Understanding through Discussion


Welcome! You are not logged in. [ Login ]
EvC Forum active members: 78 (8908 total)
Current session began: 
Page Loaded: 05-24-2019 5:39 PM
28 online now:
celestialGyoud, CosmicChimp, DrJones*, dwise1, Tanypteryx (5 members, 23 visitors)
Chatting now:  Chat room empty
Newest Member: WeloTemo
Post Volume:
Total: 852,008 Year: 7,044/19,786 Month: 1,585/1,581 Week: 407/393 Day: 41/90 Hour: 0/2


Thread  Details

Email This Thread
Newer Topic | Older Topic
  
Author Topic:   Is evolution of mammals finished?
Quetzal
Member (Idle past 4012 days)
Posts: 3228
Joined: 01-09-2002


Message 85 of 213 (386881)
02-24-2007 12:15 PM
Reply to: Message 69 by Chiroptera
02-20-2007 2:46 PM


Re: Weird.
Chiro,

One of the things that Martin appears to be claiming (and that I'm not sure has been addressed) is that competitive exclusion would preclude any adaptive radiation following the K/T extinctions, although it's really hard to follow his train of thought. IOW, because there were aquatic predators which survived the event, they would have already been in an advantageous position to exploit the newly-available resources, so any "latecomers" like the proto-whales would necessarily be unable to move in.

Obviously, there are several holes in this argument. For instance, we see successful invasions of exotics all the time (cf, European red squirrel (Scurius vulgaris) losing out to the introduced American grey squirrel (Scurius carolinensis) in the UK - even though S. vulgaris was already in place and exploiting the available resources). Now, admittedly, this is not "evolution" writ large, but it does show that no matter how full a system is, someone is often capable of horning in on the neighbors.

Secondly, competitive exclusion strong enough to preclude adaptive radiation would only be possible in a highly constrained or bounded ecosystem - which quite obviously the post-K/T-extinction world was not. It was an amazingly empty world, not only in terms of biodiversity, but in terms of sheer numbers of individuals. Picture a closet stuffed with clothes. Remove 75% of them. Lots of room for new articles, n'est-ce pas?

Another point that Martin brings out is a bit harder to explain. Why didn't the existing surviving aquatic predators match the "explosive" radiation of the terrestrial mammals - to the point that nothing else could play in their sandbox? Partly this is an insoluable problem - we simply don't know all the parameters of what makes one lineage more "adaptable" than another. We can speculate a lot, based on modern species dynamics, but the specifics would be pure guesses. In any event, since Martin appears to be fixated on sharks for some reason, their big Golden Age was the Carboniferous - 45 families of sharks appear in this period (compared to about 40 families plus the rays that are here today). Whether this order could have radiated post-K/T or not, the fact is they didn't - at least not to the extent that would have prevented some other lineage(s) from moving in to "shark niches". Same goes for the crocodillians.

I don't know whether this helps or confuses the issue even more. AZPaul3 alluded to niche construction as one reason the proto-whales could have made the transition from land to water without being excluded, and I would add niche partitioning as another (if you weren't previously aware, I'm a biodiversity "dynamic disequilibrium-ist").


This message is a reply to:
 Message 69 by Chiroptera, posted 02-20-2007 2:46 PM Chiroptera has responded

Replies to this message:
 Message 89 by MartinV, posted 02-24-2007 2:55 PM Quetzal has responded
 Message 92 by Chiroptera, posted 02-24-2007 4:59 PM Quetzal has responded

Quetzal
Member (Idle past 4012 days)
Posts: 3228
Joined: 01-09-2002


Message 93 of 213 (386916)
02-24-2007 7:00 PM
Reply to: Message 92 by Chiroptera
02-24-2007 4:59 PM


Re: Weird.
But if you think it's partly insoluble, maybe I'm wrong.

Heh. You answered your own question. The only insoluble part is, as you said,

Chiro writes:

In the same way, predicting how real species evolve (or do not evolve) in real ecosystems would require a great knowledge (with great precision) of all the factors in an environment, as well as exactly which mutations will arise. Furthermore, there may be developmental constraints as to what paths are even potentially possible.

THAT's the bit we can't really answer. Why this one and not that one? It's even worse when you're talking about time frames 30 mya. The only thing we can say is: that lineage DID, and that one DIDN'T.


