Transitional forms - evolution

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Grantywanty

Registered Senior Member
(I am not a monotheist and am not a fan of creationism)

Why are there so many missing transitional forms?
A specific case: a transitional form between non-flowering and flowering plants. Why hasn't one been found?
Further, how could one evolve via mutation ---natural selection?
A plant mutates and develops flower parts, with no partners to mate with, how could these traits - that I must add cost energy to form - remain and lead to successful sexual contacts?
We have many examples of nonflowering plants that have been around since before any tranistional forms would have existed. What have none of the transitional forms lasted or been found in fossil records?
 
Fossils are rare, and there aren't enough scientists to even collect all the ones that could be found. Many are sold off to collectors before any scientific institution can study them.
 
spidergoat said:
Fossils are rare, and there aren't enough scientists to even collect all the ones that could be found. Many are sold off to collectors before any scientific institution can study them.
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Sure, but we are talking about missing transitional forms in a wide range of species some that would have covered enormous parts of the land surface. Most collectors would realize the value of a transitional form and try to sell it to a university etc.
 
Not really. Scientifically important specimens are often unrecognizable to the non-expert. They prefer dinosaur skulls. Also, they are collected with no concern for their context, which of course is vitally important.

There are indeed so-called "transitional" forms of many types of life that have been found as fossils.



Cycads, in groves looking superficially much like pineapple orchards, were the most distinctive of the non-flowering plants, the gymnosperms. (NOTE: Various cycads during this period did develop flowers, and may well represent transitional forms between gymnosperms and the flowering plants.) Leaves of cycads are common in Arizona, the woody trunks are rare.
cycad%20living.jpg
 
Spidergoat:

You must be from Arizona! Nice link.

However, it gave no support for the claim that some Cycad fossils have "flowers". I have not seen that in the fossil record either, so perhaps you might have another source?

Cycads are similar to the conifers, though they do not have true wood like the conifers and the angiosperms. Modern cycads appear little-changed from ancient fossil cycads.

As to the general question of the thread, transitional forms [whether plants or animals] do not exist for long periods of time, and few form fossils. Once the transition is completed [over millions of years] to a more stable form, it remains existent for long ages, thrives, and produces far more fossils than the transitional forms. Thus, those are the ones we find the most often. Searching for the transitional forms is the goal of science, and we keep finding them [oftentimes in difficult to navigate locations]. The recent fossil finds of fish that had front legs, but no hind legs, and a movable head, is a case in point. It had long been surmised that such transitional forms must have existed, but no fossils had been found linking the fish to the legged amphibians. It is interesting that those fossils show the fin bones being modified to become front leg bones, similar to those of land vertebrates. Valich and I posted extensively about that in another thread last year.

Regards,


Walter

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If you stop and think about how fossils are formed, you realize that the true "miracle of life" is that we've ever found any at all. For any part of an organism--even a "virtual" part such as its shape--to be preserved well enough for us to recognize it, the proper conditions must obtain for millions of years. Consider that we call coal, petroleum and natural gas "fossil fuels." It is only by using the sophisticated scientific knowledge of the last century and a half that we can deduce that these substances are the remains of organic tissue: they have been altered by geology to the extent that the individual organisms have been combined into a single continuum of matter.

As for transitional forms, they exist aplenty as living organisms. Whales have vestigial pelvises. Kangaroos have no placenta and platypuses and echidnas just lay eggs. Almost all birds have reptilian scales on their feet. The bones that control the shape of bat wings are elongated toes. You have third molars, a tailbone and an appendix. You also have--unlike every other primate species--tiny webs between your fingers, the key evidence for the prosecution of the Aquatic Ape Theory.

But the most interesting transitional form is the human fetus. As it develops from a zygote, it clearly passes through the forms of many "lower animals," starting with invertebrates. At one point it has a tail, and IIRC even gills.
 
Fraggle Rocker said:
If you stop and think about how fossils are formed, you realize that the true "miracle of life" is that we've ever found any at all. For any part of an organism--even a "virtual" part such as its shape--to be preserved well enough for us to recognize it, the proper conditions must obtain for millions of years.
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Yes, but statistics play a role. Oil drilling, mining, archaology etc have turned up vast amounts of fossils and yet rather unpleasants gaps remain, such as the one I mentioned between non flowered and flowering plants. That a rather large number of examples of both have been found but none 'in between' is odd and against the odds or I'm missing something. I also still have trouble with that transitions period. How did mutation lead to flowers? How did the 'positive' mutations gain a foothold without partners?
 
