Reptiles 8th Grade Biology

Adaptations for Life on Land A reptile is an ectothermic vertebrate that has lungs and scaly skin. Lizards, turtles, snakes, and alligators are all reptiles. Unlike amphibians, reptiles can spend their whole life on dry land. Reptiles get their oxygen from air and breathe with lungs. Reptiles that live in water, such as sea turtles, evolved from reptiles that lived on land. They still breathe with lungs, and lay eggs on land. The skin, kidneys, and eggs of reptiles are adapted to conserve water.

Skin and Kidneys Unlike amphibians that have thin , moist skin, reptiles have dry tough skins covered with scales. This scaly skin helps keep fluids in their bodies. Kidneys, are organs that filter wastes from the blood. The waste are excreted in a watery fluid called urine. The kidneys of reptiles concentrate the urine so that reptiles lose very little water.

An egg with a shell Reptiles have internal fertilization and lay their eggs on land. A reptile’s egg has a shell and membranes that protect the developing embryo and help keep it from drying out. An egg with a shell and internal membranes to keep the embryo moist is called an amniotic egg.

Lizards and Snakes Most reptiles today are either lizards or snakes. Both lizards and snakes are reptiles that have skin covered with overlapping scales. As they grow, they shed their skin and scales. Most lizards and snakes live in warm areas. Lizards differ from snakes- have four legs, long tails, external ears, movable eyelids, and two lungs. Snakes have streamlined bodies, no external ears, no eyelids, and most have one lung.

Obtaining Food Most lizards are carnivores that capture their prey by jumping on it. Some lizards eat frogs and birds, smaller lizards eat insects.

Snakes Eating All snakes are carnivores. Most feed on small animals, such as mice, but some eat large prey. A snakes’ jaw can spread apart. In addition, the bones of the skull can move to let the snake swallow an animal larger in diameter than itself.

Snakes Eating Some snakes have curved front teeth for hooking slippery prey. Other snakes have venom glands attached to hollow teeth called fangs. They bite their prey venom flows down through the fangs and enters the prey. Example: rattle snakes, and copperheads.

Movement Lizards walk and run using their legs. Snakes move by contracting, or shortening, bands of muscles that are connected to their ribs and their backbones. Alternate contractions of muscles to the right and left sides produce a slithering side-to – side motion. Instead of slithering, sidewinder snakes lift up their bodies as they move.

Alligators and Crocodiles Both alligators and crocodiles are large, carnivorous reptiles that care for their young. Alligators have broad, rounded snouts, with only a few teeth visible when their mouth is shut. Crocodiles have pointed snouts, with most of their teeth showing when their mouth is shut.

Reproduction Unlike most other reptiles, crocodiles and alligators care for their eggs and new babies. After laying the eggs, the female stays near the nest. She comes out of the water and crawls over the nest to keep it moist. After the babies hatch, the female scoops them up in her huge mouth. She carries them from the nest to an area of the water where they will be safer. For at least a year, she will stay near her young until they can feed and protect themselves.