Amphibians

=**What are they?**=

1. Caudata (newts and salamanders) 2. Anura (frogs and toads) 3. Apoda (caecilians)
 * Amphibians are cold-blooded vertebrates. Vertebrates are animals with backbone or vertebral column and[[image:amphibian-types.gif width="152" height="190" align="right" caption="caecilian, salamander, toad"]]cold-blooded means that their internal temperature is dependent on their surroundings.
 * They belong to the phylum Amphibia and are about 4,000 species in total.
 * Those 4,000 species are further divided into three groups:

=**Caudata (newts and salamanders)**=
 * This group has about 360 species that generally have long bodies and tails, and four legs
 * Most of them live in the northern half of the world
 * These amphibians like to hide in cool, damp places during the day and come out at night
 * "Newt" refers to the species that are mainly aquatic
 * Many newts have long flaps of fin-like skin on their tails that help them swim faster. Most other amphibians lose those flaps of skin after their tadpole stage.
 * Newts, like most amphibians, has ways to protect themselves. For example, the Chinese spiny newt pushes its spiny ribs out of its skin so predators cannot eat it. Newts also sometimes have toxins on their skin and color is usually an indicator of poisons.
 * Salamanders can lay anywhere from 4 to more than 5,000 eggs depending on its species. If the eggs are laid in water, they go through a tadpole stage. Otherwise, they hatch as miniature fully-formed salamanders.
 * Some salamanders don't lay eggs at all. For instance, the fire salamander doesn't lay eggs, but gives birth to tiny salamanders.[[image:fire_salamander.jpg width="334" height="244" align="right" caption="fire salamander"]]

=**Anura (frogs and toads)**=
 * This is the largest group of amphibians and has 3,400 species.
 * These amphibians lose their tails when adults, and have long, strong back legs for leaping.
 * Their habitats range from deserts to cold mountain streams, but are most commonly found in tropical and subtropical swamps.
 * "Frog" refers to the slender, smooth-skinned types that leap.
 * "Toad" refers to the plump, rough-skinned types that waddle, but there really isn't any real difference between the two.
 * The frog's body is short and has a strong backbone that can withstand the constant jumping. There is no narrow neck.
 * Their eyes are on top of wide-mouthed heads, enabling them to see even when nearly submerged.
 * Some frogs and toads don't leave their eggs to hatch in the water.
 * For example, after fertilizing the eggs the female has laid, the male Surinam toad helps pack them into the skin pouch on the female's back.
 * They also have toxin secreting glands in their skin and bright colors is again an indicator of bad taste and poison.[[image:toad.jpg width="333" height="256" align="right" caption="toad"]]

=**Apoda (caecilians)**=
 * In this group there are 160 species.
 * These 160 species look like worms, have no legs, and are commonly found in tropical or warm forests.
 * Some are aquatic and have a fin that runs along their back that helps it swim.
 * Most are terrestrial and spend most of their time burrowing in the ground.
 * Are the only amphibians to undergo internal insemination.
 * There are three types: beaked caecilians, fish caecilians, and common caecilians. Pretty simple animals.

=﻿Where they live=
 * Amphibians are worldwide and can be found almost anywhere except in cold regions. That's because they are cold-blooded and don't do so good in the cold.
 * In the summer, when it gets too hot, they go into a state of inactivity called estivation.
 * In the winter, if its too cold, they become still and their body processes slow. In other words, they become torpid.
 * Because of this they generally are in warm, moist places.
 * They can absorb oxygen through their skin and usually lay their eggs in water so they need to live in moist places.



=**History**=
 * They evolved from fish 400 million years ago
 * They are the only modern descendants of an ancient group that gave rise to other land vertebrates
 * The present day groups of amphibians date back only 200 million years ago.
 * The early amphibians evolved and adapted to land. Some such adaptations were lungs, and breathing tubes.
 * They also developed stronger bones and limb girdles so movement became more efficient.
 * Amphibians also got sternums, breastbones, that protect and support internal organs.[[image:frog_anatomy_labeled.jpg width="507" height="471" caption="frog anatomy"]]