La Rana

The Frog

History…
The first clear frog fossil dates from early Jurassic period, 280 million years ago, by late Jurassic there many different species of frogs toads, in Europe, N.America and S.America. In early Jurasic they wern't seperate continents but one large landmass. It's likely that with the seperation of the continents the anurans were divided and so caused the diversity of thespecies.

Biology

Frogs and Toads have a fairly simple structure. Broad bodies, no identifiable neck, no tail and four legs. They have a wide mouth and tiny nostrils on their snout. Prominent eyes for almost 360' vision. And moist smooth or rough skin.

The links above explore the many different and unusual features of frog biology. From their movement, vision, breathing, skin, hearing,temperature control, and smell to their strange reproduction processes.

Movement
Frogs generally jump or hop to get about. 'Rocket Frogs' are so called because how fast and far they can jump. The Black-Spotyed tree Frog (Hyla nigromaculata) is only 1.2 inches ling, but can jump a staggering 5 feet! But other frogs know as Walking Frogs, get aroung only by walking slowly. And Narrow-mouthed Toads(Breviceps sp.) creap and crawl to their destinations.

Frogs and Toads have only five to ten vertebrae and almost no neck. Their front and back are fused together and also two bones in their ankles. This helps them leap as it reduces the stress on the bones. To compensate for their little neck movement most frogs have developed large eyes, giving them almost 360' vision.
Hands and FeetFrogs and toads have four fingers (front limb digits) and five toes (hind limb digits). Some aquatic species have webbing between digits to aid swimming. And the Flying Frog (Rhacophorus) can actualy glide from tree to tree with its modified webbing.

Two species have opposable thumbs. And African Clawed Frogs and the Burrowing toads both have thickened covering orkeratinized finger tips resembling Nails (or claws).

Vision….

Most frogs have large protruding eyes, giving them almost 360' vision. This is needed as they don't have very flexible necks. They can see in colour and can have good vision for movement, even if far away.
Many frogs are nocturnal so have good night vision. They have a mirror layer in the back of the eye (called tapetum lucidium) thatlets them reflect light at night,known as 'eye-shine'. This gives them a kind or search light for hunting by.
Deferent species have different sensitivity to light depending on their habits and habitats. This can be determined by the numbers of 'rods' and 'cones' on the frogs retina (back of the eye). Rods are sensitive to light and cones detect colour. Frogs have different colour vision tohumans. They find it hard to see red light, they respond best to yellow light.
Tadpoles have eyes at the sides of their heads, but they move forward during metamorphosis. When a frog is underwater their eyes have to change because of the different refractive properties. Frogs focus by moving the lens rather then it changing shape, like in mammals.
Vision is the main sense used while hunting. Frogshave good depth and movement perception. Also because of their wide vision range they can look about without moving, so don't scare off prey. But they find it hard to see still prey.

Frogs also have a semi-transparent membrane called the nictitating membrane that protects the eye when underwater.

Breathing

Breathing is a gas exchange, taking in oxygen from the surroundings and lettingout carbon dioxide.
All frogs start life as aquatic tadpoles, breathing underwater through internal gills and their skin. Then later most develop into land animals with lungs for breathing air. But in all stages breathing is controlled by pulsing the throat. Most frogs loose their gills when they metaorphise.

Frogs breath with their mouths closed. Their throat movements pulls air through the...