and the repair of old tissues. The unabsorbed food is sent into the large intestine.

10. What advantage over an aquatic organism does a terrestrial organism have with regard to obtaining oxygen for respiration?

Answer: Animals have evolved different organs for the uptake of oxygen from the environment and for getting rid of the carbon dioxide produced. Terrestrial animals can breathe the oxygen in the atmosphere, but animals that live in water need to use the oxygen dissolved in water.

    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. Terrestrial organisms use the oxygen in the atmosphere for respiration. This oxygen is absorbed by different organs in different animals. All these organs have a structure that increases the surface area which is in contact with the oxygen-rich atmosphere. 

11. What are the different ways in which glucose is oxidised to provide energy in various organisms? 

Answer: In the case of heterotrophic organisms, the body cells derive energy from food. Diverse organisms do this in different ways – some use oxygen to break-down glucose completely into carbon dioxide and water, some use other pathways that do not involve oxygen. In all cases, the first step is the break-down of glucose, a six-carbon molecule, into a three-carbon molecule called pyruvate. This process takes place in the cytoplasm. Further, the pyruvate may be converted into ethanol and carbon dioxide. This process takes place in yeast during fermentation. Since this process takes place in the absence of air (oxygen), it is called anaerobic respiration. Breakdown of pyruvate using oxygen takes place in the mitochondria. This process breaks up the three-carbon pyruvate molecule to give three molecules of carbon dioxide. The other product is water. Since this process takes place in the presence of air (oxygen), it is called aerobic respiration. The release of energy in this aerobic process is a lot greater than in the anaerobic process. Sometimes, when there is a lack of oxygen in our muscle cells, another pathway for the break-down of pyruvate is taken. Here the pyruvate is converted into lactic acid which is also a three-carbon molecule.

 

12. How is oxygen and carbon dioxide transported in human beings? 

Answer:  During the breathing cycle, when air is taken in and let out, the lungs always contain a residual volume of air so that there is sufficient time for oxygen to be absorbed and for the carbon dioxide to be released. When the body size of animals is large, the diffusion pressure alone cannot take care of oxygen delivery to all parts of the body. Instead, respiratory pigments take up oxygen from the air in the lungs and carry it to tissues which are deficient in oxygen before releasing it. In human beings, the respiratory pigment is haemoglobin which has a very high affinity for oxygen. This pigment is present in the red blood corpuscles. Carbon dioxide is more soluble in water than oxygen is and hence is mostly transported in the dissolved form in our blood.

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

Answer: In human beings, air is taken into the body through the nostrils. The air passing through the nostrils is filtered by fine hairs that line the passage. The passage is also lined with mucus which helps in this process. From here, the air passes through the throat and into the lungs. Rings of cartilage are present in the throat. These ensure that the air-passage does not collapse.

        Within the lungs, the passage divides into smaller and smaller tubes which finally terminate in balloon-like structures which are called alveoli. The alveoli provide a surface where the exchange of gases can take place. The walls of the alveoli contain an extensive network of blood-vessels. As we have seen in earlier years, when we breathe in, we lift our ribs and flatten our diaphragm, and the chest cavity becomes larger as a result. Because of this, air is sucked into the lungs and fills the expanded alveoli. The blood brings carbon dioxide from the rest of the body for release into the alveoli, and the oxygen in the alveolar air is taken up by blood in the alveolar blood vessels to be transported to all the cells in the body. During the breathing cycle, when air is taken in and let out, the lungs always contain a residual volume of air so that there is sufficient time for oxygen to be absorbed and for the carbon dioxide to be released.

14. What are the components of the transport system in human beings? What are the functions of these components? 

Answer: The main components of the human circulatory system are the heart, blood and blood vessels (arteries and veins).

            The heart collects de-oxygenated blood from various parts of the body and pumps it to the lungs for oxygenation. Again, the heart collects oxygenated blood from the lungs and transports it to different parts of the body.

                Blood carries oxygen, carbon dioxide, digested food, hormones, urea and other waste products to different parts of the body.

                  The blood pumped by the heart is transported through the blood vessels (arteries and veins) to different parts of the body.

15. Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds? 

Answer: It necessary to separate oxygenated and deoxygenated blood in mammals and birds. Such separation allows a highly efficient supply of oxygen to the body. This is useful in animals that have high energy needs, such as birds and mammals, which constantly use energy to maintain their body temperature.

16. What are the components of the transport system in highly organised plants? 

Answer: Plant transport systems in highly organised plants, will move energy stores from leaves and raw materials from roots. These two pathways are constructed as independently organised conducting tubes. One, the xylem moves water and minerals obtained from the soil. The other, phloem transports products of photosynthesis from the leaves where they are synthesised to other parts of the plant.

