Organisms are understood to be all the living beings that make up the different spaces of planet Earth and that can vary enormously in shape, characteristics and essential elements, going from microorganisms to gigantic animals over a hundred meters long. All organisms suppose the presence of matter as well as a permanent interaction between the interior and the exterior or environment through diverse types of biological relationships.
Organisms are characterized by being unicellular or multicellular, the former being composed of only one cell and the latter consisting of several to millions of them. In this sense, we can mention several types of organisms according to their complexity: archaea (which do not have a cell membrane and are therefore simpler), bacteria, protozoa (usually unicellular), fungi, plants and , finally, animals (the most evolved of all living organisms).
Some of the most important capacities of any type of organism is, in the first place, organization (that which makes them consist of one or more cells), irritability (or immediate response to external stimuli), homeostasis (or maintenance of a more or less permanent internal order), development (or transformations generated from evolution), metabolism (which is the ability to feed and consume energy to develop), reproduction (basically for survival), and finally adaptation (which allows you to overcome different situations).
The organisms that take place on our planet Earth are what give it its characteristic of the only known space where life can develop. These organisms require permanent contact with the environment that surrounds them and they develop with and through it different forms, phenomena and changes that lead to their evolution or eventual disappearance (if they fail to adapt).