Consider statements about human immunity: 1. Skin acts as a physical barrier. 2. White blood cells fight infections. 3. Antibiotics are effective against viruses. Which are correct? MCQ with Answer and Explanation

Question

Consider statements about human immunity: 1. Skin acts as a physical barrier. 2. White blood cells fight infections. 3. Antibiotics are effective against viruses. Which are correct?

A. 2 and 3 only

B. 1, 2 and 3

C. 1 and 3 only

D. 1 and 2 only

Answer: Option D

Solution (By JKSSB Mock Tests)

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 designed to kill or inhibit the growth of bacteria; they are completely ineffective against viruses, which lack the cellular machinery targeted by antibiotics. Thus, statements 1 and 2 are correct.

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Question #1

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The structural polysaccharide that forms the exoskeleton of arthropods is:

A. Glycogen

B. Starch

C. Chitin

D. Cellulose

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Correct Answer: Option C

Explanation:
Chitin is a polymer of N-acetylglucosamine, forming the tough exoskeleton of arthropods and the cell wall of fungi. Cellulose is a plant polysaccharide, starch and glycogen are energy storage polysaccharides in plants and animals respectively. Chitin provides protection and support.

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Question #2

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The Hardy-Weinberg equation p^2 + 2pq + q^2 = 1 is used to calculate:

A. The expected genotype frequencies in a population

B. The energy transfer between trophic levels

C. The rate of mutation in a population

D. The carrying capacity of an ecosystem

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Correct Answer: Option A

Explanation:
The Hardy-Weinberg equation is a fundamental principle in population genetics used to calculate the expected frequencies of genotypes in a population that is not evolving (in genetic equilibrium). 'p' represents the frequency of the dominant allele, and 'q' represents the frequency of the recessive allele. p^2 is the frequency of the homozygous dominant genotype, 2pq is the heterozygous genotype, and q^2 is the homozygous recessive genotype.

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Question #3

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Amoebiasis is caused by which protozoan?

A. Plasmodium vivax

B. Entamoeba histolytica

C. Trypanosoma brucei

D. Giardia lamblia

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Correct Answer: Option B

Explanation:
Amoebiasis, also known as amoebic dysentery, is an intestinal infection caused by the protozoan parasite Entamoeba histolytica. It is transmitted through ingestion of cysts in contaminated food or water. Symptoms include abdominal pain, diarrhea, and dysentery (bloody stools). It can also spread to the liver, causing amoebic liver abscesses.

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