– for biologists, the species is a taxonomic category composed of individuals
which are identical from many points of view;
– for ecologists, the species is represented by populations composed of individuals
belonging to the same species, characterised by a high fidelity for living in
specific biocoenosis, which live under specific environmental conditions and
forming together a specific hierarchic unit called an ecosystem.
The best knowledge of population is essential both for biology (through taxonomy), and for ecology (through autecology).
Ecology approaches the living world from a certain biological level upwards,
i.e. that level of the living world depends on the component of non-living environment, namely from the population (Bavaru et al. 2007; Botnariuc 1976) (Fig. 30.1)
The species exists in nature only through its populations which live in ecosystems (Bavaru et al. 2007; Bick 1998; Dediu 2007). These populations contribute
actually to building the ecosystem structure and functioning; at the same time, they
are structural components of the species and fulfil different functions which ensure
its existence, perpetuation and evolution. And it must be noticed that this process
occurs in fact through the interrelations within the ecosystems, which are informationally controlled by genetic features peculiar to the species, which take place both
in populations and in metapopulations (recombination, mutation, selection and
gene migration, natural selection of living beings). These relations determine the
improvement of the species, through new ecological adaptations, but, also, through
the generation of subspecific mutations, which leads to the emergence of new
species.
The species is a genetic entity which occurs and performs evolution through the
relations of its populations within ecosystems, having, hence, a pronounced ecological causality. This fact is, so far, poorly considered in the manifold definitions
of the species.
This is the reason why although the populational level exists both in biology and
in ecology, it is seen and approached in different manners.
Population has been defined since the past century as « a group of organisms of
one and the same species which populate a biocoenosis » (Du Rietz 1930, cit.
Donita and Ivan 1977). This short, but comprehensive definition, emphasizes a very
special reality of the living world – the occurrence of a connecting entity between
species and biocoenosis: the population of organisms, as a common feature of the
two great supraindividual units of the living world.
An accurate recognition of the populations of different species which compose a
biocoenosis allows a good progress of ecological investigations.
Winthin one biocoenosis, each species is represented by one distinct population,
which has its own ecological niche (Brewer 1994; Chapman and Reiss 1992; Dediu
2007).
Intense ecological investigations from the last half of the 20th century proved the
existence of populations and showed their role in structure and functioning of the
biocoenosis and their influence upon the habitat – the abiotic environment in which
508
N. Donița ˘ and S. Godeanu
which are identical from many points of view;
– for ecologists, the species is represented by populations composed of individuals
belonging to the same species, characterised by a high fidelity for living in
specific biocoenosis, which live under specific environmental conditions and
forming together a specific hierarchic unit called an ecosystem.
The best knowledge of population is essential both for biology (through taxonomy), and for ecology (through autecology).
Ecology approaches the living world from a certain biological level upwards,
i.e. that level of the living world depends on the component of non-living environment, namely from the population (Bavaru et al. 2007; Botnariuc 1976) (Fig. 30.1)
The species exists in nature only through its populations which live in ecosystems (Bavaru et al. 2007; Bick 1998; Dediu 2007). These populations contribute
actually to building the ecosystem structure and functioning; at the same time, they
are structural components of the species and fulfil different functions which ensure
its existence, perpetuation and evolution. And it must be noticed that this process
occurs in fact through the interrelations within the ecosystems, which are informationally controlled by genetic features peculiar to the species, which take place both
in populations and in metapopulations (recombination, mutation, selection and
gene migration, natural selection of living beings). These relations determine the
improvement of the species, through new ecological adaptations, but, also, through
the generation of subspecific mutations, which leads to the emergence of new
species.
The species is a genetic entity which occurs and performs evolution through the
relations of its populations within ecosystems, having, hence, a pronounced ecological causality. This fact is, so far, poorly considered in the manifold definitions
of the species.
This is the reason why although the populational level exists both in biology and
in ecology, it is seen and approached in different manners.
Population has been defined since the past century as « a group of organisms of
one and the same species which populate a biocoenosis » (Du Rietz 1930, cit.
Donita and Ivan 1977). This short, but comprehensive definition, emphasizes a very
special reality of the living world – the occurrence of a connecting entity between
species and biocoenosis: the population of organisms, as a common feature of the
two great supraindividual units of the living world.
An accurate recognition of the populations of different species which compose a
biocoenosis allows a good progress of ecological investigations.
Winthin one biocoenosis, each species is represented by one distinct population,
which has its own ecological niche (Brewer 1994; Chapman and Reiss 1992; Dediu
2007).
Intense ecological investigations from the last half of the 20th century proved the
existence of populations and showed their role in structure and functioning of the
biocoenosis and their influence upon the habitat – the abiotic environment in which
508
N. Donița ˘ and S. Godeanu