Green-eyed tree frog
Frogs are born with legs that are good for hopping and special pads on their toes to help them climb. In comparison, toads have shorter legs, drier skin, and are less likely to live near water. Most frogs and toads are responsible for controlling the Earth's insect population, since their diet consists mostly of insects and spiders. However, the green eyed-tree frog is also a carnivore. As a tadpole, the frogs mostly consume algae and plants. Frogs have a moist and permeable skin layer covered with mucous glands, which enables them to breathe through their skin, not just their lungs. The layer of mucus that covers them also acts as a shield, protecting them from scratches. The reason frogs have large and protruding eyes is to make up for their lack of a neck. This eye feature allows them to see everything around them. The color scheme of the green-eyed tree frog is to camouflage them from predators. Frogs with bright colors are alerting predators of their poisonous nature.
Frog
Frogs have served as experimental animals throughout the history of science. Eighteenth-century biologist Luigi Galvani discovered the link between electricity and the nervous system by studying frogs. In 1852, H. F. Stannius used a frog's heart in a procedure called a Stannius ligature to demonstrate the ventricle and atria beat independently of each other and at different rates. The African clawed frog or platanna ("Xenopus laevis") was first widely used in laboratories in pregnancy tests in the first half of the 20th century. A sample of urine from a pregnant woman injected into a female frog induces it to lay eggs, a discovery made by English zoologist Lancelot Hogben. This is because a hormone, human chorionic gonadotropin, is present in substantial quantities in the urine of women during pregnancy. In 1952, Robert Briggs and Thomas J. King cloned a frog by somatic cell nuclear transfer. This same technique was later used to create Dolly the sheep, and their experiment was the first time a successful nuclear transplantation had been accomplished in higher animals.