Deutsch: Lebewesen / Español: Ser vivo / Português: Organismo / Français: Organisme / Italiano: Organismo vivente
An organism is any form of life and may be defined as a contiguous living system consisting of one or more cells, that is capable of reproduction, growth and development, self-regulation (or homeostasis) and responding to stimuli.
Although more than 99% of all species of organisms that ever lived on the planet are estimated to be extinct, there are currently approximately 10-14 million species of life on Earth.
Organisms may be classified as either prokaryote or eukaryote. Prokaryotes are single-celled organisms that lack a membrane-bound nucleus, mitochondria, or any other membrane-bound organelles. Eukaryotes are organisms whose cells contain a nucleus and other organelles enclosed within membranes.
Organisms are also classified into taxa or clades. This science is called Taxonomy. Taxa are ranked groups of organisms, which run the gamut from general (domain) to specific (species). The hierarchical order of ranking is: