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

Answer: (a) glucose

Explanation:
1. Photosynthesis makes glucose, the food of the plant.
2. In respiration, oxygen is used to oxidise (break down) this glucose and release energy.
3. So the answer is (a) glucose.

Teacher's Note:
1. Remember the link: photosynthesis makes glucose and respiration uses it up.
2. Proteins, fats and vitamins are not the direct fuel in this equation.

Answer: (b) chemical, physical

Explanation:
1. Respiration breaks down glucose inside cells and releases energy, so it is a chemical (biochemical) process.
2. Breathing is only the intake and release of air, so it is a physical process.
3. So the pair is (b) chemical, physical.

Teacher's Note:
1. Use the first-letter trick: respiration is Reaction (chemical), breathing is just air movement (physical).
2. This pair is one of the most common questions on this chapter.

Answer: (d) day and night

Explanation:
1. Living cells need energy all the time, so plants respire continuously.
2. Photosynthesis happens only in the daytime in sunlight, but respiration does not stop at any time.
3. So respiration occurs (d) day and night.

Teacher's Note:
1. Do not mix up respiration with photosynthesis: only photosynthesis needs light.
2. At night we notice only respiration because photosynthesis has stopped.

Answer: (c) Both opening and closing

Explanation:
1. When guard cells fill with water they swell and the stoma opens.
2. When they lose water they become flaccid and the stoma closes.
3. So guard cells control both, which is (c) both opening and closing.

Teacher's Note:
1. Guard cells are like a pair of gates that can open and shut the pore.
2. Read all options before choosing; a single-action option is usually incomplete.

Answer: (b) (i), (ii), (iv)

Explanation:
1. Pneumatophores are also called breathing roots, so (i) is correct.
2. They are found in mangroves and similar swamp trees, so (ii) is correct.
3. They rise out of water to let air reach the roots (aeration), so (iv) is correct.
4. Their job is not to support the plant, so (iii) is not correct. Hence the right set is (b) (i), (ii), (iv).

Teacher's Note:
1. Think of swampy soil with very little air: the roots come up to breathe.
2. Supporting the plant is the job of other roots, such as prop roots.

Answer: (a) Both A and R are true, and R is the correct explanation of A.

Explanation:
1. Water vapour leaves through the stomata, and guard cells open and close each stoma, so they control the rate of transpiration. Assertion A is true.
2. Guard cells are indeed placed around the stomatal opening through which transpiration happens. Reason R is true.
3. Because they surround the opening, they can control it, so R explains A. The answer is (a).

Teacher's Note:
1. Check both statements separately first, then ask whether R explains A.
2. Position of the guard cells is exactly why they can control the pore.

Answer: (a) glottis

Explanation:
1. The pharynx is shared by air and food.
2. It opens into the respiratory system through the glottis and into the digestive system through the gullet.
3. So the answer is (a) glottis.

Teacher's Note:
1. Gullet goes to the food pipe; glottis goes to the windpipe.
2. The two words are often interchanged in exams, so learn them as a pair.

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

Explanation:
1. The lungs are covered by two pleural membranes.
2. The space between the membranes holds pleural fluid.
3. The membranes and the fluid together protect the lungs from injury and shock, so the answer is (c) Both (a) and (b).

Teacher's Note:
1. The pleural membranes and the fluid work as a team, like a cushion.
2. Look for the 'both' option whenever two parts act together.

Answer: (a) frog

Explanation:
1. Cutaneous respiration means gas exchange through the skin.
2. A frog respires through both skin and lungs.
3. Fish use gills, humans use lungs and mangroves use pneumatophores, so the answer is (a) frog.

Teacher's Note:
1. The word 'cutaneous' comes from skin.
2. Earthworm is the animal that uses only skin; among these options, frog is the one that does.

Answer: (a) Ribs are lifted up and diaphragm is flattened

Explanation:
1. During inhalation the ribs move up and outwards.
2. The diaphragm flattens (moves down).
3. This enlarges the chest cavity and lowers the pressure, so air enters. The answer is (a).

Teacher's Note:
1. Picture the chest getting bigger: ribs up, diaphragm down and flat.
2. In expiration, both movements are reversed.

Answer: (a) iron

Explanation:
1. Haemoglobin is the red pigment of the red blood cells.
2. It contains iron, which is why a lack of iron leads to anaemia.
3. So the answer is (a) iron.

Teacher's Note:
1. Iron gives blood its red colour in the pigment haemoglobin.
2. Iodine is linked with the thyroid and is not part of haemoglobin.

Answer: (c) Earthworm

Explanation:
1. Fish respire through gills and humans through lungs.
2. A frog uses both skin and lungs.
3. An earthworm respires only through its skin, so the answer is (c) Earthworm.

Teacher's Note:
1. The word 'only' is the clue: pick the animal with no other respiratory organ.
2. Frog is the common trap because it also uses its skin.

Answer: (a) alveoli

Explanation:
1. The trachea, bronchi and bronchioles only carry air.
2. The alveoli are thin-walled sacs surrounded by capillaries.
3. Oxygen and carbon dioxide are exchanged between the alveoli and the blood, so the answer is (a) alveoli.

Teacher's Note:
1. Think of tubes as roads and alveoli as the market where the exchange happens.
2. The thin walls of the alveoli and capillaries make the exchange easy.

Answer: (b) Lungs are covered by single membrane.

Explanation:
1. Statement (a) is true: pleural fluid cushions the lungs.
2. Statement (b) is wrong: the lungs are covered by a double membrane (two pleural membranes), not a single one.
3. Statements (c) and (d) are true. So the wrong statement is (b).

Teacher's Note:
1. In 'wrong statement' questions, test each option one by one.
2. The word 'single' is the hint, as the covering has two layers.

Answer: (d) A–(iii), B–(iv), C–(ii), D–(i)

Explanation:
1. Ribs lift up during inspiration, so A matches (iii).
2. The diaphragm flattens during inspiration, so B matches (iv).
3. Gaseous exchange happens in the alveoli, so C matches (ii).
4. The trachea is the wind pipe, so D matches (i).
5. The pattern A–(iii), B–(iv), C–(ii), D–(i) is option (d).

Teacher's Note:
1. Match the sure pairs first (trachea with wind pipe) and cut down the options.
2. Then separate ribs and diaphragm, which do opposite things to the chest.

Answer: (a) Nostril, Pharynx, Trachea, Bronchi, Bronchiole, Alveoli, Capillaries, Blood, Tissue

Explanation:
1. Air enters through the nostril and then goes to the pharynx and the trachea.
2. The trachea divides into the bronchi, each bronchus divides into bronchioles, and the bronchioles end in the alveoli.
3. Oxygen then passes into the capillaries, then into the blood and finally to the tissue.
4. The correct order is therefore (a).

Teacher's Note:
1. Follow the air, then the oxygen: tubes first, then alveoli, then blood vessels and tissues.
2. Bronchi come before bronchioles, which is the usual mistake.