Which of the following is a unique characteristic of birds (Class Aves)? MCQ with Answer and Explanation

Which of the following is a unique characteristic of birds (Class Aves)?
A. Presence of mammary glands
B. Body covered with feathers
C. Presence of external pinnae
D. Poikilothermic nature
Answer: Option B
Solution (By JKSSB Mock Tests)
The most unique and defining characteristic of Class Aves (birds) is the presence of feathers, which are modified scales used for flight and insulation. Birds are warm-blooded (homeothermic), have a four-chambered heart, and possess a beak instead of jaws. Mammary glands and external pinnae are features of mammals.

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Question #1
Consider statements about ecology: 1. Producers form the first trophic level. 2. Energy flow in an ecosystem is unidirectional. 3. The pyramid of energy can be inverted. Which are correct?
A. 1, 2 and 3
B. 1 and 3 only
C. 1 and 2 only
D. 2 and 3 only

Correct Answer: Option C


Explanation:
Green plants (producers) always occupy the first trophic level in a food chain. Energy flow is unidirectional, moving from the sun to producers and then to consumers, never returning to the sun. Due to the 10% law of energy transfer, the pyramid of energy is always upright and can never be inverted. Thus, statements 1 and 2 are correct.

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Question #2
Scurvy is characterized by bleeding gums and is caused by the deficiency of:
A. Vitamin D
B. Vitamin A
C. Vitamin B12
D. Vitamin C

Correct Answer: Option D


Explanation:
Scurvy is caused by a deficiency of Vitamin C (Ascorbic acid). Vitamin C is essential for the synthesis of collagen, a structural protein in connective tissues. Its deficiency leads to weakened blood vessels, causing symptoms like bleeding gums, loose teeth, joint pain, and poor wound healing. It was historically common among sailors lacking fresh fruits and vegetables.

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Question #3
In a cymose inflorescence, the growth of the main axis is:
A. Continuous and terminates in a flower
B. Always forming a raceme
C. Restricted to the base of the plant
D. Limited, ending in a flower, with lateral branches continuing growth

Correct Answer: Option D


Explanation:
In cymose inflorescence, the main floral axis has limited growth and terminates in a flower. Subsequent flowers are produced by lateral branches, which also terminate in flowers, creating a sympodial growth pattern. This is in contrast to racemose inflorescence, where the main axis continues to grow indefinitely (monopodial) and flowers are arranged in an acropetal or basipetal order.

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