Genes, via their influences on morphology and physiology, create a framework within which the environment acts to shape the behavior of an individual animal. The environment can affect morphological and physiological development; in turn behavior develops as a result of that animal's shape and internal workings.
Environmental factors determine all genetic traits. Why? So the organism that is gaining the trait has a better chance of survival or to be more specific a better chance at adapting to their environment. Let me give you an example, the long necks on a giraffe. The diet of a giraffe consist of mostly acacia leaves which are leaves that are on the top of a tree. This environmental factor is why giraffes have long neck so they can get to the leaves of the tree. If they did not have long necks giraffes probably would´nt survive
Now let me give you an example that is related to evolution
Evolution is the change in the characteristics of a species over several generations
An example of this happening can be shown in mosquitoes
People were using DDT (which is an insecticide used to kill bugs) on mosquitoes to harm them. Many of the mosquitoes had died but the remaining were able to produce offspring that had mutations. These mutations caused the mosquitoes to be resistant to the insecticide. This shows another example of environmental factors having an influence on genetic traits. The DDT spray was the environmental factor and the mosquito being able to produce offspring that were resistant the the insecticide is the outcome from the influence.
