Is evolution of mammals finished?

Message 31 of 213 (385694) 02-16-2007 8:39 PM

Reply to: Message 30 by MartinV 02-16-2007 8:15 PM

If you just want to call off topic then do so like this....

"Ice, I'd appreciate it if you'd stay on topic."

Any further discussion of this issue should be taken to the appropriate thread in my signature.

Message 32 of 213 (385699) 02-16-2007 9:06 PM

Reply to: Message 20 by MartinV 02-11-2007 9:43 AM

Then you would be wise as you would lose your nickle, sorry. The K-T event devastaed shallow water marine ecosystems. The ammonites, huge predatory cephalopds (coiled shells 3 meters across) were extremely widespread and diverse. These probably had a top-down control on prey items (IOW Cretaceous bad time to start evolving from terrestrial to aquatic). Belemites, another group of cephalopods were also extinct after this event. Rudists were very large bivalves (not closely related to any living bivalves) that formed massive reefs in Cretaceous seas and kilo for kilo probably accounted for most of the aquatic biomass in shallow seas. Completely absent after the Creataceous.

Echinoids (sea urchins and their kin) lost pretty much all of their diversity as did brachiopods. Large numbers of fish families became extinct. Marine phytoplankton groups like diatoms and coccolithophores crashed in both numbers and diversity. In the large vertebrate world (those that might have occupied niches to be later filled by pinnipeds and cetaceans) all of the marine reptiles went extinct. This, btw, includes the marine crocodylians. The group including modern marine crocodiles are not known until the Tertiary so your statement in another post about no change in crocodile diversity is, well, a crock (just an aside, and maybe this was an error, but you might want to avoid citing undergraduate web projects as primary sources. Especially when those sources do not contain the info you claim anyhow).

Nearly all of our shallow water marine mollusks and echindoderms are families which diversified since the K-T event. Decapod crustaceans (crabs, lobsters, shrimp) evolved prior to the event but exploded in diversity during the Tertiary.

Edited by Lithodid-Man, : Forgot to add what did diversify during the Tertiary!

Message 33 of 213 (385700) 02-16-2007 9:06 PM

Reply to: Message 27 by iceage 02-16-2007 4:25 PM

First of all, the inner quote above is NOT from NJ (in his message 23) rather it is from PaulK in message 25.

Second, I have a hard time convincing myself, that your message is anything more that a piece of #@*%.

Shall we bring up the quality of messages? Or maybe you should quit posting.

Take any replies to this message to the "General discussion..." topic, link below. Do NOT reply in this topic.

Adminnemooseus

ps: I'll probably be having a discussion with AdminAsgara, in the "Private Administration Forum".

Message 34 of 213 (385803) 02-17-2007 8:51 AM

Reply to: Message 32 by Lithodid-Man 02-16-2007 9:06 PM

Yet sharks seems to thrive as well as once. For instance:

http://web.ncf.ca/bz050/bigshift.html

Some types of sharks became even non-predatory animals - Basking shark, White shark. So I would say there were not enough "emptied niches" for all predatory sharks. It is curious that having such sharks variety there was neverthenless enough space left for land mammals to enter there and to feed themselves like pre-adapted sharks that had already occupied the niches .

Anyway crocks survived K/T as well as birds did. Arent birds and crocks close relatives btw? Crocodiles (salt-water) look like Ambulocetus - but somehow there was no selective drive into the sea.

And it seems also that there was in the air enough space and niches for mammalian bats to enter it - yet it is hard to believee that birds could not find these niches or accomodate to them before bats evolved.

Message 35 of 213 (385807) 02-17-2007 9:06 AM

Reply to: Message 34 by MartinV 02-17-2007 8:51 AM

There ... is ... no ... drive ...

Evolution is NOT driven, it is a response to opportunity.

Enjoy.

Message 36 of 213 (385835) 02-17-2007 1:26 PM

Reply to: Message 35 by RAZD 02-17-2007 9:06 AM

So whether due to Yucatan meteorite impact or not, there were many different reptiles and non-mammalian animals that survived K/T boundary. Yet they were unable to "respond to new opportunity" and to fill "emptied niches" as succesfully as mammals did. If there was not impact of the meteorite I would say (using darwinistic theory) that mammals would overpower reptiles anyway. It would had taken more time, but the observed "responses to opportunity" seems to work in favour om mammals and theirs greatest outcome - mankind.

Message 37 of 213 (385841) 02-17-2007 2:16 PM

Reply to: Message 36 by MartinV 02-17-2007 1:26 PM

Or re-filled niches that had been vacated by other birds (birds being older than the K/T event). It seems most of the birds that survived were aquatic (there was a thread that discussed this, can't find the link), and that birds today are descendants of those survivors.

