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Evolution: the Facts.

I may be skipping over a few pages, but I need some information on how species form and how geographically isolated populations can evolve into new animals....

I like the beauty of the concept, but can't grasp that sort of process happening without a few speed bumps along the way.
 
If evolution is true, then why are atheists so smart and attractive?

This facetious moment brought to by Baby Beer™, beer for BABIES.
 
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Dessi said:
If evolution is true, then why are atheists so smart and attractive?

This facetious moment brought to by Baby Beer™, beer for BABIES.
Click to expand...

We are? Sure, you are, but... wait... Yes, we are.

Dunno why.
 
Speedbumps are one of the ways it can happen.

Say you've got a small population of lizards on the southern edge of a lake. They can't expand to the west for some reason (say it's a really wide river that they can't swim), but they need to be near the water for food. They'll expand in one direction--counter-clockwise. This isn't going to be one continuously expanding population, though--it'll be small subpopulations that break off the main population, then move out. They'll still be exchanging genetic information, but it'll be at a slightly reduced rate. None of this is controversial--we see it all the time in biology.

What you get is a series of subpopulations of the species--A gives rise to B, B to C, C to D, and so on. Over time, the lizards will have completely circled the lake. Say you get A to F. The thing to remember is that any subpopulation can breed with the neighbors--so C can breed with B and D, B with A and C, E with D and F, and so on. The thing is, by the time the string meets back in the south, A cannot breed with F. Again, not a controversial topic (at least, not anymore)--they're called ring species.

Now, let's say something happens and wipes out Subpopulation C, D, and E. A and B can interbreed, but A and B cannot interbreed with F. From the biological species concept, this is a speciation event.

The other way this can happen is that you have interbreeding populations of a species, all able to interbreed with one another--pretty open genetic transfer. Then something happens--say, a lake appears in the middle of things, cutting the population in half. Over time, genetic drift (or different selection pressures) can drive differences to the point where were the lake to dry up, the two populations could no longer interbreed. Again, by the biological concept of species this constitutes a speciation event.

You'll note that I keep saying "...by the biological species concept". There's a reason for that: we really don't have a good definition of the term "species". The biological species concept is the idea that any actually OR POTENTIALLY interbreeding populations are the same species. Problem is, it's not really meaningful in many cases. I mean, if the population doesn't actually interbreed, does it make sense to talk about potentialities? For example, if you have fish in small pools, all more or less isolated and carried by birds from one lake to another, does it make sense to talk about the same species of fish in all those issolated lakes? Or, conversely, there are insects that lay their eggs on fruit. If they lay their eggs on apples they mate at one time of the year; if they lay their eggs on pears they mate at another time (not really clear why). Are they separate species? How far do you go with this? I know a lot of women who refuse to sleep with tall, lanky guys with extremely curly hair and a penchant for talking about rocks for hours on end. Are tall, lanky geologists a different species from those girls?

Other species concepts do exist. Paleontology uses the morphospecies concept--when it looks different enough, we call it a new species. As you can imagine, all kinds of fun problems arise--for example, it took a long time to realize that ammonites are sexually dimorphic. There are also species concepts defined by genetic similarities, and I believe one or two more that I'm not thinking of just now.

But yeah, that's the basics of allopatric speciation (the idea you're talking about).
 
Dinwar said:
Speedbumps are one of the ways it can happen.

But yeah, that's the basics of allopatric speciation (the idea you're talking about).
Click to expand...

Thanks for clearing that up.

But perhaps I should have reworded my question slightly. Like,...what about things like new structures or weapons that develop over the course of speciation.
 
Here's an example:

http://www.talkorigins.org/indexcc/CB/CB310.html

TalkOrigins said:
In fact, an evolutionary pathway that accounts for the bombardier beetle is not hard to come up with (Isaak 1997). One plausible sequence (much abbreviated) is thus:

Insects produce quinones for tanning their cuticle. Quinones make them distasteful, so the insects evolve to produce more of them and to produce other defensive chemicals, including hydroquinones.
The insects evolve depressions for storing quinones and muscles for ejecting them onto their surface when threatened with being eaten. The depression becomes a reservoir with secretory glands supplying hydroquinones into it. This configuration exists in many beetles, including close relatives of bombardier beetles (Forsyth 1970).
Hydrogen peroxide becomes mixed with the hydroquinones. Catalases and peroxidases appear along the output passage of the reservoir, ensuring that more quinones appear in the exuded product.
More catalases and peroxidases are produced, generating oxygen and producing a foamy discharge, as in the bombardier beetle Metrius contractus (Eisner et al. 2000).
As the output passage becomes a hardened reaction chamber, still more catalases and peroxidases are produced, gradually becoming today's bombardier beetles.


All of the steps are small or can be easily broken down into smaller ones, and all are probably selectively advantageous. Several of the intermediate stages are known to be viable by the fact that they exist in other living species.
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There's been many evolutions of homologous structures such as eyes, venom, etc etc.

