Simple Organisms

Simple Organisms

All living cells have a barrier that separates them from the environment. This barrier is the cell membrane. The material inside a cell is said to be intracellular. (intra = inside, intracellular = inside the cell) The fluid inside the cell is therefore called the intracellular fluid. Anything outside a cell is said to be extracellular. (extra = outside, extracellular = outside the cell) Take for example a simple organism like the amoeba that is often found in pond water. It is a unicellular (uni = one, unicellular = one celled, single celled) organism because it is made up of only one cell.
activity	Make sure that you understand the terms "intracellular" and "extracellular "by selecting the correct labels in the diagrams below.

The intracellular compartment of the amoeba, which contains all the living material, is separated by the cell membrane from the pond water which is its external environment. This single cell performs all the functions necessary for maintaining the life of the amoeba.
activity	Now take the example of a multicellular organism such as hydra, and see whether you can identify intracellular and extracellular compartments in this creature.