Organ Systems
Group of organs that work together to perform an important function. Examples: Digestive, Respiratory, Cardiovascular
Cell Membrane
A cell structure that controls which substances can enter or leave the cell. This surrounds the outside of an animal cell and is found under the cell wall in plants.
Single Celled Organisms
Also called unicellular. This organism is made of one cell and can perform all life's functions.
Multicellular Organisms
An organism made of more than one cell. Different cells inside this organism work together to survive.