Question

How could you explain the reasons that frogs and tadpoles have wet, slippery skin with many blood vessels?

Answer 1

The thin membranous skin is allows the respiratory gases to readily diffuse directly down their gradients between the blood vessels and the surroundings. When the frog is out of the water, mucus glands in the skin keep the frog moist, which helps absorb dissolved oxygen from the air.

Answer 2

For the exchange of gases.