| Frogs | Toads |
| Salamanders and Newts | Caecilians and Legless Amphibians |
Amphibians comprise a large and diverse class of animals. Usually placed in
the same sentence as reptiles, they are really quite different. The term
"amphibia" means aquatic and terrestrial, as amphibians are as just at
home on land as in the water. Amphibians, although thought to be soft and
squishy, do have a mostly-bone skeleton (the rest being made of cartilage).
The skin is almost always moist and is water permeable. It lacks scales, and
can be smooth (frogs) or bumpy (toads). Amphibians come in a wide
variety of shapes, sizes and colours, and some of the most poisonous
vertebrates are amphibians (arrow-point frogs). Unlike reptiles, amphibians
have many different options on how to breathe. Most species have lungs, so
they can breathe through their mouths. They also have gills, either internal
or external, for breathing underwater. Finally, the water-permeable skin
allows oxygen to diffuse through it, so they can "breathe" through their
skin and the lining of their mouths. Most amphibians are oviparous
(egg-laying) and will lay several hundred small, round eggs covered in a
gelatinous mass. Almost always the eggs are laid in water, either a pond or
puddle or pool of water in a leaf. Some species carry the eggs in their belly,
and hatch inside of the mother. Most species have four limbs with webbed
feet, although one order lacks limbs entirely. They all have three-chambered
hearts (mammals have four-chambered hearts). There are separate sexes,
but some species can change gender depending on the circumstances. There
are approximately 3000 species in 3 orders:
Gymnophiona (caecilians, legless amphibians) 160 sp
Caudata (previously Urodela — salamanders, newts) 300 sp
Anura (frogs, toads) 2500 sp
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