Assertion (A): Pea plants were chosen by Mendel for his experiments. Reason (R): Pea plants have many contrasting characters and are self-pollinating. MCQ with Answer and Explanation

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.

Explanation:
Reverse transcriptase is an enzyme unique to retroviruses that transcribes single-stranded RNA into double-stranded DNA (cDNA). This DNA integrates into the host genome. DNA polymerase synthesizes DNA from DNA, RNA polymerase from DNA. Reverse transcriptase is used in RT-PCR and cDNA synthesis.

Explanation:
The vermiform appendix is a remnant of the cecum in herbivorous ancestors, now with minor immune function, thus considered vestigial.