2. Bioinvasion – a kind of biological pollution that can
harm the economy, the environment, or
human health, refers to the introduction of
organisms into habitats where they do not
naturally belong.
Deliberate or accidental introduction of harmful
invasive species into an ecosystem can threaten local
organisms.
3. These invasive organisms may be aquatic or terrestrial
plants, animals or microorganisms that have moved from
their natural habitat and directly or indirectly introduced
in an ecosystem where they establish themselves.
Direct introduction usually involves human intervention,
whereas indirect introduction would imply that the
species hitched a ride by itself or
4. Direct introduction
Example: When people introduce biological species without
considering its long-term impact on the environment or
threat to biodiversity.
Indirect introduction
Example: when the species migrate on their own or when
they attach themselves to ships as barnacles do, or get
sucked in with the ballast waters that are eventually released
when the ship reaches
5. Species that can become invasive are usually exotic,
non-resident, or alien species.
Exotics can be viewed as foreigners coming to live in
our land.
We must control their entry, we must neverthless be
open to their presence.
6. How do communities change over
time?
Organisms in communities change in response to
changes in environmental conditions.
Succession is a continuing process that occurs in all
kinds of ecosystems, terrestrial or aquatic.
7. Nature’s Balancing Act
Nature has a way of maintaining a sense of balance.
Ecological balance is defined as the state of dynamic
equilibrium of a community of organisms.
The organism’s relationship with each other and the
environment remain relatively stable, though still
subject to gradual changes through natural
succession.
8. An ecological balance occurs when, for instance, a
predator increases its numbers and overconsumes
its prey. The resulting lack of food will then be felt,
not just by the predator but also by the entire
ecosystem.
