Simple description about frogs.

1. Frogs - Morphology And Anatomy
Frogs are carnivorous tailless amphibians which are widely found in India. A diverse variety of frogs can be found
all over the world; among them, the Indian frogs are called Rana tigrina. They are vertebrates, coming under the
class Amphibia (phylum Chordata). Frogs are cold-blooded animals (poikilotherms) whose body temperature
varies according to their environment, hence, they need to protect themselves from extreme heat and cold for
maintaining optimum body temperature. Thus, they follow aestivation and hibernation during the summer and
winter seasons respectively. Another characteristic feature of frogs is that they camouflage i.e., they can change
their skin colour according to their surroundings.
Anatomy
The body plan of frogs consists of well-developed structures which help them in their physiological activities. The
body cavity accommodates all the organ systems such as digestive, respiratory, circulatory, excretory, nervous
and reproductive systems, whose functions are almost similar to human body systems.
Digestive system
The alimentary canal together with the accessory organs makes up the digestive system of the frog. Since frogs are
carnivorous they have short intestine. The alimentary canal begins at the mouth (buccal or oral cavity), passes
through the pharynx, oesophagus or food pipe, stomach, small intestines, large intestines, rectum and finally ending
at the cloaca. The food particles get digested gradually as they travel through various compartments of the
alimentary canal.

2. Respiratory system
The amphibian has two modes of respiration – cutaneous respiration and pulmonary respiration. In an aquatic
ecosystem, the skin is the respiratory organs where the diffusion of dissolved oxygen takes place. This is called
cutaneous respiration. While on land, they use both skin and lungs for respiration. During pulmonary respiration,
air entering through nostrils passes to the lungs via the buccal cavity. But during summer and winter sleep, they use
only skin for respiration.
Circulatory system
Frogs have a well-developed muscular heart with three chambers- two atria and one ventricle. Blood and lymph
help in the transportation of food, air and other substances throughout the body via the network of blood vessels.
The blood is composed of plasma and blood cells (RBC, WBC, and platelets).
Excretory system
The frog is a ureotelic animal whose major excretory product is urea. They have a distinguishable excretory system
composed of a pair of kidneys, ureters, cloaca and urinary bladder. The kidneys have the structural unit called
nephron which filters the blood and excretes out the waste.
Coordination system
The nervous system and the endocrine system together perform the control and coordination in frogs. The
endocrine system is composed of the endocrine glands such as pituitary, thyroid, parathyroid, thymus, pineal body,

3. pancreatic islets, adrenals, and gonads. The secretions of these glands called hormones are responsible for
metamorphism and other regulatory functions.
The nervous system is divided into CNS and PNS. The brain is distinguished as forebrain, midbrain, and hindbrain
which control different parts of the body. The brain is enclosed in the cranium and the vertebral column protects
the spinal cord.
Reproductive system
Both male and female frogs have their own reproductive system where gametes for reproduction are produced.
Male frog has testes which produce sperms and eject it through the cloaca. In a female frog, a pair of ovaries
produce ovum and pass it to oviduct which opens into the cloaca. The cloaca is a common pathway for excretion
and reproduction. At a time, 2500 to 3000 eggs are laid which are fertilized externally.