Ecology Test 3

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Community

Back 1

a group of species that occupy a given area and interact directly or indirectly

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Guild

Back 2

a subset of species that share similar resources and are potential competitors ("community of seed-eating birds")
guild and functional groups are often overlapping

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functional group

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a subset of species that perform a similar functional role ("decomposer community", "habitat-forming community")
guild and functional groups are often overlapping

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richness

Back 4

total number of species

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evenness

Back 5

how many individuals in each species

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area

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where does one zone begin and the other end? geography shapes community composition; community competition provides structural complexity

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simpson's index

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D= [(sum)Pi^2]^-1
higher D= higher diversity
D weights eveness more heavily than H

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Shannon's index

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H= - (sum) Pi ln(Pi)
based on the concept of "will the individual sampled next be in the same species, or a different species?"
higher H= higher diversity

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relative abundance = ?

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= (# individuals of species i) / ( total # individuals of all species)

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species rank = ?

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= order of species from high to low.

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what does a species abundance curve show?

Back 11

a graphical method for describing richness and evenness.

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a (alpha) diversity

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richness or diversity in a single geographical location (S,D, or H)

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B (beta) diversity

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change in total # of species (or a diversity index) when you add a new location.

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y (gamma) diversity

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total # of species (or total diversity) in all locations

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Change in diversity over space equation

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a + B = y
alpha + beta = gamma

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foundation species

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"ecosystem engineers"
a species that has large, community-wide effects by virtue of its size or abundance, its strong competitive ability, or its provision of habitat or food for other species.
able to create, modify, or maintain physical habitat for themselves and other species.

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primary producers

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an organism that can produce its own food by photosynthesis or chemosynthesis (autotroph)

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primary consumer

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herbivores

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secondary consumers

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carnivores

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tertiary consumers

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carnivores that feed on secondary consumers.

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omnivores

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feed on more than one trophic level

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effects of competition on diversity

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evolutionary time scale: speciation, inc. in diversity
ecological time scale: competitive exclusion, loss of diversity (invasion)

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effects of predation/parasitism on diversity

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can reduce competitive exclusion (inc. diversity)
invasions can eliminate species (dec. diversity)

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effects of mutualism on diversity

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usually inc. diversity

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direct interactions

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occur between two species and include trophic and non-trophic interactions

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indirect interactions

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occur when the relationship between two species is mediated by a third (or more) species.

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dominant species

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a species that has large, community-wide effects by virtue of its size or abundance, its strong competitive ability, or its provision of habitat or food for other species, also called a foundation species.

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keystone species

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a strong interactor that has an effect on energy flow and community structure that is disproportionate to its abundance or biomass.

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trophic level

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a group of species that obtain energy in similar ways, classified by the number of feeding steps by which the group is removed from primary producers, which are the first trophic level

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diversity

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The number and variety of species present in an area and their spatial distribution.

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succession

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transition in community composition over time, usually following disturbance.

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primary succession

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all life eliminated. (by natural disaster)
recolonization from bare substrate

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secondary succession

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disturbance but some organisms remain
not always caused by humans (forest fire, wave disturbance on shore)

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pioneer species

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The first species of trees to establish in an area after a disturbance

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mid-successional species

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Grasses and low shrubs that are less hardy than early successional plant species

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climax species

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also called late seral, late-successional, K-selected or equilibrium species, are plant species that will remain essentially unchanged in terms of species composition for as long as a site remains undisturbed. They are the most shade-tolerant species of tree to establish in the process of forest succession.

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facilitation

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early successional species modify the environment and facilitate later successional species.
EX: weeds that colonize sand dunes retain moisture and allow other plants to colonize. Other species that can stabilize on bare sand come in because initial species have already stabilized that area.

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inhibition

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first arrivals outcompete species who arrive later
gradual transition from short-lived to long-lived species

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tolerance

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early and later successional stage species do not facilitate or inhibit each other.
later species better tolerate lower levels of some resources.
In other words, whatever species can outlast the other one will eventually be in long-term equilibrium. Any species that cannot tolerate condition will die off.

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autogenic change

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produced by successional community itself (related to facilitation)

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allogenic change

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purely abiotic environmental shifts (lake filling in)

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intermediate disturbance hypothesis

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proposing that species diversity in communities should be greatest at intermediate levels of disturbance (or stress or predation) because competitive exclusion at low levels of disturbance and mortality at high levels of disturbance should reduce species diversity.

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ecosystem

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the whole system including not only the organism-complex but also the whole complex of physical factors forming what we call the environment
basic units of nature

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energy

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the ability to perform work
potential, kinetic, gravitational, sound, electromagnetic, etc.
units: joules, calories, kilocalories (="Calories")

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work

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transfer of energy (movement of a mass over some distance)
units: joules (energy used to apply 1 newton over 1 meter)

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power

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rate at which work is done (or energy is transferred)
units: watts (1 joule transferred per second)

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force

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acceleration of a mass
units: newton (1kg accelerated by 1m/s^2)

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thermodynamics

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conservation of energy:
-energy cannot be created or destroyed, but it can change forms
-in an isolated system, the total energy remains constant
entropy always increases:
-in any exchange of energy, the total amountof entropy increases
-no energy transfer is 100% efficient (some energy always lost as heat)
-heat doesnt flow from cold to hot (without adding energy)

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entropy

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a function of thermodynamic variables, as temperature, pressure, or composition, that is a measure of the energy that is not available for work during a thermodynamic process. A closed system evolves toward a state of maximum entropy. (measures level of disturbance/disorder)

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open system

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(ecosystem) A material system in which mass or energy can be lost to or gained from the environment.

