Posts Tagged ‘evolution’
Mass Extinction Timeline
Posted by: Avi in Explore and Play on March 1st, 2009
Check out this interactive timeline by the Discovery Channel online of some of the major extinctions that have occurred from the beginning of life on earth. It explains what is known about some of the major extinctions and shows what percentage of all species died off.
2009 – The Year of Darwin
Posted by: Avi in Explore and Play on January 31st, 2009
Charles Darwin was born on February 4th of 1809. That would make him 200 years old this year if here were still alive!
But that isn’t the only Darwin related anniversary we get to celebrate in 2009. He also published his “On the Origin of Species” in 1859, making 2009 also the 150 year anniversary of that important book on the theory of evolution.
New Fossil Sheds Light on the Evolution of the Turtle Shell
Posted by: Avi in New Discoveries on December 15th, 2008
In the Guizhou Province of southwestern China, Chun Li of the Chinese Academy of Sciences, has found a new fossil that may help explain the evolution of the turtle. The oldest known turtle species is from 210 million years ago and features a full top shell , called a carapice, and a bottom shell, called a plastron. The new fossil, named Odontochelys semistestacea, lived 10 million years earlier and has only a full bottom shell. The top shell is incomplete, with only bony extensions from the back bone and ribs.
Scientist used to think that a turtle shell evolved from scales that formed plates, which then fused into a shell. This new fossil evidence tells a different story of a shell forming from changes to the animals skeleton.
Why a Speeding Shark is Like a Golf Ball
Posted by: Avi in New Discoveries on November 10th, 2008
Shortfin mako sharks can swim at an amazing, 50 miles per hour. That is fast!!! But how do they do it? Scientists think they have discovered the answer.
The sharks have special scales across their skin that they raise up when they need to swim at a fast speed. This creates tiny wells on their body and actually helps them to move faster by reducing drag. It seems strange that by raising these minute scales that they could reduce drag (wouldn’t it create drag and make them slow down like millions of tiny parachutes?). But their scales work along the same principles as a golf ball does with it many dimples.
The idea is that the dimples on the golf ball and the scales on a shark create tiny whirlpools within the cavities. These whirlpools create a “buffer layer” between the surface of the shark and the fast moving water around it. Basically it is like moving a heavy box over marbles rather than dragging it across the floor.
The whirlpools also prevent a turbulent wake from forming behind the shark. A wake behind an object (for sharks as well as boats) has the effect of slowing it down and making harder to turn.
Scientists hope to use this discovery to design faster and more manuverable underwater vehicles and aircraft.
