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MARY BELLE ALLEN
numbers of protein molecules (5, 205, 206). The suggestion has been
made that the key catalysts are those which govern the synthesis of protein (5). Some recent results by Hancock (206), who measured protein
synthesis in a thermophilic sporeformer, are in agreement with this
hypothesis.
V. Thermal Energy as a Factor in Evolution
Thermal energy has probably been a factor in the evolutionary picture from the time of the development of the first living things. Many
enzyme-catalyzed reactions will also proceed at a measurable rate in
the absence of catalysts, or with smaller, less efficient organic molecules
as catalysts. It seems probable that primitive forms of life, appearing
in a world which may have been higher in temperature than it is at
present and not being subjected to the biological competition which
today places a high premium on biochemical efficiency, may well have
carried out many reactions without enzyme catalysis, drawing from the
environment sufficient thermal energy to provide the activation energy
for these reactions. [There is, however, no reason to consider presentday thermophilic organisms as survivors of such primitive forms of life.
The enzymatic apparatus of present-day thermophils appears as complex as that of organisms living at lower temperatures (5, 12)].
After the fundamental patterns of biochemical organization of present-day living organisms had developed, thermal energy, or the lack of
it, continued to play an evolutionary part by demanding the development of numerous biochemical and physiological mechanisms in order
to enable living creatures to survive in environments of diverse, and in
some cases apparently unfavorable, temperature conditions (cf. Section
II, A). This development continued to such an extent that organisms
are found at subzero temperatures and at temperatures only a little below the boiling point of water (Section III). The "higher" animals, however, have evolved different methods for coping with temperature
changes and extremes. They have developed mechanisms for maintaining the body temperature constant, thus eliminating the need for biochemical adjustment to changing temperature (Section ΙΙ,Β).
Addendum
Two contributions summarizing recent work on the biochemistry of
adaptation of organisms to extreme temperatures have appeared since
the survey of literature for this paper was completed at the end of
1957.
The metabolic changes that occur as warm-blooded animals adapt to
a cold environment were discussed in a recent symposium (207). The
MARY BELLE ALLEN
numbers of protein molecules (5, 205, 206). The suggestion has been
made that the key catalysts are those which govern the synthesis of protein (5). Some recent results by Hancock (206), who measured protein
synthesis in a thermophilic sporeformer, are in agreement with this
hypothesis.
V. Thermal Energy as a Factor in Evolution
Thermal energy has probably been a factor in the evolutionary picture from the time of the development of the first living things. Many
enzyme-catalyzed reactions will also proceed at a measurable rate in
the absence of catalysts, or with smaller, less efficient organic molecules
as catalysts. It seems probable that primitive forms of life, appearing
in a world which may have been higher in temperature than it is at
present and not being subjected to the biological competition which
today places a high premium on biochemical efficiency, may well have
carried out many reactions without enzyme catalysis, drawing from the
environment sufficient thermal energy to provide the activation energy
for these reactions. [There is, however, no reason to consider presentday thermophilic organisms as survivors of such primitive forms of life.
The enzymatic apparatus of present-day thermophils appears as complex as that of organisms living at lower temperatures (5, 12)].
After the fundamental patterns of biochemical organization of present-day living organisms had developed, thermal energy, or the lack of
it, continued to play an evolutionary part by demanding the development of numerous biochemical and physiological mechanisms in order
to enable living creatures to survive in environments of diverse, and in
some cases apparently unfavorable, temperature conditions (cf. Section
II, A). This development continued to such an extent that organisms
are found at subzero temperatures and at temperatures only a little below the boiling point of water (Section III). The "higher" animals, however, have evolved different methods for coping with temperature
changes and extremes. They have developed mechanisms for maintaining the body temperature constant, thus eliminating the need for biochemical adjustment to changing temperature (Section ΙΙ,Β).
Addendum
Two contributions summarizing recent work on the biochemistry of
adaptation of organisms to extreme temperatures have appeared since
the survey of literature for this paper was completed at the end of
1957.
The metabolic changes that occur as warm-blooded animals adapt to
a cold environment were discussed in a recent symposium (207). The