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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 1 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 2 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 3