This message is a reply to:
 Message 92 by Chiroptera, posted 02-24-2007 4:59 PM Chiroptera has not yet responded

Quetzal
Member (Idle past 4012 days)
Posts: 3228
Joined: 01-09-2002


Message 100 of 213 (387731)
03-02-2007 9:23 AM
Reply to: Message 89 by MartinV
02-24-2007 2:55 PM


Re: Weird.
Sorry I didn't see this response earlier.

It depends what exactly you remove. If you remove 75% animals from each species I would say nothing happens - remaining individuals will geometrically fill niches. According previous information 85% of marine Orders survived K/T. So diversification of life remain partly unaffected after K/T in the Ocean.

However, that's not what occurred. The K/T extinction didn't remove 75% of the individuals from each species, it removed 75%-85% of all existing species. Also, as you move up the taxonomic scale (from species to order, for instance), the percentage gets smaller. For instance, only ~40% of all existing genera went extinct, although even here it was quite selective: 100% of the orders Ornithiscia, Sauriscia, and Pterosauria died, 75% of order Marsupialia, but only ~11% of Crocodilia, etc.

As to marine extinctions - approximately 60%-70% of all marine species went extinct. Again, selectivity is the rule: 100% of Rudists, 100% of aminoids, ~95% of the Coccolithophorids, 100% of mososaurs, pleisiosaurs, and Inoceramids went extinct. Etc.

I have a meeting. I'll try and get to your other points later today.


This message is a reply to:
 Message 89 by MartinV, posted 02-24-2007 2:55 PM MartinV has not yet responded

Quetzal
Member (Idle past 4012 days)
Posts: 3228
Joined: 01-09-2002


Message 112 of 213 (387799)
03-02-2007 6:48 PM
Reply to: Message 103 by MartinV
03-02-2007 4:08 PM


Re: Mobbing
It helps if you respond to the post directly, rather than to yourself. I almost missed this one as well.

I quote the fact that 85% of marine Orders survived K/T extinction. I am not any expert, but I give you an example. If nowadays meteorite kills 95% of mammalian species and yet 85% of mammalian Orders survive I will say nothing happened.

Which is precisely what occurred during the KT extinction. 75-85% of all terrestrial vertebrate species were wiped out. Only 15% of terrestrial vertebrate orders went extinct. As I also noted in my previous post, some 60-70% of all marine species went extinct, but only 50% of all marine genera did so. You appear to be confusing taxonomic levels somehow. The "percent extinction" goes down the higher up the taxonomic ladder you go. However, a number of orders DID go extinct - entire taxa went missing.

It means this - there will be still some living bat species, some living whale species, some living rodent species, some living carnivora species, some living primates etc...

Except if we're still talking about the KT event, bats, whales, primates, carnivora, etc hadn't yet evolved - so obviously they couldn't have gone extinct.

There will be very great diversity of animals (even if 95% of species died and each Order preserved only 2 species instead of 180) that should occupy emptied niches.

Not really. One of the striking factors about mass extinction events is that the resulting biodiversity is highly impoverished. You may have a few representatives of different orders, say, but not many. Most of the fossil record immediately following such an event is dominated by only a few species.

Because there are still left some aquatic mammals, some flying mammals, some predators, some ungulates etc...

Well, again, none of these even existed prior to the KT event. These are the result of evolution since.

All basic "body plans" that are characteristic for Order survived.

Assuming anything in the order survived, then yes. However, this may represent vastly different organisms adapted to vastly different environments - and with vastly different chances for survival, radiation, and contribution to the biotic recovery.


This message is a reply to:
 Message 103 by MartinV, posted 03-02-2007 4:08 PM MartinV has not yet responded

Quetzal
Member (Idle past 4012 days)
Posts: 3228
Joined: 01-09-2002


Message 124 of 213 (388836)
03-08-2007 7:49 AM
Reply to: Message 113 by RAZD
03-02-2007 7:14 PM


Re: Mobbing
Hummingbirds can be devastating, quick and sharp.

