Amphibiansare the first organisms to leave the water and live on land during the course of evolution. They evolved from an ancestral fish species. However, they can only live on the land part-time. When they reproduce, they must return to the water to mate and their gelatinous eggs must be kept moist during their development. Adult amphibians have a thin, moist skin. They can use their skin to breathe air along with primitive lungs....
Amphibians are the first organisms to leave the water and live on land during the course of evolution. They evolved from an ancestral fish species. However, they can only live on the land part-time. When they reproduce, they must return to the water to mate and their gelatinous eggs must be kept moist during their development. Adult amphibians have a thin, moist skin. They can use their skin to breathe air along with primitive lungs. Young amphibians begin their life in water and breathe with gills. Examples of amphibians are frogs, salamanders and newts. These are ectothermic or cold-blooded organisms and must rely on outside sources to provide heat to their bodies, along with certain behaviors.
Reptiles are the first true terrestrial (land) organisms. They can live as well as reproduce on land. Their bodies are ectothermic, covered in scales and they have lungs for breathing air. A major development in reptiles is their amniotic egg. This is similar to the type of eggs found in birds, their descendants. Amniotic eggs have hard shells, a chorion for respiration, a yolk to provide nourishment to the developing embryo and an amniotic sac surrounding and protecting the embryo. Most reptiles do not provide parental care to their young. Their eggs develop on land. Examples of reptiles include snakes, turtles, alligators and crocodiles.
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