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Author Topic:   Evolution has been caught in the act: lizard moving from egg to live birth
Taz
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Posts: 5037
From: Zerus
Joined: 07-18-2006


Message 1 of 16 (594712)
12-04-2010 7:17 PM


http://news.nationalgeographic.com/...-skink-live-birth-eggs

quote:
Evolution has been caught in the act, according to scientists who are decoding how a species of Australian lizard is abandoning egg-laying in favor of live birth.

Along the warm coastal lowlands of New South Wales (map), the yellow-bellied three-toed skink lays eggs to reproduce. But individuals of the same species living in the state's higher, colder mountains are almost all giving birth to live young.

Only two other modern reptiles—another skink species and a European lizard—use both types of reproduction. (Related: "Virgin Birth Expected at Christmas—By Komodo Dragon.")

Evolutionary records shows that nearly a hundred reptile lineages have independently made the transition from egg-laying to live birth in the past, and today about 20 percent of all living snakes and lizards give birth to live young only.

(See "Oldest Live-Birth Fossil Found; Fish Had Umbilical Cord.")

But modern reptiles that have live young provide only a single snapshot on a long evolutionary time line, said study co-author James Stewart, a biologist at East Tennessee State University. The dual behavior of the yellow-bellied three-toed skink therefore offers scientists a rare opportunity.

"By studying differences among populations that are in different stages of this process, you can begin to put together what looks like the transition from one [birth style] to the other."
Eggs-to-Baby Switch Creates Nutrient Problem

One of the mysteries of how reptiles switch from eggs to live babies is how the young get their nourishment before birth.

In mammals a highly specialized placenta connects the fetus to the uterus wall, allowing the baby to take up oxygen and nutrients from the mother's blood and pass back waste. (See related pictures of "extreme" animals in the womb.)

In egg-laying species, the embryo gets nourishment from the yolk, but calcium absorbed from the porous shell is also an important nutrient source.

Some fish and reptiles, meanwhile, use a mix of both birthing styles. The mother forms eggs, but then retains them inside her body until the very last stages of embryonic development. (Related: "Dinosaur Eggs Discovered Inside Mother—A First.")

The shells of these eggs thin dramatically so that the embryos can breathe, until live babies are born covered with only thin membranes—all that remains of the shells.

This adaptation presents a potential nourishment problem: A thinner shell has less calcium, which could cause deficiencies for the young reptiles.

Stewart and colleagues, who have studied skinks for years, decided to look for clues to the nutrient problem in the structure and chemistry of the yellow-bellied three-toed skink's uterus.

"Now we can see that the uterus secretes calcium that becomes incorporated into the embryo—it's basically the early stages of the evolution of a placenta in reptiles," Stewart explained.
Evolutionary Transition Surprisingly Simple

Both birthing styles come with evolutionary tradeoffs: Eggs are more vulnerable to external threats, such as extreme weather and predators, but internal fetuses can be more taxing for the mother.

(Related: "Human Sperm Gene Traced to Dawn of Animal Evolution.")

For the skinks, moms in balmier climates may opt to conserve their own bodies' resources by depositing eggs on the ground for the final week or so of development. Moms in harsh mountain climates, by contrast, might find that it's more efficient to protect their young by keeping them longer inside their bodies.

In general, the results suggest the move from egg-laying to live birth in reptiles is fairly common—at least in historic terms—because it's relatively easy to make the switch, Stewart said.

"We tend to think of this as a very complex transition," he said, "but it's looking like it might be much simpler in some cases than we thought."



Replies to this message:
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Larni
Member
Posts: 3645
From: UK
Joined: 09-16-2005
Member Rating: 5.3


Message 2 of 16 (594724)
12-04-2010 7:59 PM
Reply to: Message 1 by Taz
12-04-2010 7:17 PM


As there is nothing about this in the bible I fail to see how it could possibly be true; thus this evidence is refuted.

Edited by Larni, : clarity

Edited by Adminnemooseus, : Hide and Off-topic banner.


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Panda
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Posts: 2688
From: UK
Joined: 10-04-2010


Message 3 of 16 (594725)
12-04-2010 8:19 PM
Reply to: Message 1 by Taz
12-04-2010 7:17 PM


It did not turn into a crocoduck.
Therefore macro-evolution has not occurred.
Therefore evolution has not occurred.
Therefore evolutionists are wrong.
Therefore god exists and created the world 6000 years ago.
QED.

Nothing to see here: please move along.

p.s.
Please don't mention irreducible complexity.

Edited by Panda, : No reason given.

Edited by Adminnemooseus, : Hide and off-topic banner.


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subbie
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Posts: 3315
Joined: 02-26-2006
Member Rating: 6.8


Message 4 of 16 (594727)
12-04-2010 8:38 PM
Reply to: Message 1 by Taz
12-04-2010 7:17 PM


Skinks are producing skinks. Nothing evolutionary there.

Other reptiles reproduce by live birth, so nothing evolutionary there.

All remains as it was 5,000 years ago when he reached out with his noodly appendage and created us all.

R'amen.

Edited by Adminnemooseus, : Hide and off-topic banner.


This message is a reply to:
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Panda
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Posts: 2688
From: UK
Joined: 10-04-2010


Message 5 of 16 (594728)
12-04-2010 8:47 PM
Reply to: Message 4 by subbie
12-04-2010 8:38 PM


subbie writes:

Other reptiles reproduce by live birth, so nothing evolutionary there.


Correct - it is not evolution; it is imitation.
Those skinks saw live birth on TV and decided to 'give it a go'.

When asked, the skinks said: "It looked a lot less bloody on TV and a lot less painful."

Edited by Adminnemooseus, : Hide and off-topic banner.


