2. Succession
Succession is the gradual process by which the
number and type of species in the community
changes over time due to ecological
disturbances.
Primary succession
Organisms establish themselves in a new
environment e.g. sand dune or volcanic island.
This can take considerable time to colonise the
area as soil needs to develop and producers
begin to populate the area.
4. Secondary succession
Changes occur in an environment which has been
exposed to damage or disaster. These changes can be
very quick and is typical of Australian ecosystems which
have to deal with bushfires, land clearing and
deforestation. This is because there is more soil and a
greater mix of species of plants and animals.
5. Characteristics of Succession
Communities
As the ecosystem matures there is more biomass,
but productivity decreases.
There are usually more species in mature
ecosystems.
As the ecosystem matures the number of
heterotrophic species tends to increase more than
the number of autotrophic species.
Mature ecosystems are efficient at recycling
nutrients.
Mature ecosystems have organism that tend to be
more specialized.
7. Biodiversity
Biodiversity refers to the variety of diverse forms
of life on Earth and is essential for communities
to flourish and survive.
It can be seen:
1.In the genetic makeup of individuals in a
population
2. Between one species and another
3. Between the various ecosystems
8. Ecosystems are not static, they constantly
change and are shaped by the forces of
evolution.
Those that are most suited to conditions are
likely to survive and pass on their genes to the
next generation.
E.g. Natural Selection.
9. However not all species have the capacity for
effective reproduction.
Species with a high reproductive effort, short life
and many offspring are more common in early
succession (r-selected).
Species with a low reproductive effort, long life
and few offspring are more common in stable
environments (k-selected).
10. Opportunistic species (r-selected) and those
which are more stable (k-selected) are
reproductive strategies at the extremes of the
reproductive continuum.
Most organisms fall in between these two
extremes.
Image from www.trunity.net
