Question

Give a brief account of class Amphibia.

Answer 1

The class Amphibia consists of Amphibians. The Amphibia means “double life”, that is life in water and land. They have both gills as well as lung breathers.Amphibia refers to life in water and on land. It includes frogs, toads, salamanders, and caecilians.

Complete Answer:
- Skin is thin, soft, and lacks scales except in the caecilians.
- Consists of a three-chambered heart.
- Two atria and one ventricle are present.
- They are Ectothermic.
- They can breathe from both gills and lungs- gills in the larval stage (10 days to 20+ years) and lungs in the adult stage.
- The fertilization can be internal or external.
- They are unable to regulate their body temperature.
- They are generally found in lakes, streams, ponds.
- Not found in dry areas.
- Oviparous.
- Epidermal layers are highly glandular
- Mucus secretions for reduction of water loss.

Three subclasses of amphibians are:
Subclass Labyrinthodontia
Subclass Lepospondyli
Subclass Lissamphibia

All living specimens are present in subclass Lissamphibia and the three primary orders of Amphibia are:

1. Caudata- Salamanders:
   - Bearing a tail.
   - 90% of all salamanders do internal fertilization and utilize spermatophores.

2. Anura- Frogs and toads:
   - Four limbs usually of unequal size.
   - They are more widespread and vocalizations are restricted to the male.
   - Most external fertilization occurs.

3. Apoda- Caecilians:
   - They are worm-like and eyes can be covered with skin or sometimes bone.
   - They are restricted to tropic and subtropic.

Note: The Amphibians have a three-chambered heart that consists of two atria and one ventricle because they have lower metabolisms. They need less oxygen. So a heart with three chambers is ideal for their needs.