Biological Units Evolve under Environmental Pressures

10 BIOLOGICAL UNITS EVOLVE UNDER ENVIRONMENTAL PRESSURES 

In nature, there is a functional purpose and reason for the shape and color of every living thing. 

Genes will be expressed only if the environmental conditions are favorable. Thus, the presence of a gene, or set of genes, will not completely determine the appearance or behavior of the BU. If the environment is favorable, then the particular behavior or appearance coded by that gene will be manifested. Without the gene, however, the same environment will not likely lead to the same kind of behavior or appearance. The exception would be due to redundant genetic control. 

Genes will survive best if they adapt, or allow adaptation. Thus, we would expect that in the presence of a variable environment, the BU that survive best are those that are more adaptable. If the environment is relatively stable, then this adaptability is not necessary. 

Various environmental conditions that are sure to induce evolutionary changes are the same ones that induce individual adaptations on a short timescale things such as temperature, availability of food and water, light, and competition. The difference is that those BU that adapt best to new environments are also those that are expected to be more successful at reproduction. Over the course of many generations, the genes from those BU that demonstrate better harmony with their environments will predominate. 

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