respiration-in-animals MCQs for UPSC Prelims

25 practice questions on respiration-in-animals from the Life Processes in Animals section of the UPSC Prelims syllabus. 25 come with a written explanation. Try the sample set below - the answer stays hidden until you ask for it.

7 Easy 13 Medium 5 Hard

Sample questions

Q1
hard
Assertion (A): A person's breathing rate rises during heavy exercise. Reason (R): Working muscles need more oxygen so that more energy can be released from food.
  1. A Both A and R are true, and R is the correct explanation of A
  2. B Both A and R are true, but R is not the correct explanation of A
  3. C A is true, but R is false
  4. D A is false, but R is true
Show answer and explanation

Correct answer: A - Both A and R are true, and R is the correct explanation of A

Both statements are true and the reason explains the assertion. Muscles doing hard work need extra energy, that energy comes from food broken down with oxygen, and the quickest way to bring in more oxygen is to breathe faster and more deeply.
Q2
easy
A small animal kept in a tightly sealed jar becomes restless after some time. The most likely reason is that
  1. A the oxygen inside the jar has been used up
  2. B the animal has run out of food
  3. C the inside of the jar has become dark
  4. D the jar has slowly become heavier
Show answer and explanation

Correct answer: A - the oxygen inside the jar has been used up

The animal keeps using the oxygen inside the sealed jar and no fresh air can enter, so it can no longer release enough energy from its food. Darkness does not distress it in this way, sealing a jar does not remove the food inside, and the weight of the jar has no effect on the animal.
Q3
medium
When we breathe in, the chest
  1. A stays exactly the same size as before
  2. B expands, because the ribs move down and the diaphragm moves up
  3. C expands, because the ribs move up and out and the diaphragm moves down
  4. D becomes smaller, because the ribs move inwards and downwards
Show answer and explanation

Correct answer: C - expands, because the ribs move up and out and the diaphragm moves down

Breathing in makes room for the incoming air: the ribs swing upwards and outwards while the sheet of muscle below the lungs moves down, so the chest enlarges. The chest becomes smaller only while breathing out, and a chest that never changed size could not draw in any air.
Q4
medium
Read these two statements. (i) Breathing supplies the body with oxygen. (ii) An animal can live for many days without breathing as long as it has plenty of food. Which of them is correct?
  1. A Neither (i) nor (ii)
  2. B Only (i)
  3. C Both (i) and (ii)
  4. D Only (ii)
Show answer and explanation

Correct answer: B - Only (i)

Statement (i) is correct, since the air drawn in supplies the oxygen the body needs. Statement (ii) is wrong, because food is of no use without oxygen to release its energy, and no animal survives more than a few minutes without air.
Q5
easy
Respiration in an animal means
  1. A the release of energy from food inside the body
  2. B the taking in of food through the mouth
  3. C the removal of undigested waste from the body
  4. D the growth of new body parts
Show answer and explanation

Correct answer: A - the release of energy from food inside the body

Respiration is the process in which food is broken down inside the body to set free the energy stored in it. Taking food in is ingestion, removing waste is egestion, and growth is one of the things the released energy pays for, not respiration itself.
Q6
easy
One complete breath is made up of
  1. A three quick short gasps
  2. B one taking in of air and one giving out of air
  3. C one giving out of air only
  4. D two takings in of air one after the other
Show answer and explanation

Correct answer: B - one taking in of air and one giving out of air

Breathing in once and breathing out once together make one breath, and that is how a breathing rate is counted. Counting only the air going in, or only the air coming out, or counting a few quick gasps as one breath would all give the wrong number.
Q7
medium
An adult sitting quietly breathes about $15$ to $18$ times a minute. After running up four flights of stairs, the same person will most likely breathe
  1. A at exactly the same rate as before
  2. B only through the nose and never through the mouth
  3. C much more slowly, because the body has become tired
  4. D much faster, because the body now needs more oxygen
Show answer and explanation

Correct answer: D - much faster, because the body now needs more oxygen

Hard work uses energy quickly, so more oxygen is needed and the breathing rate rises well above the resting value. Tiredness does not slow breathing down, the rate certainly does change, and a person out of breath usually uses the mouth as well as the nose.
Q8
hard
A person who has eaten a good meal but cannot get enough air will still feel weak. The best explanation is that
  1. A the food will change into carbon dioxide before it is eaten
  2. B food will not be digested at all in the mouth
  3. C food cannot be swallowed unless plenty of air is available
  4. D without enough oxygen, the energy stored in the food cannot be released
Show answer and explanation

Correct answer: D - without enough oxygen, the energy stored in the food cannot be released

Food is only a store of energy, and the body sets that energy free by breaking food down with oxygen, so a shortage of air leaves the energy locked away. Swallowing does not depend on the air supply, digestion in the mouth carries on, and food does not change before it is eaten.

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