Geoscience Reference
In-Depth Information
- on the age of sexual maturity compared to the lifespan and the
number of potential reproductive opportunities;
- on the number of reproductions per year;
- on the organisms' fecundity (the more energy the parent invests
in the egg, the less productive it is, but the higher the chance of
survival of the egg, and then the juvenile);
- on the existence of parental care of the eggs and/or the young.
In a non-polluted environment, there is no “good” or “bad”
strategy in terms of a population's persistence [SPR 05]. However,
certain strategies are more “efficient” than others in terms of
persistence when pollution is added to the normal level of disruption
in the environment [KAM 96]. For example, in the case of a short and
temporary disruption lasting for the duration of the reproductive
season, species that can reproduce several times in the course of
the season will probably be less affected than those that only
reproduce once [CAL 97].
In conclusion, a cell's response to a contaminant results from the
interaction between its physiology, function and activity, and the
mode of action of the contaminant to which it is exposed.
The biological response of an individual or a population results from
the interaction between the disruptions caused by the toxin at a
cellular level and the organism's biological and ecological
characteristics. These characteristics are mainly determined by the
properties of the habitat and the organism's life history strategy.
Nevertheless, specific populations are only one element of their
communities and ecosystems. It is becoming much clearer that it is at
this level of lifeforms' organization, when exchanges of matter,
energy and genes occur, that modes of evolution, adaptation and
resilience are made permanently, notably in response to toxic
pressures. Figure 1.5, taken from [ADA 05a], shows the different
levels at which environmental stress produces direct and indirect
effects on the ecosystem's structure.
Search WWH ::
Custom Search