The skin of older people become loose and wrinkled because

Correct Answer: B

Rationale: The correct answer is B: Elasticity of dermis decreases. As people age, the dermis layer of the skin loses collagen and elastin fibers, leading to a decrease in skin elasticity, resulting in loose and wrinkled skin. The other choices are incorrect because A (Stratum germinativum becoming more active) would actually lead to increased cell turnover and potentially smoother skin, C (Stratum corneum becoming thicker) would result in thicker skin but not necessarily loose and wrinkled, and D (poor blood supply to the skin) would affect overall skin health but not directly cause loose and wrinkled skin.

Correct Answer: A

Rationale: The correct answer is A. When exposed to sunlight, the skin responds by widening the capillaries to allow more blood flow, leading to a reddish appearance. This process is known as vasodilation. Option B is incorrect as blood cells do not ooze out through skin pores. Option C is inaccurate as haemoglobin breakdown does not cause skin reddening. Option D is also incorrect since the spleen does not release more blood in response to sunlight.

Correct Answer: D

Rationale: The correct answer is D: Cold. Dense fur in cold temperature animals acts as insulation to retain body heat and protect them from the cold. The fur traps air close to the body, creating a layer of warmth. This helps regulate their body temperature and prevent heat loss. Snow (A) is not the main threat as the fur insulates against it. Air (B) is actually trapped by the fur to provide insulation. Enemies (C) are not directly protected against by dense fur, as it primarily serves to regulate body temperature in cold environments.

Correct Answer: D

Rationale: The correct answer is D: Stratum lucidum. This layer of the epidermis is known for its clear, translucent appearance and plays a key role in forming a barrier that prevents the entry of water and other substances into the body. It is located between the stratum corneum and the stratum granulosum. The other choices are incorrect because: A: Stratum spongiosum is not a recognized layer of the epidermis. B: Stratum granulosum is involved in the production of keratin and the formation of the skin barrier, but it is not specifically responsible for preventing the entry of water and other substances. C: Stratum germinativum, also known as the stratum basale, is responsible for cell division and regeneration, not primarily for barrier function.

Correct Answer: B

Rationale: Correct Answer: B Rationale: 1. Melanin is produced from the amino acid tyrosine, making choice A true. 2. Melanin protects DNA from UV radiation, making choice C true. 3. Melanin is usually some shade of brown or black, making choice D true. 4. Melanin actually increases in concentration within cells during exposure to the sun to provide more protection, making choice B false. Summary: Choices A, C, and D are true statements about melanin. Choice B is incorrect as melanin increases in concentration during sun exposure.