Naked Science Forum
Non Life Sciences => Geology, Palaeontology & Archaeology => Topic started by: JDG8R on 20/03/2006 00:02:19
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A very amatuer series of questions, perhaps, but:
Are there very many species that are alive which are found in the fossil record? And, of those, are there very many which are lone survivors with extinct members of its genus and family also in the record? And, of those, is the greater percentage those that were earth dwellers or sea dwellers?
To clarify the central question, is it more likely that "old" (say pre-quaternary maybe?--been 18 years since geology degree) species found both in the fossil record and in real life are waterborne? And if so, how does that impact our views on the violence of major events on land and in the atmosphere. Are sea creatures more likely to survive a meteor impact, for example?
I know that more "waterborne" fossils exist, due to the nature of preservation, but how about some percentages about who is more likely to survive. Common sense tells me the water creatures could survive a cataclysm better than land or air dwellers because there is more area of water than area of land, and thus many more
"crevices" of suitable environment in which the water species can survive.
FWIW, what triggered this thought --and I know it is quite possibly one which no one cares about, though I'd love an informed comment-- was a reference made in a fishing forum about a semi-rare catch of a fish in Montgomery, AL. I reproduce it here:
http://pensacolafishingforum.com/forum/forums/thread-view.asp?tid=17040&posts=8
Also, contributing to my interest here is the fact that I am now 41, and havent seen much change (haha, a joke). "Catastrophism", ie rapid transformation in the land forms and life seems a pretty plausible thing. I.E. Grand Canyon happened quickly...And my gut feeling that global warming is geologically a pimple on the ass of time that we are foolish to try to control it or lose a minute of sleep over.
P.S. Only did the geology thing for 4 years after school. Missing it.....
Jim D.
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Hi Jim,
I've heard that 99% of species ever to evolve on Earth have become extinct.
"Living fossils" (surviving species of old evolutionary lines) today include most famously the Tuatara lizard and the Coelacanth, but I'm not sure that any extant (surviving) species are also to be found as ancient fossils. On average, a given species will last for no more than about 3 million years.
If, however, we apply your line of questioning to genera or families of animals, we'd probably find that a number of sharks, crocodiles and other rather 'stable' evolutionary designs, found as fossils, still persist today.
I couldn't say whether marine environments confer such a noticeable advantage upon a species, that it is more likely to be a longer - lived species. In the KT event extinction, all the marine reptiles became extinct for example, not just the dinosaurs.
The Permian extinction was a lot harsher on marine life, wiping out most marine invertebrates of the time.
Hope this helps,
Damian.
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Species longevity is controlled by the rate of evolutionary change. this, in turn, is determined by two factors; opportunity and means.
The means is generally the random mutation effecting the DNA of germ cells. This mutation rate is thought to be reasonably constant over time. Thus, the important factor is the environment.
Two things will favour species longevity: a constant environment, a restricted environment. The first is obvious. Once the flora and fauna are well adapted to a given environment then any mutations are likely to make then less fit for that environment. such mutations will be selected against. The species, perhaps, the genera probably, and the family, almost certainly, will persist for extended periods of geological time.
The second point may be less obvious. A restricted environment will also tend to suppress species change. By restricted we mean one in which there are few ecological niches. There are, therefore, few interacting species.
These species constitute a part of each others environment. Given that there are few of them, the chance that one changes, thus changing the environment of the others, is low. In a diverse environment, with many species, the odds are good that one of them may change, upsetting the delicate balance and encouraging a small pulse of evolutionary change.
In this regard we would expect marine environments to be comparatively constant, they are certainly restricted, and the marine species should thus show the greatest longevity. I believe this is borne out by the fossil record, but can offer no research results to confirm it.
The survival of marine species over land species is probably more related to the greater inherent stability of the marine environment (though rahonavis has pointed out this did no good at the end of the Permian).
Observe; collate; conjecture; analyse; hypothesise; test; validate; theorise. Repeat until complete.
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quote:
Originally posted by JDG8R
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Also, contributing to my interest here is the fact that I am now 41, and havent seen much change (haha, a joke). "Catastrophism", ie rapid transformation in the land forms and life seems a pretty plausible thing. I.E. Grand Canyon happened quickly...And my gut feeling that global warming is geologically a pimple on the ass of time that we are foolish to try to control it or lose a minute of sleep over.
P.S. Only did the geology thing for 4 years after school. Missing it.....
Jim D.
Geologically speaking humans are a pimple on the ass of time, and I'm sure global warming is as well. However, I would personally rate the human species and the environment upon which it depends worth worrying about. I'm also sure that I'm not an impartial observer, being a member of said species. I'm sure the universe as a whole doesn't lose a moment's sleep over the fate of homo sapiens.
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John - The Eternal Pessimist.
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Ophiolite makes a good point
quote:
Two things will favour species longevity: a constant environment, a restricted environment
Would you consider adding simplicity of design to this list?
What you do speaks so loudly that I cannot hear what you say.