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Tanypteryx
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Posts: 406
From: Oregon, USA
Joined: 08-27-2006
Member Rating: 5.1


Message 6 of 16 (594729)
12-04-2010 9:07 PM


Lizsrds are still lizards, so Big Deal.

Now if mammals start laying eggs or birds start giving birth to live lizards, that would be something, but why are there still monkeys?

Edited by Adminnemooseus, : Hide and off-topic banner.


Tactimatically speaking, the molecubes are all mixed up. -- S.Valley

What if Eleanor Roosevelt had wings? -- Monty Python

You can't build a Time Machine without Weird Optics -- S. Valley


    
Blue Jay
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Posts: 2612
From: You couldn't pronounce it with your mouthparts
Joined: 02-04-2008


Message 7 of 16 (594734)
12-04-2010 10:00 PM
Reply to: Message 1 by Taz
12-04-2010 7:17 PM


I beat Moose to it!

Edited by Bluejay, : No reason given.


-Bluejay (a.k.a. Mantis, Thylacosmilus)

Darwin loves you.


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Adminnemooseus
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Posts: 3497
Joined: 09-26-2002


Message 8 of 16 (594735)
12-04-2010 10:08 PM
Reply to: Message 7 by Blue Jay
12-04-2010 10:00 PM


Pretty dismal effort at having relevant discussion
I beat Moose to it!

Damn, I was shooting for 6 straight hide with off-topic banners.

There's going to be some heavy slaps done if the above trend continues.

NO REPLIES TO THIS MESSAGE - JUST DO REAL ON-TOPIC MESSAGES.

Adminnemooseus


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bluegenes
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Posts: 2799
From: U.K.
Joined: 01-24-2007


Message 9 of 16 (594767)
12-05-2010 8:30 AM
Reply to: Message 1 by Taz
12-04-2010 7:17 PM


This is interesting, and I found it interesting 3 months ago when the article first came out, and a week later, when I bumped the thread.

Evolution in action: Transition from egg-laying to live birth in lizards. Message 1

What would be interesting to know is if future research can identify the mutations that make the difference between the slightly "egg retaining" mothers and their viviparous cousins. Also, it would be interesting to know if egg- eating predators have been identified in the "viviparous" area, as that would provide an obvious strong selection reason behind the transition.

Here's the abstract. They were mainly researching the nutrition problem.


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cavediver
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Posts: 4129
From: UK
Joined: 06-16-2005


Message 10 of 16 (594780)
12-05-2010 9:32 AM
Reply to: Message 9 by bluegenes
12-05-2010 8:30 AM


They were mainly researching the nutrition problem.

I read that as "the neutrino problem" and was suitably confused

Bloody physicists...


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Taz
Member
Posts: 5037
From: Zerus
Joined: 07-18-2006


Message 11 of 16 (594878)
12-05-2010 2:59 PM
Reply to: Message 9 by bluegenes
12-05-2010 8:30 AM


(1) You had ONE reply after you bumped it.
(2) My thread is way way way cooler.
(3) My thread has 900% more replies than yours.
(4) My thread even attracted the attention of adminmoose. This feat in itself should receive some kind of award.
This message is a reply to:
 Message 9 by bluegenes, posted 12-05-2010 8:30 AM bluegenes has responded

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bluegenes
Member
Posts: 2799
From: U.K.
Joined: 01-24-2007


Message 12 of 16 (594934)
12-05-2010 5:36 PM
Reply to: Message 11 by Taz
12-05-2010 2:59 PM


On topic skink
Taz writes:

My thread is way way way cooler.


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RAZD
Member
Posts: 15474
From: the other end of the sidewalk
Joined: 03-14-2004
Member Rating: 4.4


Message 13 of 16 (595151)
12-06-2010 11:06 PM
Reply to: Message 9 by bluegenes
12-05-2010 8:30 AM


Also, it would be interesting to know if egg- eating predators have been identified in the "viviparous" area, as that would provide an obvious strong selection reason behind the transition.

msg1 writes:

Along the warm coastal lowlands of New South Wales (map), the yellow-bellied three-toed skink lays eggs to reproduce. But individuals of the same species living in the state's higher, colder mountains are almost all giving birth to live young.

Or if the difference in the ecology\temperature\climate makes a difference.

Enjoy


we are limited in our ability to understand
by our ability to understand
Rebel American Zen Deist
... to learn ... to think ... to live ... to laugh ...
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xongsmith
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Posts: 1333
From: massachusetts US
Joined: 01-01-2009
Member Rating: 5.6


(1)
Message 14 of 16 (595162)
12-07-2010 12:42 AM
Reply to: Message 1 by Taz
12-04-2010 7:17 PM


Wow this thread is fun. Please PEEK the whole thing. Almost 6 hides in a row.
I, old man that I am, object most strenuously to the godless passing clouds above, with sweaty, heated brow and veins standing out on my neck, that they would have the unmitigated nerve to use the phrase "CAUGHT IN THE ACT"!!!! Evolution has, is, and will be always will be "CAUGHT IN THE ACT". Evolution isn't trying to hide. Never has. Evolution has, as always, been screaming at the top of it's lungs out in the middle of so many Harvard Square/Times Square/Paris/Piccadilly Circus and so ons.


- xongsmith, 5.7d
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nwr
Member
Posts: 5109
From: Geneva, Illinois
Joined: 08-08-2005
Member Rating: 4.5


Message 15 of 16 (595183)
12-07-2010 8:58 AM
Reply to: Message 14 by xongsmith
12-07-2010 12:42 AM


Hide and Peek
xongsmith writes:
Wow this thread is fun. Please PEEK the whole thing. Almost 6 hides in a row.

I'm calling this the "Hide and Peek" thread.


Jesus was a liberal hippie
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