Biology (Part-III) (UPSC)

Total Questions: 50

21. Among living organisms, which one of the following is the most responsible factor for bringing about the origin of a new species? [2002]

(a) Isolation
(b) Mutation
(c) Natural selection
(d) Sexual reproduction

Correct Answer: (b) Mutation

Solution:Mutation is the most responsible factor for origin of new species.

A mutation is a change that occurs in our DNA sequence, either due to mistakes when the DNA is copied or as the result of environmental factors such as UV light and cigarette smoke.

22. With reference to the blood in a normal person, which one of the following statements is correct? [2002]

(a) Arachnids
(b) Crustaceans
(c) Insects
(d) Myriapods

Correct Answer: (a) Arachnids

Solution:Ticks and mites are categorized under order Arachnids of phylum Arthopoda of animal kingdom.

23. With reference to the blood in a normal person, which one of the following statements is correct? [2002]

(a) Compared to arteries, veins are less numerous and hold less of the body's blood at any given time.
(b) (b) Blood cells constitute about 70 percent of the total volume of the blood.
(c) White blood cells (WBC) are made by lymph nodes only.
(d) The blood has more platelets than WBC.

Correct Answer: (d) The blood has more platelets than WBC.

Solution:Blood has more platelets than corpuscles. A microlitre of blood contains 5,000-10,000 of White blood cells (WBC) and 150,000-500,000 platelets.

24. Octopus is : [2003]

(a) an arthropod
(b) an echinoderm
(c) a hemichordate
(d) a mollusc

Correct Answer: (d) a mollusc

Solution:Octopus is an animal of class-Cephalopoda and phylum Mollusca. The shell is absent. It is found at bottom of the sea. It kills its prey with poisonous saliva. It can change its colour.

25. Consider the following conditions of a sick human body : [2003]

1. Swollen lymph nodes

2. Sweating at night

3. Loss of memory

4. Loss of weight

Which of these are symptoms of AIDS?

(a) 1 and 2
(b) 2, 3 and 4
(c) I, 3 and 4
(d) 1, 2, 3 and 4

Correct Answer: (d) 1, 2, 3 and 4

26. With reference to the work of human kidney, consider the following statements : [2003]

1. After the waste is removed in the kidney, the clean blood is sent back through renal artery.

2. From Bowman's capsule, the filtered liquid passes through tiny tubes where much of the glucose is reabsorbed and sent back to the blood in the renal vein.

Which of these statements is/are correct?

(a) Only 1
(b) Only 2
(c) Both 1 and 2
(d) Neither 1 nor 2

Correct Answer: (b) Only 2

Solution:A nephron consists of a network of tiny blood vessels, the glomerulus surrounded by Bowman's capsule. Pressure forces much of the blood plasma through the glomerulus and inte Bowman's capsule. The resulting tubular fluid, which contains water and dissolved chemicals then passes into convoluted tubule and loop of Henle. This capillary network provides a mean for pick up and delivery of materials that are reabsorbed and secreted by the kidney.

27. Which one of the following statements is not correct? [2003]

(a) Milk contains none of the B-vitamins.
(b) Vitamin-A (retinol) deficiency leads to dry and scaly skin.
(c) One of the symptoms of scurvy is pain in the joints.
(d) Vitamin B, (thiamine) deficiency can lead to heart failure.

Correct Answer: (a) Milk contains none of the B-vitamins.

Solution:Milk contains vitamin B1 (Thiamin) and vitamin B2 (riboflavin). So, statement (a) is not correct.

Milk contains various fat soluble vitamins like vitamin A, D, E, K, along with water soluble vitamins like vitamin C and B complex vitamins and provitamins. However, concentration of some of these vitamins is very less.

28. With reference to normal human beings, consider the following statements: [2003]

1. In response to the presence of HCI, secretin is produced from the duodenum.

2. Enterogastrone is produced in the small intestine in response to the presence of fatty acids.

Which of these statements is/are correct?

(a) Only 1
(b) Only 2
(c) Both 1 and 2
(d) Neither 1 nor 2

Correct Answer: (c) Both 1 and 2

Solution:Both the statement is correct. HCI is secreted, providing an acid medium for pepsin action and kill most bacteria and helps in digestion of food. When the food enters in duodenum (small intestine), secretin is produced by intestine that stimulates pancreas for pancreatic juice secretion. Enterogastrone is produced in small intestine.

29. Consider the following statements: [2004]

1. Non-functioning of lachrymal gland is an important symptom of deficiency of Vitamin A.

2. Deficiency of Vitamin B, can lead to indigestion and heart enlargement.

3. Vitamin C deficiency can lead to pain in the muscles.

4. Deficiency of Vitamin D causes increased loss of Ca in urine.

Which of the statements given above are correct?

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

Correct Answer: (d) 1, 2, 3 and 4

Solution:Lachrymal is a tear produced gland which does not function due to deficiency of vitamin -A. Deficiency of vitamin B, causes loss of appetite, heart disorders, muscular weakness etc.

30. The hormone insulin is a : [2004]

(a) glycolipid
(b) fatty acid
(c) peptide
(d) sterol

Correct Answer: (c) peptide

Solution:Insulin is a peptide hormone composed of 51 amino acids. Insulin secrets from pancreas (Islets of Langerhans).

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