Basis of Life
Rebekah Harris
Instructional Technology
Richard Holden
September 28, 2009
Basis of Life
“Cleland and Chyba (2002) have suggested that life might be
like
water,
hard
to
define
phenomenologically,
but
easy
to
define at the fundamental level. But life is like fire, not
water—it is a process, not a pure substance” (Mckay, 2004,p.1).
Life differentiates between the living and nonliving. Currently,
the characteristics used to determine if something is alive or
not are derived from characteristics that are already exhibited
by living things.
The most popular theory today is that in
order to be “alive” the first five of six requirements must be
exhibited
while
the
living organisms.
sixth
is
common
among
some
but
not
The living must be: 1. Composed of cells.
all
2.
Organized; on molecular and cellular levels. 3. Metabolize; all
living organisms must use energy of some sort. 4. Responsive to
Stimuli; simple or complex actions in response to environment.
5. Reproductive; living things must be able to reproduce, not
for the individual, but for the continuation of life. 6. Growth;
not all organisms must grow or develop, but it is common in most
living things.
Although these characteristics determine whether
an organism is living or non living there must be the basis that
supports life and the adaptations that allow organisms to adapt
to this basis and continue to be a living organism.
McKay (2004) looks at these characteristics and determines
by
method
of
elimination
what
life
needs
in
order
to
be
supported. Energy, metabolism, and motion can be found despite a
lack
of
the
presence
of
life.
So
to
determine
that
these
characteristics are needed in order to define life they are not
proof of life. In order to support the living there is one
prerequisite
solely
responsible
for
simplest form of life, liquid water.
the
existence
of
the
So while our defining of
the living includes many requirements, the support of the living
limits
these
characteristics
and
the
basis
of
provides
the
ultimate
life
on
the
presence of water.
“Photosynthesis
energetic
basis for the activities of all human and animal life
on Earth, because photosynthetically produced organic
molecules, when oxidized in respiration, can release
the energy of the photons trapped during the original
reduction of carbon dioxide. Photosynthesis is thus
our major link with the energy of the sun” (Galston,
1992, p.1).
Using
this
understanding
of
the
life
cycle
provides
another
required basis of life. The presence of humans and animals is
contingent on the presence and support of photosynthetic life
forms, plants and vegetation.
An ever-changing planet requires that living organisms must
be capable of adaptations that can endure and support the life
form through extreme situations. In order to determine evolution
as a basis of life rather than a characteristic of the living,
adaptations at a physiological level must be required while the
other
characteristics
studies
of
cells
remain
and
unchanged.
organisms
in
However,
extreme
through
the
environmental
conditions it is shown that it is by adaptations of the various
characteristics as a whole that allow for the continuation of
life.
In conclusion, while the defining of and classification of
living and non living is a task that scientist and philosophers
have struggled with for centuries it is the understanding of
life that must first be evaluated. Using characteristics that
are
exhibited
by
the
living
to
determine
whether
or
not
something is alive is the most popular method of forming many of
today’s leading theories. However, life and the basis of may not
be limited only to earth thus possibly changing the definition
of living.
References
Galston, A. (1992, July). Photosynthesis as a basis for
life support on Earth and in space. Bioscience, 42(7), 490-493.
Retrieved September 28, 2009, from Academic Search Complete
database.
McKay, CP. (2004). What Is Life—and How Do We Search for It
in Other Worlds?. PLoS Biol 2(9): e302.
doi:10.1371/journal.pbio.0020302
Römisch, K., & Matheson, T. (2003, January). Cell biology
in the Antarctic: studying life in the freezer. Nature Cell
Biology, 5(1), 3. Retrieved September 28, 2009, from Academic
Search Complete database.