Micro Evolution

The general theory of evolution is that organisms have changed over time. Usually, natural selection keeps things the way they are. This is stabilizing selection (Figure 17.9a and b, and Figure 17.10). Agouti rabbits are the best adapted rabbits to survive predation, so the agouti allele remains the most common coat color allele in rabbit populations. Unless something changes, then natural selection will ensure that this continues to be the case. However, if a new environmental factor or a new allele appears, then allele frequencies may also change. This is called directional selection (Figure 17.9c). A third type of selection, called disruptive selection, can occur when conditions favor both extremes of a population. This type of selection maintains different phenotypes (polymorphism) in a population.

So, there are various kind of evolution are ging around us like Micro-Evolution. Microevolution is defined as changes in allele frequency that can be observed within a population. In contrast to macroevolution, microevolution can be observed and measured in short periods of time, even within a single generation; macroevolution refers to the large-scale differences that can be observed between different species.

An accumulation of changes resulting from microevolution will eventually lead to macroevolution through the process of speciation. In this way, they are essentially the same process, although on a different time scale.

So, in simply microevolution is a change in gene frequency within a population. Evolution at this scale can be observed over short periods of time — for example, between one generation and the next, the frequency of a gene for pesticide resistance in a population of crop pests increases. Such a change might come about because natural selection favored the gene, because the population received new immigrants carrying the gene, because some nonresistant genes mutated to the resistant version, or because of random genetic drift from one generation to the next