Multicellular organisms

Cells in multicellular organisms undergo a process called differentiation. Figure 1:6 shows how the zygote cell leads to the development of all of the cells in the organism. A zygote is an egg cell fertilised by a sperm in humans and many other animals. We all started off as this single cell containing all of the genes we inherited from our mother and father. The process of differentiation is where some of these genes express their instructions and others are not expressed. This switching on and off of these genes allows the building of cells into different forms. This means the different cells can carry out different and specialised functions.

This means multicellular living things are a kind of highly co-ordinated team of specialist cells. This means they have what biologists call emergent properties. These can be best thought of as the sum of the abilities of these different cells is greater than the abilities of any single cells. Just like a team with different strengths can work together to achieve more than the individuals.

A good example is to think about how the human brain cells and nervous system cells work together with muscle cells to be able to perform very difficult tasks. Examples are music, dance, sports, skillful and enduring physical labour .