Does evolution gradually slow down as niches are filled?

[I don't know]

I have no education in biology, nor am I going to get it, so this is just out of curiosity: as life fills the Earth and develops into more advanced forms, filling up the different niches - does evolution slow down because of "lack of room"?

 

[bel]

Yes, a sort of "equilibrium" position can be attained. However, this is rare since the environment might be changing constantly as well, and perhaps even faster than the formation of new species. Furthermore, mutations continue to appear randomly and some mutation might still be advantageous over the predominant phenotype even if the the species are very well suited for their niches. In the course of natural history, the appearances of new species is, in fact, not evenly distributed over time, but shew long stretches of very little change punctured with explosions of a plethora of new species, and these explosions usually follow some cataclysmic environmental changes.

 

[I don't know]

Right, so evolution tends to stabilize when the environment is stable and you get more dramatic changes as the environment has dramatic changes. I assume that we're in a pretty stable situation nowadays? Or does global warming mean that we may be seeing lots of new species?

 

[Rade]

Environmental change does not always equate to increase in species diversity, the opposite also can occur. Global warming "may be" one cause--it is a hypothesis, but see that even well respected journal "Nature" has published on this linkage:
http://news.bbc.co.uk/1/hi/sci/tech/3375447.stm

 

[iansmith]

Environmental change does not always equate to increase in species diversity, the opposite also can occur. Global warming "may be" one cause--it is a hypothesis, but see that even well respected journal "Nature" has published on this linkage:
http://news.bbc.co.uk/1/hi/sci/tech/3375447.stm

Although species diversity might be lost due the climate change, diversity may increase in the long run. The niche occupied by species that disappeared becomes free and can be occupied by other species. therefore, the occupation of a new niche can produce a "new" specie and increase diversity.

Changes in niches/climates results in species that loses (i.e. become instinct) and some win. However, the winner does not always create diversity.

 

[pawelsobko]

Yes, a sort of "equilibrium" position can be attained. However, this is rare since the environment might be changing constantly as well, and perhaps even faster than the formation of new species. Furthermore, mutations continue to appear randomly and some mutation might still be advantageous over the predominant phenotype even if the the species are very well suited for their niches. In the course of natural history, the appearances of new species is, in fact, not evenly distributed over time, but shew long stretches of very little change punctured with explosions of a plethora of new species, and these explosions usually follow some cataclysmic environmental changes.

As for equilibrium, there is the famous Red Queen hypothesis: you must run as fast as you can just to stay in place. The equilibrium is very dynamical. Remember that the most of the environment we talk about is other organisms: competitors and cooperators from one's own species, organisms we eat and those that eat us etc.

The punctuated equilibrium model postulates periodically occurring times of slow and very fast rates of speciation. Whether this is just a question of varying selection rate or mutation rate as well, and whether the punctuated equilibruim is truly valid I can not say. But it would be interesting to look deeper into the different rates of change for the replicators and for the vehicles (to use Dawkin's names) or replicators and interactors (to use Hull's names).