Life Processes MCQ 1
12. The correct sequence of anaerobic reactions in yeast is
Ans. (d)
Explanation: Breakdown of pyruvate; under anaerobic condition; takes place in
cytoplasm of yeast. Ethanol and carbon dioxide are produced at the end of this
reaction.
13. Which of the following is most appropriate for aerobic respiration?
Ans. (d)
Explanation: In aerobic respiration, breakdown of pyruvate takes place in
mitochondria. Carbon dioxide and water are produced at the end of this reaction.
14. Which of the following statement(s) is (are) true about respiration?
(i) During inhalation, ribs move inward and diaphragm is raised
(ii) In the alveoli, exchange of gases takes place i.e., oxygen from alveolar
air diffuses into blood and carbon dioxide from blood into alveolar air
(iii) Haemoglobin has greater affinity for carbon dioxide than oxygen
(iv) Alveoli increase surface area for exchange of gases
(a) (i) and (iv)
(b) (ii) and (iii)
(c) (i) and (iii)
(d) (ii) and (iv)
Ans. (d) (ii) and (iv)
Explanation: Statement (i) is incorrect. During inhalation, ribs move outward
and diaphragm is lowered. Statement (iii) is incorrect because haemoglobin has
greater affinity for oxygen than carbon dioxide.
15. Which is the correct sequence of air passage during inhalation?
(a) Nostrils →larynx →pharynx →trachea →lungs
(b) Nasal passage →trachea →pharynx →larynx →alveoli
(c) larynx →nostrils →pharynx →lungs
(d) Nostrils →pharynx →larynx →trachea →alveoli
Ans. (d) Nostrils →pharynx →larynx →trachea →alveoli
Explanation: Refer to fig 6.9 (NCERT Text book) to see the correct sequence of
organs in human respirator system.
16. During respiration exchange of gases take place in
(a) trachea and larynx
(b) alveoli of lungs
(c) alveoli and throat
(d) throat and larynx
Ans. (b) Alveoli of lungs
Explanation: Trachea and larynx just serve as passage for air. Exchange of gases
takes place in alveoli; where oxygen diffuses into blood and carbon dioxide
comes out of blood.
17. Which of the following statement (s) is (are) true about heart?
(i) Left atrium receives oxygenated blood from different parts of body while
right atrium receives deoxygenated blood from lungs
(ii) Left ventricle pumps oxygenated blood to different body parts while right
ventricle pumps deoxygenated blood to lungs
(iii) Left atrium transfers oxygenated blood to right ventricle which sends it
to different body parts
(iv) Right atrium receives deoxygenated blood from different parts of the body
while left ventricle pumps oxygenated blood to different parts of the body
(a) (i)
(b) (ii)
(c) (ii) and (iv)
(d) (i) and (iii)
Ans. (c) (ii) and (iv)
Explanation: Deoxygenated blood circulates through right part of the heart,
while oxygenated blood circulates through left part of the heart. Atrium
receives blood, while ventricle pumps the blood out.
18. What prevents backflow of blood inside the heart during contraction?
(a) Valves in heart
(b) Thick muscular walls of ventricles
(c) Thin walls of atria
(d) All of the above
Ans. (a) Valves in heart
Explanation: Walls of heart facilitate the pumping action only and have no role
in preventing backflow of blood.
19. Single circulation i.e., blood flows through the heart only once during one
cycle of passage through the body, is exhibited by
(a) Labeo, Chameleon, Salamander
(b) Hippocampus, Exocoetus, Anabas
(c) Hyla, Rana, Draco
(d) Whale, Dolphin, Turtle
Ans. (b) Hippocampus, Exocoetus, Anabas
Explanation: In option �a�; salamander is amphibian, while chameleon is reptile;
and they have three chambered heart. Thus, these animals show partial double
circulation. In option �c� all animals are amphibians.
In option �d� whale is mammal, while turtle is reptile. Mammals have
four-chambered heart and completely double circulation.
20. In which of the following vertebrate group/groups, heart does not pump
oxygenated blood to different parts of the body?
(a) Pisces and amphibians
(b) Amphibians and reptiles
(c) Amphibians only
(d) Pisces only
Ans. (d) Pisces only
Explanation: This happens because of single circulation.
21. Choose the correct statement that describes arteries.
(a) They have thick elastic walls, blood flows under high pressure; collect
blood from different organs and bring it back to the heart
(b) They have thin walls with valves inside, blood flows under low pressure and
carry blood away from the heart to various organs of the body
(c) They have thick elastic walls, blood flows under low pressure; carry blood
from the heart to various organs of the body
(d) They have thick elastic walls without valves inside, blood flows under high
pressure and carry blood away from the heart to different parts of the body.
Ans. (d) They have thick elastic walls without valves inside, blood flows under
high pressure
22. The filtration units of kidneys are called
(a) Ureter
(b) Urethra
(c) Neurons
(d) Nephrons
Ans. (d) Nephrons
Explanation: Due to this, nephron is called the functional unit of Kidney.
23. Oxygen liberated during photosynthesis comes from
(a) water
(b) chlorophyll
(c) carbon dioxide
(d) glucose
Ans. (a) water
Explanation: Splitting of water molecule, results in liberation of oxygen and
hydrogen. Hydrogen is utilized for reduction of carbon dioxide so that
carbohydrate can be made.
24. The blood leaving the tissues becomes richer in
(a) carbon dioxide
(b) water
(c) heamoglobin
(d) oxygen
Ans. (a) carbon dioxide
Explanation: Carbon dioxide accumulates in tissues because of respiration in
cells. Thus, blood leaving the tissues becomes richer in carbon dioxide.
