Speciation

[Milkshake]

Can anyone explain to me how speciation occurs? Is it always geographical barriers  which contribute to it? Is there only one type of speciation or are there several?

[cypriottiger]

well i guess geographical barriers are the most obvious and common ones, but others could be considered such as disease, which would result in a population with a greater frequency in resistant allele. hmm i honestly cant think of any other types right now, but geographical speciation is by no means the only kind

as for what speciation itself is? i would define it as process by which a catalyst induces an adaption to a change. through this process only an organism capable of surviving under the new conditions is "allowed" to live, whilst others die. the surviving organisms then proceed to produce offspring that also display the characteristic that allowed them to survive, thus resulting in a new population of adapted organisms.

[Russ]

Although this isn't my forte, I'm pretty sure geographical is the biggest and most common cause you need to know.

There's also human intervention through breeding. Genetic drift would probably also be an important one.

[Milkshake]

Ok thanks .
Also, for the definition of evolution, would the NOB definition suffice?
'Process of change that produces new species from ancestral species'

[happyhappyland]

There are number of ways that speciation can occur:
1. Mainly geographical split which causes 2 populations to form in 2 different environents thus different selective pressures cause them to change over time. This is called allopatric speciation
2. The other main one is sympatric speciation, though rarer, can still occur. This is when NO geographical split occurs and a population changes due to selective breeding where one group may prefer different mates, thus slowly leading towards different reproduction time periods (example). WHen this occurs over time the population becomes split into two since there is no gene flow between them.
3. Changes in population size can also cause speciation where genetic drift, founder effect and bottleneck effect causes changes in allele frequencies and causes a "modification" of a species not necessary a population splitting into two species. For example, an introduction of a new predator to a group of deers may cause all of the deers to have longer legs. and over time become a completely new species.

The key thing to remember is... ALLELE FREQUENCIES and they are caused by MUTATIONS.

[cypriottiger]

speciation is like a development on selection pressures. They act on pre-existing variations in a populations phenotype, they are not the cause of that particular allele. A selection pressure acts like a seive, allowing only individuals with the necessary adaptions to continue breeding successfully, whilst others either die or are hampered so that few or no offspring occur. the end result is a new population with an increasing frequency of new alleles. Over time these changes will result in a population considerably different to that of the original group, and if interbreeding cannot occur then a new species has formed.

[stonecold]

if interbreeding cannot occur then a new species has formed.

imo, this is the main thing to consider...

[simpak]

1.  Allopatric (geographic) speciation.
2.  Sympatric speciation - competition for resources leads to the retreat of one group to alternate supplies.
Eg.  All birds on the ground, with big beaks to crack nuts.
Not enough food.
Some birds reolcate to the trees, and then new selection pressures blahhh, they get long beaks and then wow, new species lol dey can no longer interbreed TO PRODUCE VIABLE FERTILE OFFSPRING don't forget that bit.