Register | Sign In


Understanding through Discussion


EvC Forum active members: 65 (9162 total)
3 online now:
Newest Member: popoi
Post Volume: Total: 915,815 Year: 3,072/9,624 Month: 917/1,588 Week: 100/223 Day: 11/17 Hour: 0/0


Thread  Details

Email This Thread
Newer Topic | Older Topic
  
Author Topic:   evolution and the extinction of dinos
RAZD
Member (Idle past 1405 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 9 of 93 (607197)
03-02-2011 1:13 PM
Reply to: Message 8 by Peter
03-02-2011 12:39 PM


forams
Hi Peter.
Does anyone know if there is gap in the fossil record extending from 65 million years ago to some closer time, or just dino fossils disappear? I'm not clear in that.
Small burrowing mammals survived (and lead to us among others).
Birds (which are dinosaurs), mostly waterfowl survived.
There was some extinction in marine life but not all. An interesting element of this is shown in the foraminifera fossil record:
Geology Dept article 3
quote:
One of the last great extinctions occurred roughly 66 million years ago, and according to one popular theory it resulted from Earth's receiving a direct hit from a large asteroid. Whatever the cause, the event proved to be the dinosaurs' coup de grace, and also wiped out a good portion of Earth's marine life -- including almost all species of planktonic forams.
This period of mass death, which ended the Cretaceous Period, ushered in the modern chapter of biological development. Earth entered the new era, the Cenozoic, with a wide range of ecosystems virtually devoid of life, yet quite fertile and primed for repopulation.
Like ecologists who study how wildlife recovers from a forest fire, evolutionists are drawn to such incidences of "biological vacuum" in search of clues as to how the earliest forms of life started evolving, when competition wasn't the controlling factor in the process.
Particularly vexing are questions about what forces drive the process of natural selection -- what factors ultimately control the tempo and fate of biological struggle. But because of the traditional fragmentation of the fossil record, answers have remained elusive.
"In most cases of evolution, we're incapable of collecting the basic facts. But here's one case where we are capable," Parker said.
Since the foram record extends through a major extinction event (some of the samples date back nearly 100 million years), it represents the first, grand template against which a flock of pet theories on the beginnings of evolution may now be effectively measured, he said.
"This is the great naturalist experiment," says Parker. "How often is it that you get to almost wipe your slate clean and then watch an ecosystem start up all over again?"
Some scientists have theorized, but never been able to demonstrate, that in the absence of competition, an explosion of life takes place. The evolution of new species is greatly accelerated, and a profusion of body shapes and sizes bursts across the horizon, filling up vacant spaces like weeds overtaking a pristine lawn. An array of new forms fan out into these limited niches, where crowding soon forces most of the new forms to spin out into oblivion, as sparks from a flame.
Other observers, perhaps following Darwin's lead, have envisioned a much more sedate repopulation sequence, with speciation occurring at an immensely slow rate. None of the species die off until their numbers begin to saturate the environment, exhausting its capacity to sustain such proliferation of life.
As revealed by the ancient record left by the foram family, the story of recovery after extinction is every bit as busy and colorful as some scientists have long suspected.
"What we've found suggests that the rate of speciation increases dramatically in a biological vacuum," Parker said. "After the Cretaceous extinction, the few surviving foram species began rapidly propagating into new species, and for the first time we're able to see just how this happens, and how fast."
As foram survivors rush to occupy their new habitats, they seem to start experimenting will all sorts of body shapes, trying to find something stable, something that will work, Arnold said. Once a population in a given habitat develops a shape or other characteristic that stands up to the environment, suddenly the organisms begin to coalesce around what becomes a standardized form, the signature of a new species.
As the available niches begin to fill up with these new creatures, the speciation rate begins to slow down, and pressure from competition between species appears to bear down in earnest. The extinction rate then rises accordingly.
This scenario, Arnold says, suggests that the speciation process is sensitive to how fully packed the biosphere is with other species, not the number of individuals. Ecologists, in referring to a given environment's ability to sustain life as its carrying capacity, generally mean the natural limit, in sheer numbers, of individual organisms that any environment can support, as opposed to the number of different kinds of organisms.
Enjoy.

we are limited in our ability to understand
by our ability to understand
Rebel American Zen Deist
... to learn ... to think ... to live ... to laugh ...
to share.


Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click)

This message is a reply to:
 Message 8 by Peter, posted 03-02-2011 12:39 PM Peter has replied

Replies to this message:
 Message 10 by Peter, posted 03-03-2011 9:43 AM RAZD has seen this message but not replied

  
Newer Topic | Older Topic
Jump to:


Copyright 2001-2023 by EvC Forum, All Rights Reserved

™ Version 4.2
Innovative software from Qwixotic © 2024