Frogs all share one characteristic that differentiates them from other amphibians – the lack of a tail in their adult stage. Toads are actually a type of frog, all belonging to the same family, Bufonidae. All toads lack teeth and ribs, have thick skin, and short hind legs. Treefrogs comprise another family of frogs, the Hylidae. Treefrogs are small and they have adhesive disks on their webbed toes and horizontal pupils. Most of the frogs you commonly encounter in local ponds are “true frogs” of the family Ranidae. These frogs have large jumping hind legs with webbed toes. Most of these frogs can be found on the edges of ponds, lakes, and marshes.

The frog’s head is attached to its body without the use of a neck, with the eyes and nostrils on the top of the head. This enables the frog to see and breathe while floating on the surface of the water. All frogs have lungs, but they are also able to breathe through their skin. Their eyes are large and inclined slightly forward, creating a blind spot just in front of the snout. This is why frogs need to tilt their head slightly to feed on prey directly in front of them. Behind the eye is a large and noticeable eardrum. Frogs are the most primitive animals to have developed an ear.

The skin of frogs, as well as other amphibians, plays a vital role in water balance, respiration, and protection. The skin is kept moistened by a number of mucus glands, but many amphibians are restricted to moist habitats. Their skin is highly permeable to water, especially in terrestrial species. Many terrestrial frogs have a patch of skin located in the pelvic region that allows uptake of water from even a thin film while other tree frogs wipe fatty skin secretions over their bodies to reduce the loss of water through their skin.

REPRODUCTION AND LARVAL STAGE
Frogs generally fertilize eggs externally, as the eggs are laid. Fertilized eggs may be laid separately, in clusters, or in long strands. Frog clutch sizes can range from a single egg to many thousands of eggs. Each egg is enclosed in a gelatinous envelope known as albumen jelly. The tadpole generally hatches only five days after fertilization.. Tadpoles can be easily differentiated from adult frogs. Tadpoles lack front and hind legs, have a strong muscular tail for swimming, and have gills for “breathing” under water. Tadpoles spend most of their time propelling themselves through the water with their large tails and eating whatever they can find, primarily plankton. After eight to ten weeks after hatching, the tadpole begins its metamorphosis into a frog. The gills cover over, the front and hind legs begin to form, and many more external and internal changes occur that change a tadpole into a frog.