Organisms and Environmental Factors 17
nutrient will be whichever one of C, N, P is least available with regard to
the above proportion. Decreasing the limiting nutrient entails a proportionate decrease in the valorization of the other nutrients by the organism and
an approximately proportionate decrease in the biomass produced.
2.7 intEraction oF organiSMS
and EnvironMEnt
Every living organism interacts with its environment in a variety of ways.
The various characteristics that enter into the study of this interaction are
called environmental factors; they have traditionally been divided into
physical factors such as radiation, the wind and the temperature of the air
or water, chemical factors such as concentration of O 2 , CO 2 or nutrient
salts, and biological factors such as the presence of organisms of the same
or another species. The physical and chemical factors create the abiotic
environment, and the biological factors create the biotic environment.
The biotic environment is examined in population studies (Chapter 3),
the chemical factors in the environment are examined in the context of
biogeochemical cycles (Chapter 4) and pollution (Chapters 7, 8, 9), and
the physical factors are examined next, also in the context of energy flow
(Chapter 4).
2.7.1 Physical Factors
Organisms are affected by many physical factors in the environment, which
often interact or act in a complex manner. Thus an organism’s response to
a physical factor may vary, depending on the effect of other factors. For
example, plant transpiration is reduced if humidity is high, and increases
with the wind if humidity is low. Isolation of the relationship between each
factor and the response of the organism may give rise to misleading conclusions. Nevertheless, a breakdown into individual factors is often useful
and a greater or lesser breakdown of the study of the relevant ecological
phenomena is in general unavoidable, but particular attention must be paid
to the drawing of conclusions. On the other hand, the viewpoint that the
environment can be studied only as a unified whole often proves to be
excessive and fruitless.
The basic physical factors of the environment (i.e. temperature, wind,
humidity and radiation) have a common basis, which makes it possible to
study their combined effects on the organism being examined. Specifically,
these factors entail a transfer of energy to and from the organism, through
processes of evaporation, absorption or emission of radiation, and conduction or convection of heat. Regarding energy changes, the organism’s
thermal balance equation can be written, which links the physical factors
nutrient will be whichever one of C, N, P is least available with regard to
the above proportion. Decreasing the limiting nutrient entails a proportionate decrease in the valorization of the other nutrients by the organism and
an approximately proportionate decrease in the biomass produced.
2.7 intEraction oF organiSMS
and EnvironMEnt
Every living organism interacts with its environment in a variety of ways.
The various characteristics that enter into the study of this interaction are
called environmental factors; they have traditionally been divided into
physical factors such as radiation, the wind and the temperature of the air
or water, chemical factors such as concentration of O 2 , CO 2 or nutrient
salts, and biological factors such as the presence of organisms of the same
or another species. The physical and chemical factors create the abiotic
environment, and the biological factors create the biotic environment.
The biotic environment is examined in population studies (Chapter 3),
the chemical factors in the environment are examined in the context of
biogeochemical cycles (Chapter 4) and pollution (Chapters 7, 8, 9), and
the physical factors are examined next, also in the context of energy flow
(Chapter 4).
2.7.1 Physical Factors
Organisms are affected by many physical factors in the environment, which
often interact or act in a complex manner. Thus an organism’s response to
a physical factor may vary, depending on the effect of other factors. For
example, plant transpiration is reduced if humidity is high, and increases
with the wind if humidity is low. Isolation of the relationship between each
factor and the response of the organism may give rise to misleading conclusions. Nevertheless, a breakdown into individual factors is often useful
and a greater or lesser breakdown of the study of the relevant ecological
phenomena is in general unavoidable, but particular attention must be paid
to the drawing of conclusions. On the other hand, the viewpoint that the
environment can be studied only as a unified whole often proves to be
excessive and fruitless.
The basic physical factors of the environment (i.e. temperature, wind,
humidity and radiation) have a common basis, which makes it possible to
study their combined effects on the organism being examined. Specifically,
these factors entail a transfer of energy to and from the organism, through
processes of evaporation, absorption or emission of radiation, and conduction or convection of heat. Regarding energy changes, the organism’s
thermal balance equation can be written, which links the physical factors