1.1. What is Population Ecology?

Population ecology relative to other ecological disciplines

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     * Population ecology is the branch of ecology that studies the structure and
       dynamics of populations.
     * Physiology studies individual characteristics and individual processes. These
       are use as a basis for prediction of processes at the population level.
     * Community ecology studies the structure and dynamics of animal and plant
       communities. Population ecology provides modeling tools that can be used for
       predicting community structure and dynamics.
     * Population genetics studies gene frequencies and microevolution in
       populations. Selective advantages depend on the success of organisms in their
       survival, reproduction and competition. And these processes are studied in
       population ecology. Population ecology and population genetics are often
       considered together and called "population biology". Evolutionary ecology is
       one of the major topics in population biology.
     * Systems ecology is a relatively new ecological discipline which studies
       interaction of human population with environment. One of the major concepts
       are optimization of ecosystem exploitation and sustainable ecosystem
       management.
     * Landscape ecology is also a relatively new area in ecology. It studies
       regional large-scale ecosystems with the aid of computer-based geographic
       information systems. Population dynamics can be studied at the landscape
       level, and this is the link between landscape- and population ecology.

   The term "population" is interpreted differently in various sciences:
     * In human demography a population is a set of humans in a given area.
     * In genetics a population is a group of interbreeding individuals of the same
       species, which is isolated from other groups.
     * In population ecology a population is a group of individuals of the same
       species inhabiting the same area.

   Interbreeding is seldom considered in ecological studies of populations. The
   exceptions are studies in population genetics and evolutionary ecology.

   Populations can be defined at various spatial scales. Local populations can
   occupy very small habitat patches like a puddle. A set of local populations
   connected by dispersing individuals is called a metapopulation. Populations can
   be considered at a scale of regions, islands, continents or seas. Even the entire
   species can be viewed as a population.

   Populations differ in their stability. Some of them are stable for thousands of
   years. Other populations persist only because of continuous immigration from
   other areas. On small islands, populations often get extinct, but then these
   islands can be re-colonized. Finally, there are temporary populations that
   consist of organisms at a particular stage intheir life cycle. For example,
   larvae of dragonflies live in the water and form a hemipopulation (term of
   [1]Beklemishev).

   The major problem in population ecology is to derive population characteristics
   from characteristics of individuals and to derive population processes from the
   processes in individual organisms:

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   Main axiom of population ecology: organisms in a population are ecologically
   equivalent. Ecological equivalency means:
    1. Organisms undergo the same life-cycle
    2. Organisms in a particular stage of the life-cycle are involved in the same
       set of ecological processes
    3. The rates of these processes (or the probabilities of ecological events) are
       basically the same if organisms are put into the same environment (however
       some individual variation may be allowed).

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   [5]Alexei Sharov 1/12/96

References

   1. http://alexei.nfshost.com/~sharov/bekl/bekl.html#structure
   2. http://alexei.nfshost.com/PopEcol/lec1/popsyst.html
   3. http://alexei.nfshost.com/PopEcol/lec1/popsyst.html
   4. http://alexei.nfshost.com/PopEcol/lec1/model.html
   5. http://alexei.nfshost.com/~sharov/alexei.html