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Transcript
Community Interactions and Disturbances Chapter 35 Sections 4 and 5 Chapter 36 Section 5 What is a Community? A community is formed when populations of different species live together in a certain area. Sharing close living quarters forces them to interact. Competition Between Species Interspecific Competition occurs when two or more species rely on the same resource, such as food, water, or space. Competitive Exclusion occurs when competition leads to a clear winner and clear loser. Within a community, each species has a unique niche (or living arrangement) No two species can have the exact same niche! Kenai Fjords National Park Predation The interaction in which one organism eats another Both predators and prey evolve adaptations to survive (camouflage, stingers, poisonous chemicals, etc.) Symbiotic Relationships A close interaction between species that live in or on each other: Parasitism- One organism (parasite) obtains its nourishment at the expense of the other (host) Ex: tapeworm in intestine Mutualism- Both species benefit Ex: bees and flowers Commensalism- One organism benefits and the other is neither helped nor harmed Ex: Barnacle on a whale Disturbance in a Community Communities tend to be in a continual state of change Natural disturbances such as fires, volcanic eruptions, floods, and tornadoes can destroy organisms and their resources Fortunately, some organisms thrive in the wake of destruction. The process of rebuilding the community is called ecological succession Types of Succession PRIMARY When a community arises out of a lifeless area that has no soil Lichens and moss are pioneer species SECONDARY When a disturbance damages an existing community but leaves the soil intact Climax Community A stable group of plants and animals that is the end result of the succession process Does not always mean big trees: Grasses in prairies Cacti in deserts Human Disturbances Threaten Communities and Biodiversity Humans clear-cut forests for lumber and land We also intentionally or accidentally introduce exotic species to communities when we travel from one geographic region to another. The invasive species may out compete or prey upon native species. Overexploitation reduces population size and can threaten species to the point of extinction Conservation can slow the loss of Biodiversity Biodiversity is import to the health and sustainability of ecosystems because species are interconnected We can practice conservation by protecting “hot spots”, understanding species habitat, and balancing demands for resources. Sustainable development is about developing resources so that they can renew themselves and be available for the future.