Speciation | Prezygotic vs Postzygoic Barriers | Forms of Reproductive Isolation скачать в хорошем качестве

Speciation | Prezygotic vs Postzygoic Barriers | Forms of Reproductive Isolation

How do new species form you ask? This video has the answer, or at least talks about part of the process. Subscribe: http://bit.ly/2wJ0DHa Exmples of reproductive isolation: http://evolution.berkeley.edu/evolibr... Definitions and a much longer discussion: http://bit.ly/2xQhaWS Excellent article on: speciation:https://www.ncbi.nlm.nih.gov/pmc/arti... Speciation is the formation of one or more new unique species from a current species. In order for one species to split into two or more, a faction within the species must not share genetic information with the rest of the species. This is called reproductive isolation. There are two main categories of contributors to this isolation, prezygotic barriers and postzygotic barriers, so named for whether they occur before or after fertilization. Prezygotic barriers result when two groups within a species isolate themselves from one another in some way. Let’s look at some examples. Temporal isolation occurs when members of the same species are active at different times of the day, month, or even year. More specifically, they breed at different times. For example, if some members of the group breed during the day and others breed during the night, they are isolating themselves from one another and not sharing genetic information. The same would be true for one group breeding in the spring and the other breeding in the fall, again, both from the same species. Behavioral isolation is another, in this case, members of the same species behave differently, especially with mating practices. So these members may have slightly different mating rituals that don’t attract members of the other group, thus isolating who they mate with. Others include mechanical isolation, where some members physically can’t mate with others, Habitat isolation, where the habitat occupied by members of a species differs and thus, breeding interactions differ, and gametic isolation, which occurs in aquatic animals. You can learn more about all these by following links in the description. Now to postzygotic barriers. Again, these barriers occur after fertilization has occurs, so mating occurs but no viable or fertile offspring is produced. These include reduced hybrid viability, in which case there is successful fertilization, but development is not successful, or results in very weak offspring prone to early death. Another example is reduced hybrid fertility, in which case a mating is successful at producing offspring (a hybrid of the parents), but that offspring is not fertile thus producing no offspring of it’s own. The classic case is a mule, the offspring of a male donkey and a female horse. The mule lives a full life and can function just fine except when it comes to reproducing unfortunately. This is one reason that donkeys and horses are considered a different species. A final example of a postzygotic barrier is hybrid breakdown, in which offspring is produced, and that offspring may be able to reproduce, but that second generation will be weak and/or sterile. Speciation with respect to reproductive barriers is a complicated topic which I have done my best to simplify, if this video helped you, give it a like, and if you have any questions, throw them in the comments. If you want to learn about allopatric speciation vs sympatric speciation, watch this video, it’ll help. Thanks for watching, I’ll catch you next time.