What is an organism?
An organism is a single celled or multicellular living system that is capable of reproduction , growth and development and shows a certain degree of response to stimuli and homeostasis.
Most unicellular organism are microscopic in size. Humans are multicellular organisms composed of several millions of cells , grouped into specialised tissues and organs.
All organism consist of monomer units called cells. Organisms may be prokaryotic ( lack nuclear membranes ) or eukaryotic (have membrane bound cell nucleus ) . All cells possess DNA ( hereditary material of genes ) and RNA ( informatory material for protein synthesis ) .