Freethought & Rationalism Archive

Oolon Colluphid · 05-23-2006, 03:35 AM

As most of you will know, I have a list of weird, poor and potty design features in organisms, sometimes known here (where it started) as Oolon's Big List. The list is about poor design, especially, when we can find it, poorer than another design the Designer knew about because He used it elsewhere (eg bird through-flow lungs).

But it has occurred to me that we could do with a list running parallel with that, containing examples where different 'designs' are used to achieve the same thing. Re-invented wheels. Not where we can see one version is clearly better than another, but simply different.

The example that sparked this thought is the forelimbs of golden moles (true moles) and marsupial moles. Both have front limbs that act as shovels: very short and broad, with huge flattened claws. Yet in the marsupial moles these shovels are formed by fusion of the third and fourth digits, whereas in golden moles it is the second and third digits that are fused.

There are of course loads of examples of convergent evolution (or things that are better explained by RBH's Multiple Designers Theory) than by one (schizophrenic) designer. So let's list 'em! Examples of the Multiple Designers' handiwork!

Off the top of my head:

Cetaceans' laterally flattened (horizontal) tail flukes vs. fish dorso-ventral (vertical) ones
Mole feet (above)
The variety of placentas in mammals, and shark etc pseudo-placentas
Differences in thylacine vs wolf skull (Martin B did a good piece about it a while ago...)
Hindgut vs. ruminant digestion (actually a candidate for both lists, as hindgut fermenters are waaay less efficient)

Over to you folks!

ETA: Oh, and I think we need specific structures: rather than just 'kangaroos and rabbits are different ways of eating grass', we need the differences in teeth -- open roots in rabbits, molar replacement in kangaroos. You get the idea...

Codec · 05-23-2006, 03:58 AM

Things like:

The Pandas Thumb
The multiple designs of the eye
Oxygen transport systems
Fins and flippers

or am I off track?

Oolon Colluphid · 05-23-2006, 04:01 AM

Quote:

Originally Posted by Codec

Things like:

The Pandas Thumb
The multiple designs of the eye
Oxygen transport systems
Fins and flippers

or am I off track?

Nope, bang on track! Please explain the oxygen transport systems though

.

Codec · 05-23-2006, 04:12 AM

I thought the oxygen transport was obvious, until I went to look for more details, then I found I didn't know what I thought I knew!

Anyway, as far as I know, we have the following systems that are used to move oxygen around.

Haemoglobin - animals
Myoglobin - some insects
and hemocyanin

The last one was something I'd vaguely heard about, alternate oxygen transport in insects, or at least some insects. Also it seems in molluscs. Wow - how an innocent statement can lead to a world of discovery!

Oolon Colluphid · 05-23-2006, 04:23 AM

Quote:

Originally Posted by Codec

Wow - how an innocent statement can lead to a world of discovery!

Absolutely!

Here's a few more thoughts / questions...

We’re looking for same sort of structure but made differently in X and Y (and possibly Z).

Pangolin vs armadillo -- what specifically?

Arctic and Antarctic fish antifreeze proteins:
http://www.pbs.org/wgbh/evolution/li.../l_014_01.html

Quote:

In the frigid waters of the ocean surrounding Antarctica, fish have a special trait which allows them to survive the big chill. As scientists discovered in the 1960s, the fish have adapted by evolving a kind of antifreeze. It's composed of molecules called glycoproteins that circulate in the blood of the fishes, slightly lowering the temperature at which their body fluids would otherwise freeze and kill them. The glycoproteins surround tiny ice crystals and keep them from growing.

It's another of those ingenious evolutionary solutions that seem almost too clever to be true. But consider this: Nature did it not once, but at least twice. Fish at the other end of Earth, in the Arctic, also have antifreeze proteins. But those two populations of fish split long before they developed the antifreeze genes and proteins. And, researchers have found, the genes that produce the antifreeze proteins, north and south, are quite different.

'Convergent evolution of antifreeze glycoproteins in Antarctic notothenioid fish and Arctic cod' -- http://www.pnas.org/cgi/content/full/94/8/3817

Bird, bat and pterodactyl wings... which bones are lengthened / shortened etc?

Loads of examples in the Wikipedia:
http://en.wikipedia.org/wiki/Converg...Other_examples
...but not much on the underlying differences...

Another, sharks and tuna... but again, what's different (apart from generalities like bony vs cartilaginous

)...

Codec · 05-23-2006, 04:25 AM

I think anteaters are another case of convergent evolution.

Giant Anteater
Pangolins
Echidnas
Banded Anteater (marsupial)
Aardvarks (in the begining was the word, and the word was aardvark).

Different continents, orders and classes all come up with the same idea. I find it hard to believe there is that much meat on an ant though - still each to their own.

MrDarwin · 05-23-2006, 06:06 AM

If you want to look at "oxygen transport" look at the various and entirely different ways of breathing air--for example, contrast tetrapods, arachnids, insects, and terrestrial crustaceans like isopods. (It's especially curious that at least two major respiratory systems exist in arthropods--insects and arachnids--which have started out with the same basic morphological and genetic toolkit.) Likewise, breathing underwater: there are so many different kinds of gills that it boggles the mind, not to mention the various ways that air-breathing insects have learned to breathe underwater without gills.

Codec · 05-23-2006, 06:18 AM

Quote:

Originally Posted by MrDarwin

If you want to look at "oxygen transport" look at the various and entirely different ways of breathing air--for example, contrast tetrapods, arachnids, insects, and terrestrial crustaceans like isopods.

Got any handy links for these?

Quote:

(It's especially curious that at least two major respiratory systems exist in arthropods--insects and arachnids--which have started out with the same basic morphological and genetic toolkit.)

