ecology exam 3

Arkansas state- mangan

extinction

loss of established species fro a patch; rate of extinction increases with number of species already established on patch; model assumes extinction is random,, therefore, if more species high chance species are lost

number of species at equilibrium

species richness is stable, but species compositions might be changing

turnover rate

rate at which a species is replacing the other

structural connectivity

the physical arrangement of patches; isolated patches> low connectivity; higher connectivity> less isolates maybe connected

corridor

area of similar habitat connecting patches (facilitates dispersal of organisms from one patch to another)

edge species

boundary edges separating patches have distinct environmental conditions, and species that are adapted to specialize in edges

landscape connectivity

the degree to which the landscape allows organisms to move from one patch to another

The SIR Model

simple model that predicts how infections will move through the populaiton

what does the SIR model stand for?

susceptible, infected, recovered

infection

how quickly susceptible individuals become infected

recovery

how quickly infected people recover

what are the 3 determinants of disease spread?

population density, transmission rate, infectious period

population density

number of individuals per unit area

transmission rate

depends on rate of contact between infected and susceptible individuals that leads to new infection

infectious period

the average period of time an infected person can transmit

simple assumptions of disease spread

1. direct infection only
2. no evolution
3. does not consider new births or deaths
4. once recovered you can never get disease again

epidemic curve

red curve, number of active infections over time, flatten the curve

basic reproductive number (R0)

average number of susceptible individuals that a single infected individual infects

disease will decline

R0

disease will remain in population, but no outbreak or epidemic

R0=1

disease will increase, and outbreaks are possible

R0>1

what does basic reproductive number depend on?

disease, region/environment

herd immunity

when a large portion of the population becomes immune to a disease, making the spread of disease unlikely

what are 2 ways herd immunity can increase?

1. through immunity as a result of recovering from infection
2. through vaccination

the _________ is a critical value in understanding what percentage of the population is needed to be vaccinated to obtain herd immunity

basic reproductive number

critical information threshold

minimum number of individuals that need to be vaccinated to reach herd immunity

small R0=

less of the population needs to be vaccinated

larger R0=

much more of the population needs to be vaccinated

community

set of interacting populations of species in the same living area

direct community interactions

predation, competition, mutualism

community structure

the identities of species an environment contains and how abundant each species is in that environment

community composition

another name for community structure

relative biomass

amount of biomass each individual contributes

species diversity

1. quantifiable measure of community structure
2. the number of species a community contains
3. the number of individuals of each species in that community

species richness

the number of species in a community

species abundance

the number of individuals per species

relative species abundance

proportion (or percentage) that each species contributes to the total number of individuals of all species in a community

dominant species

species that contain the majority of individuals (or biomass) making up the community

rare species

contains few individuals

species evenness

an important characteristic of a community that refers to how equal the number of individuals are distributed across a species

David Tilman

classic cedar creek experiment

alpha diversity

species richness and evenness at a given location

examples of alpha diversity

simpson’s index, shannon’s index

simpson’s index

considers only species richness

shannon’s index

both species richness and evenness

beta diversity

the change in species identities and abundance across locations

examples of beta diversity

Jaccar’s index, Bray-Curtis index

Jaccard’s index

only species identity

Bray-Curtis Index

species identity and abundance

3 trophic levels

carnivore, herbivore, primary predator

indirect mutualism

when a higher trophic level benefits abundance of another trophic level through indirect interactions

trophic cascades

when the addition or removal of a top predator causes changes in population sizes throughout the food web

keystone species

a specie that has a disproportionate effect on the community relative to its abundance

Top-down control

the world is green because carnivores control herbivores, which allows for plant species biomass to remain high

bottom-up control

the amount of plant species biomass determines how many trophic levels the environment can support

Fredrick E Clements

viewed communities as superorganisms

Henry A Gleason

viewed species as independent, and communities are not superorganisms

ecotone

distinct transitional zones between community types

examples of ecotones

aquatic-terrestrial, grassland-forest, north versus west slopes

robert whittaker

one of the first to collect enough data to test whether clement’s or gleason’s view of the world was correct

regional species pool

which species COULD make up a community

community assembly

a more modern day view of what determines species identity and their abundance in a given community

dispersal

often times a random process

environmental filters

are the abiotic conditions suitable?

species assembly

determined by random chance, environmental filters and species interactions

species sorting

once species establish populations in a community, all of the interactions determine who stays and whose population grows

community dynamics

change in species composition over time; usually response to a minor or major disturbance

disturbance

an event that removes or changes the abundance of a species in a community

catastrophic disturbance

destroys all members of the community and exposes new substrate

non-catastrophic to minor disturbance

removes some species, or changes the abundance of some species; forest fires, invasive species, harsh winter, drought, nutrient pollution

succession

directional change in community composition over time

primary succession

occurs after catastrophic disturbance on newly exposed geological substrates that haven’t been modified by organisms; ex: new lava, newly exposed islands, melting glaciers, newly formed sand dunes

secondary succession

occurs after non-catastrophic disturbance kills some members of a community but leaves the substrate intact

chronosequence

selecting and studying sites differing in known ages; ex: sand dunes

Henry Cowles

used a chronosequence of different sand dunes of known age to study succession; determined sand dune ages of Lake Michigan based on historical photos; used primary succession

Peter Vitousek

chronosequence of Hawaiian islands to study primary succession of biological communites

william cooper

established long term monitoring plots in areas that were recently exposed because of melting glaciers

pioneer species

early successional species; good dispersers, fast growers, can tolerate harsh conditions, but are poor competitors and are short lived

late successional species

poor dispersers, slower growers, require developed substrate, are good competitors, and tend to be long lived

autogenic

when environmental changes are caused by species in the community; ex: glacier bay national park

intermediate disturbance hypothesis

species diversity is highest under moderate disturbance

what does community response to disturbance depend on?

disturbance regime (type, timing, severity, spatial extent, frequency), how the species making up the community and how they respond (resistance, return/recovery time, resilience)

resistance

indicates the degree to which a community is altered by disturbance

recovery time

time in which a disturbance-altered community returns to its original structure

resiliency

indicates the degree to which communities return to their original community structure following the disturbance

shifting mosaic

landscapes are dynamic, shifting community types over time because of small disturbances

climax community

end point succession; community is at equilibrium; no change in species composition with time; assumes disturbances are no longer occurring

landscape ecology

focuses on processes that lead to change in species composition across larger scales

patches

distinct communities or ecosystems

matrix

surrounding area that differs from the patch (can be a barrier to dispersal)

boundary

area of transition between patch and matrix

functional connectivity

degree to which landscape allows movement

tyson research center glade experiment

lots of large scale manipulative experiments looking at the effect of patch size on species diversity

glades

unique plant communities in forests similar to prairies; historically maintained by fire

two prominent models in landscape ecology

1. theory of island biogeography
2. metapopulation theory

theory of island biogeography

EO WIlson, Robert MacArthur; predicts species diversity based on patch size and isolation from mainland (species pool); predicts the number of species occupying a patch is determined by a balance of immigration and extinction

immigration

number of new species colonizing; rate of immigration declines with number of species already established on patch; less niches available, more competition

local extinction

loss of species from a patch (island); more isolated islands will have higher rates of local extinction; a species population on closer islands have higher chance of being rescued from a population established on the mainland

metapopulation

a group of spatially distinct subpopulations, but are not reproductively isolated (gene flow can occur among subpopulations)