Chapter 13, Lesson 6 Notes Microevolution and Macroevolution Introduction Microevolution is minor changes in a population from mutation, gene flow, genetic drift, and natural selection. Macroevolution is large-scale changes to a population over a long period of time that produces evolutionary trends, including mass extinctions. This may also result in formation of a new species. An Example of Microevolution During the 1800s in England, scientists kept track of a certain moth that was either light or dark in color. Before 1848, dark moths made up less than two percent of the population. But, by 1898, 95% of the moths in English cities were dark. This increase in dark moths is due to natural selection. The Industrial Revolution created soot in the city that made trees black and birds only saw and ate the light moths. The dark moths survived and continued to reproduce and hence, grew a large population of dark moths in the English cities. Darwin’s Four Main Ideas of Natural Selection 1. Organisms tend to produce more offspring than can survive. 2. Individuals in a population vary in many traits. Alleles for specific traits are inherited. 3. Individuals with alleles best suited to the environment are more likely to survive. 4. Individuals with alleles best suited to the environment usually leave more offspring. This leads to differential reproduction, which is when the gene pool changes from certain individuals leaving more offspring than others. Phenotypes and Evolution An organism’s phenotype is determined by its genes and its environment. Phenotype changes are not necessarily due to evolution. There is no change in the genes, so it is not passed onto the offspring. Scientific Study of Evolution Scientists look for causes and effects to explain the diversity of living things due to natural selection. Scientists continue to investigate theories since an explanation or theory is never complete or final. Evolutionary biology links basic scientific research to the knowledge needed to meet the needs of society, including preservation of our earth’s environment. .