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The Role Of Instinct In Natural Selection

Decent Essays

Instinct, its inheritability and the role it plays in natural selection, are explained. Unlike habit, which is learned, instinct is an innate characteristic inherited from past generations. Although the cause of instincts is unclear, Darwin states that they are molded by natural selection, just as physical variations are. Instincts that are beneficial to a species’ survival are selected for and thus propagated, eventually creating a better adapted species with higher rates of survival in the environment. Some examples of advantageous instincts include hens that lay eggs in others’ nests to produce more offspring that they do not have to take responsibility for raising. Worker ants in slave away their lives for the good of their colony while …show more content…

This sterility is often caused by the inconsistencies between the reproductive systems of the parent species, which have differently developed reproductive organs adapted for their particular species only. This also explains the often unsuccessful crosses between two separate species that fail in producing offspring. Oftentimes, even when a first generation hybrid is fertile, its offspring is sterile. Some scientists believed that whether or not parents are the same species can be determined by the fertility of their offspring, an idea rejected by Darwin. Familial interbreeding between offspring may affect the results of fertility experiments on hybrids. Studies have shown that sometimes pollen from one plant species may be more effective to other species of plants than its own species. In other cases, varieties of the same “species” have produced infertile offspring, further disproving this idea. Darwin argues that the blind use of sterility to distinguish species can lead to incorrect categorization based on lack of knowledge of the causes of sterility. “Systematic affinity”, a popular misconception, is that species can produce fertile offspring because of their similarities in appearance and structure. A counterexample, however, would be female donkeys and male stallions, whose infertile offspring is the result of the difference in their reproductive systems. Many …show more content…

Hybrids, as the product of two different species and therefore two different reproductive systems, are usually sterile. Sterility is not determined by physical traits but rather the structure of the reproductive system. Examples have proven that there are many possible reasons behind sterility, many of which are still unknown, and so sterility cannot be an accurate way to determine species and relationships between

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