The Evolution of Reptiles

The Evolution of Reptiles — page 7 — that preyed on it There are many gaps in what scientists know about ancient reptiles so every piece of information brings them closer to understanding how reptiles evolved EVOLUTION When scientists speak of evolution they are talking about the physical changes that take place in species over time These changes don't mean a group of animals is getting better but they don't mean that the group is getting worse either They simply mean that a plant or animal JEAN BAPTISTE species is changing LAMARCK In 1809 Jean Baptiste Lamarck published his The first scientist who published an theory that individual animals could acquire explanation of evolution was the French a trait and pass it down to their offspring He naturalist Jean Baptiste Lamarck in 1809 but it pointed out that giraffes reach up to feed on tree leaves Lamarck believed that all of wasn't until 1859 that an accurate description the stretching actually made their necks of the process was released English naturalist and limbs longer When these giraffes had offspring they passed down these long necks Charles Darwin wrote a book called on the and long legs It didn't take long for other Origin of Species by Means of Natural Selection scientists to disprove this theory It was clear that a person who has strong arms from hard work does not automatically have a child with strong arms

The Evolution of Reptiles — page 8 — In this book Darwin put forward the idea that nature and survival were the forces through which evolutionary change occurred Darwin observed that a species could have a number of diverse traits Because of these traits some animals would have an improved chance of survival They might be better runners or might be better able to blend with the landscape than others Because they survived longer they would have more offspring Many of these offspring would inherit the beneficial traits survive longer reproduce more and pass the traits on again to their own offspring Generation by generation the positive traits would be present in more individuals and the less beneficial traits would slowly disappear as animals with those traits failed to reproduce in large numbers As certain traits became more common and others less common the species evolved But Darwin did not understand how evolution occurred A key piece to this puzzle emerged in 1866 when scientist Gregor Mendel published some important rules of heredity Mendel noted that a tall pea plant bred with a short pea plant produced tall offspring When he bred two of these offspring three fourths of the resulting plants would be tall and one fourth would be short Mendel realized that each plant inherited traits from both parents with certain traits known as dominant traits expressed most often In pea plants tallness is dominant over shortness Scientists today know that change also occurs

The Evolution of Reptiles — page 9 — through mutations Mutations can take place when cells divide Changes in the DNA cause the production of different proteins Some mutations end up being advantageous The animals with these mutations survive and reproduce and the species evolves If a new trait spreads through an entire species the species as a whole evolves But sometimes a population of animals or plants is divided This can happen when water levels rise and create islands Animals on one island are isolated from those on a different island The two groups evolve separately As the changes accumulate the two groups grow to be so different they become separate species This is how more than 10,000 species of reptiles living today evolved from the earliest known reptile Hylonomus lyelli Hylonomus lyelli lived in what is now Canada approximately 350 MYA It looked like a lizard and was eight inches 20 cm long It sheltered in the stumps of fallen trees where it ate insects and snails Slowly over millions of years as the environment changed and new sources of food became available H. Iyelli and its descendants evolved into the crocodiles snakes turtles and lizards that populate Earth today

The Evolution of Reptiles — page 10 — A fossil of H. Lyelli shows the animal's upper jaw and teeth REPTILES DEFINED There are four orders of reptiles The order Crocodilia includes the crocodiles alligators caimans and gharials Testudines includes the tortoises turtles sea turtles terrapins and freshwater soft shelled turtles Lizards and snakes make up the order Squamata The lizard like tuatara is the only living member of the order Rhynchocephalia As different as these reptiles are they share common traits One of the first things many people notice about reptiles is their skin It is dry but may look shiny because it is covered in scales bony plates or a combination of the two Scales and plates make a reptile's skin waterproof

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