             The various components of xylem are vessel, trachea, xylem fiber and xylem parenchyma. The components of the phloem tissue, on the other hand, are the sieve tubes, companion cell, the phloem fibers, and the phloem parenchyma.

17. How are water and minerals transported in plants? 

Answer: The transport system of the plant carries the stored energy from the leaves and the raw material from the roots. These two supply routes are individually formed and operated by the circulatory system. It consists of a xylem tissue that transports water and mineral salts from the soil. The other is the phloem tissue which carries the products produced in the process of photosynthesis from the leaves to other parts of the plant body. The trachea of xylem tissue, connects the roots, stems, and leaves of the plant to form a circulating thread that can carry water to different parts of the body. Roots actively absorb ions from the soil that touch the soil. This causes a difference in the concentration of ions between the root and the soil. Therefore, roots absorbs water from the soil to bridge such differences. As a result, water flows regularly to the root's xylem and it regularly pushes the water column upwards.

        Even if it seems impossible, the pressure created by this is enough to move the water to the height of the plants we usually see. Plants use another strategy to move water in the xylem upwards to the highest points of the plant body. Provided that the plant has an adequate supply of water, the water which is lost through the stomata is replaced by water from the xylem vessels in the leaf. In fact, 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 plant is known as transpiration. Thus, transpiration helps in the absorption and upward movement of water and minerals dissolved in it from roots to the leaves. It also helps in temperature regulation. The effect of root pressure in transport of water is more important at night. During the day when the stomata are open, the transpiration pull becomes the major driving force in the movement of water in the xylem.

18. How is food transported in plants?

Answer: The process of transport of soluble products of photosynthesis from leaves, where they are formed, to other parts of the plant is called translocation and it occurs in the part of the vascular tissue known as phloem. Besides the products of photosynthesis, the phloem transports amino acids and other substances. These substances are especially delivered to the storage organs of roots, fruits and seeds and to growing organs. The translocation of food and other substances takes place in the sieve tubes with the help of adjacent companion cells both in upward and downward directions. Unlike transport in xylem which can be largely explained by simple physical forces, the translocation in phloem is achieved by utilizing energy. Material like sucrose is transferred into phloem tissue using energy from ATP. This increases the osmotic pressure of the tissue causing water to move into it. This pressure moves the material in the phloem to tissues which have less pressure. This allows the phloem to move material according to the plant’s needs.

19. Describe the structure and functioning of nephrons. 

Answer: The nephron is the primary functional units of the kidney. Just as the lungs contain a number of tiny blood vessels, the kidneys also contain numerous thin blood vessels. These blood vessels attach to the kidneys and form cup-like tubules. Such tubes help in filtration of blood. Each kidney contains a number of such tubular units. These are the nephrons. These nephrons are packed close together. Each kidney contains 1-2 million nephrons.

    Each nephron has two parts. The first part is a cup-like part called a bowmans capsule. The bowmans capsule contains cluster of number of tiny blood vessels. These are called glomeruli. One end of the glomerulus is attached to the endothelial renal artery. Endothelial renel artery brings the urea containing impure blood where all these impurities are filtered. Some substances in the initial filtrate, such as glucose, amino acids, salts and a major amount of water, are selectively re-absorbed as the urine flows along the tube. The amount of water reabsorbed depends on how much excess water there is in the body, and on how much of dissolved waste there is to be excreted. The urine forming in each kidney eventually enters a long tube, the ureter, which connects the kidneys with the urinary bladder. Urine is stored in the urinary bladder until the pressure of the expanded bladder leads to the urge to pass it out through the urethra.
 

20. What are the methods used by plants to get rid of excretory products? 

Answer: Plants use completely different strategies for excretion than those of animals. Oxygen itself can be thought of as a waste product generated during photosynthesis, and are eliminated through leaves into atmosphere. Same process is utilized to eliminate CO2 as well. They can get rid of excess water by transpiration. For other wastes, plants use the fact that many of their tissues consist of dead cells, and that they can even lose some parts such as leaves. Many plant waste products are stored in cellular vacuoles. Waste products may be stored in leaves that fall off. Other waste products are stored as resins and gums, especially in old xylem. Plants also excrete some waste substances into the soil around them.

21. How is the amount of urine produced regulated?

Answer: Some substances in the initial filtrate, such as glucose, amino acids, salts and a major amount of water, are selectively re-absorbed as the urine flows along the tube. The amount of water reabsorbed depends on how much excess water there is in the body, and on how much of dissolved waste there is to be excreted. It controls the amount of urine.

