HiSET Science: Mechanics of Evolution

Mechanisms of Evolution

Natural and Artificial Selection
Natural selection and artificial selection are both mechanisms of evolution. Natural selection is a process of nature in which a population can change over generations. Every population has variations in individual heritable traits and organisms best suited for survival typically reproduce and pass on those genetic traits to offspring to increase the likelihood of them surviving. Typically, the more advantageous a trait is, the more common that trait becomes in a population. Natural selection brings about evolutionary adaptations and is responsible for biological diversity.
Artificial selection is another mechanism of evolution. Artificial selection is a process brought about by humans. Artificial selection is the selective breeding of domesticated animals and plants such as when farmers choose animals or plants with desirable traits to reproduce. Artificial selection has led to the evolution of farm stock and crops. For example, cauliflower, broccoli, and cabbage all evolved due to artificial selection of the wild mustard plant.

Sexual Selection
Sexual selection is a special case of natural selection in animal populations. Sexual selection occurs because some animals are more likely to find mates than other animals. The two main contributors to sexual selection are competition of males and mate selection by females. An example of male competition is in the mating practices of the redwing blackbird. Some males have huge territories and numerous mates that they defend. Other males have small territories, and some even have no mates. An example of mate selection by females is the mating practices of peacocks. Male peacocks display large, colorful tail feathers to attract females. Females are more likely to choose males with the larger, more colorful displays.

Coevolution
Coevolution describes a rare phenomenon in which two populations with a close ecological relationship undergo reciprocal adaptations simultaneously and evolve together, affecting each other's evolution. General examples of coevolution include predator and prey, or plant and pollinator, and parasites and their hosts. A specific example of coevolution is the yucca moths and the yucca plants. Yucca plants can only be pollinated by the yucca moths.
The yucca moths lay their eggs in the yucca flowers, and their larvae grow inside the ovary.

Adaptive Radiation
Adaptive radiation is an evolutionary process in which a species branches out and adapts and fills numerous unoccupied ecological niches. The adaptations occur relatively quickly, driven by natural selection and resulting in new phenotypes and possibly new species eventually. An example of adaptive radiation is the finches that Darwin studied on the Galápagos Islands. Darwin recorded 13 different varieties of finches, which differed in the size and shape of their beaks. Through the process of natural selection, each type of finch adapted to the specific environment and specifically the food sources of the island to which it belonged. On newly formed islands with many unoccupied ecological niches, the adaptive radiation process occurred quickly due to the lack of competing species and predators.