Assertion (A): The pituitary gland is connected to the hypothalamus by a stalk. Reason (R): This connection allows the hypothalamus to control pituitary hormone secretion. MCQ with Answer and Explanation

Explanation:
Beriberi is due to thiamine (B₁) deficiency. It presents as two forms: wet beriberi (cardiovascular) and dry beriberi (neurological). Thiamine is a coenzyme (TPP) in decarboxylation reactions. Common in populations consuming polished rice. Riboflavin deficiency causes cheilosis, pyridoxine deficiency causes peripheral neuropathy and anemia, B₁₂ deficiency causes pernicious anemia.

Explanation:
The cerebellum is a highly folded structure located at the back of the brain, below the cerebrum. It is primarily responsible for coordinating voluntary movements, maintaining balance, posture, and equilibrium. Damage to the cerebellum results in ataxia (lack of muscle coordination). The medulla controls vital involuntary functions like breathing and heart rate.

Explanation:
The 10% law of energy transfer, which states that only about 10% of the energy from one trophic level is transferred to the next, was proposed by Raymond Lindeman in 1942. This law explains why food chains typically have only 3-4 trophic levels; there is simply not enough energy available to support higher levels.