Describe the process of natural selection.

Within any population, there is naturally variation between organisms because they all have differences in their genes. The organisms that are best suited to the environment that they live within are most likely to survive and reproduce. When subjected to a selection pressure such as cold temperatures, organisms with an advantageous gene, such as one which codes for a thick coat of fur to keep them warm, are more likely to survive and reproduce. Those which lack this advantageous gene are less likely to survive and reproduce. Through reproduction, the organisms pass on this advantageous gene to their offspring, leading to the gradual evolution of the species through natural selection in response to a selection pressure.