Transitional forms - evolution
- Thread starter Grantywanty
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The relative scarcity of intermediates, living and extinct, is in much due to their comparative lower adaptation compared with the ancestor and "finished" derivate form. It does in many instances, worse than both. This is actually one reason why species exist rather than a whole gradient between every closely related species.
Also, in the level of bigger groups than species, there's the fact that the phylogenetical tree of life already implies in a scarce number of intermediates. Between every two or more branches, there is only one "stem" branch, or linking group.
That is, we would found only a relatively small amount of intermediates, say, between fishes and amphibians, rather than an intermediate species for every amphibian species, that is because all amphibian species descends from a single amphibian ancestor, and we ought to find only a few of its closest relatives.
In this specific case, I think that the first pre-flowering plants would also have been able to reproduce by usual seeds, thus its partners would actually have been its own offspring. But I think that perhaps the heterogamete, polen prototype or whatever, could have been able to somehow "fecondate" normal seeds of the same species or something, in a sort of graft or chimera. Then both could happen at the beginning, with time, and the advantages of genetic diversity it represents, that would develop further.
But I don't really know much of plants and flowers, these are only a few ideas that came to my mind, it's likely that there are better theories developed by scientists.
But regarding the fossil record again, adding to the already mentioned problems of the rarity of fossilization (we often have only a few specimens of every animal, like, of Archaeopteryx, there is only about 12 - far less from what the total population of them over the eras must have been), and the expected scarcity of transitional forms due to their "scarcity by definition" in the tree of life, in the specific case of plants, there is an extra problem.
The classical gradualism is also somewhat challenged in a certain way. The rediscovery of genetics in Hugo de Vries' studies of plants had made some people think that "mutationism", the origin of differences by more drastic mutations, would be a better explanation for evolution than natural selection over subtle differences (which were thought to not have genetic basis). That's partly true in certain aspects, plants have a reasonably higher degree of viable variation, allowing them to have a few evolutionary leaps. Not as much as having a mutation, and bam! There are perfectly formed flowers, anyway.
I find remarkable that, even if we consider only extant species, there are already pretty much enough to assemble a single one phylogenetic tree of life. That would yet be far from what we have with fossils, but yet remarkable. For instance, we have yet intermediates between mammals and reptiles, the egg-laying mammals with no nipples such as platypus and echidna. Between feliforms and caniforms there are things like viverrids, raccoons, ferrets, and moongose, to name a few. There are humans, other apes, monkeys with tails but not bony tails (as humans eventually may have due to atavism), and monkeys with tails as other mammals. Birds have some resemblance with reptiles, such as having scales and laying eggs...
With the addition of fossils, much of these lines actually became blurry, such as the transition between birds and reptiles, with the addition of dinosaurs and/or the first birds such as Archaeopteryx - which one of its specimens was even mistakenly classified as a dinosaur, sole due to the bad impression of feathers.
At the same time, there is the molecular data, which creates a phylogenetical tree that corroborates the one from morphological data to a highly statistically significant degree, and with conceivable explanations for the instances it does not (scarce data and higher possibilities of morpholotical evolution intrinsic to certain groups). This corroboration has no explanation besides common ancestry.
I like to compare it all to a jugsw puzzle... their pieces not only match in only one specific way, pointing to a real interrelation between the pieces, but also there is another picture in its back, which is mounted at the same time... not only that, but it's almost as if the pieces were inside the box and halfway mounted already, in analogy with the way that the fossils are found, almost in sequence, rather than in a total mess.
And is interesting to have in mind that it didn't needed to be that way... if an intelligent species capable of researching the evolutionary history only arised much later, they could find only a much more obscure picture of the history, when much more convergences, divergences, extinctions and weird things happened; after much more erosion, metamorfism and other geological events literally erasing and shuffling chapters of the history... we are very lucky to have come to existance and developed science at such propitious moment to that discovery.
Evolution happens at such a pace that makes it unlikely for us to find transitional species. Not all fossils are preserved, so the few that do will create "holes" in the data big enough to prevent us from finding them. In fact, the differences we see between species determine our level of awareness of the changes in evolution. I could look at two birds and think that they are of the same species, but if a biologist look at both birds, the biologist may notice that they are from different species. Such levels of awareness cannot be ignored.
One variable left out of evolution is the impact of water. Life, at the molecular and chemical levels, evolves within an aqueous environment and therefore water itself will create its own version of natural selection at the chemical level.
For example, hydrogen bonding which is the basis for the unique properties of water, also became the basis for many aspect of life even though life may have started with simple gases like CO2, CH4, NH3, etc. Hydrogen bonding within the organic molecules of life predictably evolved and is used for template relationships as well as for the tertiary structures within life. These have conformed to water.
If you look at the transition from single to multicellular the entropy is lowering since N single cells has more degrees of freedom than N connected cells, which are mutually dependent. This also shows less surface tension in water. Again the aqueous environment is changing as the organics of life accumulate and alter the bulk potentials of the base aqueous environment. If you follow the water it is not random at all.
