Download Community Disturbances and Stability Notes

Community Disturbances and Stability
Community Disturbances
Any change to an ecological community is known as a disturbance.
Disturbances can take any number of forms such as… A natural disaster, An epidemic
disease, A loss of a keystone species, An invasive species, Human activity
A _______________________ is a species that plays an essential role in an ecosystem.
When a keystone species’ population is disturbed, the entire community can be severely affected. A keystone species can
be a predator, prey a decomposer or a plant.
For better or worse, _____________________ affects ecosystems.
What do you think: Are humans a keystone species?
_______________________ occurs when forests are cut down for timber (wood
products) and to make space for agriculture and animal grazing.
_________________________ are exotic (non-native) species with rapidly growing
populations that disrupt native communities.
_______________________ (only growing one type of plant) withholds resources from a
diverse group of plants and animals and decreases their populations.
________________________ happens when fertilizers or human and animal wastes
cause an algal bloom which can cause a “dead zone”. The increase in algae clogs waterways
and blocks sunlight from reaching other plants. When the algae die, decomposers use up most of the available
oxygen. This lack of oxygen can kill fish and other aquatic animals.
_______________________ is the introduction of harmful substances or products into
the environment.
Succession
__________________ is a series of predictable changes in a community.
___________________________________ occurs where life has not existed before.
__________________________________ are the first species to live on bare rock.
Lichens and mosses are examples of pioneer species.
Each stage of succession supports different types of plants and animals.
After hundreds of years, enough soil has been built up to support entire forests.
This final stage of succession is called the ______________________________.
______________ occurs where life has already existed and there is already soil present.
Secondary succession may follow a fire or human activity such as logging.
Although secondary succession progresses more rapidly than primary succession, it still
takes decades to reach a climax community.
Without constant upkeep, human developments are eventually taken over by secondary
succession.