Evolution is the core theme in biology. It is a change in the gene frequency (gene pool) of a population over time. The operational unit of evolution, therefore, is population that evolves over time (individuals in the population do not change but are selected). Genetic variation within that population is key to the evolutionary process. Put it simply: Genes mutate and change, members of the population are selected in favor or against, and hence population evolve. The evolutionary study of the peppered moth (dark/light) in England is a classic example of evolution.
Natural Selection is a mechanism for Darwinian evolution. it is an ongoing process between the organisms and their environment through which beneficial traits are preserved in individuals who can make contributions to the next generation – reproducing offspring. Keep in mind in the eyes of evolution; differential reproduction is all that matters. So individuals in a population with beneficial traits will be selected for (so they stay alive), and those with no beneficial traits will be selected against (so they cannot survive). As Darwin did, you can compare natural selection to the artificial selection that is being carried out by humans on plants and animals. Breeders of dogs and horses have been able to bring out the best traits and characteristics of these animals in successive generations. Nature can do the same.
Obviously natural selection acts through its forces – called selection pressure. Selection pressures include availability of food, presence of predators, geographical isolation, climate, or antibiotics to name a few. Each of these selection pressures acts on phenotypes (individuals in a population), however, evolution occurs only if there has been a change in the genotype (gene frequency) of a population.
The concept of Evolution by natural selection is discussed in chapter 13.
Answer the following questions:
- Define Natural Selection and provide an example.
- Define Evolution and provide an example.
The birds are the agent of selection (or agent of natural selection) that means they are selecting specific individual beetles in the population as food. As a result, green beetles will be eaten up and orange beetles will be left to survive. Natural selection, therefore, has discriminated between these beetles. The orange ones are more fit in this environment and they tend to reproduce and increase in numbers. Hence, the population of beetles has evolved.