BIOL&213 Chapter 53: Community Ecology

Community

Consists of all the populations of various species living in one area

Diversity

A measure of the variety of species present in a community

What are the two measures used to test the diversity of a community?

Richness and relative abundance

Species richness

the total number of species present in a community

Relative abundance

the number of individuals in each species in a community

What are the benefits of community diversity?

Stability, productivity, withstanding and recovering from environmental stressers, resistance to invasive species

Invasive species

species that become established outside their native range

Dominant species

The most prevalent species in a community, either by biomass or individual count

What are examples of species that dominate terrestrial environments?

Plants: grasses (grasslands) and trees (forests)

What are examples of species that dominate aquatic environments?

Algae/animals: kelp (kelp forests) and coral (coral reefs)

Keystone species

A species that makes up a small proportion of the community but has a significant impact

What are examples of keystone species?

Gray wolves in Yellowstone and starfish in intertidal zones

Trophic level

A representation of the type of food an organism consumes/energy sources it uses

What are the three types of trophy?

Producers (autotrophs), consumers (heterotrophs), and decomposers (saprophytes)

What is the typical organization of a food chain?

Primary producer, primary consumer, secondary consumer, tertiary consumer, quaternary consumer

Food chain

A heirarchial organization of the trophic levels of a community

Food Web Diagram

Map used to describe the food relationships between organisms, arrows point from consumed to consumer

What is an example of a typical terrestrial food chain?

Sunflower, crickets, rats, snakes, hawks

What is an example of a typical aquatic food chain?

Phytoplankton (diatom), zooplankton (copepod), herring, salmon, orca

Competition

The battle between two organisms over shared limited resources like food, space or mates

Competitive Dominance

When an organism has the ability to entirely displace another organism for space

Community stability

A measure of a community’s ability to resist change and recover after a disturbance

Disturbance

An event that changes a community, removes organisms from it, and alters resource availability

Ecological succession

The process of species composition and environmental resource or physical changes in a community post-disturbance

What are the two types of ecological succession?

Primary and secondary succession

Primary succession

When a community grows in a site previously unoccupied by a community

What is an example of primary succession?

laval flows exposing new glacial till, lichens coloinze, create new soil, plants colonize

Secondary succession

When a new community develops on already existent land or soil, taking over the vegetation in that area

What is an example of secondary succession?

Plants grow in an abandoned crop field

Pioneer species

Species that are first to colonize a new territory

What are the defining characteristics of pioneer species?

High growth rates, small size, high degree of dispersal, and high rates of per capita population growth

What are examples of pioneering species?

Bacteria, moss, grass, lichens

Late Successional Species

Species that secondarily colonize a new territory

What are the characteristics of late successional species?

Lower rates of dispersal and colonization, slower per capita growth rate, and are larger and longer-lived

What are examples of late successional species?

Shrubs, trees

Climax community

Can result from succession, is a self perpetuating plant community

What is an example of community progression?

In Glacier Bay, Alaska, firewood dominates the pioneer stage, then dryas, then alder, then spruce

Interspecific competition

Competition between two species over the same shared resources

Competitive Exclusion Principle

Two species that compete for the same resource cannot coexist in the same habitat

Resource partitioning

The differentiation of ecological niches across similar species coexisting in a community, which allows for competition minimization

What is an example of resource partitioning?

A. distichus (lizard species) sits on fence posts and other sunny surfaces, while A. insolitus prefers shady branches, allowing them to coexist on the same tree.

Species niche

The sum of all an organism’s interactions with the environment (its occupation)

Fundamental niche

The niche a species would potentially occupy

Realized niche

The niche a species actually occupies

What are the different kinds of anti-predator mechanisms?

Mechanical defenses, chemical defenses, aposematic coloration, cryptic coloration, batesian mimicry, mullerian mimicry

Examples of mechanical defenses?

Armor, quills, fangs

Examples of chemical defenses?

Poisons, obnoxious chemicals (sknunk spray), and toxins

Aposematic coloration

Bright colors that advertise toxicity

Cryptic coloration

Color patterns that blend in with the environment

Batesian mimicry

When an edible species mimics a toxic one

Mullerian mimicry

When txo toxic species mimic each other

Symbiotic relationship

Close interactions between two species where one species acts as the host and the other acts as the guest

What are the three types of symbiotic relationships?

Parasitism, commensalism, and mutualism

Parasitism

A form of symbiosis where the guest feeds directly from the host, either internally (endoparasites) or externally (exoparasites)

What is an example of parasitic species?

Mosquitos, leeches, giardia

Commensalism

A form of symbiosis where the guest benefits from its host without harming or benefitting it

What are some examples of commensalist relationships?

Cattle egret and grazers, or nesting birds and trees

Mutualism

A form of symbiosis where the guest and host species both benefit from one another

What are some examples of mutualistic relationships?

Clown fish and anemones, lichens and plants