Evolved in the Devonian period and dominated in the Carboniferous period (age of amphibians).
VVI Examples of Amphibia for Entrance Exams of Nepal:
- Ichthyophis
- Ambystoma (Tiger salamander)
- Rana tigrina (Frog)
- Bufo (Toad)
· Amphibious mode of life, Poikilothermal (cold-blooded).
· Skin: Moist, glandular, slippery with no scales.
· Respiration through the skin, buccal cavity, and lungs.
· 3-chambered heart and symmetrical aortic arches.
· Double circulation. Ventricles pump mixed blood.
· Nucleated biconvex RBCs.
· Dicondylic skull.
· Teeth homodont.
· Presence of 10 pairs of cranial nerves
· Middle ear has single bone Columella Auris and a stapedial plate.
· Digits pentadactyle.
· Egg: Mesolecithal
· Kidneys: Pronephric in the larva & Mesonephric in adults.
· Ureotelic mode of excretion (Salamanders are ammonotelic).
· Sexual dimorphism, oviparous, presence of tailed tadpole larva during development.
· Anamniota e.g. Ichthyophis, Ambystoma (Tiger salamander), Rana (Frog), Bufo (Toad)
Remember, Tree Frog is Hyla whereas Flying Frog is Rhacophorus.
a) Apoda: Limbless amphibians
· No limb.
· Also called caecilians or blindworms.
Example: Ichthyophis
b) Anura
· Commonly called frogs and toads.
· Tailless amphibians
c) Urodela
· Have tail and limbs.
· Presence of neotany and paedogenesis.
· Commonly called newts and salamanders.
Amphibians are divided into 3 orders.
a) Apoda: Limbless amphibians
· No limb.
· Also called caecilians or blindworms.
Example: Ichthyophis
b) Anura
· Commonly called frogs and toads.
· Tailless amphibians
c) Urodela
· Have tail and limbs.
· Presence of neotany and paedogenesis.
· Commonly called newts and salamanders.
DIFFERENCES BETWEEN FROG AND TOAD
| S.N | Frog | Toad |
|---|---|---|
| 1. | The frog lives mostly in water or nearby water. | Toad lives in moist damp places or in grasses, under a stone, or in dark shady places. |
| 2. | It is diurnal. | It is nocturnal. |
| 3. | Its skin is moist and slippery with numerous mucous glands. It has respiratory function also. | Its skin is rough or warty, dry, and has many poisonous glands than mucus gland |
| 4. | Its snout is pointed, has teeth in the upper jaw. | The snout is blunt and has no teeth in both jaws |
| 5. | The presence of a vocal cord in a male frog produces a croaking sound. | No vocal cord in both male and female so cannot produce sound. |
| 6. | Presence of webbed feet in hind limbs. | Absence of webbed feet. |
| 7. | Absence of parotid gland. | Presence of parotid gland. |
| 8. | The tongue is bifid. | The tongue is entire. |
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