Life and Living:
Structure and function in humans

The structure of overall living things and their individual parts determines how each part functions and how the living thing works. For example, humans can walk on two legs and have developed arms with hands for grasping, but a dog has four legs all used for walking. Our upright stance has allowed humans to develop quite differently from our four legged cousins, giving us the dexterity and brain power not displayed in other land animals.

In complete contrast to humans, some living things are very simple consisting of only one cell, like some bacteria and algae, while others are multicellular and range from simple organisms like jelly fish to the very complex like humans.

Skeletons

Complex multicellular living things have specialised organs to carry out specific functions. For example, a human has a skeleton which gives body shape and helps movement, lungs to collect the oxygen and to remove carbon dioxide waste and a heart to pump blood around the body. The muscle that the heart is made from never tires. This is an important feature as the human's heart has to beat (contract) continually to keep it alive.

Links:
Characteristics of living things Needs of living things Human reproduction A: The female system
Human reproduction B: The male system and contraception

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