The ability to move is one of the basic characteristics of living things. To make this point, let us consider a number of different sorts of movement. Most of us are intimately familiar with more or less large scale movements, such as walking or running or watching birds and insects fly. We are also aware of a good number of more subtle movements, such as our heart-beats and movements of our viscera, actions that occur within organisms.
Movements also occur at the cellular level.
Unicellular organisms are able to move themselves around, by amoeboid movement or the actions of flagella and cilia. Flagella and cilia are also found in certain cells, sperm for example, within metazoan animals. Movement takes place within cells, as well. Chromosomes are moved within cells by contractile elements of a spindle apparatus. All movements are driven by variations on two general systems of proteins.