Well didn't everything start out with the same toolkit from the MRCA?

Going back in history, do brachiopods and bivalves not solve similar problems in different ways? Two different phyla with very similar structures. (If anyone can give me a good way to distinguish the two it would really help my home study course!).

Oolon Colluphid · 05-23-2006, 06:29 AM

Quote:

Originally Posted by Codec

Going back in history, do brachiopods and bivalves not solve similar problems in different ways? Two different phyla with very similar structures. (If anyone can give me a good way to distinguish the two it would really help my home study course!).

Ha! Not long finished the OU Fossils and the History of Life course, so I know the answer! Symmetry. Bivalves have each valve (shell) symmetrical (ie the plane of symmetry passes between the valves, along the opening-and-closing line), whereas in brachiopods, the line of symmetry runs through each valve: the left and right halves of the valve are symmetrical, but one valve may be a lot different from its companion.

There's also substantial internal differences (well they are different phyla, after all) to do with how the shells are opened/closed, but I don't remember what they are!

ETA: As always, the Wiki has more: http://en.wikipedia.org/wiki/Brachiopod

Codec · 05-23-2006, 06:45 AM

Quote:

Originally Posted by Oolon Colluphid

Ha! Not long finished the OU Fossils and the History of Life course, so I know the answer! Symmetry. Bivalves have each valve (shell) symmetrical (ie the plane of symmetry passes between the valves, along the opening-and-closing line), whereas in brachiopods, the line of symmetry runs through each valve: the left and right halves of the valve are symmetrical, but one valve may be a lot different from its companion.

Thanks - guess I need to revisit the answer to question 20 of the above metioned course before submission! Doesn't help much if you only have one of the fossil shells, bivalves tend to be symmetrical about the center axis too. Good course though.

I thought brachiopods had died out, but apparently not according to the wiki article. Just mostly.

Back to the original thread, how close are ants and termites? They have very similar oganisation.
Silk - from insects and arachnids - might be a common ancestor thing though.

05-23-2006, 03:35 AM	#1
Oolon Colluphid Contributor Join Date: Sep 2000 Location: Alibi: ego ipse hinc extermino Posts: 12,591	Oolon's big list of re-invented wheels - Multiple Designers (please contribute) As most of you will know, I have a list of weird, poor and potty design features in organisms, sometimes known here (where it started) as Oolon's Big List. The list is about poor design, especially, when we can find it, poorer than another design the Designer knew about because He used it elsewhere (eg bird through-flow lungs). But it has occurred to me that we could do with a list running parallel with that, containing examples where different 'designs' are used to achieve the same thing. Re-invented wheels. Not where we can see one version is clearly better than another, but simply different. The example that sparked this thought is the forelimbs of golden moles (true moles) and marsupial moles. Both have front limbs that act as shovels: very short and broad, with huge flattened claws. Yet in the marsupial moles these shovels are formed by fusion of the third and fourth digits, whereas in golden moles it is the second and third digits that are fused. There are of course loads of examples of convergent evolution (or things that are better explained by RBH's Multiple Designers Theory) than by one (schizophrenic) designer. So let's list 'em! Examples of the Multiple Designers' handiwork! Off the top of my head: Cetaceans' laterally flattened (horizontal) tail flukes vs. fish dorso-ventral (vertical) ones Mole feet (above) The variety of placentas in mammals, and shark etc pseudo-placentas Differences in thylacine vs wolf skull (Martin B did a good piece about it a while ago...) Hindgut vs. ruminant digestion (actually a candidate for both lists, as hindgut fermenters are waaay less efficient) Over to you folks! ETA: Oh, and I think we need specific structures: rather than just 'kangaroos and rabbits are different ways of eating grass', we need the differences in teeth -- open roots in rabbits, molar replacement in kangaroos. You get the idea...

05-23-2006, 03:58 AM	#2
Codec Senior Member Join Date: Jan 2006 Location: Nottingham, UK Posts: 960	Things like: The Pandas Thumb The multiple designs of the eye Oxygen transport systems Fins and flippers or am I off track?

05-23-2006, 04:12 AM	#4
Codec Senior Member Join Date: Jan 2006 Location: Nottingham, UK Posts: 960	I thought the oxygen transport was obvious, until I went to look for more details, then I found I didn't know what I thought I knew! Anyway, as far as I know, we have the following systems that are used to move oxygen around. Haemoglobin - animals Myoglobin - some insects and hemocyanin The last one was something I'd vaguely heard about, alternate oxygen transport in insects, or at least some insects. Also it seems in molluscs. Wow - how an innocent statement can lead to a world of discovery!

05-23-2006, 04:25 AM	#6
Codec Senior Member Join Date: Jan 2006 Location: Nottingham, UK Posts: 960	I think anteaters are another case of convergent evolution. Giant Anteater Pangolins Echidnas Banded Anteater (marsupial) Aardvarks (in the begining was the word, and the word was aardvark). Different continents, orders and classes all come up with the same idea. I find it hard to believe there is that much meat on an ant though - still each to their own.

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05-23-2006, 06:06 AM	#7
MrDarwin Veteran Member Join Date: May 2001 Location: Washington, DC Posts: 4,140	If you want to look at "oxygen transport" look at the various and entirely different ways of breathing air--for example, contrast tetrapods, arachnids, insects, and terrestrial crustaceans like isopods. (It's especially curious that at least two major respiratory systems exist in arthropods--insects and arachnids--which have started out with the same basic morphological and genetic toolkit.) Likewise, breathing underwater: there are so many different kinds of gills that it boggles the mind, not to mention the various ways that air-breathing insects have learned to breathe underwater without gills.

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