Genes, inheritance and selection Study Guide

Genetic variation is the difference in DNA sequences among individuals within a population. This variation is usually extensive, meaning there's a wide range of different genetic characteristics present in a group of the same species. For example, humans are all the same species, Homo sapiens, but we show vast differences in traits like eye colour, hair colour, height, and susceptibility to certain diseases. These differences arise primarily from mutations, which are random changes in the DNA sequence. If these mutations occur in germ cells (sperm or egg), they can be passed on to offspring, introducing new alleles (different forms of a gene) into the population. Sexual reproduction also plays a significant role in increasing genetic variation. During sexual reproduction, genetic material from two parents is combined, and processes like independent assortment and crossing over during meiosis produce unique combinations of alleles in the gametes. This recombination ensures that each offspring is genetically distinct from its parents and siblings, further contributing to the overall genetic diversity within the population. This extensive genetic variation is crucial for the survival and evolution of a species, as it provides the raw material for natural selection to act upon, allowing populations to adapt to changing environments.