But opportunities are not just environmental, they also involve the available variations within the populations and behavioral patterns (such as being aquatic versus terrestrial birds).

They did. Those that survived were adapted to the environment they were in, and thus able to survive within it. They did not need to change to be adapted to that environment. They then radiated out into similar environments that had been vacated.

The question is whether they could have benefited by moving into a substantially different environment. The crocodile today is a shore feeder, and adaptation to full water life would mean giving up some of that ability. There is also the issue of warm-blooded versus cold-blooded and both being air breathers -- this would have limited the crocodile ability to dive in deep water and actively pursue prey compared to a warm-blooded competitor (or a cold-blooded water breather). This would limit the ability of crocodilians to become like whales. Evidence for this is also in the areas where crocodiles live -- only where there is warm and relatively shallow water.

Note that the similar shore environment further north is occupied by the seals and other Pinnipeds - further evidence of the benefit of warm-bloodedness - and that these are intermediate between crocodiles and whales for diving ability.

You also talk about proto-whales competing with sharks, and note that sharks diversified into many species - including herbivores.

From an evolution standpoint it doesn't really matter what the species - or how many - fill a niche, just that they do so in sufficient quantity and ability to survive and breed. There are many birds that eat the same basic seeds and live in the same basic areas - one doesn't always drive the other out (or to extinction). We see oscillations - give and take - between different species (ie like galapagos finch beaks).

Whether there are 10 shark species or 9 shark species and one whale species filling the same general habitat amounts to the same result in the end.

Opportunity = available niche, available ability, available behavior patterns.

Enjoy.

Edited by RAZD, : added pinnipeds

Message 38 of 213 (385846) 02-17-2007 3:48 PM

Reply to: Message 37 by RAZD 02-17-2007 2:16 PM

Yet according Nature 2005 crocodiles have warm-blooded ancestors.

Message 39 of 213 (385860) 02-17-2007 5:09 PM

Reply to: Message 26 by MartinV 02-16-2007 2:49 PM

quote:

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How it happened that mammals Pakicetus and Ambulocetus overcame sharks and crocodiles that survived K/T Yucatan meteorite impact very well? Subsequnetly fully adapted sharks and crocodiles were not so apt to occupy "emptied niches" of shallow warm waters of shores?

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That's a good question. When people play pachinko, why does one person's ball fall more or less straight down, while another person playing the exact same machine see her ball bounce all the way over the side? Yet, despite not being able to answer even such a basic question, no one doubts that the motion of the ball is basically described by Newton's simple laws of motion. I don't know why you want do doubt Newton's laws just because I cannot describe exactly the path of a pachinko ball.

Evolution is governed by the environment. The environment contains lots and lots of factors that will influence the evolution of a species. Crocodiles that were too far from the "basic crocodile form" didn't survive to leave offspring. Why? Maybe the right mutations didn't occur that would have given them a survival advantage. Maybe the KT-extinction did not change the shape of the "fitness vs. morphology" function.

Why did Pakicetus evolve toward an aquatic environment? Well, evidently some Pakicetus had a mutation that allowed a more efficient use of a more aquatic environment, and these Pakicetus were able to thrive. Just like the pachinko ball, that is pretty much all we can say.

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quote:

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The whole thing was planned form beginning....

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Huh? You mean the subsequent evolutionary history of life was already written in the first cell three and a half billion years ago? How does that work?

Message 40 of 213 (385863) 02-17-2007 5:42 PM

Reply to: Message 38 by MartinV 02-17-2007 3:48 PM

"Might have had." From the article linked to:

Message 41 of 213 (385865) 02-17-2007 6:13 PM

Reply to: Message 38 by MartinV 02-17-2007 3:48 PM

It comes down again to opportunities:

http://www.adelaide.edu.au/adelaidean/issues/5501/news5550.html

quote:

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"It turns out that all of these advanced cardiovascular features are valuable for today's crocodiles, enabling them to bypass the lungs and hold their breath for longer periods," Professor Seymour said. "Crocodiles typically remain hidden under water until their prey comes near, then they lunge and often drown their victims. Warm-bloodedness is not suited for this type of sit-and-wait hunting, because of a high metabolic rate and a need to breathe often.

"When I looked at the palaeontology of crocodiles, a consistent picture appeared-the earliest ancestors of crocodiles were definitely not sit-and-wait predators. Instead, many had long legs and some ran around on only two legs. These were obviously highly active, terrestrial predators which would have been well served by warm-bloodedness and a four chambered heart.

