Thread: Ask me about Genetics/Evolution

Wow, I didn't know people on here actually had university degrees.

Anyhow, I think I for the most part understand evolution, and don't make false statements. I do have a question: Has a species been pushed as far as to evolve into a different species, within a lab? I though I heard something about flies getting genetically 'reprogrammed' by letting generation after generation do with less and less of their normal food, and more and more of some other, or something... eventually, the new kind of flies couldn't have babies with the other kind, a criteria that usually used to distinguish different species.

A) Is that true, did that happen?
B) Did it happen with mammels too?

Peace out

I found this online article in the berkeley website:

http://evolution.berkeley.edu/evolib...e/0_0_0/evo_45

there is a part about the experiment you are talking about. Notice that they say that the flies showed a "preference" for flies of their own group. So this is evidence for the mechanism of speciation but not two species created (the flies could mate between groups they just "prefered" their own group).

http://evolution.berkeley.edu/evolib...experiment.gif

speciation in mammals is hard to achieve in the lab, as their generation times are a lot longer then flies (9-10 days from egg to adult). You see that with flies you can have 30 generations pass in a month while for humans (generation time ~25 yrs = 750 years - obviously there are mammals such as mice with smaller generation times but still its quite impossible to wait for them to speciate, it would just take too long).

hope this helps, and let me know if you need to clear up some point

PS: oh and the method for the flies was just that they were feeding them a different food source, but they believe that some genes that have to do with mating were under pressure (probably because of being near the food source genes)

---------- EDIT ---------------------

check this out about what species are etc:

http://www.talkorigins.org/faqs/faq-speciation.html

and this has some examples of speciation:

http://www.talkorigins.org/faqs/speciation.html

Punctuated equilibrium vs. gradualism?

Originally Posted by sogart

I found this online article in the berkeley website:

http://evolution.berkeley.edu/evolib...e/0_0_0/evo_45

lol@ this graph:

Thanks for the info, sogart. I bookmarked those links, very useful

and yeah, lol@ that graph ^__^

Punctuated equilibrium vs. gradualism?

this is one of the most interesting questions. I will look at it a bit so I can give a concise answer...

PS: its a bit late now and just came back from holidays so I need some dreaming and sleep

I read everything Stephen Jay Gould ever wrote so I am influenced by that. I wondered where the argument really stood now; any new ideas? His stuff was really before the work in genetics had progressed to the extent it has now; has that added anything?

Thanks in advance; I can't seem to keep up with any reading anymore.

Before I start with my opinion, I want to tell you that although I have studied Genetics in a high level, I have never worked on this specific problem (gradualism vs punctuated equilibrium). I understand people have talked about this problem for ages and there are too many opinions for me to go into, so the only thing left to me is to explain how I personally see things and maybe give you some food for thought.
PS: I feel free to copy from the internet without stating sources except where more interesting material can be found there...

I will start with a brief explanation of the question and the two opposing theories:

gradualism: Gradualism is selection and variation that happens more gradually. Over a short period of time it is hard to notice. Small variations that fit an organism slightly better to its environment are selected for: a few more individuals with more of the helpful trait survive, and a few more with less of the helpful trait die. Very gradually, over a long time, the population changes. Change is slow, constant, and consistent.

punctuated equilibrium: In punctuated equilibrium, change comes in spurts. There is a period of very little change, and then one or a few huge changes occur, often through mutations in the genes of a few individuals. The mutations that result in punctuated equilibrium are very helpful to the individuals in their environments. The species changes very rapidly over a few generations, then settles down again to a period of little change.

What would we expect to see in order to distinguish between these two theories?

If gradualism is the main way that species evolve, then we would expect to see a lot of genetic variation within species and also several species with extended conservation of their genetic material.

In a punctuated equilibrium world we would expect to see big differences between species and also (maybe) big differences within species (but it could also be that we see very little differences within species) with little variation.

What we really see (my opinion) when we look in genomes of closely related species, is a mosaic of very highly conserved regions (a lot of similarity) and other regions that are less conserved. I am talking about regions that actually take some part in function and not "junk" regions. My knowledge of within species variation is not large so I am not going to touch on that.

(I dont know if all this makes sense. If you need me to go deeper in this I will have to read a bit and will be happy to discuss it. I will go on to explain a bit how I see evolution happening right now and maybe this clears things up a bit)

Within species variation could very well be a gradualist process. Natural selection puts pressure on individuals and variation occurs. It could also well be that a really helpful mutation can spread fast through a population. For a new species to appear big changes have to be made. What is not easy to see is that these big changes are not so big in the genetic level (although they might seem big in the phenotypical level - what we see). Mostly these are changes in the plan (regulation) of genes and less in the actual genes.

So how I see it is: species generally follow a gradualist model and their genes change in slow rates. However, sometimes really radical phenotypical changes can occur very fast. These changes seem large but in reality the new organism is not so different genetically. So a slow gradualist model on the genetic level can seem like a punctuated equilibrium model in the population/species level.

I will stop here, I hope I haven't bored you to death with all my rambling (my brain is also a bit tired). I am waiting for any thoughts you (or anyone) might have on this and more questions.