Ecology exam 4

Explain the role of keystone species in a community. Provide an example that demonstrates that role.

Keystone predation is a type of indirect interaction in which a predator enhances the success of one or more inferior competitors by reducing the abundance of a superior competitor. Without its keystone species, ecosystems would look very different. Some ecosystems might not be able to adapt to environmental changes if their keystone species disappeared. The American Beaver is one example of a keystone species in North America.

Sere

A complete succession of plant communities, which results in the climax community. A sere is composed of a series of different plant communities that change with time. These communities are known as seral stages or seral communities.

Food webs and food chains

A food chain is a descriptive diagram—a series of arrows, each pointing from one species to another, representing the flow of food energy from prey (the consumed) to predator (the consumer). in nature, however, are not simple, straight-line food chains. Rather, they involve many food chains meshed into a complex food web with links leading from primary producers through an array of consumers

Community

A group of species that occupy a given area, interacting either directly or indirectly. Species may compete for shared resources, such as food, space. They may provide mutual aid, they may noy directly affect one another at all. The definition of community also recognizes that species living in close association may interact.

Herbivores, carnivores, and omnivores

An herbivore is an organism that mostly feeds on plants. Herbivores are primary consumers.m Herbivores are a major part of the food web. A carnivore is an organism that mostly eats meat, or the flesh of animals. Sometimes carnivores are called predators. Organisms that carnivores hunt are called prey. Omnivore is an animal that has the ability to eat and survive on both plant and animal matter. Obtaining energy and nutrients from plant and animal matter Carnivores and omnivores are secondary consumers.

Autotrophs and heterotrophs

Autotrophs are producers who prepare their own food. Examples include plants, algae, and some types of bacteria. Heterotrophs are consumers who depend on other sources for their food. Dogs, birds, fish, and humans are all examples of heterotrophs.

Community composition

Community structure is influenced by many factors, including abiotic factors, species interactions, level of disturbance, and chance events. Some species, such as keystone species, play particularly important roles in determining their communities' structure.

Species diversity

Diversity indexes provide a way to quantify the relationship between species number and relative abundance Simpson's index (D) = (ni/N)^2 = summation for all species ni = number of individuals of species i N = total number of individuals of all species D ranges between 0 and 1 and as both species' richness and evenness increase, the value approaches 0 Simpson's index of diversity = 1 - D The greater the value of D, the lower the diversity Simpson's reciprocal index or Simpson's diversity index = 1/D The lowest possible value is 1, representing a community containing only one species The maximum value is the number of species in the community (species richness: S)

Seral stage

Each seral stage is a point on a continuum of vegetation through time, it is often recognizable as a distinct community. A seral stage may last only one or two years, or it may last several decades.

Species richness

Species richness is the number of different species represented in an ecological community, landscape or region. Species richness is simply a count of species, and it does not take into account the abundances of the species or their relative abundance distributions.

Ecological community

The set of plant and animal species that occupy an area. species that are organized into food chains and webs in which each species is a consumer of resources and is itself a resource for other consumers.

total abundance

The total number of individuals of a species or type present in a given area, in a given ecosystem or within a particular habitat. Species richness refers to the number of species in an area. Species abundance refers to the number of individuals per species.

Species evenness

This term refers to the equitability in the distribution of individuals among the species. The maximum species evenness would occur if each species in the community was equally abundant

Be able to name questions ecologists study at the community level.

What controls the relative abundance of species within the community? How do the component species interact with each other? How do communities change through time? How do different communities on the larger landscape interact?

Dominant/ dominance

When a single or few species predominate within a community, these species are referred to as dominants. Dominance is the converse of diversity. Dominant species are usually defined separately for different taxonomic or functional groups of organisms within the community