Amphibians are a diverse group of animals that can live both in water and on land, including frogs, toads, salamanders, and caecilians. They are cold-blooded, have permeable skin, and undergo metamorphosis from larval to adult stages, making them important indicators of environmental health. However, amphibian populations have significantly declined since the 1980s due to habitat destruction, pollution, and climate change, highlighting the need for conservation efforts.

1. Amphibians

2. Introduction
Amphibians. Does the word conjure up images of slimy
frogs and salamanders? Or perhaps a case of warts after
handling a toad? Amphibians are a fascinating group of
animals that we don't see very often. Find out more in this
lesson.

3. Amphibian Question
Can you imagine yourself down to the size of a tree frog, a
bull frog, a salamander, or even a caecilian? How would the
world look to you?

4. What does Amphibian Mean?
Amphibian means 'both kinds of life' in ancient Greek. It
basically means animals that can live in both in water and
on land. The smallest amphibian is the microhylid frog from
New Guinea that was first discovered in 2012. It grows to
about one third of an inch long, or 7.7 millimeters. The
largest is the Chinese giant salamander at 5 feet 11 inches
long, or 1.8 meters long. The African Goliath frog is the
largest frog at 13 inches, or 32 centimeters, and 6.6 pounds,
or 3 kilograms.

5. Types of Amphibians
The class 'amphibians' includes Anura, which means
'without tails' and includes frogs and toads; Caudata, which
means 'with tail' and is comprised of salamanders; and
Gymnophiona, which means 'naked serpent' and is
comprised of caecilians. There are about 7,000.

6. Traits
There are several characteristics all amphibians share:
● Have a back bone and are considered vertebrates
● Are cold-blooded, which means they are unable to regulate their
own body temperature
● Spend part of their lives in water and on land
● Do not have scales but have permeable skin, which means that
molecules and gases can pass through it
● Have gills for at least part, or all, of their lives
● Undergo metamorphosis, which means their bodies are transformed
from their larval stage to their mature, adult stage

7. Anura
Anura is the group of frogs and toads. Their hind limbs are
longer than their front ones. They have webbed toes but no
claws, no tails, big eyes, and moist skin. We generally think of
frogs as having smooth skin and toads having warts, but this
is not always true. Toads tend to have shorter hind legs than
frogs and drier skin, but not always. Most Anura live near
water and/or damp areas, but some have adapted to life in
trees, like the South American tree frogs, or in deserts. They
can be found worldwide, except in polar regions.

8. Caudata
Caudata is the group for salamanders. Although they
resemble lizards, they are not related. Salamanders are
elongated with short legs, have no claws, smooth skin
without scales, and tails that are usually flattened from
side to side and may have fins. They also can regrow their
tails. Most are under 6 inches, or 15 centimeters, in length.
They may live either on land or in water, and many spend
parts of each year in both habitats.

9. Gymnophiona
Gymnophiona is comprised of caecilians. These animals are long,
cylindrical, and limbless, similar to a snake or worm. Most are
between 3-30 inches, or 8-75 cm, in length. The Thompson's
caecilian can grow up to almost 5 feet, or 150 cm, in length. Their
skin has folds, and a few have tiny scales. Their eyes are covered
with skin, and their eyesight is poor. Most live underground in
damp soil, but some live in water. Most lay eggs underground,
and the larva make their way to nearby water once they hatch.
They are found in tropical Africa, Asia, and Central and South
America.

10. Roles
Amphibians play important roles, particularly in their reactions
to the state of their environment. They are considered to be
good indicators of environmental health because their skin
easily absorbs poisons from the air, water, and soil. They
require specific habitats, so they are not able to move away
from changes that disturb them. They are easily affected by
habitat destruction, over-exploitation (such as too many people
wanting to eat frog legs), pollution, climate change, and
destruction to the ozone layer, which causes damage to their
eyes, eggs, and skin.

11. Decline in Population
Since the 1980s, there have been major declines in
amphibian populations all over the world. Whatever affects
their population will impact the entire ecosystem. For
example, where frog legs are a popular menu item, the
decline in frogs has been linked to an increase in
mosquitoes. A decline in amphibians will also result in a
decline of their predators, such as snakes.

12. Ways to Prevent Decrease in Amphibians
If we know about the declines in the amphibian
populations, we can take steps to improve the health of the
environment by cleaning up pollutants in the water, air,
and soil. We can relocate them to more conducive
environments they cannot get to on their own. Amphibians
can give us clues as to what is happening in our world and
what we can do to properly share the earth with all species.

13. Lesson Summary
Amphibians are animals who live both on land and in the
water. They include frogs and toads in the Anura group,
salamanders from the Caudata group, and the caecilians
from the Gymnphiona group. They are cold-blooded, have
permeable skin, and they undergo metamorphosis between
the larval stage to the adult stage.

14. Lesson Summary (cont.)
Amphibians are excellent indicators of environmental
health because they react to poisons in the air, water, and
soil. They give us clues to what is happening in our
environment and what we need to do to make it safe for all
creatures.
Have you thought about how you would see the world as an
amphibian? The view might be rather blurry - no long
range views here!