In
biology
and
ecology,
an
organism (in
Greek organon = instrument) is a
living being.
The
origin of life and the relationships between its
major lineages are controversial. Two main grades may
be distinguished, the
prokaryotes and
eukaryotes. The prokaryotes are generally
considered to represent two separate
domains, called the
Bacteria and
Archaea, which are not closer to one another than
to the eukaryotes. The gap between prokaryotes and
eukaryotes is widely considered a major missing link
in evolutionary history. Two eukaryotic
organelles, namely
mitochondria and
chloroplasts, are generally considered to be
derived from
endosymbiotic bacteria.
The phrase complex organism describes any
organism with more than one cell.
Characteristics common to many organisms include:
These are not universal, however. Many organisms
are incapable of independent movement, and do not
respond directly to their environment.
Microorganisms such as bacteria may not conduct
respiration, using alternate chemical pathways
instead. And many organisms are incapable of
reproduction.
Biological Organization
Environmental Organization
Classification
The following articles are entry points for
information about the classification of organisms:
Viruses
Viruses are not typically considered to be
organisms because they are not capable of
independent
reproduction or
metabolism. However, according to the
United States Code, they are considered to be
microorganisms in the sense of biological weaponry and
malicious use. This controversy is problematic,
though, since some
parasites and
endosymbionts are incapable of independent life
either. Although viruses do have
enzymes and molecules characteristic of living
organisms, they are incapable of surviving outside a
host cell and most of their metabolic processes
require a host and its 'genetic machinery'. The origin
of such parasites is uncertain, but it appears most
likely that they are derived from their hosts.
Life span
One of the basic parameters of organism is its
life span. Some animals live as short as one day,
while some plants can live thousands of years.
Aging is important when determining life span of
most organisms, bacterium, a virus or even a
prion.
External links
-
NCBI Taxonomy entry: root (http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Root)
(rich)
-
Species 2000 Indexing the world's known species (http://www.species2000.org/).
Species 2000 has the objective of enumerating all
known species of plants, animals, fungi and microbes
on Earth as the baseline dataset for studies of
global biodiversity. It will also provide a simple
access point enabling users to link from here to
other data systems for all groups of organisms,
using direct species-links.
-
The Tree of Life (http://tolweb.org/tree/phylogeny.html).
-
BBCNews: 27 September, 2000, When slime is not so
thick (http://news.bbc.co.uk/1/hi/sci/tech/944790.stm)
Citat: "...It means that some of the lowliest
creatures in the plant and animal kingdoms, such as
slime and amoeba, may not be as primitive as once
thought...."
-
BBCNews, 18 December, 2002, 'Space bugs' grown in
lab (http://news.bbc.co.uk/1/hi/sci/tech/2585235.stm)
Citat: "...Bacillus simplex and
Staphylococcus pasteuri...Engyodontium album...The
strains cultured by Dr Wainwright seemed to be
resistant to the effects of UV - one quality
required for survival in space...."
-
BBCNews, 19 June, 2003, Ancient organism challenges
cell evolution (http://news.bbc.co.uk/1/hi/sci/tech/3003946.stm)
Citat: "..."It appears that this organelle has been
conserved in evolution from prokaryotes to
eukaryotes, since it is present in both,"..."
-
Saint Anselm College: Survey of representatives of
the major Kingdoms (http://www.anselm.edu/homepage/jpitocch/genbios/surveybi04.html)
Citat: "...Number of
kingdoms has not been resolved...Bacteria
present a problem with their diversity...Protista
present a problem with their diversity...",
Interactive Syllabus for General Biology - BI 04,
Saint Anselm College, Summer 2003 (http://www.anselm.edu/homepage/jpitocch/genbios/bi04syllabsu03.html)
-
Jacob Feldman: Stramenopila (http://www.personal.psu.edu/users/j/s/jsf165/Bio110.html)
-
The largest organism in the world may be a fungus
carpeting nearly 10 square kilometers of an Oregon
forest, and may be as old as 8500 years. (http://www.abc.net.au/science/news/enviro/EnviroRepublish_828525.htm)
See also
