The hair of mammalian skin get erected when the temperature is low. The muscles which pull the hair follicles and hairs is-

Correct Answer: A

Rationale: The correct answer is A: Arrector muscles. Arrector muscles are responsible for pulling the hair follicles and hairs upright when the temperature is low, a response known as piloerection. This physiological response helps to trap heat and maintain body temperature. Abductor muscles (Choice B) are not involved in hair erection. Petrihydroid muscles (Choice C) and Contractor muscles (Choice D) are not anatomical terms related to hair erection.

Correct Answer: D

Rationale: The correct answer is D: Almost hairless skin. Elephants living in hot climates need to regulate their body temperature efficiently. Having almost hairless skin helps them dissipate heat effectively through their skin. This adaptation is crucial for elephants to thrive in hot environments. A: Its huge size is not a direct indicator of its ability to survive in a hot climate. B: Small eye size is not necessarily related to their adaptation to hot climates. C: Fleshy feet do not specifically indicate their preference for hot climates.

Correct Answer: C

Rationale: The correct answer is C: Skin. The skin is known as the 'Jack of all trades' because it performs multiple functions such as protection, regulation of body temperature, sensation, and synthesis of Vitamin D. It acts as a barrier against pathogens and harmful substances, regulates body temperature through sweat production, contains sensory receptors for touch, pressure, and pain, and plays a role in the synthesis of Vitamin D when exposed to sunlight. Rationale for other choices: A: Kidney - While the kidney plays a crucial role in filtering waste and maintaining electrolyte balance, it doesn't perform as wide a range of functions as the skin. B: Brain - The brain is the control center of the body, responsible for processing information, coordinating movements, and regulating bodily functions. However, it doesn't have the same versatility in functions as the skin. D: All of the above - This choice is incorrect because not all organs mentioned (kidney, brain) are known as the 'Jack of all

Correct Answer: C

Rationale: The correct order for the stages in skin regeneration following an injury is: 1) Blood clot/scab formation, 2) Epidermis covers granulation tissue, 3) Epidermis covers scar tissue, and 4) Calcium injection. Rationale: 1) Blood clot/scab formation occurs first to stop bleeding and prevent infection. 2) Epidermis covering granulation tissue signifies the growth of new tissue. 3) Epidermis covering scar tissue indicates the completion of tissue repair. 4) Calcium injection is not a typical stage in skin regeneration; it does not play a direct role in the natural healing process. Summary: Choice A is incorrect as it starts with covering scar tissue, which is a later stage. Choice B is incorrect as it introduces calcium injection, which is not a standard stage. Choice D is incorrect as it places calcium injection before blood clot formation, which is inaccurate.

Correct Answer: B

Rationale: The correct answer is B: Keratin. Keratin is a structural protein found in the skin that forms a protective barrier to reduce water loss. It is abundant in the outermost layer of the skin, the epidermis, helping to prevent dehydration. A: Keratin is the same as the correct answer, so it is not the correct choice. C: Melanin is a pigment that gives color to the skin and provides some protection against UV radiation, but it does not directly reduce water loss. D: Eleidin is a precursor to keratin in the skin, but it is not the protein responsible for reducing water loss.