NCERT Solutions for Class 10 Science Chapter 5 Life Processes

Answer: In multicellular organisms like humans, all body cells are not in direct contact with the external environment. Diffusion is a slow physical process that cannot move oxygen quickly over large distances to reach deep-seated tissues. Therefore, complex circulatory systems with respiratory pigments (hemoglobin) are required.

Answer: The most important criterion is molecular movement inside body cells. Additionally, visible external movements (such as breathing, growth, locomotion, and response to stimuli) help determine if an organism is living.

Autotrophic Nutrition: Organisms synthesize their own organic food from simple inorganic raw materials (CO₂ and H₂O) using sunlight and chlorophyll. Example: Green plants and autotrophic bacteria.

Heterotrophic Nutrition: Organisms cannot synthesize their own food and depend directly or indirectly on producers for nutrition. Example: Animals, fungi, and human beings.

Answer: Hydrochloric acid (HCl) in the stomach:

1. Creates an acidic medium (pH ~ 1.5 - 2.5) necessary for the activation and proper functioning of the protein-digesting enzyme pepsin.

2. Kills harmful bacteria and microbes present in swallowed food.

Answer: The inner lining of the small intestine features millions of tiny finger-like projections called villi. These villi greatly increase the surface area available for absorption and are richly supplied with blood capillaries to transport absorbed nutrients to all body cells.

Answer: Terrestrial organisms obtain oxygen from the atmosphere, where the concentration of oxygen is significantly higher (~21%). Aquatic organisms extract dissolved oxygen from water, which is present in much lower concentrations. Thus, terrestrial organisms do not need to breathe as rapidly as aquatic animals to get sufficient oxygen.

Answer: Inside the lungs, the passage divides into smaller tubes called bronchioles, terminating in balloon-like structures called alveoli. Alveoli provide an extremely thin, highly vascularized network of blood capillaries with a huge surface area (approx. 80 m²) for rapid exchange of gases.

1. Heart: A muscular pumping organ that pumps oxygenated blood to tissues and deoxygenated blood to lungs.

2. Blood: Fluid connective tissue containing RBCs (carries O₂), WBCs (fights infections), Platelets (blood clotting), and Plasma (transports nutrients, CO₂, and nitrogenous wastes).

3. Blood Vessels: Arteries (carry blood away from heart), Veins (carry blood towards heart), and Capillaries (allow exchange between blood and tissues).

(a) nutrition
(b) respiration
(c) excretion
(d) transportation

Correct Answer: (c) excretion.

(a) transport of water
(b) transport of food
(c) transport of amino acids
(d) transport of oxygen

Correct Answer: (a) transport of water.

Aerobic Respiration: Takes place in the presence of oxygen in mitochondria, produces CO₂, H₂O, and releases a high amount of energy (38 ATP).

Anaerobic Respiration: Takes place in the absence of oxygen in cytoplasm, produces Ethanol/Lactic acid and CO₂, and releases very little energy (2 ATP).

Answer:

• Structure: A nephron is the structural unit of a kidney consisting of a cup-shaped Bowman's capsule containing a cluster of capillaries called Glomerulus, connected to a long coiled renal tubule surrounded by capillaries.

• Functioning: Blood enters the glomerulus under high pressure where glucose, amino acids, salts, and urea are filtered into Bowman's capsule (Ultrafiltration). As filtrate moves down the tubular part, essential substances (glucose, water, salts) are selectively reabsorbed back into capillaries, while concentrated urine containing urea passes into the collecting duct.