1) Amoeba has no special respiratory organs so, there is a free exchange of gases through the general body surface by diffusion as the body surface is permeable to the gases dissolved in water.
2)Hydra too has no respiratory organ a respire by diffusion.
3)Fishes respire the dissolved oxygen in the water bodies. They respire with the help of special organs called gills.
4)Earthworm absorbs oxygen through its moist skin by the process of diffusion and gives off carbon dioxide in the same process. The body of earthworm is covered by the epidermis which continuously secretes to retain the moisture throughout the skin.
5) Frogs and toads breathe (and take in moisture) through their skin through a process called cutaneous gas exchange, but they also have lungs with which they breathe. During the time they stay submerged under water or buried in soil (such as during hibernation) they ONLY breathe through their skin.
6)Snakes breath through the nostrils (tiny pores present on its fang) . They have only one main functional lung where gaseous exchange occurs.
7)The mechanism of respiration in birds is totally different from other vertebrates. The birds lungs apparently smaller and are connected to air sacs which help in respiration.
During respiration, when a bird inhale air passes through the trachea to the posterior air sacs. When exhale the air reaches lungs from the air sacs. In second inhalation the air moves from lungs to the anterior air sacs. Second exhalation throws the air outside from the air sacs through the trachea.
This is the way how birds respire.
8)Whales and dolphins breathe air through their lungs like other mammals and therefore they have to come to the surface of water regularly. The nostrils of whales and dolphins are located at the top of their heads and are called 'blowholes' . They come to the surface or jump into the air regularly to inhale and exhale air through these blowholes.
9)Plants respire through the tiny holes present in the leaves commonly known as Stomata..They take in Carbon Dioxide and in return give out Oxygen through stomata by simple diffusion..This is how respiration is taken place in plants...
10)Insects breathe through a system of tubes called tracheae. The tracheae of insects are attached to holes in their exoskeleton called spiracles which help to exchange the air with environment.
