Questions about Evolution?

[linwood]

I love this thread.

I don`t want to see it trashed with a creo/evo argument.

You`ll get no decent debate from this creo so I`d like to ask that this "debate" be taken elsewhere please.

[Autodidact]

Maybe a mod could move the non-informational posts?

[linwood]

Originally Posted by Autodidact

Maybe a mod could move the non-informational posts?

It`s not that big a deal.

If Carico continues we should just point him to a more appropriate thread.

Thanks Auto

[Alceste]

You`ll get no decent debate from this creo so I`d like to ask that this "debate" be taken elsewhere please.

I haven't read a single one of its posts. I tried to read the first one, but my eyes just slid off after four words. I've tried to read a few more since, with the exact same results. Anyway, whatever it is, it will go away if we don't feed it.

Questions about evolution...

What is the largest single celled organism, how old is it, and what is its ancestry?

[painted wolf]

What is the largest single celled organism, how old is it, and what is its ancestry?

Oooh... fun and difficult question.

The largest virus is about the size of a bacteria (both physically and in terms of it's genome).. This is Mimiviurs and it's between 900 and 1,200 genes make it more complex than the simplest bacteria. It's really important in blurring that line between 'life' and 'not-life'.
It's a DNA virus that infects amoeba. Mimivirus

The largest bacteria can be seen with the naked eye. 0.75mm long! Thiomargarita namibiensis. WHOI : Oceanus : Image : Is Life Thriving Deep Beneath the Seafloor?

One of the largest protists is Syringammina fragilissima who can reach 8 inches across!
http://deepseanews.com/2008/10/the-2...enophyophores/

Then you have Caulerpa an algae who can apparently grow to more than nine feet long! This one I don't know a lot about... or how much it really counts as a single cell.
http://www.brookscole.com/biology_d/...t/ch04-01.html

I can't give you specific ages for each species unfortunately.

wa:do

[Alceste]

Originally Posted by painted wolf

Oooh... fun and difficult question.

The largest virus is about the size of a bacteria (both physically and in terms of it's genome).. This is Mimiviurs and it's between 900 and 1,200 genes make it more complex than the simplest bacteria. It's really important in blurring that line between 'life' and 'not-life'.
It's a DNA virus that infects amoeba. Mimivirus

The largest bacteria can be seen with the naked eye. 0.75mm long! Thiomargarita namibiensis. WHOI : Oceanus : Image : Is Life Thriving Deep Beneath the Seafloor?

One of the largest protists is Syringammina fragilissima who can reach 8 inches across!
The 27 Best Deep-Sea Species: #22 Xenophyophores | Deep Sea News

Then you have Caulerpa an algae who can apparently grow to more than nine feet long! This one I don't know a lot about... or how much it really counts as a single cell.
http://www.brookscole.com/biology_d/...t/ch04-01.html

I can't give you specific ages for each species unfortunately.

wa:do

No worries, I just threw the "ancestry" thing in there to make it more "about evolution", as per the topic of the thread. I remembered it was some kind of sea thingy, but for some reason I thought it was a jelly-like thingy.

That sticky, spongy thing is extremely cool. I will keep my eyes peeled next time I get a chance to go diving.

[Inky]

Originally Posted by painted wolf

Polyploidy (an increase in the number of chromosomes) is caused by a 'goof up' in meiosis.
During meiosis the chromosomes are supposed to divide up into two half sets... sometimes this doesn't happen and you end up with a gamete (sex cell) that has a full set of chromosomes.

Plants are highly resistant to changes in ploidy and they can essentially go crazy with chromosome numbers... This may have to do with the fact that upping the number of chromosomes in a cell also increases the size of the cell and plants with their cell walls are better able to cope with that increase.

wa:do

That's very interesting, thanks. : ) Do differences in ploidy between animal species with a common ancestor start out with one individual who got the "wrong" number, who ended up founding a new species? Or is it more complicated than that? I got really interested in this for some reason and Wikipedia has failed me!

[painted wolf]

That's very interesting, thanks. : )

You're welcome.

Do differences in ploidy between animal species with a common ancestor start out with one individual who got the "wrong" number, who ended up founding a new species? Or is it more complicated than that? I got really interested in this for some reason and Wikipedia has failed me!

With plants it's that simple... most polyploid plants are capable of asexual reproduction.
With animals it's a little more complicated... while a whole litter of offspring can be born with the same ploidy.. the exact nature of how such species get a foothold is still being studied.
Most of that research is being done on a group of rodent species called Viscascha Rats. They have a couple of species that seem to have recently developed due to ploidy events.

There is still quite a bit to learn about this aspect of evolution.

wa:do

[DarkSun]

Originally Posted by painted wolf

Plants are highly resistant to changes in ploidy and they can essentially go crazy with chromosome numbers... This may have to do with the fact that upping the number of chromosomes in a cell also increases the size of the cell and plants with their cell walls are better able to cope with that increase.

wa:do

But why are plants immune to conditions like trisomy 21, karyotype 47 XXY, karyotype 45X and so forth. I can understand how the cell-wall could restrict their size, but surely that has no bearing on the biological/chemical pathways determined by the DNA of the cell.

Forgive me if I sound silly in saying this.

[painted wolf]

But why are plants immune to conditions like trisomy 21, karyotype 47 XXY, karyotype 45X and so fourth. I can understand how the cell-wall could restrict their size, but surely that has no bearing on the biological/chemical pathways determined by the DNA of the cell.

Forgive me if I sound silly in saying this.

Not at all...
They aren't immune per say... but they are far more resistant.
Plants seem to be able to handle the extra product that the additional chromosomes produce.

I'm not 100% sure why personally... though my guess is that it's because plants don't use biochemical signals in quite the same way as animals, and thus extra product may not be as damaging.

So it's totally not a silly question... it's actually something that I wonder about too... I'll have to see if the botany professor at my university has any idea.

wa:do