in their metabolism. When cells derived from a tissue of homeotherms, the cells
show adaptation to temperature of culture. The adaptation indicates that cells of
homeotherms have acquired genetic information of mechanism to adapt change of
environmental temperature in long history of evolution and preserve it in DNA. Both
single cell and multi-cells organisms live in surrounding environment, and they
maintains constant state to survive in variable environment (¼‘homeostasis’). Their
direct environment is water molecules, and water molecules mediate interaction
between cells. Each cell uses genetic information on DNA correspondent to external
stimulus and responds to that. Temperature of environment is an important factor
and physical property has temperature dependency. Therefore biological functions
are greater or lesser extent affected by temperature. Homeotherms have been born as
living organisms whose enzyme activities unaffected by change of external temperature in evolution. All animals and plants are under environment of variable temperature and are affected by temperature directly or indirectly. And these living
organisms provide mechanisms to adapt temperature change at level of cell. And the
mechanism to adapt to temperature change is observed in cultured cells derived from
homeotherms such as rat or chines hamster. This mechanism is response of the cell
itself to temperature change, and the mechanism has been preserved in evolution
process. The mechanisms of adapting to environment at level of gene are called
‘stress-induced gene expression’. Temperature acclimation of cell is one of them.
Living organisms provide mechanism responding to change of environment at gene
level essentially and becomes possible to maintain their life.
8.2 Mechanism of Adaptation to Environment on Gene
Level
Living organisms respond to change of external environment; the mechanism of
response exists on level of an individual and a cell. And this is called ‘response to
stress’. The response to stress has been acquired in process of evolution, and it is
essential for living organisms on the earth. Environmental factors such as temperature, pressure, radiation, ultraviolet light, metal ions, oxygen and various compounds
are candidates of stress. When a cell is exposed to a stress, protein synthesis at
normal state is lowered and some species of protein are newly synthesized instead of
them. Typical stress is heat shock and proteins synthesized in this state are called
‘heat shock proteins’. When a cells or individuals are exposed to temperature higher
than physiological temperature by a few degrees, heat shock response is observed in
every level from cell to individual. This response is observed in deep-sea fish living
in below zero temperature and thermophilic bacteria living in hot spring. The
maximum response of heat shock is observed at 5~10 degrees higher than physiological temperature. Ritossa first observed three new puffs in chromatin of drosophila larva exposed to high temperature [1].
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show adaptation to temperature of culture. The adaptation indicates that cells of
homeotherms have acquired genetic information of mechanism to adapt change of
environmental temperature in long history of evolution and preserve it in DNA. Both
single cell and multi-cells organisms live in surrounding environment, and they
maintains constant state to survive in variable environment (¼‘homeostasis’). Their
direct environment is water molecules, and water molecules mediate interaction
between cells. Each cell uses genetic information on DNA correspondent to external
stimulus and responds to that. Temperature of environment is an important factor
and physical property has temperature dependency. Therefore biological functions
are greater or lesser extent affected by temperature. Homeotherms have been born as
living organisms whose enzyme activities unaffected by change of external temperature in evolution. All animals and plants are under environment of variable temperature and are affected by temperature directly or indirectly. And these living
organisms provide mechanisms to adapt temperature change at level of cell. And the
mechanism to adapt to temperature change is observed in cultured cells derived from
homeotherms such as rat or chines hamster. This mechanism is response of the cell
itself to temperature change, and the mechanism has been preserved in evolution
process. The mechanisms of adapting to environment at level of gene are called
‘stress-induced gene expression’. Temperature acclimation of cell is one of them.
Living organisms provide mechanism responding to change of environment at gene
level essentially and becomes possible to maintain their life.
8.2 Mechanism of Adaptation to Environment on Gene
Level
Living organisms respond to change of external environment; the mechanism of
response exists on level of an individual and a cell. And this is called ‘response to
stress’. The response to stress has been acquired in process of evolution, and it is
essential for living organisms on the earth. Environmental factors such as temperature, pressure, radiation, ultraviolet light, metal ions, oxygen and various compounds
are candidates of stress. When a cell is exposed to a stress, protein synthesis at
normal state is lowered and some species of protein are newly synthesized instead of
them. Typical stress is heat shock and proteins synthesized in this state are called
‘heat shock proteins’. When a cells or individuals are exposed to temperature higher
than physiological temperature by a few degrees, heat shock response is observed in
every level from cell to individual. This response is observed in deep-sea fish living
in below zero temperature and thermophilic bacteria living in hot spring. The
maximum response of heat shock is observed at 5~10 degrees higher than physiological temperature. Ritossa first observed three new puffs in chromatin of drosophila larva exposed to high temperature [1].
160
8 Global Environment and Biophysics