Microevolution: The Causes Of Evolutionary Change

If evolution is descent with modification applied to life on Earth, then microevolution can be called the small, measurable evolutionary changes within a population while macroevolution is large evolutionary change over long periods of time - short term and long term/big picture evolution, essentially. Microevolution works on a single population’s genetics and could be said to be the status quo of evolution that occurs consistently and universally while macroevolution occurs over many years or as a result of a drastic change in the population or environment (because a changed environment forces organisms to change to adapt to it or die off). Causes of evolution may include genetic mutation, gene migration, nonrandom mating, and genetic drift,
When natural selection acts on the population, allowing only the fittest members to live, and as the population continues to die and reproduce over time, the population’s overall gene pool has changed from what it originally was, which is the first step in evolution. Mutations are chance alterations in an organism’s DNA that causes their genetic makeup to change. Mutations can affect a population as a whole but also affects the individual, whose mutated genotype may affect its phenotype, causing it to become different from it’s grorup. Natural selection will either allow this individual to live and reproduce (if the mutation is beneficial) or cause it to die due to its genetically induced lack of fitness. Migration occurs when genes are transfered (typically by the travel of organisms) from one population to another, adding diversity as well as adding members to the population it migrates to, causing natural selection to work on this changed group to keep the population number under control and suited to the environment. Nonrandom mating affects a population when organisms sexually reproduce by selecting a mate to reproduce with for a certain reason or a desirable trait. This can be a human controlled mechanism; for example, breeders mate dogs who both have a desirable trait to try and produce an offspring with both desirable traits. This mechanism is wide spread, however, and both humans and other animals tend to select their mates for certain traits, such as female birds tend to select mates who have attractive plummage and ‘singing’ - a subcategory of nonrandom mating called sexual selection. Nonrandom mating results in a