CBSE Class 7 Science Advanced Biology Transportation in Plants and Animals MCQs Set 01

Answer: (d) unidirectional and bidirectional

Explanation:
1. Xylem carries water and minerals only upwards, from the roots to the aerial parts, so its flow is one-way (unidirectional).
2. Phloem carries food from the leaves to the roots and storage organs and the flow can go both ways (bidirectional).
3. So the blanks are filled by unidirectional and bidirectional, option (d).

Teacher's Note:
1. Remember the order: xylem comes first and is one-way, phloem comes second and is two-way.
2. Water has no reason to travel downwards for photosynthesis, which is why xylem flow stays upward.

Answer: (a) chlorophyll

Explanation:
1. The green colour of leaves is due to a pigment that traps sunlight for photosynthesis. This pigment is chlorophyll.
2. Haemolymph is the body fluid of insects, haemoglobin is the red pigment of RBCs, and chloroplast is the cell part (organelle) that contains chlorophyll, not the pigment itself.

Teacher's Note:
1. A pigment is a coloured substance; a chloroplast is a structure that holds it.
2. Chlorophyll and haemoglobin sound alike but belong to plants and blood respectively.

Answer: (b) transpiration

Explanation:
1. Water evaporates as vapour from the leaves through the stomata (transpiration).
2. This loss creates a pull that draws water up through the xylem from the roots.
3. So the driving force is transpiration.

Teacher's Note:
1. Think of transpiration as a suction that starts at the leaves and pulls water up.
2. Guttation is the oozing of liquid water drops from leaf edges and is not the main force.

Answer: (c) Transpiration provides a cooling effect to plants.

Explanation:
1. (a) is wrong because transpiration is the loss of water as water vapour, not as liquid.
2. (b) is wrong because the opening is the stoma; guard cells only surround it and control its opening and closing.
3. (d) is wrong because phloem transport is bidirectional, and xylem is the one that carries water upwards.
4. (c) is right: evaporation of water from the leaves cools the plant. The answer is (c).

Teacher's Note:
1. In a 'correct statement' question, test each option one by one.
2. Evaporation cools surfaces, just as sweating cools our body.

Answer: (a) osmosis

Explanation:
1. Movement of water molecules from a region of high water concentration to one of low water concentration across a semi-permeable membrane is osmosis.
2. Diffusion is the general spreading of gas, liquid or solid particles and does not need a membrane, and transpiration is loss of water vapour from leaves.
3. Hence option (d) is also wrong.

Teacher's Note:
1. The phrase 'semi-permeable membrane' is the clue for osmosis.
2. Osmosis is a special kind of diffusion that involves water and a membrane.

Answer: (a) One atrium and one ventricle

Explanation:
1. A fish has a two-chambered heart.
2. The two chambers are one atrium and one ventricle, so the answer is (a).
3. Two atria and one ventricle belong to amphibians and reptiles, and two atria with two ventricles to birds and mammals.

Teacher's Note:
1. Learn the series 2, 3, 4 chambers as fish, amphibians and reptiles, birds and mammals.
2. Two chambers always means one atrium plus one ventricle.

Answer: (d) Both (a) and (c)

Explanation:
1. The inferior vena cava brings deoxygenated (impure) blood from the lower part of the body to the heart.
2. The superior vena cava brings deoxygenated blood from the upper part of the body.
3. The aorta is an artery, not a vein. So both (a) and (c) are correct and the answer is (d).

Teacher's Note:
1. Both the large veins end in the right atrium.
2. Vena cava means hollow vein, and aorta is always an artery.

Answer: (a) Left ventricle to body parts

Explanation:
1. The left ventricle pumps oxygenated (pure) blood into the aorta.
2. The aorta branches and supplies all the body parts.
3. So the aorta carries pure blood from the left ventricle to body parts, option (a).

Teacher's Note:
1. Arteries carry blood away from the heart, so the aorta cannot bring blood to an atrium.
2. The right ventricle sends blood to the lungs, not to the body.

Answer: (b) Lungs to heart

Explanation:
1. After gas exchange in the lungs the blood is oxygenated.
2. The pulmonary vein carries this blood from the lungs to the heart (the left atrium).
3. The vessel from the heart to the lungs is the pulmonary artery.

Teacher's Note:
1. Pulmonary means 'of the lungs'.
2. The pulmonary vein is the only vein that carries oxygenated blood.

Answer: (d) Two atria and two ventricles

Explanation:
1. Most reptiles have a three-chambered heart with two atria and one ventricle.
2. Crocodiles are the exception: they have a four-chambered heart.
3. So a crocodile heart has two atria and two ventricles, option (d).

Teacher's Note:
1. Crocodiles are the reptile exception that exam questions love to ask.
2. Four chambers always mean two atria and two ventricles.