Evolution in Action: Lizard Moving From Eggs to Live Birth | TigerDroppings.com

Posted byMessage
JOJO Hammer
Nicholls St. Fan
Getting a barbed wire tribal tat
Member since Nov 2010
6109 posts

Evolution in Action: Lizard Moving From Eggs to Live Birth


LINK

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."










Back to top
Share:
Ba Ba Boooey
LSU Fan
NOLA
Member since May 2010
2846 posts
 Online 

re: Evolution in Action: Lizard Moving From Eggs to Live Birth


TL;DR

But very interesting






Back to top
Carson123987
LSU Fan
Middle Court at the Rec
Member since Jul 2011
36045 posts

re: Evolution in Action: Lizard Moving From Eggs to Live Birth


cliffs? no way im reading that





Back to top
WikiTiger
LSU Fan
Member since Sep 2007
40721 posts

re: Evolution in Action: Lizard Moving From Eggs to Live Birth


here come the "it's adaptation, not evolution" arguments





Back to top
Dr. 3
LSU Fan
Member since Mar 2005
10972 posts

re: Evolution in Action: Lizard Moving From Eggs to Live Birth


Thats Gawd testin' ya





Back to top
TK421
LSU Fan
Baton Rouge
Member since Oct 2011
7394 posts

re: Evolution in Action: Lizard Moving From Eggs to Live Birth


quote:

here come the "it's adaptation, not evolution" arguments



And as usual, it was started by an atheist.






Back to top
Quentin Compson
LSU Fan
Member since Jun 2013
3117 posts

re: Evolution in Action: Lizard Moving From Eggs to Live Birth


in





Back to top
7thWardTiger
New Orleans Saints Fan
Richmond, Texas
Member since Nov 2009
21978 posts

re: Evolution in Action: Lizard Moving From Eggs to Live Birth


That pic def needs a "come at me bro"





Back to top
HNTIGER1980
LSU Fan
Member since Oct 2011
439 posts

re: Evolution in Action: Lizard Moving From Eggs to Live Birth


So the chicken did come first.






Back to top
Tigah in the ATL
LSU Fan
Atlanta
Member since Feb 2005
23821 posts
 Online 

re: Evolution in Action: Lizard Moving From Eggs to Live Birth


But every time I open peanut butter there is no life I there; therefore, evolution is false.





Back to top
TheIndulger
Longwood Fan
Laffy Taffy
Member since Sep 2011
8894 posts

re: Evolution in Action: Lizard Moving From Eggs to Live Birth


TK421's got ya on that one wiki





Back to top
goldenbadger08
LSU Fan
Da Boot
Member since Oct 2011
25394 posts

re: Evolution in Action: Lizard Moving From Eggs to Live Birth


That damn monkey saying I has banana now get's me every time


This post was edited on 6/16 at 6:28 pm


Back to top
mach316
LSU Fan
Jonesboro, AR
Member since Jul 2012
1786 posts

re: Evolution in Action: Lizard Moving From Eggs to Live Birth


Is there gonna be a test on this?





Back to top
Rickety Cricket
Navy Fan
Premium Member
Member since Aug 2007
33509 posts
 Online 

re: Evolution in Action: Lizard Moving From Eggs to Live Birth


Sounds like a trap set by Lucifer. I don't buy it.





Back to top
TK421
LSU Fan
Baton Rouge
Member since Oct 2011
7394 posts

re: Evolution in Action: Lizard Moving From Eggs to Live Birth


Another atheist bringing up religion.

Your lives would be utterly meaningless without religion.






Back to top
HNTIGER1980
LSU Fan
Member since Oct 2011
439 posts

re: Evolution in Action: Lizard Moving From Eggs to Live Birth


quote:


Your lives would be utterly meaningless without religion.


"Yes, without religion my life would be meaningless" -Said no Atheist ever.






Back to top
TK421
LSU Fan
Baton Rouge
Member since Oct 2011
7394 posts

re: Evolution in Action: Lizard Moving From Eggs to Live Birth


quote:

"Yes, without religion my life would be meaningless" -Said no Atheist ever.


Of course they don't say it. But their hatred for religion is a major driving force in their lives. In a way, these guys love religion more than Jimmy Swaggart.






Back to top
DrSteveBrule
LSU Fan
Baton Rouge
Member since Sep 2009
6160 posts

re: Evolution in Action: Lizard Moving From Eggs to Live Birth


quote:

Of course they don't say it. But their hatred for religion is a major driving force in their lives. In a way, these guys love religion more than Jimmy Swaggart.


Stop making general statements about a group. It makes you look stupid.






Back to top
blueboy
LSU Fan
between here and there
Member since Apr 2006
17565 posts

re: Evolution in Action: Lizard Moving From Eggs to Live Birth


it's not the faith they hate. it's the faithful.

anchors aweigh, btw.






Back to top
JOJO Hammer
Nicholls St. Fan
Getting a barbed wire tribal tat
Member since Nov 2010
6109 posts

re: Evolution in Action: Lizard Moving From Eggs to Live Birth


bump for day crew





Back to top


Back to top




//