Final answer:
Variation is the genetic difference between individuals within a population and is essential for evolution.
Step-by-step explanation:
Variation is best described as:
Variation is the genetic difference between individuals within a population. It is the raw material for adaptation and is essential for evolution. Without variation, there would be no genetic differences for natural selection to act upon.
Examples of variation include population variation, which refers to the distribution of phenotypes and genotypes in a population. For instance, the diversity in fur colors and patterns in domestic dogs or the different forms of prokaryotes and eukaryotes are examples of population variation.