Class Amphibia

INTRODUCTION
I started from this topic because today I'm now reading this ^^
Amphibians are the FIRST successful land vertebrates or tetrapods.
During the Carboniferous (age of amphibians), there are abundant food and relatively little competition. However during the late Carboniferous, the amphibians began to decline in numbers and diversity. Most surviving lineages of amphibians during Mesozoic era (Dinosour time) resembles modern species.
Now there's an extincted animal called Labyrinthodonts which are believed to have gave rise to frogs and salamanders.

LARVAE
Amphibians are said to have "two lives", which is referring to the amphibians which undergo metamorphosis into an adult.
***Many amphibians do not live a dualistic life (aquatic and terrestrial).***
FROGS
The larvae for frogs (tadpoles) are herbivores.
The adult frogs are carnivorous predators.
SALAMANDERS AND CAECILIANS
Their larvae look like adults and are carnivorous.

HABITATS
Most amphibians are found in damp habitats. Even those which are adapted to drier habitats will tend to live in places with higher humidity (such as under moist leaves).
This is because most of them rely on their moist skin to carry out gas exchange.
***Some terrestrial species lack lungs and rely fully on their skin and oral cavity for breathing.***

EGGS
No shell, dehydrate quickly in dry air.
Hence eggs are laid in moist environments or in water.
Most species carry out external fertilization.
Some species display various types of parental care. eg: house eggs on back, in mouth etc.
Some are ovoviviparous or viviparous (retain the developing eggs in female reproductive tract until it hatches)

SOCIAL BEHAVIOR
Many male frogs will have mating calls to defend territories or attract females.
Some terrestrial species need to migrate to specific breeding sites. This may require vocal communication, celestial navigation or chemical signaling.

The amphibians are divided into a few orders:

1. Order Urodela (tailed ones) e.g. salamanders
2. Order Anura (without tail) e.g. frogs
3. Order Apoda (without legs) e.g. caecilians

ORDER URODELA
- 500 species
- Some are entirely aquatic, some live on land as adult, some live on land for entire life.
- Some groups of salamanders undergo paedomorphosis. There are retention of some larval features in a sexually mature adult.

ORDER ANURA
- 4200 species
- More specialized than urodela for moving on land
e.g. adult frogs hop along terrain using powerful legs
e.g. frogs use their sticky tongue to catch insects
- For self-protection, may be camouflaged, or secret a yucky or poisonous mucus from skin glands. Some are brightly coloured - warn predators that they are poisonous.

ORDER APODA
- about 150 species
- Legless and nearly blind (but their ancestors are legged)
- Looks like earthworm. Most species burrow in moist forest soil in the tropics.


Environmental degradation (acid rain) and the spread of chytrid fungus had caused the amphibian populations to decline in an alarming rate.

WE SHOULD TAKE GOOD CARE OF OUR ENVIRONMENT!!!!!