For every gene, there may be several possible versions. Different genes carry instructions for making different proteins. If the gene copies are heterozygous, two types of protein are produced, if the gene copies are h0m0zyg0us, one type of protein is produced.
It may mean that the two proteins evolve in slightly different directions, so that one version works better in one set of conditions and the other under different conditions.
Please note that the cost to the organism of making two proteins instead of one is minimal. Basically, it involves adding one coding gene to the tens of thousands of genes that are already there (assuming that the sum of the amounts of the two proteins is about the same as the amount of the original one protein).
Different versions of the same protein may also be made by differential splicing of the mRNA, or by the many mechanisms of post-translational modification.
Living things require specific organic molecules in order to survive. The picture above represents some specific examples of foods that are mainly composed of one of these necessary organic molecules. The organic molecules found in these types of food are
