Life Processes

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

Ans. In multicellular organisms, all the cells may not be in direct contact with the surrounding environment. Hence diffusion will not meet all the requirements of all the cells.

Q2. What criteria do we use to decide whether something is alive? 

Ans. Movement in response to external stimuli, breathing, growth, etc.

Q3. What are outside raw materials used for by an organism? 

Ans. Outside raw materials are used for the maintenance and sustenance of life by an organism.

Q4. What processes would you consider essential for maintaining life? 

Ans. All processes that perform the maintenance function of living organisms are called life processes. All life processes are essential for maintaining life.

Q5. What are the differences between autotrophic nutrition and heterotrophic nutrition? 

Ans. 

(Note: Draw a Comparison Table)

Autotrophic Nutrition: 

1) Food is made from inorganic components.

2) Chlorophyll and sunlight are required. 

3) Photosynthesis or chemosynthesis takes place.

4) It occurs in green plants and some bacteria. 

Heterotrophic Nutrition: 

1) Food is obtained from organic components.

2) Chlorophyll and sunlight are not required.

3) These processes do not occur.

4) It occurs in animals and insectivorous plants.

Q6. Where do plants get each of the raw materials required for photosynthesis? 

Ans. For photosynthesis, plants obtain the following raw materials:

(i) Water: Roots absorb it from the soil. 

(ii) Carbon Dioxide: Stomata in leaves allow the carbon dioxide gas to enter the plant.

(iii) Chlorophyll: It is already present in the leaves.

(iv) Sunlight: From the sun.

Q7. What is the role of acid in our stomach? 

Ans. Acid (HCl) present in our stomach makes the medium acidic to facilitate the action of the enzyme pepsin and it kills the bacteria ingested with food.

Q8. What is the function of digestive enzymes? 

Ans. Digestive enzymes act on complex food to break them into simpler components.

Q9. How is the small intestine designed to absorb the digested food? 

Ans. The small intestine has finger-like projections in the inner lining which increases the surface area for the absorption of food. These finger-like projections are called villi. The villi are richly supplied with blood vessels that take the absorbed food to every cell of the body.

Q10. What advantages over an aquatic organism does a terrestrial organism have in obtaining oxygen for respiration? 

Ans. The aquatic organisms take in the oxygen dissolved in water which is in less percentage than the oxygen present in the air. Terrestrial organisms can take in more amount of oxygen at a time than aquatic organisms.

Q11. What are the different ways in which glucose is oxidized to provide energy in various organisms? 

Ans. (T.B. Figure 5.8) 

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Q12. How are oxygen and carbon dioxide transported in human beings? 

Ans. Oxygen is carried by haemoglobin present in the RBC of the blood, carbon dioxide is soluble in water and hence is transported by the blood in dissolved form.

Q13. How are lungs designed in human beings to maximize the area for the exchange of gases? 

Ans. In human beings, lungs have tubes called bronchioles which divide into smaller tubes and terminate into balloon-like structures called alveoli. The alveoli provide a large surface area where the exchange of gases can take place.

Q14. What are the components of the transport system in human beings? What are the functions of these components? 

Ans. In human beings the transport system consists of the following:

(i) Heart: It acts as a pumping organ. 

(ii) Blood: It is the transport medium. It is made up of 

(a) Plasma-Carries food molecules, nitrogenous wastes, salts, carbon dioxide, hormones proteins, etc. in a dissolved form. 

(b) RBC-Consists of haemoglobin and transports oxygen. 

(c) WBC-Helps to fight infection. 

(d) Platelets-Helps in the clotting of blood.

(iii) Blood vessels:

(a) Arteries-Carry oxygenated blood away from the heart to each and every cell. 

(b) Veins-Bring de-oxygenated blood to the heart for purification.

Q15. Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds? 

Ans. Mammals and birds need large amounts of energy for their life processes and hence the oxygenated blood can help them to obtain this energy by breaking down the food.

Q16. What are the components of the transport system in highly organized plants? 

Ans. The components of the transport system are the xylem and the phloem in highly organized plants.

Q17. How are water and minerals transported in plants?

Ans. Water and minerals are transported in plants with the help of xylem tissue. Roots absorb the water from the soil by actively taking up ions, creating a difference in the concentration of these ions between the root and the soil. Water enters the root cells. The water moves up creating a column of water that is steadily pushed upwards in vessels and tracheids of the roots, stem, and leaves, and are interconnected to form a continuous system of water-conducting channels reaching all parts of the plant. The water loss by leaves through stomata is called transpiration. It creates a suction pull, which pulls water from the xylem cells of roots.

Q18. How is food transported in plants? 

Ans. The transport of food in plants is called translocation. It takes place with the help of a conducting tissue called phloem. The phloem transports glucose, amino acids, and other substances from leaves to roots, shoots, fruits, and seeds. Sieve tubes and companion cells help in transporting the food in upward and downward directions. Sucrose-like materials are transported using energy from ATP and osmotic pressure, which is caused due to water. This pressure moves the material in the phloem to tissues that have less pressure. This pressure helps in the movement of material in plants.

Q19. Describe the structure and functioning of nephrons. 

Ans. Structure of nephrons: 

It consists of a Bowman's capsule in which glomerulus is present (cluster of capillaries). The afferent artery brings impure blood to the nephron. The cup-shaped structure (Bowman’s capsule) forms a tubular part of the nephron which leads to the collecting duct. 

Working of Nephron: 

(i) Filtration: The renal artery or afferent artery is wider and slowly becomes a narrow tube in the glomerulus. Due to the difference in the width, a pressure difference is caused and water with dissolved impurities is squeezed out from the tube. It is collected in the Bowman's capsule which is a cup-like structure and passes into the tube. 