For example, hydrogen bonding which is the basis for the unique properties of water, also became the basis for many aspect of life even though life may have started with simple gases like CO2, CH4, NH3, etc. Hydrogen bonding within the organic molecules of life predictably evolved and is used for template relationships as well as for the tertiary structures within life. These have conformed to water.
If you look at the transition from single to multicellular the entropy is lowering since N single cells has more degrees of freedom than N connected cells, which are mutually dependent. This also shows less surface tension in water. Again the aqueous environment is changing as the organics of life accumulate and alter the bulk potentials of the base aqueous environment. If you follow the water it is not random at all.
New evidence has pushed the date of the first flowering plants back into the age of reptiles, the Triassic.
They would have been fertilised by beetles or other insects, not bees, which would not appear for 100 million years.
http://www.mediadesk.uzh.ch/article...en-jahre-aelter-als-bisher-angenommen_en.html
I think that the preponderance of early plant fossils may be to do with the lack of rotting bacteria, or was it fungi?
There are a huge number of fern fossils laid down in coal seams, because they weren't actively broken down.
Fraggle knows this.
What was that information, Fraggle?
They would have been fertilised by beetles or other insects, not bees, which would not appear for 100 million years.
http://www.mediadesk.uzh.ch/article...en-jahre-aelter-als-bisher-angenommen_en.html
I think that the preponderance of early plant fossils may be to do with the lack of rotting bacteria, or was it fungi?
There are a huge number of fern fossils laid down in coal seams, because they weren't actively broken down.
Fraggle knows this.
What was that information, Fraggle?
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Complete hand waving Bovine crap. Water has nothing to do with evolution except for the fact that if you remove all of the water from all living organisms they would die, which would put a bit of a crimp in evolution.
"Again the aqueous environment is changing as the organics of life accumulate and alter the bulk potentials of the base aqueous environment."
Could you elaborate?
Could you elaborate?
exchemist
Valued Senior Member
I fail to understand why you are so obsessive about water and H-bonding. You seem to try to work this into almost every subject.
Can you explain what you mean by water being a "variable left out of evolution"? As evolution is not a chemical process, I cannot see what you are driving at here.
Secondly, what do you mean by "water itself will create its own version of natural selection at the chemical level."? What selection at the chemical level do you think goes on, and can you give an example?
I write about a lot of this stuff in my book....
Fraggle Rocker
Staff member
Bees (and many insects) have seven kinds of photoreceptors instead of our three. This gives them the ability to determine which flowers are "ripe" and have the pollen they want.
More likely because there weren't a lot of land animals yet. Many species of animals subsist by eating plant tissue, living or dead. For example, almost all of the artiodactyls (cattle, deer, sheep, giraffes, camels, hippopotamuses, etc.), all of the perissodactyls (a smaller group, just equines, tapirs and rhinoceroses), plus elephants and several other species in other orders, are full-time grazers.
Perhaps only slightly relevant to this discussion. Many fungi are detritivores, digesting the tissue of dead plants. Mushrooms are the most amazing, since they have the enzyme lignase, which can decompose lignin, allowing them to use dead trees for food. Before mushrooms evolved, dead trees just lay there, decomposing only by the extremely slow forces of water and pressure, becoming petrified wood, coal, petroleum and natural gas. None of these things will ever be created again, thanks to mushrooms.
Walk through a forest and note that all the dead tree trunks are absolutely covered with mushrooms.
Evolution must have at some point been a largely chemical process.
Proto-life must have been no more than a single chemical, or a simple grouping of chemicals.
Looking for an external matrix is not nonsensical, though hydrogen bonds are unlikely, I think.
The surface of water, bounded with air is a possibility.
Some natural membrane, or mineral, or whatever, may have played its part.
Aren't there many kinds of insects that also feed off the dead tree trunks? Or they just happen to live there in a more closed ecosystem without actually consuming the trunk?
Kudos to the Magical School Bus for teaching me that.
We can see the natural membrane in unicellular organisms. I wonder what exactly caused them to develop the phospholipid combination to allow the first cells to be formed. Mitochondria, plastids, and perhaps other organelles as wel, used to be separate organisms, likely different forms of bacteria that learned to live together in what we now call "cells".
http://en.wikipedia.org/wiki/Endosymbiotic_theory
http://phys.org/news/2013-10-paleontologist-life-theory.html
I think this hypothesis might have some legs
Grumpy
I think this hypothesis might have some legs
Grumpy
Oh good! Thank you very much, I will add that source to my book!http://phys.org/news/2013-10-paleontologist-life-theory.html
I think this hypothesis might have some legs
Grumpy
http://phys.org/news/2013-10-paleontologist-life-theory.html
I think this hypothesis might have some legs
Grumpy
Fats from meteorites. Interesting.
The question remains how loose RNA and protein material floating in this soup protected itself in a membrane. Chatterjee believes University of California professor David Deamer's hypothesis that membranous material existed in the primordial soup. Deamer isolated fatty acid vesicles from the Murchison meteorite that fell in 1969 in Australia. The cosmic fatty bubbles extracted from the meteorite mimic cell membranes.
Read more at: http://phys.org/news/2013-10-paleontologist-life-theory.html#jCp
Do many meteorites contain fat?