Chapter 55: Community Ecology

What is a community?
A group of populations of different species living close

What does community ecology study?
How the interactions between species affect community structure and organization

What do species primarily fight over in competition?
Resources that limit survival; sun, water, nutrients

What can competition result in for a species?
Elimiation, change in niche, change in morphology

What are the primary outcomes of competitve exclusion?
The stronger species will use resources more efficiently and reproduce

What is the species ‘profession’?
Its ecological niche, sum of abiotic and biotic resources

What allows species to coexist in similar habitats?
Resource paritioning

What is the niche with a species greatest potential?
Fundamental niche

What is the niche that a species actually occupies?
Realized niche

What is an example of fundamental vs. realized niche?
The muscles on a beach population changes during the tide

What is an example of temporarl paritioning?
The golden and common mice sleep cycles

Character displacement occurs most frequently in what type of populations?
Sympatric, ones derived from a common ancestor

What are the most important advantages predators have evolved?
Acute senses, speed, physical features, ambush or agile

What adaptations have prey evolved to protect?
Hiding, herding, alarm calls; physical changes

What is the difference between cryptic and aposematic coloration?
Hiding vs. a warning not to eat

What is the purpose of batesian mimicry?
A harmless species mimics a harmful or unpalatable one

What is the advantage of Mullerian mimicry?
Both species benefit from added protection from predators

What are the ways plants defend against herbivory?
Spines, thorns and chemical toxins (which humans enjoy)

What is symbiosis?
When two or more species live in direct, intimate contact with each other

What does the parasite gain?
Nourishment from its host

What is an example of mutualism in plants?
Nitrogen fixing bacteria and legumes

What is faculative symbiosim?
When each species can live independently

What is the benefical outcomes of facilitation?
Species 1 is either positive or no change, species 2 benefits — salt marsh example

What does the trophic structure describe?
The feeding structure between organisms

What is the food chain?
Transfer of energy up trophic

What is the food web?
The links between food chain

What does the energitic hyptohesis argue for short food chains?
Length is limited by primary producers and energy

What is different about the dynamic stability hypothesis from the energetic hypothesis?
Long food chains are unstable, and problems lower in the chain get magnified at the top

What could be one example of the dynamic hyopthesis?
Low levels of phytoplankton having a dramatic effect on fish population

What defines the dominant species?
Most abundant species; good at resource exploition.

How can the impact of a dominant species be tested?
Removing the domnant species and measuring its impact on other species — American Chestnut

What is unique about the American Chestnut experiment?
A fungus destroyed the dominant species (chestnut), but had little impact on the community (forest)

What is a keystone species?
Exerts a strong influence

What is an example of a keystone species?
When the sea otter eats the urchin, if removed the other populations are affected

What is the most important factor in the bottom-up model?
Nutrient levels at the lowest level (plant) determine trophic numbers higher up

What community structure is in the Top Down model?
Predators influence the # of herbivores, in turn the # of plants.

What is another name for the Tropic Cascade Model
The Top Down model

What can be the impact of a disturbance on a community?
Resource availaibilty changes or a species gets removed

What hypothesis says disturbances can be good for a community diversity?
The intermediate disturbance hypothesis

What occurs after a new species takes over an area after disturabnce?
Ecological succession

What is a primary succession?
A community forms from a non-existant one

What is unique about glacier bay in Alaska?
An ecologican community evolved from a moraine rock

What succession happens after a community leaves but the soil is left?
Secondary succession

What is species diversity?
The variety of organisms in a community

What is species richness
The number of different species in a community

What is relative abundance?
The proportion of each species to individuals

What does the Shannon diversity index measure?
The differences between richness and abundance

What is the Area Effect
The larger the geographic area, the more species it has

What is the single most important factor in species extinction?
Habitat degradation

Why is sudden oak death a good example of community ecology?
Pathogens, temperature, mouse population all impact the death rate of oak

What is the difference between direct contact and a vector for disease transmission?
vectors transmit pathogens from one host to another, ticks, lice, mosquitoes

Look up last slides on Lyme Disease

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