[16/08, 7:46 PM] Abhi: The energy and carbon requirements of the autotrophic organism are obtained by the process of photosynthesis. It is defined as the process by which autotrophs take in substances from the outside surroundings and convert them into stored forms of energy. This substance is taken in the form of carbon dioxide and water, which are converted into carbohydrates in the presence of sunlight and chlorophyll. The main purpose of carbohydrates is to provide energy to the plant. The carbohydrates are not utilised immediately, but they are stored in the form of starch, which serves as an internal energy reserve. The stored energy can be used as and when required by the plant. 8. What are the differences between aerobic and anaerobic respiration? Name some organisms that use the anaerobic mode of respiration. Solution: Aerobic respiration The process takes place in the presence of free oxygen. The products of aerobic respiration are CO2, water and energy. The first step of aerobic respiration (glycolysis) takes place in the cytoplasm, while the next step takes place in mitochondria. The process of aerobic respiration takes place in all higher organisms. In this process, complete oxidation of glucose takes place. Anaerobic respiration The process takes place in the absence of free oxygen. The products of anaerobic respiration are ethyl alcohol, CO2 and a little energy. Even in anaerobic respiration, the first step takes place in the cytoplasm, while the next step takes place in mitochondria. In this process, the glucose molecules are incompletely broken down. The process of anaerobic respiration takes place in lower organisms like yeast, some species of bacteria and parasites like tapeworms. 9. How are the alveoli designed to maximise the exchange of gases? Solution: The lung is an important part of the body. The passage inside the lungs divides into smaller and smaller tubes, which finally terminate in balloon-like structures called alveoli. The alveoli provide a surface where the exchange of gases can take place. The walls of the alveoli usually contain an extensive network of blood vessels. We know that when we breathe in, we lift our ribs, flatten our diaphragm and the chest cavity becomes larger. Because of this action, the air is sucked into the lungs and fills up the expanded alveoli. The blood brings the essential carbon dioxide from the rest of the body and supplies it to the alveoli; the oxygen in the alveolar air is taken up by the blood in the alveolar blood vessels to be transported to all other cells of the body. During the normal 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 carbon dioxide to be released. 10. What would be the consequences of a deficiency of haemoglobin in our bodies? Solution: Haemoglobin is a protein responsible for the transportation of oxygen to the body cells for cellular respiration. A deficiency of Haemoglobin can affect the oxygen-carrying capacity of RBCs. This lead to a lack of oxygen in our body cells. Haemoglobin deficiency leads to a disease called anaemia. 11. Describe the double circulation of blood in human beings. Why is it necessary? Solution: Double circulation means, in a single cycle, blood goes twice in the heart. The process helps in separating oxygenated and deoxygenated blood to maintain a constant body temperature. The double circulatory system of blood includes Pulmonary circulation Systemic circulation. Pulmonary circulation The right ventricle pumps deoxygenated blood into the lungs, where it is oxygenated. The oxygenated blood is brought back to the left atrium, and from there, it is pumped into the left ventricle. Finally, blood goes into the aorta for systemic circulation. Systemic circulation The oxygenated blood is pumped to various parts of the body from the left ventricle. The deoxygenated blood from different parts of the body passes through the vena cava to reach the right atrium. The right atrium transfers the blood into the right ventricle. 826 12. What are the differences between the transport of materials in the xylem and phloem? Solution: Transport of Materials in Xylem Transport of Materials in Phloem Xylem tissue helps in the transport of water and minerals. Phloem tissue helps in the transport of food. Water is transported upwards from roots to all other plant parts. Food is transported in both upward and downward directions. 291 13. Compare the functioning of alveoli in the lungs and nephrons in the kidneys with respect to their structure and functioning. Solution: Alveoli Nephrons Structure Structure (i) Alveoli are tiny balloon-like structures present inside the lungs. (i) Nephrons are tubular structures present inside the kidneys. (ii) The walls of the alveoli are one cell thick, and it contains an extensive network of blood capillaries. (ii) Nephrons are made of glomerulus, Bowman’s capsule, and a long renal tube. Function Function (i) The exchange of O2 and CO2 takes place between the blood of the capillaries that surround the alveoli and the gases present in the alveoli. (i) The blood enters the kidneys through the renal artery. The blood is entered here, and the nitrogenous waste in the form of urine is collected by the collecting duct. (ii) Alveoli are the site of gaseous exchange. (ii) Nephrons are the basic filtration unit. [16/08, 8:31 PM] ABHIJIT: K
