Community ecology

what is community?

assemblage of many populations that live in the same place at the same time

how can community ecology occur

in a wide variety of scales and can be nested

what is community ecology

studies the factors that influence the number of abundance of species in a community

what is an ecosystem

system formed by the interaction between a community of organisms and it’s physical environment

what is ecosystem ecology

studies the flow of energy and the production of biomass (the total mass of living matter in a given area

what is species richness

number species in each community

what varies according to geographic range

the number of species of most taxa

what is increased in geographic range

polar temperate to maximum in tropical areas

what happens to topographical variation in geographic range

it increases

what is reduced by by geographical range

peninsular effet

how many hypotheses for latitudinal gradient’s are there

4

what is species -time hypothesis

an area that is stable and available will be occupied

how do communities differ with time

communities diversify, and/or gain species

why do temperate regions have less rich communities than tropical ones

they are younger and have only more recently recovered from glaciation.

what Is a support factor in species-time hypothesis

more worms in comparable unglaciated lakes than glaciated

what is a drawback for species-time hypothesis

limited applicability to Marine organisms

what is species-area hypothesis

a big area with space available will be occupied

why do larger areas have more species

they can support larger populations and a greater range of habitats

what support is there for species- area hypothesis

significant relationship between insect diversity and host tree range (species area effect

what is the problem with species - area hypothesis

there are not more species in Asia, tundra is the largest biome but low richness, open ocean with largest volume has fewer species than tropical surface waters

what is a species richness and evolutionary Time and area

as long as food is there, more animals will explore the land

what does this picture show

Insect species richness increases on older tree species

what is the picture showing

insect species richness increases on more widely occurring tree species

what is the species- productivity hypothesis

greater production of plants results in greater overall species richness

how can species - productivity hypothesis be represented

by evapotranspiration rate

how is the species productivity hypothesis supported

plants grow better where it is warm and wet and species richness in tress can be predicted by the evapotranspiration rate

what problems are there in the species - productivity hypothesis

some tropical seas have low productivity but high richness, sub-antarctic ocean has high productivity but low species richness

what is species richness

the number of species in a community

what is species diversity

relative role of species in a community

how can species richness and diversity be calculated

for various measures of importance (e.g, abundance, biomass, productivity)

what must you consider when you calculate species diversity

you must consider the number of species and their relative abundances within the community.

what is the Shannon diversity index

it measures the species diversity of a community

what does the formula show

the Shannon diversity index

what does Pi mean

proportion of individuals in species i

what does ln mean

natural logarithm

what does the photo mean

the summation sign

what is resistance in regards to the role of diversity in ecological community

the ability of a community to tolerate enviromental disturbance

wha does resilience in regards to the role of diversity in ecological community

a measure of speed with which a community returns to it’s original state following enviromental disturbance

what is Elton’s diversity - stability hypothesis

disturbances in a species-rich community would be cushions by large numbers of interacting species and would not produce as drastic as it would on a less diverse community

how long of a study did they researchers do to examine species richness and stability in grassland plots

11 years

what did the 11 year research find

year to year variation in plant community biomass lower in plots with greater species-richness

what is community change

a gradual and continuous change in species composition and community structure over time

what is primary succession

on newly exposed site not previously occupied by soil and vegetation

what is secondary succession

on a site that already supported life but has undergone a disturbance, such as fire, tornado, hurricane, or flood

what did Cedric Clements emphasize

succession has a distinct end point - the climax community

what can disturbance do

set the community back to an earlier stage

what happened after a community goes through a disturbance

it then proceeds again toward climax community

what does each colonizing species do to an environment

makes the environment a little different

what is facilitation

colonizing species change the environment so that is becomes more suitable for the next species

what did glacier bay use facilitation for

a mechanism of succession

over the past 200 years, how much has glaciers retreated

100 kilometers

what path has succession followed in regards to glacier bay

a distinct pattern of vegetation

what are some characteristics of a pioneer community

harsh environment, biomass increasing, energy consumption inefficient, some nutrient loss, low species diversity, fluctuations common, and r-adapted

what are some characteristics of climax community

favourable environment, biomass stable energy, consumption efficient nutrient, cycling, high species diversity, and low fluctuations and k-adapted

what is inhibition

early colonies may exclude subsequent colonists (if you got there first, you chose what the community looks like)

what is a primary method of succession in marine intertidal zone

early successional species at a great advantage in maintaining possession of valuable space

what is an example of inhibition

by removing the early colonist, Ulva, the red alga Chrondracanthus was able to to colonize more quickly

what is tolerance

any species can start the succession, but the eventual climax community is reached in a somewhat orderly fashion

what do species that establish and remain do to the environment

they do not change the environment in ways either facilitate or inhibit subsequent colonists

what is competition-intolerant tolerance

species more successful at first

what is competition-tolerant tolerance

species appear later and at climax

what are key differences between three models in the manner succession proceeds

facilitation, inhibition, and tolerance

what is facilitation in regards to the progression of succession

species replacement facilitated by previous colonists

what is inhibition in regards to the progression of succession

species replacement is inhibited by previous colonists

what is tolerance in regards to the progression of succession

species replacement is unaffected by previous colonists

can other factors influence succession

yes

what is the equilibrium number

what does the equilibrium number mean

reflects balance between rate of immigration and rate of extinction

how can these rates be curved

species arrive at different rates, and extinctions accelerate as more species arrive and complete

what are some example of the different curve rates h

how was the strength of island biogeography model created

generating testable predictions

what is the species-area effect

a number of species should increase with increasing island size

how should the number of species react with increasing distance from the mainland (the source pool)

should decrease

how would the turnover of species react even though the number may be at equilibrium

should be considerable

what is a prediction being made according to species richness and island size

the number of species should increase with increasing island size

what does this prediction summarize

the available data on the richness of species of four groups of animals (birds, bats, reptiles and amphibians, and butterflies)

how many islands are apart of this prediction

19 islands varied in an area over two orders of magnitude

what type of correlation was found between area and species richness

positive correlation

what is another prediction being made according to species richness and island size

number of species decreases with increasing distance from the source pool

what happened to the number of forest bird species in Polynesia

they decreased with the distance from New Guinea, the source pool

what is the latest prediction being made according to species richness and island size

species turnover on islands

why is it difficult to perform tests (for the prediction about species turnover on islands)

because detailed and complete species lists are needed over long periods of time

what was discovered in a review about turnover

less than 1% a year, due to immigrants that never became established and not due to extinction of well established species

what is a food chain

a linear depiction of energy flow

what is each feeding level in a food chain called

a trophic level

what do more complex models of interconnected food Chains have

a food web

what are autotrophs

harvest light or chemical energy and store it in carbon bonds

where are primary producers founded

from the base of the food chain

what is a chemoautotroph

oxidize inorganic compounds

what are heterotrophs

they eat other organisms

what do primary consumers do

they eat primary producers

what eats primary producers

herbivores

what do secondary consumers do

eat primary consumers

who eats primary consumers

carnivores

what do detritivores or decomposers eat

detritus

what are detritus

unconsumed plants, animal remains, and waste products

are food chains or food webs more realistic?

food webs

what is being shown in this photo

a food web

how long are chains lengths usually in food web

short (in most cases)

what does a chain length refer to

the number of links between the trophic levels involved