CHAPTER 11
Utilization of Thermal Energy by Living Organisms
MARY BELLE ALLEN
Kaiser Foundation Research Institute, Laboratory of Comparative Biology,
Richmond, California
I. The Need of All Organisms for Thermal Energy: General Considerations
487
II. Methods of Meeting Thermal Requirements
490
A. Poikilotherms
490
B. Homoiotherms
494
III. Organisms with Unusual Thermal Requirements
497
A. Cryophils
497
B. Thermophils
498
IV. Methods of Protection against the Destructive Effects of Thermal Energy
501
V. Thermal Energy as a Factor in Evolution
508
Addendum
508
References
509
I. The Need of All Organisms for Thermal Energy:
General Considerations
The life of all organisms depends upon the maintenance of an adequate supply of thermal energy. This energy is partly received from the
environment and partly generated by the organisms themselves during
their metabolism. Living creatures require thermal energy to maintain
their cellular constituents in a physical state which makes metabolism
possible and to supply the activation energy needed for vital reactions.
Although enzymes are known which will continue to react in the frozen
state (IS),
no organism has been found which can carry on its life
processes when the cellular contents are frozen. Enzyme catalysis may
reduce, but does not eliminate, the need for activation energy to carry
out the chemical reactions necessary for life and growth. At the same
time, however, thermal energy is a destructive force which tends to
break down the delicate mechanisms of the cell. Metabolic work must
be expended to repair enzymes and other cellular constituents which
have been disrupted by thermal effects. For some organisms living at
* Contribution No. 14 from the Laboratory of Comparative Biology, Kaiser
Foundation Research Institute.
487
Utilization of Thermal Energy by Living Organisms
MARY BELLE ALLEN
Kaiser Foundation Research Institute, Laboratory of Comparative Biology,
Richmond, California
I. The Need of All Organisms for Thermal Energy: General Considerations
487
II. Methods of Meeting Thermal Requirements
490
A. Poikilotherms
490
B. Homoiotherms
494
III. Organisms with Unusual Thermal Requirements
497
A. Cryophils
497
B. Thermophils
498
IV. Methods of Protection against the Destructive Effects of Thermal Energy
501
V. Thermal Energy as a Factor in Evolution
508
Addendum
508
References
509
I. The Need of All Organisms for Thermal Energy:
General Considerations
The life of all organisms depends upon the maintenance of an adequate supply of thermal energy. This energy is partly received from the
environment and partly generated by the organisms themselves during
their metabolism. Living creatures require thermal energy to maintain
their cellular constituents in a physical state which makes metabolism
possible and to supply the activation energy needed for vital reactions.
Although enzymes are known which will continue to react in the frozen
state (IS),
no organism has been found which can carry on its life
processes when the cellular contents are frozen. Enzyme catalysis may
reduce, but does not eliminate, the need for activation energy to carry
out the chemical reactions necessary for life and growth. At the same
time, however, thermal energy is a destructive force which tends to
break down the delicate mechanisms of the cell. Metabolic work must
be expended to repair enzymes and other cellular constituents which
have been disrupted by thermal effects. For some organisms living at
* Contribution No. 14 from the Laboratory of Comparative Biology, Kaiser
Foundation Research Institute.
487