Natural selectionEvolution is descent with modification and includes small-scale evolutionary change (microevolution) as measured by changes in gene frequency in a population from one generation to the next and large-scale evolutionary (macroevolution) change as evidenced by speciation events. Several mechanisms contribute to evolutionary change, such as , a process in which individuals with certain beneficial traits are more likely to survive and reproduce. Natural selection is also responsible for the loss of lethal or detrimental traits from a population. It is important to keep in mind that does not act on individuals; it acts on populations. Natural selection, however, does act on individuals within a population and can result in evolutionary change of that population over time.Populations do not always change due to Natural Selection, since there are several conditions that must be met in order for Natural selection to occur:IF these conditions are met, then in successive generations, more offspring will exhibit the beneficial trait (or conversely, a detrimental trait will be lost).Recall that DNA contains sequences that code for particular proteins or traits, these sequences are called . The alternate forms of genes are called and these alleles exist in pairs because chromosomes exist in pairs. A dominant allele is one that masks another (recessive) allele; dominant does NOT mean a given allele is more frequent or necessarily better. A recessive allele is one that requires two copies to be expressed. Evolutionary biologists are interested in the frequency of alleles within a population and how they change over time (= microevolution).Be sure that you read through our Unit 7 online lecture this unit on as well as your text book readings. Open the and work through the first two exercises.