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an association of pops of different species interacting with one another in the same location, habitat or environment.

defining feature of communities

species composition (richness) and diversity (evenness).

defining feature of communities

the kinds of interactions between community members

defining feature of communities

abiotic interactions between climate, topography and habitat, and their affects on community members

defining feature of communities

the availability of food and resources

defining feature of communities

the adaptations or ecological roles (niche) of community members.

defining feature of communities

ongoing trends, changes, or dynamics impacting community structure.

ecological niche

the specific role that each species plays in its community, including its habitat resource requirements (food, nutrients, energy, shelter) and the kinds of interactions with other species.

Producers (autotrophs)

organisms that produce the food or chemical energy that sustains the community. includes photoautotrophs and chemoautotrophs.

Consumers (heterotrophs)

organisms that feed on other members of the community to obtain their energy and resources.


consumer that only eats plants


consumer feeding on decayed particles of organic matter


consumer that eats meat


interaction occurs between members of one or more species utilizing the same resources (e.g. light, space, nutrients, etc) of a given habitat which are in limited supply.


most common interaction between members of a community


does not occur when resources are abundant


always has neg effects (suppressed growth) on both species

Competitive exclusion principle

document by G.F Gause studies of two species--paramecium---which formulates ___ ____ _____ that no two species can indefinitely occupy the same niche at the same time.


the gradual and orderly process of change in an ecosystem brought about by the progressive replacement of one community by another until a stable (climax) community is established. (get pioneer species--most plants are going to be annuals)


plants that produce a lot of seeds, seeds dispersed, germinate, plant grows for one cycle, then parent plant dies back. Next group of plants referred to as perrenials (persist from one year to the next)


plants that persist from one year to the next.

Climax species


Primary succession

succession that occurs in newly exposed or created barren habitats that have no prior history of plant or animal life

Secondary succession

succession that occurs in disturbed habitats where plant and animal communities previously existed.

Bare-rock succession

watering and soil formation are critical; pioneer species include bacteria, algae, lichens, mosses; accumulation of dust and organic mater contribute to soil developmen; progressive habitat modification or improvement allows new successional species to invade and take over; may take ~1000 years.

Bare-rock succession

islands of Hawaii were created by this

lichens, mosses, algae, bacteria

first things to grow in bare-rock succession

stone crops

primitive vascular plants that appear to grow on stones--actually grows on poor soil (no water in rock--so dry out but rehydrate during next available rainfall)

lichens and algae

provide nitrogen to the rock area in rock-barren succession

Agricultural land succession

soil is already formed; seeds of many pioneer species are already present in the soil, others invade; pioneers include weedy annuals, then weedy perennials.

Relay Floristics Models

groups of species migrate to habitat at the same time, then occupy and modify habitat for the next association; the same climax community is eventually established; aka the facilittation model

Initial floristic composition model

almost all species are randomly present at abandonment; abundance depends on how fast they mature and reproduce; slower, long-lived species eventually dominate; aka the "tolerance model"


a dynamic, often changing web of interactions between all the living (biotic) species or components of a specific habitat, including their interactions with the non-living (abiotic) physical components of the environment associated with that habitat.

Biotic components

producers, consumers, decomposers, detritivores

Abiotic components

climate conditions (temp, rain, seasons, etc.), resource pools.


bears, turtles are both


part of food chain, feeding on reminents of organic matter (earthworm, etc)


breakdown organic matter after detritivores got to it; break down the last of it and release minerals

energy flow

flows through ecosystem in every possible way; law of thermodynamics says no ___ ____ is not 100%

energy flow

is directional (into, through and out of the ecosystem).

chemical flow

is cyclical (remaining within an ecosystem).


source of energy in all ecosystems--captured by plants which is reflected back by water, clouds, etc. 20% absorbed by the atmosphere. Rest of it used to heat the land/water.


an important chemical that cycles in the atmosphere

Biogeochemical cycles

a pathway (or process) by which nutrients (or chemicals) and abiotic (lithosphere, atmospher and hydrosphere) components (or compartments) of an ecosystem.

energy flow

this flow is often modeled after carbon flow. Once Photosynthesis occurs, we have something to estimate ___ ____ in the ecosystem.

Hydrologic Cycle

Balanced by P = E + T + R + I (Evaporation + Transpiration + Runoff + Infiltration)

Hydrologic Cycle

a major driving force for nutrient cycling.

20 barrels

amount of water transpired in an oak forest--removes moisture from soil and moves back to the atmosphere--cools the leaves


soil percolation in the oak forest hydrologic cycle


how botanists measure the amount of moisture in a plant; uses standard inverted pipettes (equilibrium stuff that measures mm increments).


in oak trees, they measure transpiration by making a huge cut in the tree and making a giant ____. Build scaffolding around it to support tree. put a huge vessel beneath it and pour water continuously.

quantify moisture evaporated by trees

reasons for measuring moisture in a forest

clear cutting

way of quantifying the amount of moisture in the trees


device plant ecologists use to measure transpiration in cut plant parts. (DOES NOT MEASURE EVAPO-TRANSPIRATION)


reduced carbon that measures energy.

Carbon Cycle

the cycle of CO2 through the atmosphere; use biomass to measure reduced carbon that measures energy

Sediments and rocks (carbonate ions--limestone)

the largest amount of carbon reserve on Earth.

Limestone (carbonate ion), fossil fuels (coal, oil)

the forms of the largest amount of carbon reserve on Earth.

Bicarbonate ion

main form of carbon in the oceans on Earth.

bicarbonate ion

main for of carbon in the soil on Earth.


creates the greatest flux of carbon on earth. 120 tons move from atmosphere to plants.

Cellular respiration

represents the same amount of carbon (60 gigatons each) back to the atmosphere that photosynthesis takes away (120)

global warming/greenhouse effect

increase in CO2 in the atmosphere causes _____.

greenhouse effect

CO2 levels arising steadily and, thus, causing global warming.

infrared wavelengths

wavelengths that cannot pass through glass.

Nitrogen Cycle

cycle of nitrogen throughout the ecosystem.


has the largest reservoir of nitrogen (78% nitrogen)


second largest reservoir of nitrogen on Earth.


third and biggest jump in amount of reservoir percentage reserve on Earth.

Terrestrial biomass

35 billion metric tons for nitrogen reserve

marine biomass

0.37 billions of metric tons of nitrogen reserve on Earth.

N2 fixation

microbial--(4N2+6H20-->4NH3) how atmospheric nitrogen gets introduced into the ecosystem in bacteria and animals; chemical (N2+3H2-->2NH3)--requires high temp and pressure--convert nitrogen and hydrogen into ammonia--processed for fertilizer.


conversion of ammonia or ammonium to nitrate. Plants prefer nitrate--biological activity to convert this--two step reaction. Step 1: (2NH4 + 3O2 --> 2NO2 + 4H + 2H2O); Step 2 (2NO2 + O2 -->2NO3)

Uptake and Assimilation

(NH4 + NO3-->amino acids)


NO3-->N2 (and other N gases) via obligate anaerobic bacteria.


conversion of already reduced ammonia (nitrogen) in form of amino acids back to ammonium-->ammonium plus one charge easily coverts to ammonia gas.

N Deficiency in corn

corn is one of the most nitrogen intensive crops we have typically in form of nitrate; patches of yellow in the crop is due to ___.


plants love this chemical

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