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Selection
Selection
Selection is a process by which biological populations are altered over time, as a result of the propagation of heritable traits that affect the capacity of individual organisms to survive and reproduce. It is one of several mechanisms that give rise to the evolution of biological species.

Natural selection is the differential survival and/or reproduction of individuals within a population based on hereditary characteristics. Sexual selection is a type of selection that promotes traits that will increase an organism's success in mating and ensuring that its gametes are successful in fertilization. This is distinct from natural selection which acts simply on traits which influence fecundity and survival. Artificial selection is differential reproduction within a population that is correlated with the genotypes of individuals and the result of purposeful breeding choices by humans. This type of selection is the only type in which outside influences (such as humans) interfere with natural processes.

Evolution is the long-term process through which a population of organisms accumulates genetic changes that enable its members to successfully adapt to environmental conditions. Whereas selection is a process by which biological populations are altered over time, as a result of the propagation of heritable traits that affect the capacity of individual organisms to survive and reproduce. It is one of several mechanisms that give rise to the evolution of biological species. The mechanisms of evolution are mutation and natural selection. These two processes result in changes at the genetic (mutation) and physiological level (selection of function).

An example of natural selection is if some plants grow taller than others and so are better able to avoid shading by others, they will produce more offspring. However, if the reason they grow tall is because of the soil in which their seeds happened to land, and not because they have the genes to grow tall, than no evolution will occur. The Galápagos finches are also an excellent example of this process. Among the birds that ended up in arid environments, the ones with beaks better suited for eating cactus got more food. As a result, they were in better condition to mate. Similarly, those with beak shapes that were better suited to getting nectar from flowers or eating hard seeds in other environments were at an advantage there. In a very real sense, nature selected the best adapted varieties to survive and to reproduce.

An example of sexual selection is found in peacocks. Male peacocks have large tails that were sexually selected for by female peacocks. Male peacocks fan out their feathers and strut as a mating show for the female peacocks who select between them based on color and physical prowess.
The most obvious examples of artificial selection can be found in the range of specialized body shapes and even personality types in domesticated dogs. The wide range of sizes and shapes, from Chihuahua to the Great Dane, shows the power of artificial selection through selective breeding.

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