Consider statements about human immunity: 1. Skin is a physical barrier. 2. White blood cells fight infection. 3. Antibiotics kill viruses. Which are correct? MCQ with Answer and Explanation

Question

Consider statements about human immunity: 1. Skin is a physical barrier. 2. White blood cells fight infection. 3. Antibiotics kill viruses. Which are correct?

A. 1 and 3 only

B. 2 and 3 only

C. 1 and 2 only

D. 1, 2 and 3

Answer: Option C

Solution (By JKExamLibrary)

The skin and mucous membranes form the first line of defense (innate immunity), acting as physical barriers that prevent pathogens from entering the body. White blood cells (leukocytes), including phagocytes and lymphocytes, are the cellular components of the immune system that identify, attack, and destroy pathogens. Antibiotics are drugs specifically designed to kill or inhibit the growth of bacteria by targeting their unique structures or metabolic pathways; they are completely ineffective against viruses. Thus, statements 1 and 2 are correct.

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Question #1

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Which of the following is considered a direct ancestor of modern humans (Homo sapiens)?

A. Australopithecus

B. Neanderthal man

C. Ramapithecus

D. Dryopithecus

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Correct Answer: Option A

Explanation:
Australopithecus (e.g., 'Lucy') is considered one of the earliest direct ancestors or a very close relative of the genus Homo. They were bipedal hominins who lived in Africa about 4 to 2 million years ago. Dryopithecus and Ramapithecus are earlier ape-like ancestors. Homo neanderthalensis was a close relative but is generally considered a separate species that went extinct, though some interbreeding occurred.

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Question #2

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Which tissue provides mechanical support and flexibility to the growing parts of a plant?

A. Parenchyma

B. Sclerenchyma

C. Collenchyma

D. Xylem

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Correct Answer: Option C

Explanation:
Collenchyma is a simple permanent tissue characterized by cells with thickened corners due to the deposition of cellulose and pectin. It provides mechanical support, tensile strength, and flexibility to the growing parts of the plant (like stems and petioles), allowing them to bend without breaking. Parenchyma is for storage, and sclerenchyma provides rigid support.

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Question #3

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Consider statements about vitamins: 1. Vitamin B12 contains cobalt. 2. Vitamin K is essential for blood clotting. 3. Beriberi is caused by Vitamin C deficiency. Which are correct?

A. 1 and 2 only

B. 2 and 3 only

C. 1, 2 and 3

D. 1 and 3 only

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Correct Answer: Option A

Explanation:
Vitamin B12 (cyanocobalamin) is a complex vitamin that contains the trace mineral cobalt. Vitamin K is essential for the synthesis of prothrombin and other clotting factors in the liver. Beriberi is caused by a deficiency of Vitamin B1 (thiamine), whereas Vitamin C deficiency causes scurvy. Thus, statements 1 and 2 are correct.

This question belongs to: Science Biology

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