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?
What is the niche with a species greatest potential?
What is the niche that a species actually occupies?
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?
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?
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?
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