Consider statements about human immunity: 1. Skin is a physical barrier. 2. Phagocytosis is a specific immune response. 3. Memory cells provide long-term immunity. Which are correct? MCQ with Answer and Explanation

Question

Consider statements about human immunity: 1. Skin is a physical barrier. 2. Phagocytosis is a specific immune response. 3. Memory cells provide long-term immunity. Which are correct?

A. 2 and 3 only

B. 1, 2 and 3

C. 1 and 2 only

D. 1 and 3 only

Answer: Option D

Solution (By JKExamLibrary)

The skin and mucous membranes act as primary physical barriers in innate immunity, preventing pathogen entry. Phagocytosis by macrophages and neutrophils is a non-specific (innate) cellular defense mechanism, not a specific immune response. Memory B and T cells are produced during the primary specific immune response and provide rapid, long-lasting immunity upon re-exposure. Thus, statements 1 and 3 are correct.

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Question #1

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The blood vessel with the thinnest wall, allowing exchange of substances, is:

A. Vein

B. Capillary

C. Artery

D. Arteriole

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Correct Answer: Option B

Explanation:
Capillaries are the smallest blood vessels, with walls only one cell thick (endothelium), facilitating diffusion of oxygen, carbon dioxide, nutrients, and waste products between blood and tissues. Arteries and veins have thicker walls with smooth muscle and connective tissue. Capillaries form extensive networks (capillary beds) throughout the body.

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Question #2

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Jointed appendages are the defining characteristic of which phylum?

A. Arthropoda

B. Annelida

C. Mollusca

D. Echinodermata

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Correct Answer: Option A

Explanation:
Arthropoda is the largest phylum of the animal kingdom, and its defining characteristic is the presence of jointed appendages (legs, antennae, etc.). The word 'Arthropoda' literally means 'jointed legs'. They also have a chitinous exoskeleton and a hemocoel (blood-filled body cavity). Examples include insects, spiders, and crustaceans.

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Question #3

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Consider statements about leaves: 1. The flat part is called the lamina. 2. Stomata are more abundant on the upper epidermis in dicots. 3. The petiole attaches the leaf to the stem. Which are correct?

A. 2 and 3 only

B. 1 and 2 only

C. 1 and 3 only

D. 1, 2 and 3

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Correct Answer: Option C

Explanation:
A typical leaf consists of the leaf base, petiole (stalk), and lamina (leaf blade). In dicotyledonous leaves, stomata are generally more abundant on the lower epidermis to reduce excessive water loss from direct sunlight, unlike monocots where they may be equal. Therefore, statements 1 and 3 are correct, while statement 2 is incorrect.

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