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There are other terms that describe subtle differences along the continuum of speciation precursors, the order along this spectrum is (all share 'patric') sym, para, peri, and allo. I will only expand on the 2 you mentioned...
Sympatric speciation occurs from within one population of a species (i.e. living in and sharing the same area). What happens is that for many reasons (I will offer an example in a minute) some individuals will only breed with certain other individuals that are in some way appealing to them. This can lead to speciation due to the fact that only a specified group of genes are passed among a specified population of individuals within the wider species population. This can be understood in the following example - suppose the genotype (the gene alleles present within an individual specimen) of a bird gives it a particular set of phenotypical expressions (a phenotype is any trait expressed by an individual due to its genes such as big ear lobes).
One such phenotype characteristic is a male beak of a particular shape that produces a unique kind of call to a prospective mate. The female finds only this call attractive, therefore only males able to produce that sound have a chance of mating.
That part explains the selective aspect of mating, but not how speciation may arise from it. Consider the implications of it - the gene pool of these discerning individuals is limited to what they themselves contain (their collective genotypes). As such the normal route of speciation (that is, at the level of the gene) - mutation, has a much more limited set of genes on which it can act. It is not surprising therefore that such a targeted passing on of genes that are subjected to, in isolation, the effects of mutation can lead to a specific set of individuals that have a distinctive look from others in the same area. What has just happened ? Sympatric speciation.
Allopatric speciation is much more straghtforward to explain, comprehend and accept ! Here, the physical nature of the region inhabited by a species can lead to a geographic split (isolation). Events such as the formation of a river, the eruption of a volcano or the splitting of a land mass can all lead to speciation. It is not really necessary to state why, briefly - if individuals cannot physically reach others, the normal means of gene transfer, selection, mutation etc. are limited to those that can still mix. This in turn leads to significant variation in the now isolated populations - they have become separate species.
B. McCool - it hardly needs to be said...what nonsense !
Sympatric speciation occurs from within one population of a species (i.e. living in and sharing the same area). What happens is that for many reasons (I will offer an example in a minute) some individuals will only breed with certain other individuals that are in some way appealing to them. This can lead to speciation due to the fact that only a specified group of genes are passed among a specified population of individuals within the wider species population. This can be understood in the following example - suppose the genotype (the gene alleles present within an individual specimen) of a bird gives it a particular set of phenotypical expressions (a phenotype is any trait expressed by an individual due to its genes such as big ear lobes).
One such phenotype characteristic is a male beak of a particular shape that produces a unique kind of call to a prospective mate. The female finds only this call attractive, therefore only males able to produce that sound have a chance of mating.
That part explains the selective aspect of mating, but not how speciation may arise from it. Consider the implications of it - the gene pool of these discerning individuals is limited to what they themselves contain (their collective genotypes). As such the normal route of speciation (that is, at the level of the gene) - mutation, has a much more limited set of genes on which it can act. It is not surprising therefore that such a targeted passing on of genes that are subjected to, in isolation, the effects of mutation can lead to a specific set of individuals that have a distinctive look from others in the same area. What has just happened ? Sympatric speciation.
Allopatric speciation is much more straghtforward to explain, comprehend and accept ! Here, the physical nature of the region inhabited by a species can lead to a geographic split (isolation). Events such as the formation of a river, the eruption of a volcano or the splitting of a land mass can all lead to speciation. It is not really necessary to state why, briefly - if individuals cannot physically reach others, the normal means of gene transfer, selection, mutation etc. are limited to those that can still mix. This in turn leads to significant variation in the now isolated populations - they have become separate species.
B. McCool - it hardly needs to be said...what nonsense !
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They must mean the same thing, because the only way new species start is when different species get freaky with each other.