write the difference between single and double circulation?why is double circulation is necessary in human beings?

Single circulation
1. Occurrence: Found in only fishes.
2. Mode of circulation: Blood passes only once through the heart to supply once to the body.
3. Nature of blood: Only venous blood passes through the heart.
4. Efficiency: Less efficient as gill capillaries slow down the blood flow so the body receives blood at a low pressure which decreases the rate of oxygen supply to the cells.
Double circulation
1. Occurrence: Found in amphibians, reptiles, birds and mammals.
2. Mode of circulation: Blood passes twice through the heart to supply once to the body.
3. Nature of blood: Mixed or oxygenated or venous blood passes through heart.
4. Efficiency: More efficient as blood flows at higher pressure, especially in birds and mammals, which increases the rate of food and oxygen supply to the cell and also rapid removal of wastes from them.

You might be familiar with the circulation of blood. Now look at this image, this image is a schematic representation of blood circulation.

Here you can observe that the blood passes through the heart twice. Since the blood goes twice through the heart, it is known as double circulation. Warm-blooded animals like mammals have this type of blood circulation.

in double circulation blood is circulated simunaneously beween heart and lungs and heart and body parts

it is necessary to maintain body temprature

which is one time is single and two times double

THAT ONE I KNOW BUT ANY OTHER DIFFERENCE????

@akash jeeneea there's one more point

in single circulation the energy level is low. the body temp. is not maintained.(cold blooded)

in double circulation the energy level is high. the body temp. is well maintained.(warm blooded)