Hobbies And Interests
Evolution
All life on earth originated in the ocean. Amphibians represent the evolutionary stage between fish and reptiles. They are considered the most primitive land vertebrates, and for the first part of their lives, they live and breathe under water.
Reptiles evolved from ancient amphibians into the first vertebrates based entirely on land. While some reptiles spend a great deal of time in the water, no reptile can breathe under water.
Amphibians: Metamorphosis
Amphibians lay eggs in water or moist places. The eggs lack shells or moisture-retaining membranes. Most amphibians, including frogs, toads and newts, hatch as tadpoles, or limbless, water-dwelling larva with gills. Over time, the tadpoles go through metamorphosis, developing legs and lungs and moving to live on land. However, a few rare types of salamanders undergo the larval stage in the egg and emerge as young adults with legs and lungs. Still other types of salamanders gain lungs but also retain their gills as adults.
Reptiles: Born on Land
Most reptiles, including turtles, tortoises and alligators, as well as many lizards and snakes, lay eggs on land. Unlike amphibian eggs, reptile eggs have protective shells and membranes to retain moisture. A few reptiles, including various lizards, snakes and chameleons, give birth to live young on land. While some reptiles, such as alligators and water turtles, live much of their lives in the water, they must surface to breathe. Reptiles do not have gills except as embryos in the egg, and they develop lungs before hatching.
Body Temperature and Moisture
Both reptiles and amphibians are cold-blooded animals, meaning that their body temperature varies according to the environment. Both types of animals move around their environment to regulate their temperature. However, amphibians also require moisture from their environment. Their skin, which lacks scales, absorbs oxygen and water but is prone to drying out. Amphibians dehydrate and die without a moist environment. By contrast, reptiles have scaly, horny or leathery skin that seals in moisture. They are found throughout the world in both wet and dry environments.