Chapter 7 Community Ecology By Anna Kimsey

What determines number of species in a community? Species richness: The number of different species a community contains. Species richness depends largely on the climate and climate structure of the area. Also dependent on niche structure: how many ecological niches occur in the area. Dependent on geographical location. The most species rich environments are tropical rain forests, coral reefs, the deep sea, and large tropical lakes.

How can we classify species according to their roles in a community? Native, nonnative, indicator, keystone, and foundation species play different ecological roles in communities. -Native: those that normally live and thrive in a particular community. -Nonnative: invasive or alien species; migrate into or are deliberately or accidentally introduced into a community; some helpful. Ex: wild African bees moving northward -Indicator: species that serve as early warnings of damage to a community or ecosystem. Ex: presence/absence of trout -Keystone: Keystone species help determine the types and numbers of other species in a community; eliminating a keystone species may dramatically alter the structure and function of a community. Ex: pollination species -Foundation: create and enhance habitats that can benefit other species in a community. Ex: elephants

How do species interact with one another? Species can interact through competition, predation, parasitism, mutualism, and commensalism. -Competition: instead of fighting for resources, most competition involves the ability of one species to become more efficient in acquiring food or other resources. Ex: two lions -Predation: members of one species feed directly on all or part of a living organism of another species. Ex: lions and zebras -Parasitism: Parasitism occurs when one species feeds on part of another organism, usually by living on or in the host. Ex: ticks on humans -Mutualism: two species or a network of species interact in a way that benefits both. Ex: birds on the backs of buffalo -Commensalism: interaction that benefits one species but has little, if any, effect on the other species. Ex: epiphytes and large trees

How do communities respond to changes in environmental conditions? New environmental conditions allow one group of species in a community to replace other groups. Ecological succession: the gradual change of species composition of a given area. Two main types of succession: 1.Primary succession: gradual establishment of various biotic communities in lifeless areas where there is no soil in a terrestrial community or no bottom sediment in an aquatic community. Ex: bare rock exposed by a retreating glacier or severe soil erosion; newly cooled lava 2.Secondary succession: a series of communities with different species develop in places containing soil or bottom sediment. Ex: abandoned farmland; burned or cut forests Scientists cannot predict the course of succession or view it as a preordained progress toward a stable climax community that is in balance with its environment.

Does high species biodiversity increase the stability and sustainability of a community? Living systems maintain some degree of stability through constant change in response to changing environmental conditions. Having many different species appears to increase the sustainability of many communities. Communities with more species tend to have higher net primary productivity (NPP) and can be more resilient than simpler ones.

Extra Vocabulary to know Species evenness: the abundance of individuals within each species in a community Resource partitioning: occurs when species competing for similar scarce resources evolve more specialized traits that allow them to use shared resources at different times, in different ways, or in different places.