Category Zoology

   The main reason for the frog being chosen for the laboratory is that it has a similar orientation to the human body.

When students take a look into the anatomy of a frog, they can become more familiar with the inner workings of our own body. The frog also has an intricate internal structure that displays all the major bodily systems. Apart from this, the frog is available in plenty and is small enough to be handled easily. 

Frogs have very special skin- it not only protects them but they drink and breathe through it. Frogs don’t usually swallow water like we do. Instead they absorb most of the moisture they need through their skin. They also get extra oxygen from the water absorbed through their skin. So it is important for frogs to keep their skin moist or they might suffocate. Some times you’ll find frogs that are slimy. This is because the frog skin secretes mucus that helps keep it moist. Even with the slimy skin, these frogs need to stay near water.

Frogs shed their skin regularly to keep it healthy. Some frogs shed their skin weekly, others as often as every day. To do this, they start to twist and turn so as to stretch themselves out of their old skin. Finally, the frog pulls the skin off over its head, like a sweater, and eats it! 

 Frogs and toads are both amphibians, and they are very similar. There are some differences however. Frogs generally have bulging eyes, strong long webbed hind legs for leaping and jumping, and smooth or slimy skin. Frogs also usually lay their eggs in clusters. Toads, on the other hand, have stubby bodies with short hind legs, and warty and dry skin. Their eyes are less bulging and more football shaped, with poison glands behind them. Toads move in short hops and jumps, and they lay eggs in long chains. However, there is really no hard and fast rule. Toads belong to the frog family, but they are not true frogs. To make things more complicated, it is not uncommon, for example, to find a warty skinned frog that isn’t a toad, or even a slimy toad! 

The first true frogs evolved about 200 million years ago during the time of the dinosaurs. Frogs are amphibians – in fact, about 90% of amphibian are frogs. They spend their lives near water, because they must return to the water to lay their eggs. Frog eggs are laid in the water. When they hatch into tadpoles, they breathe with gills, and swim using a tail. As they mature, they lose their tail, develop lungs for breathing air, and live on land. Though adult frogs have no tail, they have well developed hind legs, and are experts at leaping and jumping. They are found on every continent except Antarctica. There are thousands of species of frogs and they come in all shapes, colours and sizes.

 Amphibians hear very well- they can even hear sounds which we can’t hear. If you look closely at a frog, you will see small circles covered with a membrane behind its eyes, on the side of its head. This membrane is the frog’s eardrum. Sound waves in the air make the membrane vibrate. The vibrations are transmitted to the inner ear, and from there to the brain, which recognizes it as a sound.

Not all amphibians hear in this way. Burrowing, limbless amphibians pick up vibrations through their lower jaw. Salamanders lack middle and external ears, but have inner ears that can process sound. In some species of salamanders, sound causes the animal’s chest to vibrate, and the vibrations are carried by air from the lungs to the animal’s inner ear.

 Since amphibians have been around a long time, and have adapted to a variety of environments, their eye structures vary slightly for different environments. The frog has large, bulging eyes, which sit at the top of its head. Its eyes bulge out so far that it can see in nearly all different directions, which is helpful for an animal that can’t turn its head. A transparent inner eyelid called the nictitating membrane protects the frog’s eyes when the animal is underwater. A frog can also shut its eyes completely. To do this, the frog pulls its eyeballs deep into their sockets. This closes the upper and lower eyelids together.

Most species of salamanders view their world with colour vision, but they see in the ultraviolet range, which is impossible for the human eye. Salamanders use this special vision adaptation to hunt prey. Some species of amphibians, such as the Texas blind salamander, live their entire lives underground in places like caves. These amphibians do not have eyes, since they live in complete darkness.