It should be adaption, because it means the species change themselves as the environment changes to make them survive. a simple example is cactus, like you know the ones in the desert. they have needle shaped leaves to adapt the dry and hot environment, reduce the loss of water during transpiration.
1.Alleles are a pair of genes that occupy a specific location on a particular chromosome and control the same trait.
<em><u>2</u></em><em><u>.</u></em><em><u>An allele is one of two or more versions of a gene. An individual inherits two alleles for each gene, one from each parent.</u></em>