Frogs belong to phylum Chordata of the Amphibia Class. The distinguishing characteristic of amphibians is the ability to live two lives; both in water and on land. In the water, frogs lay eggs which hatch into tadpoles. When fully grown, the frogs live on land. Some species have adaptations that make them live on trees or in the desert. The life of a frog is centered in moist places though some species have special adaptations to live in dry habitats. Other distinguishing characteristics of amphibians are permeable skin, laying of unshelled eggs, and a ritualized courtship and mating behavior. Most adult amphibians are carnivorous. A frog can survive in any climate except Antarctica. All amphibians are cold-blooded. Their bodies adapt to the temperature of the surrounding. When too hot they will go inside water or shades to cool off their bodies and if too cold, frogs will lay in the sun or warm surfaces for warmth.
Morphology and Physiology of Frogs
A frog has long hind legs, an elongated ankle bone, and webbed clawless feet. The eyes are large and project outwards at the top on either side of the head. The eyes have a binocular vision that can see across the front at a field of 100 degrees, though the total round visual field can be up to 360 degrees in some species. The eyes have three eyelid membranes. The first membrane is transparent to offer protection under water. The other two membranes can be either opaque or transparent.
Adult frogs do not have a tail while the vertebral column is short. There are huge as well as small frogs. The smallest frogs are found in Papua New Guinea and measure only 0.03 inches while the goliath frog of Cameroon can grow up to 12 inches long. The hearing is made possible by a tympanum on both sides of the head. Frogs have a dental formula of pedicellate teeth on the upper jaw only. Feeding is by swallowing food whole. The hearing ability is very efficient and can detect both high and low-frequency sounds.
The Skin of a Frog
Skins of frogs are highly permeable hence susceptible to dehydration. A frog cannot, therefore, survive in the sea or any salty water. The skin of a frog is unique and has several functions in the life of a frog. The functions are respiratory, protection, and controlling body temperatures. The skin can absorb water. Frogs have a skin that hangs loosely on their body. Protective and camouflage function is performed by the skin which can exude distasteful and sometimes toxic substance in case of perceived attack. The secretion keeps frogs moist, retains slipperiness of the skin, and keeps off molds and bacteria. The color of the skin assists in thermoregulation meaning that in a cool damp environment the color is darker than on a dry hot environment. A frog sheds its skin regularly.
Frogs and the Environment
Frogs are excellent biological indicators of the health status of a certain ecosystem. Their presence or absence will point out at issues such as pollution levels and the presence of other animals due to their position in the food chain. Amphibians are the first animals to be affected by environmental degradation. The characteristics of the skin make the frog highly susceptible to harmful substances thereby endangering the lives of frogs. Preservation of their habitats is important to prevent the extinction of frogs.
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