Oh yeah. Never, NEVER wear a bright red tee-shirt in a tropical forest. The disappointed (and very annoyed) hummingbirds who thought you were the world's largest flower can get very aggressive - and occasionally painful. :D


This message is a reply to:
 Message 113 by RAZD, posted 03-02-2007 7:14 PM RAZD has not yet responded

Quetzal
Member (Idle past 4012 days)
Posts: 3228
Joined: 01-09-2002


Message 131 of 213 (389023)
03-10-2007 7:47 AM
Reply to: Message 126 by MartinV
03-09-2007 1:49 PM


Re: Mobbing
So why are swans white?

Not all of them are. Cygnus melanocorypha (black-necked swan, S. America) and C. atratus (black swan, Australia) aren't white. You might as well ask why several species of white swans have black beaks (for instance, C. buccinator, C. columbianus), or blue beaks for that matter (C. cygnus). Sexual selection is the most likely reason, as you've been told.


This message is a reply to:
 Message 126 by MartinV, posted 03-09-2007 1:49 PM MartinV has responded

Replies to this message:
 Message 133 by MartinV, posted 03-10-2007 2:50 PM Quetzal has responded
 Message 161 by Trae, posted 03-25-2007 6:13 PM Quetzal has responded

Quetzal
Member (Idle past 4012 days)
Posts: 3228
Joined: 01-09-2002


Message 143 of 213 (389154)
03-11-2007 10:32 AM
Reply to: Message 133 by MartinV
03-10-2007 2:50 PM


Re: Mobbing
So the motor of evolution is not "Random mutation and Natural selection" but "Sexual selection" instead? Does it mean that reason why ancient fish became feathered eagle is only due to "sexual selection"?

In the first place, sexual selection is a mechanism of natural selection/random mutation. Obviously, variation has to occur for sexual selection to operate. Basically, the selection pressure, rather than being some other biotic or abiotic factor in the environment, is mate choice and "success" is measured by differential reproductive rate rather than survival. There is one additional (and I use that word advisedly) component of sexual selection relating to the direct feedback between different genders in sexually dimorphic species (c.f., Muller's ratchet). In other words, the mechanism of sexual selection explains the male peacock's tail, but not why there are peacocks.

Or better question - can "sexual selection" lead to speciation? Are there any examples where "sexual selection" created new species, genera, family, order?

While to the best of my knowledge no speciation event has been directly attributable to sexual selection alone (I'm open to correction here), studies of many species indicate that sexually selected characteristics do serve as reproductive barriers between populations of genetically closely-related species (see, for example, Ritchie MG et al, 2005, Patterns of speciation in endemic Mexican Goodeid fish: sexual conflict or early radiation?, Journal of Evolutionary Biology, 18:922-929). In this case, the variation in the family Goodeinae is based almost solely on selection for male coloration and other characteristics. In addition, there are a number of bird families and amphibian complexes where genetics and range are similar, and the only apparent difference is behavior or some male characteristic.

As an example, in the Physalaemus spp. complex (family Leptodactylidae) of Central and South America the different species' ranges overlap to a great extent and their genetics are closely related (to the point where allozyme differences are practically non-existent). However, each species can be distinguished by its particular call. Close studies have shown that females almost invariably respond only to the calls of conspecific males - even though there is no obvious genetic barrier preventing interbreeding (see, for example, Ryan MJ, Rand, AS, 1993, Sexual selection and signal evolution - the ghost of biases past, Philosophical Transactions:Biology of the Royal Society, 340:187-195).

The evidence for sexual selection of certain species (to the point of speciation) is compelling and based on two major lines of observations:

1) sexually selected characteristics act as barriers to interbreeding

2) high species richness in many taxa in which sexual selection appears to be intense and diverse (Futuyma DJ, 1998, Evolutionary Biology, Sinauer, pg. 490). In my opinion, sexual selection is a good candidate as an explanation for sympatric speciation.


This message is a reply to:
 Message 133 by MartinV, posted 03-10-2007 2:50 PM MartinV has responded

Replies to this message:
 Message 146 by MartinV, posted 03-13-2007 3:55 PM Quetzal has responded

Quetzal
Member (Idle past 4012 days)
Posts: 3228
Joined: 01-09-2002


Message 147 of 213 (389463)
03-13-2007 6:16 PM
Reply to: Message 146 by MartinV
03-13-2007 3:55 PM


Re: Colors
This has what to do with your misunderstanding of sexual selection, exactly? Is there anything in any part of my post that claimed fungal coloration had anything to do with sexual selection? I have absolutely no idea why fungus have different colors. I've never studied them.

