Freethought & Rationalism Archive

ishalon · 06-19-2002, 04:27 PM

<a href="http://www.secularhumanism.org/library/fi/dawkins_21_4.html" target="_blank">Article.</a>

How many creationists are like that? Firm unchanging-in-the-face-of-anything beliefs that have no ground at all?

tgamble · 06-19-2002, 04:30 PM

Quote:

Originally posted by ishalon:
<a href="http://www.secularhumanism.org/library/fi/dawkins_21_4.html" target="_blank">Article.</a>

How many creationists are like that? Firm unchanging-in-the-face-of-anything beliefs that have no ground at all?

All of em.

KeithHarwood · 06-19-2002, 05:02 PM

Quote:

Originally posted by tgamble:


All of em.

I don't agree. It seems to me (looking from a distance of 10,000 miles) that most of the ground troops are simply ignorant and, when challenged by evidence simply put their fingers in their ears and sing `la la la'. They want to stay ignorant. And for the leaders, it looks as if they are in it for the money, their personal beliefs have nothing to do with it. I'm told that Duane Gish seems very sincere, but hey, if you can fake that you've got it made.

lpetrich · 06-19-2002, 06:56 PM

I was searching for some discussion of the evolution of the frog's tadpole phase when I came across <a href="http://www.users.bigpond.com/rdoolan/amphrep.html" target="_blank">this creationist page</a>, which flatly denied that amphibians can evolve into reptiles.

However, some of the supposedly impossible steps can be seed in living amphibians, notably frogs sensu lato. These may be divided into frogs sensu stricto, which are not very well adapted to dryness, and toads, which are better-adapted. What helps toads is their thicker skin, which makes them more reptile-like.

Also, while most frogs go through a tadpole phase, some species of frogs are direct-developing, hatching from their eggs in their adult form. This has happened several times; some species with this feature are closely related to species that still feature indirect, through-tadpole development. Direct-developing frogs lay larger eggs than is average for frogs, which allows longer development and makes it more difficult for water to escape. And inside the egg, direct-developing frog embryos have some tadpole features. All these features are essentially reptile-like; reptile, bird, and mammal embryos still have tadpole-like features like gill pouches and associated circulation.

What I had been looking for was some discussion of the question of whether early amphibians had also had an aquatic tadpole-like phase, and whether frogs' tadpole phase is a vestige of that. But I couldn't find anything, even though I suspect that both are correct.

scigirl · 06-19-2002, 10:18 PM

<a href="http://www.westernwildlife.com.au/frogs/evo.htm" target="_blank">http://www.westernwildlife.com.au/frogs/evo.htm</a>

Quote:

Amphibia are thought to have evolved from bony fish of the Class Osteichthyes which was widespread during the period that Amphibia emerged.[...]But amphibians made their first appearance at the end of the Devonian period about 345 million years ago. Primitive amphibians were creatures called Labyrinthodonts (many specimens have been dug up in Sydney) and were long bodied, short limbed animals resembling crocodiles with fins on their tail. They were up to 4 m in length. The earliest known frog-like fossil is Triadobatrachus, from Madagascar. The skull is frog-like being broad with large eye sockets, but the fossil has a number of other features differing to modern amphibia. These include a different ilium, a longer body with more vertebrae, the lack of a urostyle and vertebrae in its tail. It is now viewed as pre-anuran, and the transitional stock from which modern frogs evolved.

Reptiles probably split off from these more-like-reptile-frogs, I'm guessing, and did not evolve from what we now know as frogs.

Quote:

Modern frogs first appear in the fossil record in the Jurassic period of North and South America and Europe, about 280 million years ago. Many of them are assigned to the same families as living genera of frogs. It thus seems likely that the evolution of modern anura was completed by the Jurassic period. The main evolutionary changes involved shortening of the body and loss of the tail.

Here's another site:
<a href="http://sln.fi.edu/inquirer/frog.html" target="_blank">http://sln.fi.edu/inquirer/frog.html</a>

Quote:

Species that survived into the Jurassic included ancestral turtles, crocodiles, and tiny rodent-like mammals. Also carrying over were the frog's predecessors. Shubin and Jenkins compared their frog with these earlier fossils to figure out how frogs evolved.

