CBSE Class 10 Biology Life Processes MCQs Set 20

Answer: (b) Blood

Explanation:
1. Blood is a fluid connective tissue that transports food, gases, hormones and wastes.
2. Lymph helps too, but blood is the main transport fluid.

Teacher's Note:
1. Blood has plasma and cells.
2. About 5 litres of blood circulate in an adult.

Answer: (d) Red blood cells

Explanation:
1. Haemoglobin in RBCs binds oxygen.
2. White cells defend against infection and platelets help in clotting.

Teacher's Note:
1. RBCs also carry some carbon dioxide.
2. Mature RBCs in humans lack a nucleus.

Answer: (c) white blood cells

Explanation:
1. WBCs have a nucleus while mature human RBCs and platelets do not.
2. This is why WBCs can be used to extract DNA.

Teacher's Note:
1. WBCs protect the body from disease.
2. Platelets are small cell fragments.

Answer: (b) blood clotting

Explanation:
1. Platelets gather at an injury and help form a clot.
2. Oxygen is carried by RBCs and germs are attacked by WBCs.

Teacher's Note:
1. Clotting reduces blood loss.
2. Fibrinogen is changed into fibrin in the clot.

Answer: (c) veins

Explanation:
1. Valves in veins prevent backward flow of blood at low pressure.
2. Arteries do not have valves except at the base of the aorta and pulmonary artery inside the heart.

Teacher's Note:
1. Veins have thin walls and wide lumen.
2. Muscular movement also helps push blood in veins.

Answer: (b) capillaries

Explanation:
1. Capillaries have walls only one cell thick.
2. This allows diffusion of gases, nutrients and wastes.

Teacher's Note:
1. They connect arterioles with venules.
2. There is no muscle in the capillary wall.

Answer: (c) They pump blood to the lungs and the whole body

Explanation:
1. Ventricles need strong contraction to push blood out for long distances.
2. Atria only receive blood and push it into the ventricles.

Teacher's Note:
1. The left ventricle is the thickest of all.
2. Strong muscles give high pressure.

Answer: (a) right atrium

Explanation:
1. Superior and inferior venae cavae pour blood into the right atrium.
2. Oxygenated blood enters the left atrium via pulmonary veins.

Teacher's Note:
1. The right side of the heart is called the pulmonary heart.
2. Remember: right side has deoxygenated blood.

Answer: (c) it supplies enough oxygen to meet high energy needs of warm blooded animals

Explanation:
1. Complete separation gives oxygen rich blood to tissues, which is important for birds and mammals that maintain body temperature.
2. Mixed blood would reduce the oxygen supply.

Teacher's Note:
1. This is the reason birds and mammals have a double circulation with four chambers.
2. Amphibians have three chambers and some mixing of blood.

Answer: (b) once in a complete circuit

Explanation:
1. Fishes have a two chambered heart and single circulation.
2. Only deoxygenated blood passes through the heart.

Teacher's Note:
1. In double circulation blood passes twice through the heart.
2. Single circulation is suitable for low energy needs.

Answer: (a) passes twice through the heart in one complete circuit

Explanation:
1. Blood goes through the heart to the lungs and returns, and then goes through the heart again to the body.
2. The two parts are pulmonary and systemic circulation.

Teacher's Note:
1. Birds and mammals show double circulation.
2. This keeps the blood pressure high.

Answer: (d) Right ventricle, pulmonary artery, lungs, pulmonary vein, left atrium

Explanation:
1. Deoxygenated blood goes from the right ventricle to the lungs and returns oxygenated to the left atrium.
2. The other routes mix vessels from the systemic circuit.

Teacher's Note:
1. Pulmonary circulation is the shorter circuit.
2. Systemic circulation begins at the left ventricle.

Answer: (c) 120/80 mm Hg

Explanation:
1. Systolic pressure is about 120 and diastolic about 80 mm Hg.
2. Systolic pressure is greater, as it is measured at contraction of ventricles.

Teacher's Note:
1. The instrument used is a sphygmomanometer.
2. High blood pressure is called hypertension.

Answer: (b) when the ventricles are contracting

Explanation:
1. At the time of maximum contraction the pressure in the arteries is highest.
2. Diastolic pressure is measured at relaxation.

Teacher's Note:
1. Systole means contraction.
2. The pulse also matches the heartbeat.

Answer: (d) Transport of oxygen to tissues

Explanation:
1. Oxygen is carried by red blood cells, not by lymph.
2. Lymph collects tissue fluid, has lymphocytes against germs and carries digested fats.

Teacher's Note:
1. Lymph nodes filter germs.
2. Lymphatic system is called an open circulatory system.

Answer: (b) Xylem parenchyma

Explanation:
1. Only xylem parenchyma is a living tissue.
2. Vessels, tracheids and fibres are dead and lignified.

Teacher's Note:
1. Phloem has all living cells except phloem fibres.
2. Dead conducting cells make a continuous hollow channel.

Answer: (d) stomata

Explanation:
1. About 80 to 90 percent of the water is lost through stomata.
2. The cuticle loses about 9 percent and lenticels about 1 percent.

Teacher's Note:
1. Stomata are more numerous on the lower side of dorsiventral leaves.
2. Transpiration also cools the plant.

Answer: (c) translocation

Explanation:
1. Translocation takes place through the phloem.
2. Transpiration is loss of water vapour and ascent of sap is upward movement of water.

Teacher's Note:
1. It can be upward or downward.
2. It needs energy in the form of ATP.

Answer: (b) sieve tubes with help of companion cells

Explanation:
1. Sugars are loaded into sieve tubes with the help of the adjacent companion cells.
2. Vessels and tracheids are the conducting cells of xylem.

Teacher's Note:
1. Sieve plates join the sieve tube elements.
2. Mature sieve tubes lack a nucleus.