ABE: Now please address the substance of my post.

Edited by Quetzal, : No reason given.


This message is a reply to:
 Message 146 by MartinV, posted 03-13-2007 3:55 PM MartinV has not yet responded

Quetzal
Member (Idle past 4012 days)
Posts: 3228
Joined: 01-09-2002


Message 163 of 213 (391577)
03-26-2007 9:29 AM
Reply to: Message 161 by Trae
03-25-2007 6:13 PM


Re: Mobbing
I am a bit confused, is it not the case that a mutation can be passed where it is not beneficial? In the cases of blue beaks does not the ToE permit that the swan’s ancestor was selected for reasons apart of beak color and it just simply was the case that the blue beaks became dominate for reasons apart of beak color?

You're not confused, you're absolutely correct. Any number of traits - provided they have no fitness implication - can be passed down generations simply because they happen to exist in an organism that is being selected for some other trait. I don't know if you bothered to wade through the current thread What is Natural Selection... (if you did - more power to you, if not - you didn't miss anything), but it did briefly cover the difference between selected for and selected of. The analogy was a bunch of colored marbles being selected for size, while color was selected of the set of marbles (i.e., all the littlest marbles were also red).

In the case of the Cygnus species, the various colors were discussed in the context of sexual selection, although the specific post you responded to was an answer to one of MartinV's typical "nyah nyah" type questions ("Why are swans white?"). The rejoinder was intended to convey the ridiculousness of the question by noting that, in fact, not all swans are white.

I guess what I am asking, is does the ToE not make provision for a species simply acquiring traits that are neutral to natural selection?

Indeed it does, although I'm not sure "acquiring" is the right word. Posessing neutral traits is certainly expected under the ToE.

Seems to me Creationists spend a lot of time trying to trip up biologists for explanations of traits as if the lack of an explanation from some specific trait somehow disproves ToE. Isn’t an answer that simply sometimes variations within an acceptable range can be insignificant to the overall natural selection process?

Yep. It's one of their irritating little habits. Like I said above, they like to come up with an endless stream of "nyah nyah" questions as though that was going to disprove ~150 years of scientific inquiry.


This message is a reply to:
 Message 161 by Trae, posted 03-25-2007 6:13 PM Trae has responded

Replies to this message:
 Message 167 by Trae, posted 03-27-2007 12:26 AM Quetzal has responded

Quetzal
Member (Idle past 4012 days)
Posts: 3228
Joined: 01-09-2002


Message 168 of 213 (391757)
03-27-2007 9:59 AM
Reply to: Message 167 by Trae
03-27-2007 12:26 AM


Re: Mobbing
On a side note, I wonder if all these claims by IDists and creationists feeling they’re being told half-truths, that scientists waffle, and are making overinflated claims, might not be due in small part to explanations which are over simplifications geared towards lay people.

Short answer: quite likely, although there are some nuances to that answer. This isn't really the thread to discuss it, unfortunately.


This message is a reply to:
 Message 167 by Trae, posted 03-27-2007 12:26 AM Trae has acknowledged this reply

Quetzal
Member (Idle past 4012 days)
Posts: 3228
Joined: 01-09-2002


Message 169 of 213 (391758)
03-27-2007 10:02 AM
Reply to: Message 166 by Mike O Risal
03-26-2007 8:43 PM


Re: Colors (var. fancy)
Brilliant reply, Mike! Thanks so much for providing it - I learned more about Fungi in one post than I have in, well, forever. Almost a shame it is wasted on Martin.

ABE: Oh, and welcome to EvCForum!

Edited by Quetzal, : No reason given.


This message is a reply to:
 Message 166 by Mike O Risal, posted 03-26-2007 8:43 PM Mike O Risal has responded

Replies to this message:
 Message 172 by Mike O Risal, posted 03-27-2007 4:13 PM Quetzal has not yet responded

Newer Topic | Older Topic
Jump to:


Copyright 2001-2018 by EvC Forum, All Rights Reserved

™ Version 4.0 Beta
Innovative software from Qwixotic © 2019