directional,stablizing, and distuptive

     Directional selection favors those individuals who have extreme variations in traits within a population. Stabilizing selection favors the norm, the common, average traits in a population .Disruptive selection, like directional selection, favors the extremes traits in a population. Disruptive selection differs in that sudden changes in the environment creates a sudden forces favoring that extreme. Directional occurs when selection favors one extreme trait value over the other extreme. This typically results in a change in the mean value of the trait under selection. Distuptive occurs when selection favors the extreme trait values over the intermediate trait values. In this case the variance increases as the population is divided into two distinct groups. Disruptive selection plays an important role in speciation. Stablizing occurs when selection favors the intermediate trait value over the extreme values. Populations under this type of selection typically experience a decrease in the amount of additive genetic variation for the trait under selection.

The fossil Record

   The fossil record is incomplete because very few organisms were preserved as fossils. organisms tend to decay before becoming a fossil. Animals with hard parts are preserved more easily and geological processes may destroy fossils. Darwin believed that the fossil record showed the history of life on earth.The fossil record of all species is not complete because the circumstances for fossils to occur is very rare.

Microevolution

          Microevolution is a change in gene frequency within a population. This change is due to four different processes mutation selection , gene flow and genetic drift
population genetics is the branch of biology that provides the mathematical structure for the study of the process of microevolution. Ecological genetics concerns itself with observing microevolution in the wild. Typically, observable instances of evolution are examples of microevolution; for example, bacterial strains that have antibiotic resistance
Microevolution can be contrasted with  marcoevolution, which is the occurrence of large-scale changes in gene frequencies in a population over a geological time period  difference is largely one of approach. Microevolution is reductionist, but macroevolution is . Each approach offers different insights into the evolution process. Macroevolution can be seen as the sum of long periods of microevolution, and thus the two are qualitatively identical while being quantitatively different.

why is evolution a theory and not a law

  Different theories and laws can end up to be wrong, and must be tested by considering what evidence we should find if the theory or law were false, and then looking for such evidence. For example if the theory of evolution were false then we shouldn't expect the similarities between living things to show a nested hierarchy, where in two species share many similarities some of which are shared by more distantly related species, and some of those of which are shared by more distantly related species; etc. Since we do in fact find such nested hierarchies of similarities, and since we would not expect to find such hierarchies if everything were made from scratch to look as it does now, that is strong support to indicate the theory is correct