What defines a recessive trait?

A recessive trait is defined as one that will only manifest in the phenotype when an individual possesses two copies of the recessive allele, one inherited from each parent. This characteristic highlights the need for both parents to contribute the recessive trait for it to be expressed. In cases where an individual has one dominant allele, the dominant trait will overshadow the recessive trait, preventing it from being observed in the phenotype.

In the context of the other options, a dominant trait can show up even if only one copy is present, which is contrary to the definition of a recessive trait. Traits that are favored in natural selection are not inherently recessive or dominant; rather, their prevalence is dependent on environmental factors and survival advantages. Lastly, a trait that affects the phenotype regardless of its allelic combination implies that it does not rely on the presence of two alleles, which is not true for recessive traits since their expression requires homozygosity for the recessive allele. Thus, the explanation of the recessive trait clearly aligns with the choice provided, emphasizing the necessity of receiving the recessive allele from both parents for expression in the phenotype.