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Perhaps this will help you understand how new species are created...
Speciation often begins when a single species becomes geographically separated into two populations. Individuals cannot travel between the populations, preventing the two populations from interbreeding.
Because the two populations cannot exchange genes, and because they may be subject to different environmental conditions, they slowly evolve differences.
Eventually the two populations become different enough that they do not interbreed even if they come into contact (in other words, they are ‘reproductively isolated’), and are therefore separate species.
Speciation usually takes too long to observe in one lifetime.
Ring Species...
A ring species is a ring of populations in which there is only one place where two distinct species meet. Ernst Mayr called ring species “the perfect demonstration of speciation” because they show a range of intermediate forms between two species. They allow us to use variation in space to infer how changes occurred over time. This approach is especially powerful when we can reconstruct the biogeographical history of a ring species, as has been done in two cases.
Give an example of geographic isolation in which 'Individuals cannot travel between the populations, preventing the two populations from interbreeding.'
Give an example of geographic isolation in which 'Individuals cannot travel between the populations, preventing the two populations from interbreeding.'
(this should be good)
I gave you a bunch...Don't you know how to use the link I provided?
"During allopatric speciation, a population splits into two geographically isolated allopatric populations (for example, by habitat fragmentation due to geographical change such as mountain building...."
Picture this poor group of critters.
A mountain range springs up in the middle of them one day, forever separating them into two groups.
"During allopatric speciation, a population splits into two geographically isolated allopatric populations (for example, by habitat fragmentation due to geographical change such as mountain building...."
Picture this poor group of critters.
A mountain range springs up in the middle of them one day, forever separating them into two groups.
Geographic separation/isolation is often cited as a mechanism which can lead to speciation.
The separated group breeds among themselves and eventually are unable to breed with the 'mother' group.
But what REALLY happens when you separate a small group of critters and only let them breed among themselves?
What animal breeders know is that inbreeding of this nature is often detrimental to producing healthy animals. Far from producing new 'species' that will thrive, inbreeding is more likely to produce a group of sickly critters which would be LESS able to survive in the wild.
While I am almost excited to see you use the term "geographic separation/isolation" in a seemingly correct context, your argument only works if you ASSume that the separated population is really quite small. Quite frankly, that is not always the case. Of course inbreeding is often unhealthy (but not always). It decreases genetic variation and raises the probability for both parents to possess that same deleterous recessive alleles. On the other hand, it also increases the probability that both parents will carry the same beneficial alleles, thus fixing them in the population faster. I think I was still in middle school when I first learned that; so I am pretty sure most other biologists are aware of it too.
An interesting aside: Darwin published quite a bit on the topic of inbreeding. He was married to his first cousin.
Give me an example of geographic isolation where individuals cannot travel between the populations, preventing the two populations from interbreeding.
What would commonly cause such a separation?
Anything that reduces or eliminates gene flow between two populations is a type of isolation. The first thing that comes to my mind is an island versus mainland situation where part of a population somehow got to an island (like rats from a wrecked ship) and couldn't get back to the mainland. Another is through dispersal. For example, when a group of American finches colonized the Hawaiian islands, the group became geographically isolated from other populations of the species. These finches eventually gave rise to the 23 species of Hawaiian honeycreepers.
A real common example that most people don't even bother to think about is habitat destruction caused by humans. For example, the Chrysopsis floridana (a species of golden aster) only grows in the Florida scrub habitat. Every time a new housing development goes up, the population of plants gets separated to the point where some populations are so far away from each other that there is no way for cross pollination to occur.
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