How Is a Lizard Like a Motorcycle?

Dushwari · Jun 14th, 2008, 06:44 PM

can you believe it?

every reptile has some hidden skill.
share what you know about other insects and reptiles.

How Is a Lizard Like a Motorcycle?

By Elsa Youngsteadt
ScienceNOW Daily News
13 June 2008

When they're on the run, some lizards take to their hind legs, dashing about like miniature dinosaurs. But their bipedal gait is largely accidental, according to a new study. The findings refute earlier proposals that getting off all fours might help lizards go farther and faster.
No one knows why some lizards run bipedally. In the mid-1900s, zoologist Richard Snyder of the University of Washington, Seattle, proposed that lizards could run faster and more efficiently on two legs than on four, but he was unable to thoroughly test the theory. In 2003, biomechanist Peter Aerts of the University of Antwerp in Belgium suggested that bipedal running might not be adaptive but rather that it occurs as a side effect of a different adaptation: a rearward shift in the center of mass that makes a fast-moving object better able to execute sharp turns. His model indicated that a lizard would start to run on two legs when it reached a certain rate of acceleration--the same way a powerboat rears out of the water and a motorcycle pops a wheelie.

Comparative physiologist Christofer Clemente of the University of Cambridge in the U.K. and colleagues tested both possibilities in real lizards. The team snared 16 species of Australian dragon lizards from the family Agamidae, insect-eaters that range from hand-sized to nearly a meter long. They plunked each reptile down on a treadmill and measured the percentage of its strides that were two-legged and four-legged. For four species, the team also recorded the lizards' speeds and accelerations.

Two equals four? Ornate rock dragons (Ctenophorus ornatus) run no farther or faster on two legs than on four. Here, the animals try it both ways on a treadmill.

Credit: Christofer Clemente
After correcting for the lizards' overall size, the researchers found that bipedality did not improve endurance--in fact, the more bipedal the lizards were, the shorter their sprints. Nor did the lizards run faster on two legs than on four. The acceleration that brought the four species up on their hind legs did, however, generally jibe with the predictions from Aerts's model. Indeed, for some lizards, bipedality looked accidental, Clemente says. Even after an animal's front legs lifted off the ground, they would continue to move as if they were on the ground.
Although Aerts's model was correct in its general predictions about which lizards would go bipedal first, the numbers were a little off. Three of the four species got off the ground before they reached the predicted acceleration, apparently by using their tails and forearms to shift the center of gravity farther back, the team reports today in the Journal of Experimental Biology. Clemente thinks these lizards might have co-opted accidental bipedality for some advantage. But if not to improve speed or endurance, why do it? Perhaps two legs are less likely than four to get tangled up in vegetation, Clemente hypothesizes.

Physiologist Thomas Roberts of Brown University describes the new results as a cautionary tale. "There's been a dangerous history," he says, of looking at an animal and "making up a story" about how its various features must be beneficial. "This nice, comprehensive study," he says, quashes just such a made-up story. In fact, Aerts says, the work is among the first to do so experimentally--and he's excited to hear that his model was on the right track.

http://sciencenow.sciencemag.org/cgi...008/613/1?etoc

K337 · Jun 20th, 2008, 10:20 AM

its like saying that monkeys are like human being

Dushwari · Jun 21st, 2008, 06:27 PM

really penguin? :>

samraali22 · Jul 16th, 2008, 03:25 PM

the most amazing thing i ve seen is ants keeping caterpillers as domestic animals truely breathtaking read it
Mitton: Ants defend caterpillars in exchange for food : Science Columnists : Boulder Daily Camera
Myrmecophilous (ant-loving) caterpillars of the family Lycaenidae (e.g., blues, coppers, or hairstreaks) are herded by the ants, led to feeding areas in the daytime, and brought inside the ants' nest at night. The caterpillars have a gland which secretes honeydew when the ants massage them. Some caterpillars produce vibrations and sounds that are perceived by the ants.[93] Other caterpillars have evolved from ant-loving to ant-eating: these myrmecophagous caterpillars secrete a pheromone that makes the ants act as if the caterpillar is one of their own larvae. The caterpillar is then taken into the ants' nest where it feeds on the ant larvae.[94]

moazzam.mbs · Jul 16th, 2008, 03:29 PM

i have read some where that ants never sleep

samraali22 · Jul 16th, 2008, 03:44 PM

lolz i spend all my life reading about reptiles well i know about another all female species lizard taht called uni sex whiptail lizard.

The three Whiptail Lizards on view in the Hall of Reptiles and Amphibians all play a part in one of the greatest mysteries of nature.The New Mexico Whiptail, pictured here, is an all-female species that is actually a mixture of the other two examples on display at the Museum -- the Western Whiptail, which lives in the desert, and the Little Striped Whiptail, a denizen of grasslands.
Most products of crossbreeding, such as the mule, are sterile. But the New Mexico Whiptail, as well as several other all-female species of whiptail lizard, does reproduce, and all of its offspring are female. Moreover, it reproduces by parthenogenesis -- its eggs require no fertilization, and its offspring are exact and complete genetic duplicates of the mother.
Scientists understand only partially how this reproductive mode developed, and it raises many questions. One of the most intriguing is how this cloning affects the lizard's ability to adapt to environmental changes. Since there is no genetic variation except that which occurs through mutation, the New Mexico Whiptail cannot evolve as other species do.
The New Mexico Whiptail Lizard also offers an extraordinary opportunity to learn more about the role of sperm in fertilization, as well as about cloning. Through this anomaly, scientists may learn more about the norm.