“Dino-era Delivery At Sea”
By: Sid Perkins
Reptiles that lived in the sea during the dinosaur-era evolved successfully because their ancestors decided the gender of the offspring by genetics other than incubation temperature.
Now, there are about sixty species of sea snakes, which are the only reptiles to spend their entire lives underwater. They even give birth in the water. Reptiles such as turtles and crocodiles have to go to shore to lay eggs. But there is a huge difference between reptiles that are fully aquatic and the non-fully aquatic reptiles. With sea snakes the gender of their offspring is determined genetically, not by incubation temperature. Chris Organ an evolutionary biologist at Harvard University took apart the reptile family tree to include only these species: the porpoise-shaped ichthyosaurs, the long-necked plesiosaurs and the snake-shaped mosasaurs. Organ added bird species that lay eggs, and long ago evolved from reptiles to birds and a few mammals. He and researcher found that reptiles that give birth to live young also have sex chromosomes; they determine the gender of the offspring. When they expanded the family tree to fit in the ancient marine reptiles, all three groups ended up on the same part of the tree near the groups of species with genetically determined gender. Therefore the analyses states that the ancient marine reptiles had a better than ninety percent chance of having genetically determined gender.
When I read this article I was fascinated by the way Organ studied the aquatic reptiles and figured out how, once in their lifetime, they were related to the ancient marine reptiles. That would be the dinosaur era. This was interesting to me because I like hearing about how some animals could be living descents of Dinosaurs. This is related to Earth Science because it’s a study of earth’s history, and what lived on land millions and millions of years ago. It would...