CBSE Class 10 Biology Life Processes MCQs Set 29

Answer: (a) Fishes

Explanation:
1. In fishes, blood passes through the heart only once in a complete circuit of the body.
2. Man has double circulation.

Teacher's Note:
1. Fish heart has two chambers.
2. Blood goes heart, gills, body, heart.

Answer: (b) 120/80 mm Hg

Explanation:
1. Normal blood pressure is 120 mm Hg during systole and 80 mm Hg during diastole.
2. It is written as 120/80.

Teacher's Note:
1. The systolic value is always higher than the diastolic value.
2. High blood pressure is called hypertension.

Answer: (d) Sphygmomanometer

Explanation:
1. A sphygmomanometer measures arterial blood pressure.
2. It is used with a stethoscope to hear the sounds.

Teacher's Note:
1. A stethoscope alone only helps listen to sounds.
2. ECG records electrical activity of the heart.

Answer: (c) 70 to 80 times

Explanation:
1. The normal resting heart rate is about 72 beats per minute (70 to 80).
2. It increases during exercise.

Teacher's Note:
1. The rate is counted as pulse rate.
2. It is higher in children.

Answer: (c) Stethoscope

Explanation:
1. A stethoscope amplifies the sounds of the heart.
2. The 'lub-dub' sounds come from the closing of heart valves.

Teacher's Note:
1. An electrocardiograph records the electrical activity as an ECG.
2. A sphygmomanometer measures blood pressure.

Answer: (b) Fish

Explanation:
1. In a closed system, blood stays inside the vessels throughout.
2. Fishes, like all vertebrates and annelids, have a closed system.

Teacher's Note:
1. Cockroaches, scorpions and most molluscs have an open system.
2. In an open system, blood flows into body cavities.

Answer: (b) Arthropods

Explanation:
1. Arthropods (insects, spiders, crustaceans) have an open system with blood bathing the tissues in a haemocoel.
2. Fishes, amphibians and earthworms have a closed system.

Teacher's Note:
1. Open systems have low pressure.
2. In insects the blood does not carry oxygen.

Answer: (a) The concentration of solutes in the cell sap is high

Explanation:
1. Water moves by osmosis from a region of low solute concentration (soil water) to high solute concentration (cell sap).
2. So the root hair cell sap must be more concentrated than the soil water.

Teacher's Note:
1. If the soil had more salts, water would move out.
2. This is why too much fertiliser can damage plants.

Answer: (a) Xylem vessel system

Explanation:
1. Water and minerals move upwards through xylem vessels and tracheids.
2. Phloem carries food.

Teacher's Note:
1. Xylem has dead cells with thick, lignified walls.
2. Water moves from roots to leaves in a continuous column.

Answer: (c) Sucrose

Explanation:
1. Sucrose is the main form in which sugar is translocated in phloem.
2. It is soluble and chemically stable.

Teacher's Note:
1. Starch is insoluble and is only stored.
2. Translocation in phloem needs energy and is two-way.

Answer: (b) Cohesion of water and transpiration pull

Explanation:
1. Transpiration from leaves creates a suction (pull).
2. Cohesion between water molecules keeps the water column continuous, so water is pulled up even to the top of tall trees.

Teacher's Note:
1. Root pressure can push water only a few metres.
2. Capillary rise is too small for tall trees.

Answer: (a) Increase

Explanation:
1. A higher temperature increases evaporation of water from leaves and opens the stomata wider.
2. So transpiration increases.

Teacher's Note:
1. Humidity lowers the rate of transpiration.
2. Wind increases it.

Answer: (a) There is high humidity in the atmosphere

Explanation:
1. In humid air, the air is already full of water vapour, so little evaporation takes place.
2. Dry air and wind increase transpiration.

Teacher's Note:
1. The diffusion of vapour depends on the difference in concentration.
2. Closing the stomata also reduces transpiration.

Answer: (a) Excretion of minerals

Explanation:
1. Transpiration pulls water and the minerals dissolved in it up the plant, and cools the leaves.
2. Minerals are not excreted through transpiration.

Teacher's Note:
1. Water vapour leaves, but the minerals stay in the plant.
2. Excess water loss can cause wilting.

Answer: (b) a-(ii), b-(iii), c-(i), d-(v), e-(iv)

Explanation:
1. Phloem translocates food; arteries carry oxygenated blood away from the heart (except the pulmonary artery).
2. Red blood cells contain haemoglobin; xylem conducts water to leaves; veins have thin walls.

Teacher's Note:
1. Match the vessel with its direction of flow and its walls.
2. Haemoglobin is the respiratory pigment.

Answer: (b) Into the guard cells

Explanation:
1. When water enters the guard cells they swell and the stomatal pore opens.
2. When water leaves, they shrink and close the pore.

Teacher's Note:
1. Opening is regulated by potassium ion movement.
2. Stomata usually open in light.

Answer: (b) Removal of useless substances and harmful metabolic nitrogenous waste

Explanation:
1. Excretion is the removal of metabolic waste, especially nitrogenous waste, from the body.
2. Substances the body needs are not excreted.

Teacher's Note:
1. Excretion removes products such as urea and CO₂.
2. It helps keep the internal environment steady.

Answer: (d) Every cell of the body

Explanation:
1. Waste products are formed by metabolism, which takes place in every cell.
2. Kidneys and other organs only remove them.

Teacher's Note:
1. The liver forms urea but cells form ammonia first.
2. The rectum stores undigested waste, which is not excreted waste.

Answer: (b) Ammonia in tadpole and urea in adult frog

Explanation:
1. The tadpole lives in water and excretes ammonia (ammonotelic).
2. The adult frog lives on land and excretes urea (ureotelic).

Teacher's Note:
1. Ammonia is very toxic but easily dissolves in water.
2. Land animals convert it into less toxic urea or uric acid.

Answer: (b) Reptiles

Explanation:
1. Reptiles, birds and insects excrete nitrogen as uric acid.
2. It is almost insoluble and saves water.

Teacher's Note:
1. Mammals and adult amphibians excrete urea.
2. Bony fishes excrete ammonia.

Answer: (b) Lizards and birds

Explanation:
1. Uricotelic animals excrete uric acid, as lizards and birds do.
2. Frogs, cattle and man are ureotelic.

Teacher's Note:
1. Uric acid is excreted as a semi-solid paste.
2. This helps the animals to conserve water.

Answer: (b) Flame cell - bird

Explanation:
1. Flame cells are the excretory organs of flatworms.
2. Birds have kidneys with nephrons.

Teacher's Note:
1. Earthworms have nephridia and insects have Malpighian tubules.
2. Apes, being mammals, have nephrons.

Answer: (b) Uric acid

Explanation:
1. Insects excrete uric acid through Malpighian tubules.
2. This conserves water.

Teacher's Note:
1. Uric acid is passed with the faeces.
2. Insects are uricotelic.