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What evidence must be considered when determining whether or not a trait is an adaptation? (Site 1)

An adaptation is a trait that "evolved" for a particular condition that allows the animal to survive. Something is adaptive if it is a useful trait but not necessarily one that occurred in response to a particular selection pressure. Basically a trait is an adaptation if it is the product of selection, and adaptive if it is beneficial in the present time.

Explanation:

genetic variation can be caused by mutation (which can create entirely new alleles in a population), random mating, random fertilization, and recombination between homologous chromosomes during meiosis (which reshuffles alleles within an organism's offspring).

igneous rocks which formed by the crystallization of magma at the surface of the earth called extrusive rocks. they are characterized by fine-grained textures because the rapid cooling at or near the surface did not provide enough time for large crystals to grow.