11. With reference to reproduction in plants, the "Double fertilisation" explains:
[A] how each single pollen grain is able to produce twin sperm cells
[B] how two pollen grains produce single sperm cells
[C] how two pollen grains produce two sperm cells
[D] how single pollen grain produces single sperm cell
Show Answer
Correct Answer: A [ how each single pollen grain is able to produce twin sperm cells]
Notes:
In Angiosperms plant reproduction, two structures are created: a zygote and the endosperm. A zygote will grow and develop into an embryo, or baby plant.The process of single pollen grain producing two sperm cells with one combining with egg to form a zygote and other to form endosperm is called double fertilization.
12. Consider the following pairs:
- Nyctalopia – It is caused due to deficiency of Vitamin A
- Pellagra – It is caused due to deficiency of Vitamin B3
- Rickets – It is caused due to deficiency of Vitamin D
Which of the above is/are correct?
[A] 1 & 2 Only
[B] 2 Only
[C] 2 & 3 Only
[D] 1, 2 & 3
Show Answer
Correct Answer: D [1, 2 & 3]
Notes:
All of the above are correct
13. Anatomically, the beak of birds is equivalent of which of the following?
[A] Teeth
[B] Cheeks
[C] Jaws
[D] None of the above
Show Answer
Correct Answer: C [Jaws]
Notes:
The beak, bill or rostrum is an external anatomical structure of birds that is used for eating and for preening, manipulating objects, killing prey, fighting, probing for food, etc. All beaks are composed of two jaws, generally known as the upper mandible (or maxilla) and lower mandible (or mandible).
14. Which of the following is an example of Symbiotic bacteria?
[A] Rhizobium
[B] Protozoa
[C] Flat worms
[D] None of the above
Show Answer
Correct Answer: A [Rhizobium]
Notes:
Rhizobium is a kind of symbiotic bacteria. Many legumes have root nodules that provide a home for symbiotic nitrogen-fixing bacteria called rhizobia. This relationship is particularly common in nitrogen-limited conditions. The Rhizobia convert nitrogen gas from the atmosphere into ammonia.
15. Which of the following carries oxygen to various parts of human body?
[A] Red blood cells
[B] Nerves
[C] Plasma
[D] White blood cells
Show Answer
Correct Answer: A [Red blood cells]
Notes:
Hemoglobin is the protein inside red blood cells that carries oxygen. Red blood cells also remove carbon dioxide from your body, transporting it to the lungs for you to exhale.
16. Which of the following is the reason behind bleeding through nose in high mountain regions? (UPSC Prelims 1979).
[A] The pressure of the blood capillaries is higher than the outside pressure
[B] The pressure at high altitudes is greater than that in the plains
[C] The blood pressure increases at high altitudes
[D] The blood pressure decreases at high altitudes
Show Answer
Correct Answer: A [The pressure of the blood capillaries is higher than the outside pressure]
Notes:
As altitude increases, the availability of oxygen decreases, making the air thinner and drier. Dry climates can cause drying and cracking inside the nose, which can lead to a nosebleed. The climate inside nose gets drier. This makes the blood vessels exposed inside your nose more likely to burst there than at lower altitudes.
17. Where does pearls are formed? (UPSC Prelims 1982)
[A] Inside squids
[B] Inside snails
[C] Inside oysters
[D] Inside mollusks
Show Answer
Correct Answer: C [Inside oysters]
Notes:
Natural Pearls are formed when an irritant usually a parasite works its way into an oyster, mussel, or clam. As a defense mechanism, a fluid is used to coat the irritant. Layer upon layer of this coating, called nacre, is deposited until a lustrous pearl is formed.
18. Consider the following effects of genetic engineering:
- Disease resistance
- Growth promotion
- Closing
- Longevity
Of these effects, those that have be entried out with a certain amount of success include (UPSC Prelims 1990)
[A] 1, 3 and 4
[B] 2, 3 and 4
[C] 1, 2 and 4
[D] 1, 2 and 3
Show Answer
Correct Answer: D [1, 2 and 3]
Notes:
Genetic engineering can have effects on many things but till now the scientists have not found any way to increase longevity by genetic engineering.
19. Oxygen transportation in a human body takes place through
I. Blood
II. Lungs
III. Tissue
The correct sequence of transportation is (UPSC Prelims 1997)
[A] I, II, III
[B] III, I, II
[C] II, I, III
[D] I, III, II
Show Answer
Correct Answer: C [II, I, III]
Notes:
The lungs serve to exchange the two gases in the blood. Oxygen enters the blood from the lungs and carbon dioxide is expelled out of the blood into the lungs. The blood serves to transport both gases. Oxygen is carried to the cells and tissues.
20. Which of the following classes belongs to an Octopus? (UPSC Prelims 2003)
[A] an arthropod
[B] an echinoderm
[C] a heimchordate
[D] a mollusc
Show Answer
Correct Answer: D [a mollusc]
Notes:
The octopus is a soft-bodied, eight-limbed mollusc of the order Octopoda. Around 300 species are recognised, and the order is grouped within the class Cephalopoda with squids, cuttlefish, and nautiloids.
