Quetzal

Hi Tricia: Just to add a bit on what Oolon said about spiders.

I'm not sure where your teacher? got this tidbit. Every species of web-spinning spider (both the orb spiders - "garden spider" and funnel spiders) spin different webs - I mean each species has its own design. The statement doesn't really mean anything without knowing which of the myriad "garden spiders" your teacher is talking about. In any event, IIRC they don't spin seven different kinds of web - they may use multiple types of thread - but each species=one style, varied slightly by condition (like available anchor points, etc.) If you're really interested, <a href="http://www.ufsia.ac.be/Arachnology/Pages/Silk.html" target="_blank">this page</a> is a web portal that links to dozens of sites talking about everything you ever wanted to know about spider silk and spider webs. <a href="http://www.unibas.ch/dib/nlu/staff/sz/webconstruct.html" target="_blank">This website</a> is another great site that has a step by step explanation of the construction of a web by Araneus diadematus, a fairly typical European garden spider.

[ May 07, 2002: Message edited by: Morpho ]</p>

DMB

Tricia: I strongly suggest you read Climbing Mount Improbable by Richard Dawkins to understand how things can evolve in tiny bits, even though the fully developed feature we see now wasn't there at all of the intermediate stages.

pseudobug

This is a neat thread that I wish that I had been keeping up with.

Concerning the evolution of the giraffe's neck, I happened upon <a href="http://www.cs.uop.edu/~eb0003/GIRAFFE2.htm" target="_blank">this brief discussion on the issue</a>. It goes on about the validity of several of the proposals of how the long neck came about.

Most interesting is the proposal that the neck length is the result of sexual selection in male giraffes. Seems like when the boys start courting for affection, the bang each other with their necks and and "neck wrestle" for who gets the opportunity to mate. So, those with the biggest, strongest..er...neck get more opportunities.

Anyway, there a couple of links to journal articles if anyone is interested in the bibliography:

4. Simmons, R. & Scheepers, L. (1996). Winning By A Neck: Sexual Selection In The Evolution Of Giraffe. The American Naturalist, 148, 772-786.


5. Stevens, J. (1993). Familiar Strangers. International Wildlife, 23, 6-10.


6. du Toit, J. (1992). Winning By A Neck. Natural History, 101, 29-32.

[Edited by Oolon to fix the link]

[ May 07, 2002: Message edited by: Oolon Colluphid ]</p>

pseudobug

Hey Oolon, thanks for fixing my link. I was in a rush to make a seminar and didn't check it.

Tricia

Just a post to let you know I'm alive. I have a lot of reading to do, so I'll get back to you soon.

Later
~Tricia

Tricia

Here's one to start off with, good luck.


the way to think about it is this: it would not have evolved in a big single jump, but by step-by step improvements on what already works. But evolution does not propose things happening in huge jumps.

Yeah, I understand the step-by-step improvements bit. I don’t believe the evolutionary theory, but it would be insane to think that some things just pop out of nothing. Well wait, isn’t that what you believe about the creation of the universe? Sure sure, the Big Bang, but where did all the matter come from to gather in that one dot of incredibly bright light? How did it get there? Something can’t come from nothing. (Unless you are God. )

About the lizard and what allows it to grasp the ceiling or other lateral and upside surfaces, I am going to have to read a little bit more about that because the link you posted totally goes against what Martin said.


Well it’s got to get excess salt out somehow (suggest you look up ‘homeostasis’).

Know about homeostasis. I guess a vital part that I didn’t include in my post was that if the chuckwalla lizard doesn’t sneeze out that salt, he will explode. And if evolution is trial and error, how did he survive? Let’s say, for instance, that he does explode because he didn’t get the salt out. He’s dead, finito. How are the other chuckwallas going to know what to do? IOW, is the part that mutates the body apart of the brain? If so, wouldn’t the brain have to be extremely smart to be able to go to the dead body and figure out how he died, so that he wouldn’t make the same mistake? And how would the brain (or whatever tells the body to mutate) know what to change?


Don’t know. Why not look it up and tell us?

Why not? I’ll get back to you later about the spider. J

Dusting the eggs so they don’t stick is an advantage, something that can be selected for. Or rather, those spiders that didn’t do it are disadvantaged compared to those that do.

Yes, but how intelligent are the animals that are supposedly morphing into other kinds? If I moved from where I live now to Siberia, I wouldn’t know exactly what to do, which is what it sounds like you are telling me.

why would a creator create eggs that would stick together in the first place, and so have to create an additional anti-sticking mechanism?

I would give you an answer, but you’d probably laugh. Oh well. Why does every animal have to have a purpose? I believe God created all different animals, reptiles, amphibians, etc, just because He wanted to. For His enjoyment, and ours. Not very scientific, but I believe it.