(ii) Reabsorption: The above filtrate passes through the tubule where the major amounts of water, glucose, and amino acids are selectively reabsorbed by the capillaries which are surrounding the tubule. 

(iii) Urine formation: The water and impurities which are not reabsorbed is sent to a collecting duct. This filtrate contains more dissolved nitrogenous wastes i.e. urea and hence it is termed urine. From here the urine enters the ureter and is collected in the urinary bladder.

Q20. What are the methods used by plants to get rid of excretory products? 

Ans. Wastes excreted from plants are 

(i) Gaseous wastes: through stomatal pores, CO2 is given out during respiration, and O2 is given out during photosynthesis. 

(ii) Liquid wastes (water): through stomata pores by transpiration. 

(iii) Other wastes: are stored in leaves' dead cells and the leaves fall off. 

Some other waste products are stored as resins and gums in the old xylem of the plant and other wastes are also thrown out from nodes into the soil.

Q21. How the amount of urine is produced regulated? 

Ans. The amount of urine produced depends on how much excess water there is in the body and how much-dissolved waste there is to be excreted. On a hot day, when we sweat and lose a lot of body water and salts, most of the water and salts in the kidney will be reabsorbed into the blood from the filtrate in the tubule. Thus the volume of urine produced will be less. In winter, when we do not sweat a lot, a little water and salts will be reabsorbed and the volume of urine produced will be more. Thus there is perfect osmoregulation in the body.

Q1. The kidneys in human beings are a part of the system for

(a) nutrition  

(b) respiration 

(c) excretion 

(d) transportation 

Ans. (c) excretion.

Q2. The xylem in plants is responsible for

(a) the transport of water 

(b) the transport of food 

(c) the transport of amino acids 

(d) the transport of oxygen. 

Ans. (a) transport of water.

Q3. 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.

Q4. The breakdown of pyruvate to give carbon dioxide, water, and energy takes place in

(a) cytoplasm 

(b) chloroplast 

(c) mitochondria 

(d) nucleus. 

Ans. (c) mitochondria.

Q5. How are fats digested in our bodies? Where does this process take place? 

Ans. Fats are digested in the small intestine. The secretion of the liver, called bile breaks down the large globules of fat into smaller globules. This is called the emulsification of fats. The bile also makes the medium alkaline so that the pancreatic enzyme containing lipase further digests fats to form fatty acids. The alkaline medium is required for the pancreatic enzyme to act on lipase.

Q6. What is the role of saliva in the digestion of food? 

Ans. Saliva contains enzymes, and salivary amylase and is released in our mouth. It breaks down starch into sugar (complex carbohydrates into simpler ones).

Q7. What are the necessary conditions for autotrophic nutrition and what are its byproducts?

Ans. For autotrophic nutrition to take place the conditions necessary are light, carbon dioxide, and water should reach a cell that contains chlorophyll in it. Water first splits to release oxygen and hydrogen. This process is the photolysis of water. The hydrogen then combines with carbon dioxide to form glucose. 

The byproduct of autotrophic nutrition is oxygen which is released through stomata.

Q8. What are the differences between aerobic and anaerobic respiration? Name some organisms that use the anaerobic mode of respiration. 

Ans. 

(Note: Draw a Comparison Table)

Aerobic Respiration: 

1) Takes place in the presence of oxygen. 

2) Its end products are carbon dioxide and water. 

3) More energy is released. 

4) It takes place in the cytoplasm and mitochondria. 

5) Complete oxidation of glucose takes place. 

Anaerobic Respiration: 

1) Takes place in the absence of oxygen. 

2) Its end products are ethanol and carbon dioxide. 

3) Less energy is released. 

4) It takes place only in the cytoplasm. 

5) Incomplete oxidation of glucose takes place. 

Some organisms that use the anaerobic mode of respiration are yeast and bacteria.

Q9. How are the alveoli designed to maximize the exchange of gases? 

Ans. The alveoli are present at the terminal of the bronchioles. They are balloon-shaped structures that increase the surface area for the exchange of gases and are richly supplied with blood vessels to take oxygen to different cells.

Q10. What would be the consequences of a deficiency of haemoglobin in our bodies? 

Ans. Haemoglobin is a red pigment present in our blood that carries oxygen to all the parts of the body. If there is a deficiency of haemoglobin then the amount of oxygen reaching our body cells will decrease. This may lead to the release of less energy in our body, leading to a disease called anemia, Breathlessness, tiredness, and weakness are the symptoms of anemia.

Q11. Describe double circulation in human beings. Why is it necessary? 

Ans. The heart of human beings consists of two sides right and left. The right side of the heart receives de-oxygenated blood from the cells and tissues and sends it further for purification to the lungs. The left side of the 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 demand of human beings is too large and hence it is necessary for the separation of oxygenated and deoxygenated blood to meet this energy demand.

Q12. What are the differences between the transport of materials in the xylem and phloem? 

Ans. 

(Note: Draw a Comparison Table)

Transport in Xylem: 

1) Water and mineral salts are transported. 

2) The transport is generally passive. 

3) Trachieds and Vessels are dead cells. 

Transport in Phloem: 

1) Food in aqueous form is translocated. 

2) The transport is active. 

3) Sieve tubes and companion cells are living cells. 

Q13) Compare the functioning of alveoli in the lungs and nephrons in the kidneys with respect to their structure and functioning. 

Ans. 

Alveoli: 

1) It is the structural and functional unit of the lungs. 

2) It is thin-walled, has a large surface area, and is richly supplied with blood vessels. 

3) It removes carbon dioxide from the blood. 

Nephron: 

1) It is the structural and functional unit of kidneys. 

2) It is thin-walled, has a large surface area, and is richly supplied with blood vessels. 

3) It removes nitrogenous wastes from the blood.