Life Processes: 10 CBSE Science Biology

Question: What are the differences between autotrophic nutrition and heterotrophic nutrition? Draw a diagram showing cross-section of a leaf and label on it: Phloem, Xylem, Vascular bundle, Lamina.

Answer:

Autotrophic Nutrition:

1. Food is made from inorganic components.
2. Chlorophyll and sunlight is required.
3. Photosynthesis or chemo-synthesis takes place.
4. It occurs in green plants and some bacteria.

Heterotrophic Nutrition:

1. Food is obtained from organic components
2. Chlorophyll and sunlight is not required.
3. These processes do not occur.
4. It occurs in animals and insectivorous plants.

Question: Where do plants get each of the raw materials required for photosynthesis?

Answer: For photosynthesis plants obtain the following raw materials:

1. Water: Roots absorb it from the soil.
2. Carbondioxide: Stomata in leaves allow the carbon dioxide gas to enter into the plant.
3. Chlorophyll: It is already present in the leaves.
4. Sunlight: From the sun.

Question: What is the role of acid in our stomach?

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

Question: What is the function of digestive enzymes?

Answer: Digestive enzymes act on the complex food to break them into simpler components.

Question: How is the small intestine designed to absorb the digested food?

Answer: Small intestine has finger like projection in the inner lining which increases the surface area for absorption of food. These finger like projections are called villi. The villi are richly supplied with blood vessels which take the absorbed food to each and every cell of the body.

Question: What advantages over an aquatic organism does a terrestrial organism have with regard to obtaining oxygen for respiration?

Answer: Aquatic organism takes in the oxygen dissolved in water which is in less percentage than the oxygen present in air. Terrestrial organism can take in more amount of oxygen at a time than aquatic organisms.

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

Answer: Glucose (6 carbon  molecules) is broken down first into pyruvate (3 carbon molecules) in the cytoplasm. This step is same in all organisms. This step is known as Glycolysis and some amount of energy (2 ATP molecules) is also released during this step. Further breakdown of pyruvate takes place in the following ways:

1. In yeast: In the absence of oxygen, pyruvate is broken down into ethanol (C₂H₅OH), carbon dioxide and some amount of energy is also released.
2. In muscle cells: Due to lack of oxygen, pyruvate is broken down into lactic acid energy is also released.
3. In most of aerobic organisms: In the presence of oxygen, pyruvate is broken down into carbon dioxide, water and large amount of energy is place in the mitochondria of cells and is called Krebs cycle.

Question: How is oxygen and carbon dioxide transported in human beings?

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

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

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

Question: What are the components of transport system in human beings? What are the functions of these components?

Answer: In human beings the transport system consists of the following:

1. Heart: It acts as a pumping organ.
2. Blood: It is the transport medium. It is made up of:
   (i) Plasma: It carries food molecules, nitrogenous wastes, salts, carbon dioxide, hormones proteins etc. in a dissolved form.
   (ii) RBC: Consists of haemoglobin and transports oxygen.
   (iii) WBC: Helps to fight infection.
   (iv) Platelets: Helps in the clotting of blood.
3. Blood vessels:
   (i) Arteries: Carry oxygenated blood away from the heart to each and every cell.
   (ii) Veins: Bring de-oxygenated blood to heart for purification.

Question: Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds?

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

Question: What are the components of the transport system in highly organised plants?

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

Question: How are water and minerals transported in plants?

Answer: 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, creates the 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.

Question: How is food transported in plants?

Answer: The transport of food in plants is called translocation. It takes place with the help of a conducting tissue called phloem. Phloem transports glucose, amino acids and other substances from leaves to root, shoot, fruits and seeds. Sieve tube 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 which have less pressure. This pressure helps in the movement of material in plants.

Question: (a) Describe the structure and functioning of nephrons.
(b) What happens to glucose that enters the nephron along with filtrate?

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

Working of Nephron:

1. Filtration: The renal artery or afferent artery is wider and slowly it becomes a narrow tube in the glomerulus. Due to difference in the width, pressure difference is caused and water with dissolved impurities are squeezed out from the tube. It is collected in the Bowman’s capsule which is cup like structure and passes into the tube.
2. Reabsorbtion: The above filtrate passes through the tubule where the major amount of water, glucose, amino acids are selectively reabsorbed by the capillaries which are surrounding the tubule.
3. Urine formation: The water and impurities which is not reabsorbed is sent to a collecting duct. This filtrate contains more of dissolved nitrogenous wastes i.e. urea and hence it is termed as urine. From here the urine enters the ureter and is collected in urinary bladder.

(b) Glucose that enters the nephron along with the filtrate after passing through the glomerulus, passes from the tubule of nephron where it is selectively reabsorbed and sent back to blood.

Question: What are the methods used by plants to get rid of excretory products?

Answer: Wastes excreted from plants are:

1. Gaseous wastes: through stomata pores CO2 is given out during respiration and O2 is given out during photosynthesis.
2. Liquid wastes (water): through stomata pores by transpiration.
3. Other wastes: are stored in leaves dead cells and the leaves fall off. Some other waste products are stored as resins and gums in old xylem of the plant and other wastes are also thrown out from nodes into the soil.

Question: How is the amount of urine produced regulated?

Answer: The amount of urine produced depends on how much excess water there is in the body and how much of 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 kidney will be reabsorbed into the blood from the filtrate in the tubule. Thus the volume of urine produced will be less.
In winters, when we do not sweat a lot, a lite water and salts will be reabsorbed and the volume of urine produced will be more.
Thus there is perfect osmoregulation in the body.

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

Answer: 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 make 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.

Question: What is the role of saliva in the digestion of food?

Answer: When we eat something we like, our mouth ‘waters’. This is actually not only water, but also a fluid called saliva secreted by the salivary glands. Another aspect of the food we ingest is its complex nature. If it is to be absorbed from the alimentary canal, it has to be broken into smaller molecules. This is done with the help of biological catalysts called enzymes. 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.

Question: What are the necessary conditions for autotrophic nutrition and what are its byproducts?

Answer: Carbon and energy requirements of the autotrophic organism are fulfilled by photosynthesis. It is the process by which autotrophs take in substances from the outside and convert them into stored forms of energy. This material is taken in the form of carbon dioxide and water, which is converted into carbohydrates in the presence of sunlight and chlorophyll. Carbohydrates are utilized for providing energy to the plant. The carbohydrates, which are not used immediately, are stored in the form of starch, which serves as the internal energy reserve to be used as and when required by the plant.

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

Answer: Aerobic respiration:

1. Takes place in presence of oxygen.
2. Its end products are carbon dioxide and water.
3. More energy is released.
4. It takes place in cytoplasm and mitochondria.
5. Complete oxidation of glucose takes place.

Anaerobic respiration:

1. Takes place in 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.

Question: How are the alveoli designed to maximize the exchange of gases?

Answer: 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.