Ecosystem

A recessive allele is not destroyed when a dominant allele is present. In the F1 generation of a typical cross, plants may be heterozygous, such as Tt, so the dominant allele determines the visible trait while the recessive allele remains hidden. During gamete formation and recombination, two recessive alleles can meet in F2, producing tt and the recessive phenotype. Option B is correct.

Decomposers such as bacteria and fungi break down dead plants, animals, and organic wastes into simpler substances. This returns nutrients to the soil and environment and enables recycling of matter. Food production and oxygen release through photosynthesis are mainly functions of green plants, not decomposers. Exam tip: Link decomposers with nutrient recycling.