Shubin says he believes the frog descended from a salamander-like amphibian with a long tail. Fossils of such creatures are found dating back about 260 million years.

But by 225 million years ago, the creatures started to look more leggy, as shown by a fossil that dates from that period, found in Madagascar. Around that time, the pelvis was becoming elongated and lined up with the spine, and the tail was receding inside the pelvis.

Eventually, the tail vertebrae fused and became a structure called the urostyle, which Shubin says is crucial in transferring forces from the legs to the body during a jump.

And while other animals have a pelvis that is fused to the spine, frogs developed a movable joint that allows the pelvis to slide up and down the backbone, a configuration that helps catapult frogs into the air.[...]Some of the frogs today have evolved more advanced jumping mechanisms while others are considered "primitive" - meaning they are little changed from their ancestors. The more primitive frogs have little control over their jumping, says McGill's Carroll.

Ribbet!

froggie

scigirl · 06-19-2002, 10:24 PM

About the specific tadpole question:

<a href="http://www.science.duq.edu/biology/faculty/elinson.html" target="_blank">http://www.science.duq.edu/biology/faculty/elinson.html</a>

This lab is trying to answer that very question:

Quote:

Dr. Richard P. Elinson,
Professor, Dept. of Zoology, University of Toronto
We are investigating the development of a very interesting frog, the Puerto Rican tree frog, Eleutherodactylus coqui. This frog develops differently from other frogs. It has a large egg that develops on land directly to a frog, without ever being a tadpole. We are investigating how this frog got rid of its tadpole, and whether this frog is following the similar evolutionary path that once gave rise to the reptiles, birds, and mammals.

froggie whoops I mean scigirl

Oh, here's a pic from the jurassic frog site in my previous post:

Quetzal · 06-20-2002, 01:15 AM

Great photo scigirl! Two of my favorite frog species in there! Red-eyed tree frog (Agalychnis callidryas) upper right and poison arrow frog (Dendrobates spp.) lower right.

We used the red-eyed tree frog as a keystone species in one of our contracts: the elimination of riparian vegetation (by cattle) destroyed their nesting spots and caused the local population to go extinct over the space of only a couple years. We were able to show how the cattle knocked/trampled down the overhanging vegetation (where the female attaches her eggs) in their quest for water. We correlated this with the multiple-times increase in cattle in the area: which gave us additional impetus to have the area declared a wildlife preserve.

Poison arrow frogs are cool not only for their toxicity but also 'cause they're so tiny. They make this little teeny "peep" sound when disturbed.

Anyway, sorry for the digression.

[Edited to add: I just realized the Dendrobates photo is faked! They're solitary - you'd never see 'em in a bunch like that!]

[ June 20, 2002: Message edited by: Morpho ]

Oolon Colluphid · 06-20-2002, 03:39 AM

Quote:

Originally posted by Morpho:
[Edited to add: I just realized the Dendrobates photo is faked! They're solitary - you'd never see 'em in a bunch like that!]

I've seen twos and threes in close proximity -- not cuddling up, admittedly -- at Marwell Zoo ( <a href="http://www.marwell.org.uk" target="_blank">www.marwell.org.uk</a> ). They've got a huge glass tank in the tropical house, with yellow, blue and green Dendrobates spp., and they're cute as hell.

What about at mating time? Could the pic be males jostling for a female? Just guessing, it's probably faked

.

Oolon

Quetzal · 06-20-2002, 04:47 AM

Oolon:

1. Dendrobates are exceptionally territorial - males have been known to fight to the death. Females search out males to mate.

2. They don't sit on top of leaves - they're mostly hidden underneath - that's why they're usually really hard to spot, in spite of their coloration. (Picture Morpho & co running around looking under leaf litter and on the sides/underneath of small plants looking for something going "peep" every 10-15 secs). That is, except to lay their eggs - and that's almost always a bromiliad or other plant with a water source nearby, 'cause that's where the tadpoles develop.

