Ecosystems and Communities Chapter 4 Section 2

What Shapes an Ecosystem? Abiotic Factors Non-living parts of the environment such as rocks, the sun, and temperature Non-living parts of the environment such as rocks, the sun, and temperature

What shapes an ecosystem? Biotic Factors The living parts of the environment such as plants, bacteria, and animals The living parts of the environment such as plants, bacteria, and animals

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.

Community Interactions Competition Competition Predation Predation Symbiosis Symbiosis Mutualism Mutualism Commensalism Commensalism Parasitism Parasitism

Competition Between Species Competition occurs when two or more species rely on the same resource, such as food, water, or space. 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. 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) Within a community, each species has a unique niche (or living arrangement) No two species can have the exact same niche! No two species can have the exact same niche!

Kenai Fjords National Park

Predation The interaction in which one organism eats another The interaction in which one organism eats another Both predators and prey evolve adaptations to survive (camouflage, stingers, poisonous chemicals, etc.) 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) Parasitism- One organism (parasite) obtains its nourishment at the expense of the other (host) Ex: tapeworm in intestine Mutualism- Both species benefit Mutualism- Both species benefit Ex: bees and flowers Commensalism- One organism benefits and the other is neither helped nor harmed 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 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 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 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 SECONDARY When a disturbance damages an existing community but leaves the soil intact Lichens and moss are pioneer species

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 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. 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 Overexploitation reduces population size and can threaten species to the point of extinction