Background and Origin:
Evolving from four-legged fish called Ichthyostega that lived over 370 million years ago, modern frogs have appeared in their current shape and form for the past 200 million years. Contemporaries of the dinosaurs, they have hopped across earth and time with great success. And though mass extinction brought the dinosaur's reign to an end, frogs somehow survived. Many scientists believe that its unique jumping ability allowed the frog to spread around the world and persist through so many periods of history. They also retain an inherent adaptability which aids their continuous prosperity. As amphibians, frogs lead a double-life: one that takes place both under water and on land. This quality has also helped them to thrive for ages, since they have more arenas in which to find food.
Important Physical Characteristics:
When thinking of frogs, most people immediately envision them jumping. Their powerful, hind legs give them incredible leaping ability, as they often fly up to twenty times their body weight. A frog's two front legs have four toes each, while the back legs have five toes each. Hence, they are able to move easily in water and on land. Aside from its legs that allow it to jump and crawl, a frog's skin is a highly developed and essential characteristic to its survival. Since they never swallow water and spend much of their time submerged, frogs both drink and breathe through their skin. And though they do have lungs for breathing on land, they also absorb oxygen via their skin while underwater. Moisture is imperative for this process to occur. If a frog's skin dries out, oxygen can't pass easily through it and they will suffocate. Therefore, most species prefer to live near ponds, lakes or marshes. They also secrete a mucus that helps their skin stay properly moist. Frogs' large eyes see a wide range of colors and also see well in dim light. It's nearly impossible to sneak up on a frog, because their bulging eyes help it to see in all different directions without moving its head. The positioning of the eyes -- on top of head -- allows a frog to sit in the water with only its eyes and nose above the surface.
Hunting for Food:
Frogs will eat nearly anything they can manage to swallow. Their list of potential prey includes small fish, insects, spiders, and sometimes tiny mammals such as mice -- though the frog must be particularly large (like an ornate horned frog of Argentina) to handle that mouthful. Usually, however, insects are the meal of choice. Some frogs even have especially springy tongues, capable of being deployed in a split-second to snag unsuspecting victims. Precise photography has revealed that during this process a frog will in fact close its eyes. Thus, they must take great care to aim well before attempting to use their tongues. Their large eyes and keen sight help them distinguish prey, which improves their tongue accuracy. Not all frogs have this ability though, and tongueless members of the species catch prey with their front legs and then stuff it into their mouths.
Over the last several decades, amphibians around the world have been disappearing -- including frogs. There may be several factors working to diminish the world's frog population. Among these are climate changes, including global warming and thinning of the ozone layer. Destruction of habitat is certainly a problem; when rain forests get chopped down and marshes get filled in, frogs are left with nowhere to go. Pollution is also probably connected to the decline. Since frogs absorb water directly through their skin, they're especially vulnerable to water pollutants like pesticides and acid rain. Metals and soil irregularities may also be contributing to frog deformation. Recently, many frogs throughout the U.S. have been found with either superfluous legs or missing legs. Researchers have been studying potential causes of this phenomenon. However, no direct correlation of any kind has been decided upon. Most likely, the deformities stem from a series of environmental factors. Overall though, it has become apparent that the harm humans have done to the environment may be effecting frogs. Yet, another reason why we should act now to improve our natural surroundings.