Biology (Part-III) (UPSC)

Total Questions: 50

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

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?

Correct Answer: (d) 1 & 4
Solution:

• Testis is composed of seminiferous tubules and stromal or interstitial tissue. The Leydig cells or interstitial cells, which are present in the intertubular spaces produce a group of hormones called androgens mainly testosterone.
• Androgens regulate the development, maturation and functions of the male accessory sex organs like epididymis, vas deferens, seminal vesicles, prostate gland, urethra etc.
• Ovary is composed of ovarian follicles and stromal tissues. The estrogen is synthesized and secreted mainly by the growing ovarian follicles. After ovulation, the ruptured follicle is converted to a structure called corpus luteum, which secretes mainly progesterone.
• Estrogens produce wide ranging actions such as stimulation of growth and activities of female secondary sex organs, development of growing ovarian follicles, appearance of female secondary sex characters (e.g., high pitch of voice, etc.), mammary gland development. Estrogens also regulate female sexual behavior.

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

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.
◦ Foot and Mouth Disease is a highly contagious viral disease that affects cloven-hoofed animals such as cattle, buffaloes, goats, sheep, pigs, and deer. It causes fever, painful blisters, and lameness, severely impacting animal productivity and economic output.
• Historical Overview:
◦ First identified: In the United States in 1870 and eradicated by 1929.
◦ Current Status: Endemic in many parts of Asia, Africa, and the Middle East.
◦ Zoonotic Potential: FMD does not affect humans and is not a food safety threat.
• Transmission and Symptoms:
◦ Transmission: Direct contact, contaminated feed, tools, vehicles, and airborne particles.
◦ Vector Hosts: Cattle, pigs, goats, sheep, deer (like the Pune zoo chitals).
◦ Incubation: 2–14 days.
◦ Symptoms:
▪ High fever for 2–3 days.
▪ Blisters on mouth, tongue, hooves, mammary glands.
▪ Excessive salivation and lameness.
▪ Low milk yield, abortions, and sterility.
◦ Diagnosis: Laboratory testing at accredited institutes (e.g., ICAR-NIFMD, Bhubaneswar).

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 ass1. Boselaphus tragocamelus
B. Barasingha2. Cervus duvauceli
C. Chinkara3. Equus hemionus
D. Nilgai4. Gazella gazella

Codes:

ABCD
(a)2314
(b)3241
(c)2341
(d)3214
Correct Answer: (b)
Solution:
List-I (Indian wild life species) List-II (Scientific names)
A. Asiatic wild assEquus hemionus
B. BarasinghaCervus duvauceli
C. ChinkaraGazella gazella
D. NilgaiBoselaphus tragocamelus

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

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]

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.
• Viviparous animals give birth to live young. In these animals, the fertilization and development of the embryo happen within the female reproductive system. Once the fetus is fully developed, the mother gives birth. This process is called matrotrophy, where the embryo gets nutrients directly from the mother instead of from the yolk.
• In most oviparous animals, fertilization happens internally. The male’s sperm fertilizes the female’s egg inside her reproductive tract. After fertilization, the female’s body adds protective outer layers, including the albumen (egg white), membranes, and a tough outer shell, around the fertilized egg, known as the zygote.
• Ovoviviparity is the mode of reproduction where fertilized eggs are retained and develop within the mother’s body. As such, unlike true viviparous animals, the embryos get nourishment through the yolk of the egg and do not get nourishment through any placental connection to the mother. The eggs hatch inside the mother’s reproductive tract, and she gives birth to live young that are fully developed.

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 Smith1. Developed transgenic plants with Agrobacterium T-DNA
B. Feldman2. Discovered endonucleases
C. Mullis3. Discovered reverse transcriptase
D. Temin and Baltimore4. Discovered polymerase chain reaction

Codes:

ABCD
(a)2143
(b)1243
(c)2134
(d)1234
Correct Answer: (a)
Solution:
List-I (Scientists) List-II (Achievements)
A. Arber and SmithDiscovered endonucleases
B. FeldmanDeveloped transgenic plants with Agrobacterium T-DNA
C. MullisDiscovered polymerase chain reaction
D. Temin and BaltimoreDiscovered reverse transcriptase

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

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.

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.

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.
• Amino acids are organic compounds containing an amino group [NH2] and an acidic group [COOH] as substituents on the same carbon i.e., the α-carbon. Hence, they are called α-amino acids. They are substituted methanes.
• All proteins are polymers of α-amino acids.
• Amino acids contain amino (-NH2) and carboxyl (-COOH) functional groups.
• Depending upon the relative position of amino group with respect to carboxyl group, the amino acids can be classified as α, β, γ & and so on.
• Only α-amino acids are obtained on hydrolysis of proteins.
• α-amino acids have trivial names, which usually reflect the property of that compound or its source.
• Glycine is so named since it has sweet taste (in Greek glykos means sweet) and tyrosine was first obtained from cheese (in Greek, tyros means cheese.)
• Amino acids are classified as acidic, basic or neutral depending upon the relative number of amino and carboxyl groups in their molecule