In artificial selection, what factor substitutes for naturally occurring selection pressures?
http://en.wikipedia.org/wiki/Artificial_selection
In artificial selection, the factor that substitutes for naturally occurring selection pressures is human intervention. Unlike in natural selection, where environmental factors and competition among individuals determine which traits are advantageous for survival and reproduction, artificial selection involves the deliberate selection and breeding of organisms by humans based on desired traits.
To understand how artificial selection works, let's break it down into steps:
1. Identifying desired traits: Humans choose certain traits that they want to enhance or suppress in a particular species. These traits can be related to physical characteristics, behaviors, yield, or any other aspect of an organism.
2. Selecting individuals with desired traits: Individuals within the species that exhibit the desired traits are selected by humans to be bred.
3. Breeding individuals: The selected individuals are intentionally paired together to reproduce, increasing the likelihood of passing on the desired traits to offspring.
4. Repeating the process: This selective breeding process is repeated over multiple generations to further enhance the desired traits.
Through these steps, humans effectively replace the natural selection pressures that typically shape the traits of a species. Instead of relying on the environment, predators, or competition for resources, artificial selection allows humans to directly manipulate the genetic composition of a population.
Examples of artificial selection include domestication of animals like dogs, where specific traits such as size, temperament, or coat color are selected and bred for. Another example is crop breeding, where plants are selected and cross-bred to enhance characteristics like yield, disease resistance, or nutritional value.
Overall, artificial selection involves human intervention in selecting and breeding individuals with desired traits, allowing for the deliberate shaping of the genetic makeup of a population.