EXERCISES 

1. The kidneys in human beings are a part of the system for 

(a) nutrition. 

(b) respiration. 

(c) excretion. 

(d) transportation. 

Answer: (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. 

Answer: (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. 

Answer: (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. 

Answer: (b) mitochondria. 

5. How are fats digested in our bodies? Where does this process take place? 

Answer: Fats are present in the intestine in the form of large globules which makes it difficult for enzymes to act on them. Bile salts break them down into smaller globules increasing the efficiency of enzyme action. This is similar to the emulsifying action of soaps on dirt. The pancreas secretes pancreatic juice which contains enzymes lipase for breaking down emulsified fats. The walls of the small intestine contain glands which secrete intestinal juice. The enzymes present in it finally convert the fats into fatty acids and glycerol.

6. What is the role of saliva in the digestion of food? 

Answer: The saliva contains an enzyme called salivary amylase that breaks down starch which is a complex molecule to give sugar. The food is mixed thoroughly with saliva and moved around the mouth while chewing by the muscular tongue.

7. What are the necessary conditions for autotrophic nutrition and what are its byproducts? 

Answer: The necessary conditions for autotrophic nutrition are sunlight, carbon dioxide gas and water. Its byproducts are oxygen and water.

8. What are the differences between aerobic and anaerobic respiration? Name some organisms that use the anaerobic mode of respiration. 

Answer: Differences between aerobic and anaerobic respiration are-

Aerobic Respiration	Anaerobic Respiration
1. Occurs in the presence of oxygen	1. Occurs in the absence of oxygen
2. Glucose molecules are completely broke down to carbon dioxide, water and energy are produced.	2. Glucose molecules are partially oxidized to produce carbon dioxide, ethyl alcohol and energy.
3. The amount of energy generated is higher.	3. The amount of energy generated is low.
4. It occurs in the mitochondria.	4. It occurs in the cell nucleus.

9. How are the alveoli designed to maximise the exchange of gases? 

Answer: Within the lungs, the air passage divides into smaller and smaller tubes which finally terminate in balloon-like structures which are called alveoli. The alveoli provide a surface where the exchange of gases can take place. The walls of the alveoli contain an extensive network of blood-vessels. As we have seen in earlier years, when we breathe in, we lift our ribs and flatten our diaphragm, and the chest cavity becomes larger as a result. Because of this, air is sucked into the lungs and fills the expanded alveoli. The blood brings carbon dioxide from the rest of the body for release into the alveoli, and the oxygen in the alveolar air is taken up by blood in the alveolar blood vessels to be transported to all the cells in the body. During the breathing cycle, when air is taken in and let out, the lungs always contain a residual volume of air so that there is sufficient time for oxygen to be absorbed and for the carbon dioxide to be released.

10. What would be the consequences of a deficiency of haemoglobin in our bodies? 

Answer: Deficiency of haemoglobin in our bodies will lead to the less supply of oxygen to different parts of the body. When the amount of oxygen in our body decreases, our body will become deficient in energy, our immune system will be weakened and our body will become pale.

11. Describe double circulation in human beings. Why is it necessary? 

Answer: When the human body completes one cycle of  circulation of blood, blood is passed twice through the heart. This is called double circulation of blood. De-oxygeneted  blood from various parts of the human body enters the right atrium of the heart, from which it enters the right ventricle, and then the right ventricle contracts and the blood goes to the lungs where the blood is oxygenated. This oxygenated blood then enters the left atrium and travels through the left ventricle to all parts of the body. During this entire cycle, the blood is transmitted twice through the heart.

           Double circulation is required because-

     1. This ensures complete separation of oxygenated and de-oxygenated blood.

     2. This ensures adequate supply of oxygen to the cells of the body.

12. What are the differences between the transport of materials in xylem and phloem? 

Answer: The differences in the transportation of xylem and phloem are:

                    (1) The xylem carries water and mineral salts in the plant body, the phloem carries the food prepared in the leaves to various organs.

                    (2) The transport of xylem is in upward direction, the transport of phloem is in both upward and downward direction.

                (3) The circulation through the xylem tissue occurs with the help of simple physical forces. Transportation through phloem always uses stored energy.

13. Compare the functioning of alveoli in the lungs and nephrons in the kidneys with respect to their structure and functioning.

Answer:

Alveoli	Nephron
1. It looks like a sack	1. They are funnel shaped
2. The outer walls of the alveoli are thick	2. The outer walls of nephron are thin
3. It exchanges gases between lungs and blood	3. They collect purified urine
4. Gas exchange occurs through diffusion	4. Substances are exchanged due to pressure differences.