Organisms and Environmental Factors 19
stronger metabolism has to be. At environmental temperatures of T e > T o ,
the organism gives off heat through the evaporation of water. Activation of
water for evaporation also requires consumption of energy.
Poikilothermic animals (fish, reptiles, etc.) are able to exercise only slight
internal control over their temperature. The temperature of the environment
largely controls the rates of their biochemical functions, which approximately
double for every 10°C temperature increase. Thus, these organisms regulate
their temperature mainly through the appropriate behaviour. Fish choose
the area of the aquatic environment that is at the right temperature. Reptiles
regulate their temperature by moving between shade and sun, by changing
their orientation in relation to the sun, and even by changing their shape.
It is noteworthy that the death toll inflicted on fish and other aquatic
organisms by thermal pollution of bodies of water (Chapter 8) is associated
with the poikilothermia of those organisms. Thermal pollution is a rise in
water temperature due to drainage of warm water, which has usually been
used by power plants and other factories for cooling purposes. The high
mortality rate is due to suffocation, because it causes the fishes’ metabolism
to rise and thus their requirements for oxygen increase proportionally, to
such an extent that the oxygen dissolved in the water is not enough. In addition, the higher water temperature causes a decrease in the concentration
of dissolved oxygen.
The wind causes air masses in contact with an organism’s body to be
replaced by other masses that may contain different amounts of heat, water
vapour or carbon dioxide. Thus the wind affects heat exchange between
the organism and the environment, as well as the elimination of water and
carbon dioxide by the organism.
Atmospheric humidity is of importance mainly due to its impact on the
rate of evaporation from the bodies of organisms.
2.7.1.2 Radiation
The radiation an organism receives is terrestrial or extra-terrestrial in
origin . In the first case it originates from various bodies on Earth. In the
second case it originates from the sun or is cosmic radiation. Solar radiation is of primary importance for the functions of ecosystems, because for
them it constitutes a basic source of energy (Chapter 4). It also plays a decisive part in the planet’s thermal equilibrium and affects organisms’ survival
(Chapter 9).
Depending on its wavelength (in μ = 10 –6 meter) or its frequency, the spectrum of electromagnetic radiation can be divided into the following regions:
• Microwaves and radio waves (wavelength >1000 μ)
• Infrared radiation (wavelength 0.7–1000 μ)
• Visible light (wavelength 0.4–0.7 μ)
stronger metabolism has to be. At environmental temperatures of T e > T o ,
the organism gives off heat through the evaporation of water. Activation of
water for evaporation also requires consumption of energy.
Poikilothermic animals (fish, reptiles, etc.) are able to exercise only slight
internal control over their temperature. The temperature of the environment
largely controls the rates of their biochemical functions, which approximately
double for every 10°C temperature increase. Thus, these organisms regulate
their temperature mainly through the appropriate behaviour. Fish choose
the area of the aquatic environment that is at the right temperature. Reptiles
regulate their temperature by moving between shade and sun, by changing
their orientation in relation to the sun, and even by changing their shape.
It is noteworthy that the death toll inflicted on fish and other aquatic
organisms by thermal pollution of bodies of water (Chapter 8) is associated
with the poikilothermia of those organisms. Thermal pollution is a rise in
water temperature due to drainage of warm water, which has usually been
used by power plants and other factories for cooling purposes. The high
mortality rate is due to suffocation, because it causes the fishes’ metabolism
to rise and thus their requirements for oxygen increase proportionally, to
such an extent that the oxygen dissolved in the water is not enough. In addition, the higher water temperature causes a decrease in the concentration
of dissolved oxygen.
The wind causes air masses in contact with an organism’s body to be
replaced by other masses that may contain different amounts of heat, water
vapour or carbon dioxide. Thus the wind affects heat exchange between
the organism and the environment, as well as the elimination of water and
carbon dioxide by the organism.
Atmospheric humidity is of importance mainly due to its impact on the
rate of evaporation from the bodies of organisms.
2.7.1.2 Radiation
The radiation an organism receives is terrestrial or extra-terrestrial in
origin . In the first case it originates from various bodies on Earth. In the
second case it originates from the sun or is cosmic radiation. Solar radiation is of primary importance for the functions of ecosystems, because for
them it constitutes a basic source of energy (Chapter 4). It also plays a decisive part in the planet’s thermal equilibrium and affects organisms’ survival
(Chapter 9).
Depending on its wavelength (in μ = 10 –6 meter) or its frequency, the spectrum of electromagnetic radiation can be divided into the following regions:
• Microwaves and radio waves (wavelength >1000 μ)
• Infrared radiation (wavelength 0.7–1000 μ)
• Visible light (wavelength 0.4–0.7 μ)