Changes that create a new species?

Question

Can anyone give me an example of a geographical or physical barrier that has acted like an "agent" of change to create a species?

I am having a really tough time finding one. Thanks!

Answer 1

we wont grow anytaller due to the invetion of the ladder?

Answer 2

Anything that physically or temporally isolates a group from the main group.  Physical isolation examples separate groups by preventing or making it difficult for the group to mate with the main group.  Mountain ranges that the groups can not or will not traverse can do this.  If there is sufficient supply of food on both sides of the mountain range neither group has the necessity to travel to the other side.  Over time they will evolve separately based on their environment.  Rivers, Oceans, Forests or even Elevation (tree tops vs. ground) can accomplish this.  Temporal separation would be species that are active at different times of the day.

Answer 3

An active agent would be a barrier that came along and divided existing populations, which eventually evolve into different species.  

For instance, the South Atlantic Ocean now separating Africa and South America.  This ocean did not always exist (see Pangea).  When the two continents split apart, creating the South Atlantic between them, the ocean began acting as an agent by being a physical barrier to, for example, primate populations on the two continents to continue inter-breeding.  

Eventually we ended up with today's situation where we have "Old World" monkeys (superfamily Cercopithecoidea) and New World monkeys (four families :Cebidae, Aotidae, Pitheciidae and Atelidae, which make up the Platyrrhini parvorder).

Within these groups we have dozens of species 'created' by the agency of the formation of the South Atlantic.

Answer 4

Best and most obvious example is Darwin's finches in the Galapagos Islands.

Answer 5

you can start wit hthe ocean