There are three types of hearts that a found in most living things. a 2 chamber heart, a 3 chamber heart and a 4 chamber heart. These three hearts take are used in most living animals such as pigs,birds and fish. Some animals such as insects do not have or need a heart because they are so small, meaning they don't need a heart to pump blood around there body because there body's are so small. Also because they have a low need of energy.
Information from:
http://www.worldinvisible.com/apologet/humbody/heart.htm
http://library.thinkquest.org/C003758/Development/fish.htm
My work book.
google
http://www.worldinvisible.com/apologet/humbody/heart.htm
http://library.thinkquest.org/C003758/Development/fish.htm
My work book.