None of them refute evolution; there being bits we don’t yet know is what keeps biologists employed!
Cheers, Oolon

Gotcha. I don’t know if you understood my reply above, heh heh, usually people don’t understand what goes on inside my head. But anyways, if you don’t, just ask and I’ll try to ask in a more coherent manner.

~Tricia

The Lone Ranger

Originally posted by Tricia:

All mammals have baroreceptors in the carotid arteries and aortic arch which continuously monitor blood pressure and "report" to the Cardiovascular Center of the brain. The linings of arteries (and to a lesser extent, of veins) are muscular, and in response to signals from the CV center of the brain, these muscles can contract or relax to regulate the flow of blood to the brain. If we didn't have such regulatory mechanisms, we'd pass out from lack of blood flow to the brain every time we stood up suddenly. There's nothing mysterious about how the system could have been strengthened in ancestral giraffes, to accomadate animals with ever-lengthening necks.



Now this looks suspiciously like outright dishonesty on Martin's part. I grew up on a farm, and I can assure you that I never noticed this phenomenon. Quite the opposite, in fact. Until they're ready to hatch, chickens' eggs must remain unbroken. Crack an egg with a developing chick in it even a little, and it quickly dehydrates, leaving you with a very dead chick. Chicks store their bodily wastes in the egg; they don't expel them. Ask any farmer if you doubt this.

Cheers,

Michael

KeithHarwood

Happens all the time. You have a piece of empty space. Suddenly, out of nowhere, with nothing causing it, an electron and a positron will appear. They will wander around for a little while and then come together and annihilate each other. Or perhaps they will annihilate some other electron or positron that has just popped out of nowhere. Or perhaps the positron will annihilate some electron that was being used for something important, like holding two atoms together or transmitting an electrical signal and the effect becomes noticable.

If this wasn't happening, the computer you are using wouldn't work. It's not only something that can be observed in the laboratory, it's something that multi-billion dollar industries rely on.

Mutation isn't something an animal does to itself, or even to its progeny. The animals themselves have no knowlege or control. It's just that within a large population all the animals are slightly different. Some can't get rid of the salt as easily as others. The ones that can't die earlier, the ones that can live longer. How do they know what to do? All they need to do is breed. They already know how to do that. After a while the ones that can't have died out completely and the only ones left are those that can.

You are a mutant. About half of your inheritance comes from your mother, half comes from your father, but a few, perhaps three or four, spots on your DNA are yours alone. You will pass them on to your children just as your parents passed theirs on to you.

You are unique. If what makes you unique helps you, just a tiny little bit, to have more children or to help what children you do have to have more children themselves, then your unique difference will be spread among the human race and help it evolve.

But it is not a personal choice. You didn't ask to be a mutant, you don't know what effect your mutations have, your parents didn't choose those mutations for you. The only choice you have is whether to have children or not. If you choose to have children your mutations will be passed to your children and you will have helped human beings evolve. If you choose to become a Roman Catholic priest (but could you pass the physical?) or otherwise decide not to have children, you will remove your entire genetic inheritance from the gene pool and will have helped human beings evolve.

The chuckwallas have exactly the same choices that you have, though I doubt many want to become Catholic priests. (Though there was that story about a bear that wanted to become a rabbi. It was called `Yentl Ben'.)

Not terribly intelligent at all. Bacteria mutate and evolve very fast and, while I don't actually have their scores on, say, the Cattell test, I doubt if they would do very well. The only intelligence that is needed is enough to survive long enough to leave progeny.

Why do you believe it? Do you have a good reason, or is it just because you want to? And if it is the latter, is that a sensible thing to do?

Quetzal

Hi Tricia,

There's a bit here that I thought needed clarifying. I don't know about the exploding bit, but you might be surprised to learn that there are literally hundreds of species that excrete salt! The definitive work on this subject is M. Peaker and J.L. Linzell 1975 "Salt Glands in Birds and Reptiles". Besides the chuckwalla, the book lists 15 species of reptiles, and a number of birds including the ostrich and geese that have the same (or a similar) homeostatic mechanism. In addition, there are dozens of plant species, from mangrove to salt grass, living in highly saline environments that excrete salt (mangroves do it from their leaves). Let's not forget sea turtles! Sea-going crocodiles have a salt secreting gland on their tongues!

Basically, this is a pretty common system.

As to the evolution of the ability, the one thing you need to remember is that the ability to excrete salt (or anything else) is not something that had to appear suddenly. Some ancestral chuckwalla didn't all of a sudden decide to move from a lush environment into one that had lots of salt in it. Some ancestor was able to move into an area - adapt - to the environment a little bit at a time.

On a final note, desert adaptations in animals like the chuckwalla are not necessarily a response to a high-salt environment, rather the adaptation is a method of retaining water, while maintaining homeostasis.

