The pore through which pollen tube enters the ovule is the: MCQ with Answer and Explanation

Explanation:
Niacin (vitamin B₃) is the precursor of NAD⁺ and NADP⁺, essential electron carriers in redox reactions. Thiamine is TPP, riboflavin FAD, biotin for carboxylation.

Explanation:
Edward Jenner, an English physician, is known as the 'father of immunology'. In 1796, he developed the world's first successful vaccine against smallpox. He observed that milkmaids who had contracted cowpox (a mild disease) were immune to smallpox. He inoculated a boy with material from a cowpox blister, successfully conferring immunity to smallpox, thus pioneering the concept of vaccination.

Explanation:
Producers (autotrophs like green plants) form the first trophic level and the base of all food chains, converting solar energy into chemical energy. Decomposers (bacteria and fungi) break down dead organic matter and waste, releasing essential inorganic nutrients back into the soil for producers to use, thus completing the nutrient cycle. Energy flow in an ecosystem is strictly unidirectional, moving from the sun to producers and then to consumers, and is eventually lost as heat; it does not flow bidirectionally. Thus, statements 1 and 2 are correct.