f99u4le1 - COASTAL REPTILES Unit 4: Coastal Reptiles Lesson...

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© PROJECT OCEANOGRAPHY COASTAL REPTILES 130 C OASTAL R EPTILES Unit 4: Coastal Reptiles Lesson Objectives: This chapter introduces students to sea turtles. Students will become familiar with the several different kinds of sea turtles, their nesting habits and conservation. Students will learn what they can do to help protect the sea turtle. Lesson I : Sea Turtles Turtles are reptiles (cold-blood creatures) that have roamed the Earth for more than 185 million years. They were around during the times of their reptilian cousins, the dinosaurs. As the Earth's climate changed, so did turtles, finding ways to adapt and survive. Some turtles (called tortoises) live solely on land, while some turtles adapted to live in the water. We will focus on the sea turtles. Physiology The turtle's most distinctive feature is its hard shell that encompasses its body and protects its organs. All turtles, even the sea turtles, have these bony shells, although some may be soft- shelled. The top part of the shell is called the carapace and has distinctive markings and patterns, according to different turtle species. This pattern is determined by the arrangement of a layer of thin horn-like material made up of scales or plates called scutes . The carapace has a second layer of tightly joined bones underneath the scutes, forming the frame of the upper shell. The carapace attaches to the bottom shell, called a plastron . All reptiles, including turtles, are cold-blooded. Since they have no internal temperature regulation to keep their
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© PROJECT OCEANOGRAPHY COASTAL REPTILES 131 C OASTAL R EPTILES temperature constant, their body's temperature adjusts to the same temperature as whatever environment they are in. A sea turtle's shell is a little different from the land turtles. It is streamlined, with a flatter carapace, to help it move through the water. Also, the shell tends to be a little lighter and more flexible, containing fewer bones, which also aids in swimming. The sea turtle also adapted its limbs into paddle- shaped flippers, rather than the clawed legs that the land dwellers of the species have. Unlike the land species which can completely withdraw into their shells when threatened, the sea turtles can only withdraw slightly into their shell. They tend to swim away from danger rather than hide in their shells, as the land turtles do. Male sea turtles spend their entire lives in the sea, while the females leave the safety of the sea and come ashore only to lay their eggs. When they swim, sea turtles rely mainly on their front flippers, moving both of them forward at the same time. Although they also use their hind flippers to aid in swimming, they are also used as rudders to steer and as brakes. Sea turtles are graceful and fast swimmers, some clocked up to 20 miles per hour. When the females come onshore to lay eggs, however, they are clumsy and slow, pulling themselves along with their front flippers. Rather than walking, they drag themselves along the ground,
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f99u4le1 - COASTAL REPTILES Unit 4: Coastal Reptiles Lesson...

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