In biological terms, a species is defined as a group of organisms that are able to interbreed to produce fertile and viable offspring under natural conditions. This description of a species can further be characterized as reproductive isolation, where physical and sometimes behavioral traits of an organism will only allow them to reproduce with an organism that has the same traits. Using the aforementioned definition of a species, different breeds of dogs are able to produce fertile and viable offspring because they are all the same species, but dogs and cats are unable to interbreed because they are two different species.
Now, extend the definition of a species to a group of the same species living in the same geographic area. This would represent a population. What would happen if the species within this population were suddenly split into two groups by an earthquake, creating a physical barrier such as a canyon? If a population is divided indefinitely by a barrier, members of the divided population will not have the opportunity to breed with each other.
Over many years, the abiotic (nonliving) and biotic (living) conditions on either side of the physical barrier will vary from one another. As a result, natural selection will cause different selective and adaptive pressures to occur between the two divided populations, and they will evolve differently. Over time, this will result in speciation, which is the creation of two new species. This occurs because of reproductive isolation.
Use the timeline to view the impact of speciation.
Your observations from the animation should be used to complete the lab worksheet.
(Audesirk, Audesirk, & Byers, 2008)
Audesirk, T., Audesirk, G., & Byers, B. E. (2008). Biology: Life on earth with physiology. Upper Saddle River, NJ: Prentice Hall.
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