Cell differentiation

Animals and plants produced by sexual reproduction begin life as a single cell - a fertilised egg or zygote.

This cell must divide to produce a multicellular organism. It must also differentiate, so that its cells develop features that enable them to become more efficient at fulfilling specific functions.

Examples in animals include:

Cells of the...Specialised to...
Circulatory systemTransport substances, defend the body, regulate temperature.
Excretory systemRemove waste products and unwanted substances, regulate the water content of the body.
Muscular systemBring about movement.
Nervous systemRespond to internal and external stimuli and conditions, carry messages for the body to work as a coordinated whole.
Respiratory systemDeliver oxygen for respiration and remove waste.
Reproductive systemBring about fertilisation to produce new offspring.
Skeletal systemTo bring about movement, support and protect internal structures, produce blood cells, store and release calcium.

Some specialised cells of plants:

Cells of the...Specialised to...
LeafPalisade mesophyll cellsCarry out photosynthesis.
Spongy mesophyll cellsCells are arranged to let gases circulate, allowing the exchange of gases between the leaf and the environment. They also carry out some photosynthesis.
Guard cellsOpen and close to control the exchange of gases - carbon dioxide, water vapour and oxygen.
PhloemSieve tubesTransport products of photosynthesis, including sugars and amino acids, from the leaf to where they are needed.
Companion cellsProvide the ATP required for transporting substances into sieve tubes.
XylemXylem vesselsTransport water and dissolved minerals from the roots, up the plant.