Biology (Part-III) (UPSC)

Total Questions: 50

11. When one gene controls two or more different characters simultaneously, the phenomenon is called : [2002]

(a) apomixis
(b) pleiotropy
(c) polyploidy
(d) polyteny

Correct Answer: (b) pleiotropy

Solution:Polyploidy occurs in cells and organisms when there are more than two paired (homologous) set of chromosome founds which controls more than one characters simultaneously. Apomixis is the process of asexual reproduction in which the embryo grow from egg cells without being fertilized. Pleiotropy occurs when a single gene influences multiple phenotypic traits. Polytene is a giant chromosomes found in some two-winged flies.

Polytene chromosomes are giant interphase chromosomes with several DNA strands placed side by side. They were discovered in the year 1881 by Balbiani in salivary glands, intestine, muscles, malpighian tubules, and hypoderm of larvae Chironomus plumosus. Hence, these are also called "Salivary gland chromosomes."

12. With reference to the human body, consider the following statements: [2002]

1. The production of somatotropin goes up when a person exercises.

2. Men's testes produce progesterone.

3. Women's adrenal glands secrete testosterone.

4. Stress causes the adrenals to release very less amount of cortisol than usual.

Which of the these statements are correct?

(a) 1, 2, 3 & 4
(b) 1, 2 & 3
(c) 2, 3 & 4
(d) 1 & 4

Correct Answer: (d) 1 & 4

Solution:Testes of man produce hormone testos tero neand proge sterone hormone is secreted by ovary of woman. Adrenal hormone releases the hormone cortisol.

13. Foot and Mouth disease in animals, a current epidemic in some parts of the world, is caused by :

(a) bacterium
(b) fungus
(c) protozoan
(d) virus

Correct Answer: (d) virus

Solution:Footand mouth disease in animals (hoof and mouth disease) is a viral infection affecting cloven hoofed domestic and wild animals. The viruses belong to the family picornaviridae.

14. Match List-1 (Indian wild life species) with List-II (Scientific names) and select the correct answer using the codes given below: [2002]

List-I (Indian wild life species)	List-II (Scientific names)
A. Asiatic wild ass	1. Boselaphus tragocamelus
B. Barasingha	2. Cervus duvauceli
C. Chinkara	3. Equus hemionus
D. Nilgai	4. Gazella gazella

Codes:

	A	B	C	D
(a)	2	3	1	4
(b)	3	2	4	1
(c)	2	3	4	1
(d)	3	2	1	4

Correct Answer: (b)

Solution:

List-I (Indian wild life species)	List-II (Scientific names)
A. Asiatic wild ass	Equus hemionus
B. Barasingha	Cervus duvauceli
C. Chinkara	Gazella gazella
D. Nilgai	Boselaphus tragocamelus

15. Which one of the following is monogamous? [2002]

(a) Wolf
(b) Walrus
(c) Seal
(d) Deer

Correct Answer: (a) Wolf

Solution:Wolfis monogamous. Monogamous is the organism which has only one spouse and mate at any one time.

Sexual monogamy, where animals have only one mate forever, is rare because evolution favours promiscuity.

16. Which one of the following statements is not correct? [2002]

(a) All echinoderms are viviparous.
(b) Roundworm has no circulatory system.
(c) In bony fishes, swim bladder is usually present.
(d) In cartilaginous fishes, fertilization is internal.

Correct Answer: (a) All echinoderms are viviparous.

Solution:The sexes are separate except few echinoderm species. There is no sexual dimorphism. Fertilization is external and few forms are viviparous.

17. Match List-I (Scientists) with List-II (Achievements) and select the correct answer using the codes given below: [2002]

List-I (Scientists)	List-II (Achievements)
A. Arber and Smith	1. Developed transgenic plants with Agrobacterium T-DNA
B. Feldman	2. Discovered endonucleases
C. Mullis	3. Discovered reverse transcriptase
D. Temin and Baltimore	4. Discovered polymerase chain reaction

Codes:

	A	B	C	D
(a)	2	1	4	3
(b)	1	2	4	3
(c)	2	1	3	4
(d)	1	2	3	4

Correct Answer: (a)

Solution:

List-I (Scientists)	List-II (Achievements)
A. Arber and Smith	Discovered endonucleases
B. Feldman	Developed transgenic plants with Agrobacterium T-DNA
C. Mullis	Discovered polymerase chain reaction
D. Temin and Baltimore	Discovered reverse transcriptase

18. Which one of the following statements is correct? [2002]

(a) Prions are the smallest free-living cells.
(b) The cell wall of Mycoplasma is made up of amino sugars.
(c) Viroid's consist of single-stranded RNA molecule.
(d) A is false but R is true.

Correct Answer: (c) Viroid's consist of single-stranded RNA molecule.

Solution:Viroids are plant pathogens that consists of a short stretch of highly complementary, circular, single-stranded RNA molecule. Prion is an infectious agent composed primarily of protein. Mycoplasma is a genus of bacteria that lack of cell wall. Rickettsias possess cell wall.

19. Assertion (A): Drinking of whisky increases the frequency of urination. [2002]

Reason (R): Alcohol intake speeds up the secretion of vasopressin in the body.

(a) Both A and R are true and R is the correct explanation of A
(b) Both A and R are true but R is not a correct explanation of A
(c) A is true but R is false
(d) A is false but R is true

Correct Answer: (c) A is true but R is false

Solution:Urination can be induced within some minutes after a person consumes alcohol, because when the kidney filters the waste, the capillaries constricts and affects the filtering ability of kidney. When the body needs to conserve water, the pituitary gland excretes a hormone called vasopressin, which causes the nephron filters to become permeable retaining more water in the blood stream and allowing less water to be excreted in the urine. Alcohol decreases vasopressin secretion.

20. Assertion (A): Human diet should compulsorily contains glycine, serine and tyrosine. [2002]

Reason (R): Essential amino acids can not be synthesized in the human body.

(a) Both A and R are true and R is the correct explanation of A
(b) Both A and R are true but R is not a correct explanation of A
(c) A is true but R is false
(d) A is false but R is true

Correct Answer: (d) A is false but R is true

Solution:Assertion is false, but reason is true. Essential amino acids are those which are taken form food and not synthesised in the body, whereas non-essential amino acids need not be supplied in the diet and synthesised in the body. Glycine, serine and tyrosine are non-essential amino acids.

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