Theory of Natural Selection
Introduction to theory of natural selection:
Theory of Natural, in evolution, the process by which environmental effects lead to varying degrees of reproductive success among individuals of a population of organisms with different hereditary characters, or traits.
This theory of Natural selection sorts out the useful changes in the gene pool. When this happens, populations evolve. Beneficial new genes quickly spread through a population because members who carry them have a greater reproductive success, or evolutionary fitness, and consequently pass the beneficial genes to more offspring. Conversely, genes that are not as good for an organism are eliminated from the population--sometimes quickly and sometimes more gradually, depending on the severity of the gene--because the individuals who carry them do not survive and reproduce as well as individuals without the bad gene. Over the course of several generations, the gene and most of its carriers are eliminated from the population. Severely detrimental genes may persist at very low levels in a population, however, because they can be reintroduced each generation by mutation.
Natural selection only allows organisms to adapt to their current environment. Should environmental conditions change, new traits may prevail. Moreover, theory of natural selection does not always favor a single version of a trait. In some cases, multiple versions of the same trait may instill their carriers with equal evolutionary benefit. Nor does natural selection always favor change. If environmental conditions so dictate, natural selection maintains the status quo by eliminating extreme versions of a particular trait from the population.
Theory of Types of Natural Seclection
According to theory of, it can be classified into following types:
Directional selection
Stabilizing Selection
Disruptive Selection
Sexual selection
Directional Selection:
Often, shifts in environmental conditions, such as climate change or the presence of a new disease or predator, can push a population toward one extreme for a trait. In periods of prolonged cold temperatures, for example, may favor larger animals because they are better able to withstand extreme temperatures. This mode of known as directional selection, is evident in cheetahs. About 4 million years ago, cheetahs were more than twice as heavy as modern cheetahs. But quicker and lighter members of the population had greater reproductive success than did larger members of the population. Over time, favored smaller and smaller cheetahs
Stabilizing Selection:
Sometimes natural selection acts to preserve the status quo by favoring the intermediate version of a characteristic instead of one of two extremes. An example of this selective force, known as stabilizing selection, was evident in a study of the birth weight of human babies published in the middle of the 20th century. It showed that babies of intermediate weight, about 3.5 kg (8 lb), were more likely to survive. Babies with a heftier birth weight had lower chances for survival because they were more likely to cause complications during the delivery process, and lightweight babies were often born premature or with other health problems. Babies of intermediate birth weight, then, were more likely to survive to reproductive age.
Theory of Natural, in evolution, the process by which environmental effects lead to varying degrees of reproductive success among individuals of a population of organisms with different hereditary characters, or traits.
This theory of Natural selection sorts out the useful changes in the gene pool. When this happens, populations evolve. Beneficial new genes quickly spread through a population because members who carry them have a greater reproductive success, or evolutionary fitness, and consequently pass the beneficial genes to more offspring. Conversely, genes that are not as good for an organism are eliminated from the population--sometimes quickly and sometimes more gradually, depending on the severity of the gene--because the individuals who carry them do not survive and reproduce as well as individuals without the bad gene. Over the course of several generations, the gene and most of its carriers are eliminated from the population. Severely detrimental genes may persist at very low levels in a population, however, because they can be reintroduced each generation by mutation.
Natural selection only allows organisms to adapt to their current environment. Should environmental conditions change, new traits may prevail. Moreover, theory of natural selection does not always favor a single version of a trait. In some cases, multiple versions of the same trait may instill their carriers with equal evolutionary benefit. Nor does natural selection always favor change. If environmental conditions so dictate, natural selection maintains the status quo by eliminating extreme versions of a particular trait from the population.
Theory of Types of Natural Seclection
According to theory of, it can be classified into following types:
Directional selection
Stabilizing Selection
Disruptive Selection
Sexual selection
Directional Selection:
Often, shifts in environmental conditions, such as climate change or the presence of a new disease or predator, can push a population toward one extreme for a trait. In periods of prolonged cold temperatures, for example, may favor larger animals because they are better able to withstand extreme temperatures. This mode of known as directional selection, is evident in cheetahs. About 4 million years ago, cheetahs were more than twice as heavy as modern cheetahs. But quicker and lighter members of the population had greater reproductive success than did larger members of the population. Over time, favored smaller and smaller cheetahs
Stabilizing Selection:
Sometimes natural selection acts to preserve the status quo by favoring the intermediate version of a characteristic instead of one of two extremes. An example of this selective force, known as stabilizing selection, was evident in a study of the birth weight of human babies published in the middle of the 20th century. It showed that babies of intermediate weight, about 3.5 kg (8 lb), were more likely to survive. Babies with a heftier birth weight had lower chances for survival because they were more likely to cause complications during the delivery process, and lightweight babies were often born premature or with other health problems. Babies of intermediate birth weight, then, were more likely to survive to reproductive age.
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