Evolution isn't really "trial and error" - that's a bit misleading. Evolution deals with selecting for traits that allow differential survival. In the case of the chuckwalla, my "guess" would be that water loss/retention was the key factor in their adaptation.

Hope this helps.

Oolon Colluphid

Sorry, but in which case I don’t think you do understand the step-by-step thing. One doesn’t believe evolution. It is supported by logic and evidence. So-called ‘microevolutionary’ step-by-step changes are an observed fact: I second the recommendation for you to get a copy of Weiner’s The Beak of the Finch (try <a href="http://www.abebooks.com" target="_blank">www.abebooks.com</a> for a cheap second-hand copy), which amongst other things covers Peter and Rosemary Grant’s work on Galapagos finches. Most creationists accept these smaller changes, and have to then explain why these changes cannot accumulate over time -- a lot of time -- to produce radically different organisms. I’ve yet to see one succeed. Take a look at the <a href="http://iidb.org/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=8&t=000008" target="_blank">‘debate’ between Douglas and Scigirl</a>, for instance.

Well wait, isn’t that what you believe about the creation of the universe and living things?

That’s not the way of it. Sorry Tricia, you’re slipping back into your old ways, disagreeing with something you don’t understand. Have a look at the encyclopedia entry here: <a href="http://www.bartleby.com/65/co/cosmolog.html" target="_blank">http://www.bartleby.com/65/co/cosmolog.html</a> But this has nothing to do with biological evolution.

Why am I not surprised? Why, by now, should you be surprised?

Oddly enough, if we didn’t pee, we’d explode too. Why aren’t we dead? Sneezing is a reflex. How is this supposed to be a problem?

They don’t need to know anything. The ones that sneeze -- and if you had salty mucus up your nose, you’d probably sneeze too -- are the ones that have, by accident, if you like, expelled the salt. Chances are that no special mechanism is required, just the straightforward sneezing reflex. Even if a more complex mechanism were involved, the salt-excreting evolved gradually, so there’s time for modification of the sneezing too along the way. Sneeze sometimes with a little salt (natural reflex for expelling any unpleasant matter from nostrils) --&gt; sneeze more often with more salt --&gt; wait till there’s lots of salty snot and have a good blow. Or whatever. This is no more difficult than genes for sharp canines being selected for along with genes for digesting meat. The only rule is: No big jumps. Not too much change at once, because the changes are random, and a big random change is much more likely to be a cock-up. If your computer is playing up, a gentle thump might jog it back to life by moving something inside a little bit; a big random change, say with a screwdriver, will very probably not help . The chances of a big change being an improvement get diminishingly smaller with the size of the change.

Ah come on, are you serious? Nothing needs to be known by anything. Copying errors in DNA (the genotype) can bring about changes in the body (the phenotype). These are random. Some will be harmful, some may be improvements, most will be neutral.

And whether it’s harmful, beneficial or neutral depends on the environment (including other genes) that the change occurs in. A gene for sharper teeth might be of no use in a cow, where they get worn down anyway. A gene that makes a slightly more efficient enzyme for protein digestion from meat might be great in a lion, but might upset other digestive enzymes in a herbivore. Natural selection is blind to neutral changes -- by definition -- but ‘harmful’ and ‘beneficial’ are what selection picks up on. Or rather, these things automatically and blindly affect their owners’ success or failure, and so whether the genes -- changes and all -- make it to the next round, the next generation.

They don’t have to know anything. It’s mechanical, no thought required. Those that do it, whatever ‘it’ is, are the ones that get to pass their genes on. Till we know more details about the spider in question, I can’t be more specific than that I’m afraid.

why would a creator create eggs that would stick together in the first place, and so have to create an additional anti-sticking mechanism?

No no, you misunderstand. It’s nothing to do with what purpose they might serve. It is a matter of taking the creation claim at face value. The creator started with a blank slate, and being supposedly a bit clever, could do whatever designs he liked. In this case, what he in fact saw fit to do was to give spiders sticky eggs and a method of stopping them sticking. Erm, if he’s so clever, why not make the eggs less sticky? If god is a designer, he’s not a very clever one.

Here’s a perspective on design: the manufacturing researcher and consultant Terry Hill, in his book Manufacturing Strategy, says that “any third-rate engineer can design complexity”; the hallmark of truly intelligent design is not complexity, but rather simplicity, or more specifically, it is the ability to take a complex process or product spec and create the least complicated design that will meet all project parameters. Having sticky eggs that need dusting to stop them sticking together is not a good design. There are countless other examples of this sort of unintelligent design, just ask!

Fine. He created them through evolution. Unless of course he deliberately forged all the evidence of evolution to mislead us.

You’re doing fine

Cheers, Oolon