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Grade 7 - Notes
Grade 7 Science Chapter 3:
Natural events and human activities cause changes in
ecosystems
3.1 Natural Disturbances and Succession
Ecosystems may be disturbed by natural events such as storms and floods
and by human activities such as logging and farming.
Succession is the process by which a biological community changes over
time.
There are 2 types of succession
1. Primary succession is the sequence of changes that starts with bare rock
and eventually develops into a complex community of plants and animals.
Example: Primary succession occurs when something happens to remove
everything down to the bare rock. This can happen after a natural event such
as volcanic activity or glaciation or after a human activity such as mining.
Interactions Within Ecosystems
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Grade 7 - Notes
2. Secondary Succession is the re-growth of a community in an area that
has changed dramatically after a disturbance such as a fire.
Example: After fires or farming a climax community can be relatively
quickly returned to its original state.
Pioneer Species are species that is the first to appear in an area and can
establish themselves with little or no soil and few nutrients.
Example: Lichens are the pioneer species in the picture above.
Climax Community is a diverse group of species that form a stable
ecosystem which can remain relatively unchanged for centuries if there is no
disturbance.
Example: The boreal forest is an example of a climax community in our
province.
3.2 The Impact of People on Ecosystems
Humans have influenced the natural environment.
Examples include
- habitat loss / destruction
- harvesting resources
- polluting
- introducing new species
Conservation Pros and Cons
Pros
Sustainability of the resource
Preservation of biodiversity
Eco-tourism
Interactions Within Ecosystems
Cons
Artificial habitats
Economic loss
Limited human use
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Grade 7 - Notes
3.3 Monitoring and Managing Ecosystems
Individuals and groups interested in protecting the environment.
Local
Shane Mahoney
K.E.E.P.
Protected Areas Association
Conservation Corps
National
David Suzuki
Parks Canada
Canadian Nature Federation
Nature Conservancy of
Canada
Interactions Within Ecosystems
International
Friends of the Earth
Greenpeace
World Wildlife Fund
Ducks Unlimited
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