Chapter 6: Life Processes

Answer: In multi-cellular organisms, the cells are not in direct contact with the environment. Diffusion is a slow process and cannot transport oxygen to all body cells efficiently. Hence, specialised respiratory systems are needed.

Answer: The most common criterion is movement (visible or at cellular level) and metabolism. Other signs include growth, respiration, response to stimuli, reproduction, and excretion.

Answer: Organisms use outside raw materials for growth, repair, energy production, and maintaining life processes. These include food (carbohydrates, proteins, fats), water, and oxygen.

Answer: Nutrition, respiration, transportation, and excretion are essential for maintaining life. These processes help obtain and utilise energy, distribute materials, and remove wastes.

Answer: Autotrophs (e.g., plants) synthesize their own food using carbon dioxide, water, and sunlight. Heterotrophs (e.g., animals) obtain food from other organisms. Autotrophs use inorganic sources; heterotrophs depend on organic compounds.

Answer: (i) Carbon dioxide – from air through stomata. (ii) Water – from soil through roots. (iii) Sunlight – solar energy absorbed by chlorophyll. (iv) Minerals – from soil via roots.

Answer: Hydrochloric acid (HCl) in the stomach (i) creates an acidic medium for the enzyme pepsin to act on proteins, (ii) kills harmful bacteria that enter with food, and (iii) helps in the digestion of food.

Answer: Digestive enzymes break down complex food molecules (carbohydrates, proteins, fats) into simpler, absorbable forms. For example, amylase breaks starch, pepsin breaks proteins, and lipase breaks fats.

Answer: The small intestine has finger-like projections called villi that increase the surface area for absorption. Villi are richly supplied with blood vessels that carry absorbed nutrients to all body parts.

Answer: Terrestrial organisms obtain oxygen directly from the air, which contains a much higher concentration of oxygen than water. Aquatic organisms must extract dissolved oxygen from water, which is harder and less efficient.

Answer: (i) Aerobic respiration: Glucose → Pyruvate (in cytoplasm) → CO₂ + H₂O + energy (in mitochondria, using O₂). (ii) Anaerobic respiration in yeast: Glucose → Pyruvate → Ethanol + CO₂ + energy. (iii) Anaerobic respiration in muscles (during exercise): Glucose → Pyruvate → Lactic acid + energy.

Answer: Oxygen is transported by haemoglobin in red blood cells. Carbon dioxide is transported mainly as bicarbonate ions in plasma (about 70%), some dissolved in plasma, and some bound to haemoglobin as carbaminohaemoglobin.

Answer: Lungs contain millions of tiny air sacs called alveoli. Alveoli have thin walls, a rich network of capillaries, and a large surface area, which maximises gas exchange (O₂ and CO₂).

Answer: Components: (i) Heart – pumps blood. (ii) Blood vessels (arteries, veins, capillaries) – carry blood. (iii) Blood – transports oxygen, nutrients, hormones, and wastes. (iv) Lymph – helps in immunity and fluid balance.

Answer: Mammals and birds have high energy needs and maintain a constant body temperature. Separation of oxygenated and deoxygenated blood allows efficient oxygen supply to tissues, supporting high metabolic rate.

Answer: Xylem transports water and minerals from roots to other parts. Phloem transports food (sucrose) from leaves to other parts. Both are vascular tissues.

Answer: Water and minerals are absorbed by roots and transported upward through xylem vessels. Transpiration pull (due to evaporation from leaves) and root pressure drive the movement.

Answer: (c) excretion.

Answer: (a) transport of water.

Answer: (d) all of the above.

Answer: (b) mitochondria.

Answer: Fats are digested in the small intestine. Bile (from liver) emulsifies fats into small droplets. Pancreatic lipase breaks them into fatty acids and glycerol.

Answer: Saliva contains the enzyme salivary amylase, which breaks down starch into simple sugars. It also moistens food, making it easier to swallow.

Answer: Conditions: sunlight, chlorophyll, carbon dioxide, water, and minerals. By-products: oxygen (released) and glucose (used as food).

Answer: Aerobic: uses O₂, produces CO₂ + H₂O + large energy, occurs in mitochondria. Anaerobic: no O₂, produces lactic acid (animals) or ethanol + CO₂ (yeast) + small energy, occurs in cytoplasm. Anaerobic organisms: yeast, some bacteria, and sometimes human muscle cells during exercise.

Answer: Alveoli have thin walls, a large surface area, and extensive capillary network. This allows efficient diffusion of O₂ into blood and CO₂ out of blood.

Answer: Haemoglobin carries oxygen. Deficiency leads to anaemia: fatigue, weakness, shortness of breath, pale skin, and reduced oxygen supply to tissues.

Answer: Double circulation: blood passes through the heart twice in one cycle. Pulmonary circuit (heart → lungs → heart) and systemic circuit (heart → body → heart). It ensures oxygenated and deoxygenated blood are separate, providing efficient oxygen delivery for high metabolic needs.

Answer: Xylem transports water and minerals (upward, using transpiration pull and root pressure). Phloem transports food (bidirectional, using energy). Xylem cells are dead, phloem cells are living.

Answer: Alveoli: thin-walled sacs for gas exchange (O₂/CO₂). Nephrons: tubular structures for filtration and urine formation (waste removal). Both have large surface area and capillary networks.

Answer: Liver produces bile that emulsifies fats, stores glycogen, detoxifies harmful substances, and synthesizes blood proteins.

Answer: Pulmonary artery. It carries deoxygenated blood from the right ventricle to the lungs.

Answer: Oxygen concentration is low in water. Aquatic animals need to breathe faster to extract sufficient oxygen.