"Between 200 and 65 million years ago, the crocodilian lineage diversified into more than 150 genera in all kinds of habitats from land-based to fresh water and the ocean," he said.

"Only one relatively small group that were aquatic and sat and waited for food to come to them managed to survive until today. All the rest became extinct about 65 million years ago with the big extinction when most of the dinosaurs died out," he said. "The cold-bloodedness that this group evolved may have been a factor that saved it."

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When the mass extinction occurred the ancestors of today's crocodiles had already taken the opportunity to be cold-blooded again to augment their behavior pattern of ambush predation.

Those that were deep sea predators or warm-blooded predators were killed in the mass extinction, leaving those niches open for later animals to take the opportunities available.

Enjoy.

Message 42 of 213 (385905) 02-18-2007 12:35 AM

Reply to: Message 34 by MartinV 02-17-2007 8:51 AM

You either failed to read or failed to understand your source. The page you cited, "The Big Shift by Richard Martin (http://web.ncf.ca/bz050/bigshift.html) is about the diversification of elasmobranchs after the K-T event. Meaning that the species which survived the event subsequently filled the niches left empty. In the quote above Martin states clearly "The most recent elasmobranch radiation coincided with the mammalian radiation..." (bold mine). He is talking about what occured after the event which destroyed nearly all shallow water and terrestrial species over 50 kg.

First of all, and I am sure it is a typo, white sharks are indeed predatory. The evolution of 'filter feeding' (btw, I hate that term. In my classes it is known as the "F-word" because I take off points when I see it used on a paper) has absolutely nothing to do with a lack of emptied niches. It makes no more sense than to say whales evolved to swim because all of the walking niches were filled. Suspension feeding (<-- used instead of the F-word) typically evolves as predators specialize in capturing small but abundant prey.

Message 43 of 213 (385919) 02-18-2007 7:47 AM

Reply to: Message 42 by Lithodid-Man 02-18-2007 12:35 AM

He also states that marine extinction hit only 15% of marine invertebrate families. Even if we assume that 90% of species died out
the diversity of invertebrate families reminded pretty well preserved due to fact that 85% families survived. Might be that the same numbers are applicable to other marine families, I don't know.

Yet sharks survived K/T boundary as well as crocodiles did. The salt-water crocodiles distributed in Asia nowadays are well adapted for hunting in estuaries. So combining predators sharks and crocodiles I don't see how Pakiceus in Pakistan managed avoid these well-adapted pre K/T predators and entered the sea neverethenless - and even share with them same niches obviously. I personally fail to see there "emptied niches".

It is also interesting that according some latest conceptions there were not only warm-blooded crocodiles but also dinos. Yet they didn't survived K/T boundary. What seems to had been once advantage for mammals seems to be disatvantage for crocs and dinos in the same area at the same time. Yet cold-blooded reptilians survived K/T boundary mostly unaffected and neverthenless they were unable to fill "emtied niches" as succesfully as mammals did.

Than behind evolution are other forces than darwinistic "struggle for survival" or random mutations, the best of which are picked by Natural selection to fill "emptied niches". If a bear had creeks full of salmons all the year than there wouldn't be need for them to became a whale I suppose.

If there is abundance of great prey I do not see reason why to transform to small-prey eater. Only if the predator somehow foresee in advance that environment could change... That means if the species possess some kind of "spirit" and is not formed by blind adaption to existing environment.

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Message 44 of 213 (385920) 02-18-2007 8:02 AM

Reply to: Message 39 by Chiroptera 02-17-2007 5:09 PM

Pachinko ball doesn't have predators hunting it like crocs and sharks. Try game again using pachinko ball made of meat in the pool overcrowded with crocks or sharks.

Problem is difficult. According some popular medieval conceptions (Giordano Bruno was it's follower) matter possesed spirit once. Might be that spirit is going upwards and is now fully presented in humans. The spirit presented himself and his creativity in mammals during "adaptive radiation" during Eocene and before during "Cambrian evolution" in lowest phyla. That's why evolution of mammals is finished. Species do not possess as much spirit as once. At least -according Chardin - we see during evolution increasing perfection of nervous system.
Just an idea.

Message 45 of 213 (385922) 02-18-2007 8:18 AM

Reply to: Message 41 by RAZD 02-17-2007 6:13 PM

Warm-blooded predators were superseded by other warm-blooded mammalian predators and cold-blooded reptilian predators. What was the disatvatage of this warm-blooded predators to be replaced by another ones (it is claimed by darwinists that warm-blooded feature was one of the reason of succesfull mammalian radiation during Eocene)?