Evolution , or a change in the genetic composition of a population over time, is often the outcome of natural selection operating over successive generations. Also, natural selection may not always result in evolution due to opposition by the factors above or a lack of time for genetic change to accumulate. Adaptation is a confusing term in evolutionary biology because it is often used to refer both to a process and a product. Process - Adaptation is a term often applied to the process through which individuals in a population become structurally or functionally better suited to their environment. Adaptive evolution either maintains or increases the mean fitness of individuals in a population.
Mean fitness is the weighted average of the fitness of all types in a population.
Product - An adaptation is a morphological, physiological, or behavioral trait that enhances an organism's fitness. However, not all structures, functions, or behaviors, even if they are adaptive, are the result of selection for their current functions. Sometimes traits that arose for an unrelated reason turn out to be advantageous when placed in a new context. Such traits were once called preadaptations . The mechanism of inheritance is also an important characteristic when studying the process of evolution, whether in the context of plant-animal interactions or any other.