That's my attempt to address it; if you want to get to specifics you'll have to. At the most basic fundamental level structures evolve as they are selected for.
 
At times like this, when the creatards are absent, this thread makes for fascinating reading!

Thanks!
 
Dinwar said:
... Are they separate species? How far do you go with this? I know a lot of women who refuse to sleep with tall, lanky guys with extremely curly hair and a penchant for talking about rocks for hours on end. Are tall, lanky geologists a different species from those girls?
Click to expand...

Clearly not on that basis, since many tall, lanky guys with extremely curly hair and a penchant for talking about rocks for hours on end refuse to sleep with other tall, lanky guys with extremely curly hair and a penchant for talking about rocks for hours on end, yet are treated as the same species.
 
sphenisc said:
since many tall, lanky guys with extremely curly hair and a penchant for talking about rocks for hours on end refuse to sleep with other tall, lanky guys with extremely curly hair and a penchant for talking about rocks for hours on end,
Click to expand...
Well....Let's just leave that evening aside, shall we? :P

IIIClovisIII said:
Like,...what about things like new structures or weapons that develop over the course of speciation.
Click to expand...
I think in part you're equating two different things.

The Mojave Green rattlesnake experienced a mutation about 20 years ago. It was always a nasty little serpent, but it become even nastier--20 years ago, it gained a new toxin in its venom. I forget which came first, but it now has both a neurotoxin and a hemotoxin. Because apparently shutting down one major organ system isn't enough when you eat rodents. Anyway, the thing is, they're still the same species. A Mojave Green is a Mojave Green, whether it's 1920 or 2010. So evolution, even of weapons, can happen outside of speciation.

The other thing to consider is that evolution can only work with what it has. It can twist and mold what it hsa in ways that are utterly unpredictable and truly bizzar, but it only works with the materials at hand. Claws have been a part of tetrapod anatomy since the beginning--the fish didn't have it, but the amphibians did. Those claws, over millions of years and many, many successive speciation events, took on the form of deadly 6" long scythes in Utahraptor. They also became our fingernails--which is important, because it illustrates that 1) side branches in evolution often are perfectly viable, and 2) different selection pressures produce different results.
 
Dinwar, thanks for that explanation of ring species. I had heard of them, but I didn't actually know what they were. Makes sense. I really regret not doing biology at high school. If I had, I think I might have studied biology instead of physics, or at least biology as well.
Stupid religious indoctrination making me to think that evolution was a load of BS.:mad: Thankfully I have seen the light of reason.:)
 
Glad to hear it helped! :)

To be honest, I didn't learn about ring species until college. My high school bio class taught me how to play paper football.
 
Evolution is not a progression towards anything except reproductive success.
 
jimbob said:
Evolution is not a progression towards anything except reproductive success.
Click to expand...

Acquiring energy is pretty important.


"Surveying the long chequered, but on the whole continuous,
ascent of man from primeval conditions to the
summit of his present-day powers, what has it all been at
bottom but a fight with Nature for energy for that
ordinary physical energy of which we have said so much ?
Physical science sums up accurately in that one generalisation
the most fundamental aspect of life in the sense
already defined.
Of course life depends also on a continual supply of
matter as well as on a continual supply of energy, but
the struggle for physical energy is probably the more
fundamental and general aspect of existence in all its
forms. The same matter, the same chemical elements,
serve the purposes of life over and over again, but the
supply of fresh energy must be continuous. By the law
of the availability of energy, which, whether universal
or not, applies universally within our own experience,
the transformations of energy which occur in Nature
are invariably in the one direction, the more available
forms passing into the waste and useless unavailable
kind, and this process, so far as we yet know, is never
reversed. The same energy is available but once. The
struggle for existence is at the bottom a continuous
struggle for fresh physical energy"

FREDERICK SODDY
 
h.g.Whiz said:
Acquiring energy is pretty important.


"Surveying the long chequered, but on the whole continuous,
ascent of man from primeval conditions to the
summit of his present-day powers, what has it all been at
bottom but a fight with Nature for energy for that
ordinary physical energy of which we have said so much ?
Physical science sums up accurately in that one generalisation
the most fundamental aspect of life in the sense
already defined.
Of course life depends also on a continual supply of
matter as well as on a continual supply of energy, but
the struggle for physical energy is probably the more
fundamental and general aspect of existence in all its
forms. The same matter, the same chemical elements,
serve the purposes of life over and over again, but the
supply of fresh energy must be continuous. By the law
of the availability of energy, which, whether universal
or not, applies universally within our own experience,
the transformations of energy which occur in Nature
are invariably in the one direction, the more available
forms passing into the waste and useless unavailable
kind, and this process, so far as we yet know, is never
reversed. The same energy is available but once. The
struggle for existence is at the bottom a continuous
struggle for fresh physical energy"

FREDERICK SODDY
Click to expand...

That's just a means to an end.

"A chicken is an eggs way of making another egg".

Survival is unimportant except in as far as it promotes reproductive success, which is what natural selection "measures".
 
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