CBSE Class 10 Science Life Processes MCQs Set 14

Answer: (b) autotrophs. Autotrophs use CO₂, water and sunlight to prepare carbohydrates.

Teacher's Note:
1. Green plants are the main autotrophs.
2. Heterotrophs depend on others for food.

Answer: (a) 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂. Carbon dioxide and water, in the presence of sunlight and chlorophyll, form glucose and oxygen.

Teacher's Note:
1. Option 2 is the equation of respiration.
2. Photosynthesis stores energy, whereas respiration releases it.

Answer: (b) chloroplasts. Chloroplasts contain chlorophyll that traps light energy.

Teacher's Note:
1. Mitochondria are the site of aerobic respiration.
2. Leaves have many chloroplasts in the mesophyll.

Answer: (b) water. Light energy splits water molecules into hydrogen and oxygen.

Teacher's Note:
1. Hydrogen is then used to reduce CO₂.
2. This is the light reaction.

Answer: (b) take in water and swell. Water enters the guard cells, which swell and curve, opening the pore.

Teacher's Note:
1. When water leaves, the pore closes.
2. Stomata exchange gases and release water vapour.

Answer: (b) Iodine solution. Starch turns iodine solution blue-black.

Teacher's Note:
1. The leaf is first boiled in alcohol to remove chlorophyll.
2. A leaf kept in the dark shows no such change.

Answer: (b) pseudopodia surrounding the particle. It engulfs food with finger-like pseudopodia and forms a food vacuole.

Teacher's Note:
1. This type of nutrition is holozoic.
2. Digestion occurs inside the vacuole.

Answer: (b) starch to sugar (maltose). Saliva starts the digestion of starch in the mouth.

Teacher's Note:
1. Salivary amylase is the enzyme in saliva.
2. Chewing mixes food with it.

Answer: (c) Liver. The liver is a digestive gland; food does not pass through it.

Teacher's Note:
1. The liver secretes bile into the duodenum.
2. The alimentary canal is the food passage from mouth to anus.

Answer: (a) peristalsis. Peristaltic waves move food along the tract.

Teacher's Note:
1. These movements occur in the oesophagus and intestines.
2. They are involuntary.

Answer: (b) kills bacteria and activates pepsin. It creates an acidic medium for pepsin and destroys germs in food.

Teacher's Note:
1. Mucus lining protects the stomach wall from this acid.
2. Pepsin digests proteins.

Answer: (b) liver, emulsification of fats. The liver makes bile; it makes the medium alkaline and breaks large fat globules into smaller ones.

Teacher's Note:
1. Bile is stored in the gall bladder.
2. It contains no digestive enzymes.

Answer: (b) Trypsin. Trypsin digests proteins, and pancreatic juice also has lipase and amylase.

Teacher's Note:
1. Pepsin is secreted by the stomach.
2. The pancreas thus acts on all three food types.

Answer: (b) increase the surface area for absorption. Finger-like villi are richly supplied with blood vessels.

Teacher's Note:
1. A large surface area allows fast absorption of digested food.
2. The small intestine is very long for the same reason.

Answer: (b) cytoplasm. Glucose is split into pyruvate (a 3-carbon molecule) in the cytoplasm.

Teacher's Note:
1. Pyruvate then follows aerobic or anaerobic routes.
2. This step is common to all forms of respiration.

Answer: (b) ethanol and CO₂. Pyruvate is converted to ethanol and carbon dioxide with little energy released.

Teacher's Note:
1. In muscles lactic acid forms instead and can cause cramps.
2. Fermentation uses this process.

Answer: (b) ATP. ATP releases energy when its terminal phosphate bond is broken.

Teacher's Note:
1. Energy from respiration is used to make ATP from ADP and phosphate.
2. ATP is used for contraction and synthesis.

Answer: (a) water has less dissolved oxygen than air. The amount of oxygen dissolved in water is much lower than in air.

Teacher's Note:
1. Fish take in water through the mouth and pass it over gills.
2. Gills have thin, richly supplied filaments.

Answer: (c) alveoli. Alveoli are thin-walled balloon-like sacs surrounded by capillaries.

Teacher's Note:
1. They provide a very large surface area.
2. Oxygen enters the blood while carbon dioxide leaves.

Answer: (b) haemoglobin. Haemoglobin in red blood cells has a high affinity for oxygen.

Teacher's Note:
1. Its deficiency causes anaemia.
2. Most CO₂ is carried in dissolved form in plasma.

Answer: (b) pulmonary vein. The pulmonary vein is the exception among veins as it carries oxygenated blood.

Teacher's Note:
1. The pulmonary artery carries deoxygenated blood to the lungs.
2. Remember this pair of exceptions.

Answer: (c) four chambers. There are two atria and two ventricles, which keep oxygenated and deoxygenated blood separate.

Teacher's Note:
1. This separation supports a high metabolic rate.
2. Birds and mammals have four-chambered hearts.

Answer: (b) double circulation. Blood goes through the heart once for the lungs and once for the body.

Teacher's Note:
1. Fishes have single circulation.
2. Humans have double circulation.

Answer: (b) 120/80 mm Hg. Systolic pressure is about 120 mm Hg and diastolic about 80 mm Hg.

Teacher's Note:
1. Systolic pressure is measured when the ventricles contract.
2. Diastolic is during relaxation.

Answer: (c) Platelets. Platelets plug leaks and start clot formation at injuries.

Teacher's Note:
1. Clotting prevents loss of blood.
2. Plasma carries food, CO₂ and nitrogenous wastes.

Answer: (b) xylem. Xylem vessels and tracheids conduct water and minerals upwards.

Teacher's Note:
1. Transpiration pull helps in the ascent.
2. Phloem carries food made in leaves.

Answer: (b) translocation. Translocation occurs through the phloem and uses energy from ATP.

Teacher's Note:
1. It moves sucrose to growing parts and storage organs.
2. It works in both upward and downward directions.

Answer: (b) nephron. Each nephron filters blood, reabsorbs useful substances and passes out urine.

Teacher's Note:
1. Glomerulus and Bowman's capsule form the filtering part.
2. A human kidney has about a million nephrons.

Answer: (a) dialysis. Nitrogenous wastes diffuse from the blood into dialysing fluid across a semipermeable membrane.

Teacher's Note:
1. The cleaned blood is returned to the patient.
2. This treatment is called haemodialysis.

Answer: (a) Both A and R are true and R is the correct explanation of A. A long intestine gives time for digestion of cellulose, so R explains A.

Teacher's Note:
1. Carnivores have a shorter intestine since meat digests easily.
2. The size of the intestine depends on the diet.