Frogs belong to Class Amphibia of Phylum Chordata.The most common frog species found in India is Euphlyctis hexadactylus (formerly known as Rana tigrina).
- Frogs can live both on land and in water. Some they mainly feed on insects. Some species also live on trees. Most of them are carnivorous.
- Frogs are poikilotherms or cold-blooded organisms. They do not have constant body temperature i.e. their body temperature varies with the temperature of the environment.
- Some species have the ability to change the colour to hide them from their enemies (camouflage). This protective coloration is called mimicry.
- During extreme climatic conditions, frogs take shelter in deep burrows to protect them from the heat and cold. This is known as summer sleep (aestivation) and winter sleep (hibernation) respectively.
- The skin is smooth and moist due to the presence of mucus.
- The frog never drinks water but absorb it through the skin.
- The body of a frog is divisible into head and trunk, while the tadpole larva has a tail also.
- The dorsal surface of the body is greenish yellow with dark irregular spots. The ventral surface is pale yellow in color.
- The head is triangular. The snout is pointed.
- Mouth is present at the anterior end.
- A pair of nostrils is present above the mouth. It leads to buccal-pharyngeal cavity.
- The eyes are found behind the nostrils.
- Each eye is protected by an immovable upper and lower eyelid.
- The lower eyelid is further extended to form a thin transparent protecting sheath called nictitating membrane. It is water-proof and protects the eyeballs while the animal is in water.
- Beneath each eye, there is a circular patch of skin which represents the ear. It is called tympanic membrane (tympanum) or eardrum.
- It receives sound signals.
- External ear (pinna) is absent.
- The trunk is broad and flat.
- There is small hump on the posterior dorsal side.
- The trunk bears a pair of short forelimbs and a pair of long hindlimbs.
- The posterior end of the trunk has an opening called cloaca, which is the common exterior opening of excretory and reproductive system.
- The forelimbs have 3 parts – upper arm (brachium), forearm (antebrachium) and hand (manus). Only 4 digits are present on the forelimb.
- The hind limb is divided into – thigh (femur), shank (crus) and foot (pes).
- Foot has 5 webbed digits that aids in swimming.
- The limbs help in swimming, walking, leaping and burrowing.