3. A glass tank isn't the wild.

4. I did the same damn thing for a photo used on our website.

[ June 20, 2002: Message edited by: Morpho ]

Oolon Colluphid · 06-20-2002, 04:58 AM

Morpho:

Quote:

3. A glass tank isn't the wild.

It's a really big tank <pouts peevishly>

Quote:

4. I did the same damn thing for a photo used on our website.

Worth a look? URL?

Oolon

06-19-2002, 04:27 PM	#1
ishalon Regular Member Join Date: May 2002 Location: From: Posts: 203	Creationist hollow beliefs vs truth... <a href="http://www.secularhumanism.org/library/fi/dawkins_21_4.html" target="_blank">Article.</a> How many creationists are like that? Firm unchanging-in-the-face-of-anything beliefs that have no ground at all?

06-20-2002, 01:15 AM	#7
Quetzal Senior Member Join Date: Nov 2001 Location: Ecuador Posts: 738	Great photo scigirl! Two of my favorite frog species in there! Red-eyed tree frog (Agalychnis callidryas) upper right and poison arrow frog (Dendrobates spp.) lower right. We used the red-eyed tree frog as a keystone species in one of our contracts: the elimination of riparian vegetation (by cattle) destroyed their nesting spots and caused the local population to go extinct over the space of only a couple years. We were able to show how the cattle knocked/trampled down the overhanging vegetation (where the female attaches her eggs) in their quest for water. We correlated this with the multiple-times increase in cattle in the area: which gave us additional impetus to have the area declared a wildlife preserve. Poison arrow frogs are cool not only for their toxicity but also 'cause they're so tiny. They make this little teeny "peep" sound when disturbed. Anyway, sorry for the digression. [Edited to add: I just realized the Dendrobates photo is faked! They're solitary - you'd never see 'em in a bunch like that!] [ June 20, 2002: Message edited by: Morpho ]</p>

06-20-2002, 04:47 AM	#9
Quetzal Senior Member Join Date: Nov 2001 Location: Ecuador Posts: 738	Oolon: 1. Dendrobates are exceptionally territorial - males have been known to fight to the death. Females search out males to mate. 2. They don't sit on top of leaves - they're mostly hidden underneath - that's why they're usually really hard to spot, in spite of their coloration. (Picture Morpho & co running around looking under leaf litter and on the sides/underneath of small plants looking for something going "peep" every 10-15 secs). That is, except to lay their eggs - and that's almost always a bromiliad or other plant with a water source nearby, 'cause that's where the tadpoles develop. 3. A glass tank isn't the wild. 4. I did the same damn thing for a photo used on our website. [ June 20, 2002: Message edited by: Morpho ]</p>

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06-19-2002, 06:56 PM	#4
lpetrich Contributor Join Date: Jul 2000 Location: Lebanon, OR, USA Posts: 16,829	I was searching for some discussion of the evolution of the frog's tadpole phase when I came across <a href="http://www.users.bigpond.com/rdoolan/amphrep.html" target="_blank">this creationist page</a>, which flatly denied that amphibians can evolve into reptiles. However, some of the supposedly impossible steps can be seed in living amphibians, notably frogs sensu lato. These may be divided into frogs sensu stricto, which are not very well adapted to dryness, and toads, which are better-adapted. What helps toads is their thicker skin, which makes them more reptile-like. Also, while most frogs go through a tadpole phase, some species of frogs are direct-developing, hatching from their eggs in their adult form. This has happened several times; some species with this feature are closely related to species that still feature indirect, through-tadpole development. Direct-developing frogs lay larger eggs than is average for frogs, which allows longer development and makes it more difficult for water to escape. And inside the egg, direct-developing frog embryos have some tadpole features. All these features are essentially reptile-like; reptile, bird, and mammal embryos still have tadpole-like features like gill pouches and associated circulation. What I had been looking for was some discussion of the question of whether early amphibians had also had an aquatic tadpole-like phase, and whether frogs' tadpole phase is a vestige of that. But I couldn't find anything, even though I suspect that both are correct.

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