The problem is that every time you find a new fossil, you create two new gaps. Plus, gaps in fossilisation occur, and can be on the order of millions of years, long enough for changes in species to take place. Finally, why on earth would you expect flowers to fossilise at all?
 
Or in other words, the only answer to your question is for you to go away and read a great deal on paleontology.
 
Remember the part in my first post about conditions having to be absolutely perfect--for millions of years in a row--for fossils to form. I'll have to wait for a geologist to weigh in here, but I'll bet that the odds of any single species exisiting in a time and place where those conditions obtain are astoundingly small. And that statistically it's not remarkable that far more species are lost than preserved.
 
Fraggle Rocker said:
Remember the part in my first post about conditions having to be absolutely perfect--for millions of years in a row--for fossils to form. I'll have to wait for a geologist to weigh in here, but I'll bet that the odds of any single species exisiting in a time and place where those conditions obtain are astoundingly small. And that statistically it's not remarkable that far more species are lost than preserved.
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The fossil record of the horse seems fairly complete, spanning over 60 million years, and has become a classic example of evolution. I wonder why it is so complete when compared to other animals.

Here's a diagram made for school use by the BBC.
http://images.google.co.uk/imgres?i...rse&um=1&start=1&sa=X&oi=images&ct=image&cd=1
 
Off the top of my head, I imagine it is that:
1) The horse has, in this period, lived in environments whcih have not been massively changed through geological action.
2) Its bones fossilise well
3) It had a wide range, therefore maximising the chances of being fossilised by something eg a flash flood carrying the bdoies down into an anaerobic swamp.
 
Yes, the horse has been a remarkably successful evolutionary line. Just look at how well it has adaptetd to arguably the greatest perturbation to the global ecosystem ever: civilization. How many tens of billions of individuals in the horse line do you think have lived, in order to gift us with the fossils we've found?

As I have posted elsewhere, multiple times... In my observation, people are not very good at drawing conclusions from data that contains very large numbers, like tens of millions of years. The way the law of averages plays out during that time span is not intuitively obvious.
 
I just read this and thought of you granty:

...When ancestors of whales, dolphins and manatees changed their swimming stroke from paddling with paws to graceful tail movements, Fish said, their swimming performance improved and used energy more efficiently.

With the new discovery of whale fossils, scientists have only recently been able to study the efficiency of limbless swimming. However, bones alone cannot tell us the whole story of how and why mammals lost their limbs in the water.

"Because only the bones have been preserved, we still do not know when these transitional forms started to insulate the body with blubber and how the fluke's design changed to generate large propulsive forces with high efficiency for high-speed swimming," Fish told LiveScience....
 
Orleander said:
When ancestors of whales, dolphins and manatees changed their swimming stroke from paddling with paws to graceful tail movements, Fish said, their swimming performance improved and used energy more efficiently.
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It's certainly a classic case of convergent evolution. Until the cetaceans evolved, fish were the most highly advanced aquatic creatures, and they also swim by flapping their tails. This gave them an efficiency advantage over older types of aquatic locomotion such as spitting out pressurized streams of water or flapping a bivalve shell. Whales evolved the same mode of transit, apparently it's a good one that nature has built twice. The only difference is that fish oscillate their tails sideways, whereas cetaceans do it vertically.

BTW, with DNA analysis we've learned that the cetaceans are artiodactyls--even-toed ungulates like pigs, sheep, cattle, antelope and giraffes. Their ancestors were primitive hippopotamuses who swam all the way to the end of the river and kept going. Life is so easy for an air-breathing warm-blooded animal in the water, with its tremendous advantage in energy production. Seals, penguins, otters, ducks, polar bears... almost every mammal or bird that has completely or partially readapted to an aquatic environment is near the top of its food chain.
 
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perissodactyla.

i am pretty sure that a whale fluke only pushes it forward on the downward thrust. so it works somewhat differently than a fishes tail. i assume it is a true aerofoil.

also horses are perissodactyla.
 
It is interesting to note that even with much bigger gaps in the fossil record, evolution of some sort would be strongly indicated by the time line of various types of species: Single celled creatures first, followed in order by invertebrates, fish, land animals.

The above omits any mention of the order in which exo-skeletal creatures, amphibians, reptiles, & mammals first appeared.
 
Grantywanty said:
Why are there so many missing transitional forms?
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Mostly because a definition of species is used that automatically reclassifies a transitional form as a new species, hence immediately eliminating the transitional form as a transitional form, and immediately requiring a new transitional form for people who struggle with this concept.
 
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