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User:Nabusada/new_sandbox       * this is the one with the reflective essay

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Despeciation

 * convergent evolution is one of the main causes of despeciation
 * evolve analogous structures due to similar environments
 * analogous structures= structures that are similar in function and appearance but not necessarily due to common ancestry
 * going back to their ancestral population lineage can create some difficulties in adapting to dynamic environment
 * Ravens and humans have gone through despeciation
 * humans went to one lineage when we used to have two (denisovans and neanderthals)


 * Convergent evolution- animals evolve similar morphological structure, coloration, and internal anatomy due to similar living environment.
 * some species, such as butterflies, experience convergent evolution due to Mullerian or Batesian mimicry.
 * Mullerian mimicry is the process in which two organisms are commonly mistaken as each other as to prevent either species from being killed by predator
 * Batesian mimicry is when one species that is harmless mimics a threatening species as to prevent it from being killed from predators.

Actual Article Draft

Despeciation is the loss of a unique species of animal due to its combining with another previously distinct species. It is the opposite of Speciation and is much more rare. It is similar to extinction in that there is a loss of a unique species but without the associated loss of a biological lineage. Despeciation has been noted in species of butterflies, sunflowers, mosquitoes, fish, wolves, and even humans.

A prime example of despeciation is convergent evolution when it causes two species that live in same environment to become the same due to the similar functions and behaviors that it must partake in to survive in that habitat. Common examples of convergent evolution are Mullerian and Batesian mimicry. Batesian mimicry is when one species that is harmless mimics a more threatening, or intimidating, species as to prevent it from being killed. Mullerian mimicry is when two organisms mimic each other as to prevent either species form being killed by predators.

Another possible cause for despeciation is increased gene flow and hybridization due to changes in the environment. One of these changes could include the loss of essential nourishment resources for each individual species. An example of this can be seen in the case of the 'limnetic' and 'benthic' species of three-spine stickleback fish (Gasterosteus aculeatus) in Canada's Enos Lake. Morphological and genetic analyses conducted by researchers on a sample of fish dating from 1977 to 2002 found that by 1997 these two species populations had been replaced by a new single species. The new species is a hybrid and shows an intermediate form of the parental genotype. As a result, it is more genetically diverse than the two previous distinct species.

Despeciation also occurs when two diverged species begin to interact in the same region. Ravens provide a prime example of this. Holarctic Ravens and Californian Ravens had been two separate species for 1.5 million years until tens of thousands of years ago when their regions overlapped and they began to merge into a new species. This new raven species contains genes coming from both the Holarctic and Californian Raven. This was possible because they occupy the same area of the Western United States.

Other common examples of despeciation pertain to Homo sapiens. Homo sapiens once were two lineages, Neanderthals and Denisovans. However, due to common ecological niches, common ancestry, similar environment, and interbreeding, they merged into one species.