Introduction of Amphibians
- Amphibians are the first group among the chordates that live outside water.
- Several new features for terrestrial life also developed in amphibians.
- Organs of locomotion and protection against desiccation are characteristics.
- They are not the true land vertebrates though they were the first to emerge from water.
- Most of the amphibians are well adapted to the particular environment in which they live.
- The terrestrial amphibians are the central stock from which divergence towards different modes of life is seen.
- They are as aquatic, burrowing, cave dwelling, volant and arboreal forms.
- The amphibians show both terrestrial and aquatic adaptations.
Adaptations for living in water
1) Body contour
- The body is compact boat shaped or streamlined, which offers least resistance during swimming and diving.
2) Hind limbs
- The hind limbs are long, muscular and powerful.
- The webs between the toes work like oar while swimming.
Image source: exploringnature
- Amphibians show cutaneous respiration in water.
- They show gill respiration in larval stage.
- External gills are present in their adult stage.
4) Position of nostril
- The nostril is present at the tip of the snout.
- This help to respire through the lungs, while floating in water as the animals keep its snout above the surface of water surface.
5) Eye-lids (nictitating membrane)
- The transparent nictitating membrane protects the eyes from the dirt in water.
- It also helps in preying.
6) Lateral line systems
- Lateral line receptors are found in amphibians.
- These help them to detect pressure changes in surrounding water.
Adaptations for living on land
- The terrestrial forms are the frogs and toads.
- The toads are more terrestrial than frogs.
Image source: brittanica
- They have two pairs of limbs for walking or swimming and leaping.
- The fore limbs are short and strong which support the front part of the body at the time of landing after a leap.
2) Eye lids
- Eyes are provided with eye lids which are movable in nature.
- It takes place by lungs and moist skin.
5) Protrusible tongue
- The long protrusible and sticky tongue helps in catching the prey.
- A number of anurans such as Hyla, Rana and its allies have taken to a tree living habit and thus exhibit many adaptations for arboreal life.
- The tree frog, Rachophorous shows volant (flying) adaptation. It uses its large webbed feet in making long sailing leaps among the trees. The webbed feet serve to increase the area of the supporting column of air. It also partly checks the speed before landing and further reduces the impact.