42 Ecology and Applied Environmental Science
the alternations of a warm–cold environment may consist of an intermediate size of the individuals, in successful adaptation to one extreme only
(e.g. to the cold environment), in polymorphism of the individuals with
a different degree of adaptations for each one, in changing the size of the
individuals according to the season etc.
Any survival strategy has a cost for the population, which is finally reduced
to energy expenditure. For this reason, the developed mechanism should substantially increase the population’s fitness and the ensuing benefit must be
greater than the cost of the mechanism in order to be eventually advantageous.
In the end, the value of a survival strategy is a function of the relation
“development to cost.” This value will form a natural selection criterion
of the specific strategy and will define the final success of the endeavour,
i.e. the population’s survival.
The strategies are connected, inter alia, with parameters as the population’s natality and mortality. The available energy can be used by priority
either for the increase of offspring production or for the enhancement of
every organism’s size and viability. In the first case, this energy is mainly
invested in increase of natality, and in the second, in decrease of mortality.
The population dynamics approaches, especially the exponential and the
logistic model, set off two basic parameters:
• Parameter r, the intrinsic rate of natural increase. It is the current rate
and not the maximum possible.
• Parameter K, the carrying capacity of the environment. It is not the
highest limit, but an equilibrium point.
These fundamental population parameters refer to a specific period of time,
are independent from the population’s state and may depend on environmental conditions. They contribute to the determination of two basic survival
strategies of populations:
• Strategy r: r’s increase tendency, investment in natality
• Strategy K: K’s increase tendency, investment in viability
Every ecological manifestation or behaviour can be considered as an r or
K strategy element, as shown by these examples:
r: Generally small size.
K: Generally big size.
r: Energy investment in the population’s biomass increase through reproduction. The population’s survival is achieved even after a disaster
(e.g. 99% deaths).
K: Energy investment in reserves and protection mechanisms of the individual against adverse environmental effects. The population survives
only if an adequate number of individuals survive.
the alternations of a warm–cold environment may consist of an intermediate size of the individuals, in successful adaptation to one extreme only
(e.g. to the cold environment), in polymorphism of the individuals with
a different degree of adaptations for each one, in changing the size of the
individuals according to the season etc.
Any survival strategy has a cost for the population, which is finally reduced
to energy expenditure. For this reason, the developed mechanism should substantially increase the population’s fitness and the ensuing benefit must be
greater than the cost of the mechanism in order to be eventually advantageous.
In the end, the value of a survival strategy is a function of the relation
“development to cost.” This value will form a natural selection criterion
of the specific strategy and will define the final success of the endeavour,
i.e. the population’s survival.
The strategies are connected, inter alia, with parameters as the population’s natality and mortality. The available energy can be used by priority
either for the increase of offspring production or for the enhancement of
every organism’s size and viability. In the first case, this energy is mainly
invested in increase of natality, and in the second, in decrease of mortality.
The population dynamics approaches, especially the exponential and the
logistic model, set off two basic parameters:
• Parameter r, the intrinsic rate of natural increase. It is the current rate
and not the maximum possible.
• Parameter K, the carrying capacity of the environment. It is not the
highest limit, but an equilibrium point.
These fundamental population parameters refer to a specific period of time,
are independent from the population’s state and may depend on environmental conditions. They contribute to the determination of two basic survival
strategies of populations:
• Strategy r: r’s increase tendency, investment in natality
• Strategy K: K’s increase tendency, investment in viability
Every ecological manifestation or behaviour can be considered as an r or
K strategy element, as shown by these examples:
r: Generally small size.
K: Generally big size.
r: Energy investment in the population’s biomass increase through reproduction. The population’s survival is achieved even after a disaster
(e.g. 99% deaths).
K: Energy investment in reserves and protection mechanisms of the individual against adverse environmental effects. The population survives
only if an adequate number of individuals survive.