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closed system

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(earth) no transfer of matter

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isolated system

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a physical system without any external exchange. If it has any surroundings, it does not interact with them. It obeys in particular the first of the conservation laws: its total energy - mass stays constant. Matter and energy cannot enter or exit, but can only move around inside.

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biomass

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. the amount of energy captured by autotrophs that results in an inc. in living plant matter, or biomass. the amount of organic matter present
units: gm^-2 (dry organic matter)
(the gas in your tank)

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GPP productivity

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gross primary productivity- the amount of carbon fixed by the autotrophs in an ecosystem.

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NPP productivity

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net primary productivity- the total rate of photosynthesis or energy assimilated by autotrophs. the balance between GPP and autotroph respiration
(=change in standing crop biomass + death + consumption)
affected by precipitation, temperature, nitrogen mineralization)
temp, water, and nutrients all combine to limit NPP

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trophic efficiency

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the amount of energy at one trophic level divided by the amount of energy at the trophic level immediately below it.

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primary productivity

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the chemical energy generated by autotrophs. is derived from the fixation of carbon during photosynthesis and chemosynthesis.
-the conversion of light energy from the sun into chemical energy that can be used by autotrophs and consumed by heterotrophs. "rate of primary production"

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secondary productivity

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energy that is dervied from the consumption of organic compounds produced by other organisms- heterotrophs.

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net ecosystem productivity

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the balance between ingestion, respiratory loss, and egestion

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oxidation reaction

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low potential energy compound that gives up or donates electrons.

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reduction reaction

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high potential energy
compound that accepts electrons

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Herbivores

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organism that feeds on plant tissue
ex:Rabbit, Cows, Horses

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Ecosystem Engineers

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any organism that creates or modifies a habitat.
Allogenic engineers modify the environment by mechanically changing materials from one form to another. Ex: Beavers - effects of their dams on channel flow
Autogenic engineers modify the environment by modifying themselves. Ex: trees growing branches and trunks giving habitats to others.

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Fragmentation

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reduction of a large habitat area into small, scattered remnants. Reduction of leaves and other organic matter into smaller particles.

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Mineralization

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Microbial breakdown of humus and other organic matter in soil to inorganic substances.

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Dissolved Organic Matter (DOM)

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material less than 0.5 micrometer in solution. One source of DOM is rainwater dropping through overhanging leaves, dissolving the nutrient-rich exudates on them.

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Particulate Organic Matter (POM)

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Dead organisms and other organic material that drifts toward the bottom.
Usually found in open water of ponds and lakes and in sea.

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Treatment

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The manipulation of a variable in a predetermined way and to monitor the response of the dependent variable.

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Control

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A group of individuals (replicates) that do not receive the treatment, but otherwise are handled exactly like the treated plant.

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Replicate

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Individuals receiving the treatment

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fragmentation

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enhances the chemical breakdown of the litter by increasing its surface area.

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mineralization

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the chemical conversion of organic matter into inorganic nutrients (it is the result of the breakdown of organic macromolecules in the soil by enzymes released by heterotrophic microorganisms.

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DOM

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dissolved organic matter (excretion,photosynthetic exudate

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POM

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particulate organic matter (dead planktonic organisms)

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CDOM

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colored dissolved organic matter (DOM with tannins, many other components

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allochthonous inputs

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energy produced outside the ecosystem. plants leaves stems, wood, and dissolved organic matter that fall from adjacent terrestrial ecosystems or flow in via ground water to aquatic ecosystems. usually lower quality

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autochthonous input

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energy produced inside the ecosystem.

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atmospheric nitrogen

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N2
organism cant use directly

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Nitrogen oxides

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NO, NO2, N2O
organism cant use directly

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nitrite

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NO2-
form accessible to plants

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nitrate

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NO3-
form accessible to plants (most)

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ammonium

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NH3, NH4+
form accessible to plants

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organic forms of nitrogen

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form accessible to plants are mineralized into the organic form
amino acids, nucleic acids, other organic forms.

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nitrogen fixation

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N2 ---> NH3, NO3-

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ammonification/ mineralization

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organic N ----> NH3

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nitrification

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NH3 -----> NO2- ------> NO3-

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denitrification

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NO3- -----> N2

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anommox

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NO2- + NH4+ -------> N2

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top-down regulation

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regulation on population and community structure through consumers. higher level decrease, lower level increases.

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bottom-up regulation

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regulation of population and community structure through the producers. level above influenced by the recourses provided by the level below.

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Pseudoreplication

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Sampling one area or individual instead of multiple or diverse areas. Data in dependent not independent.

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equilibrium

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point at which system no longer changes on its own

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stability

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does the system exhibit a "return tendency" if perturbed?

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invasibility

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can X increase in abundance if at low density of frequency?
-if x is invasible, it will be part of the equilibrium.
-invasibility is context-dependent.

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Abiotic

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N03 ---> N2

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alternative stable states

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different communities develop in the same area under similar environmental conditions. (kelp forest vs. barren)

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net vs. gross primary production

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GPP is total ecosystem photosynthesis, NPP is the energy remaining after respiratory loss.

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factors affecting NPP on land and sea

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land: climate factors
-inc. as average annual precipitation inc. then dec at higher levels
-inc. w/ average annual temp.
(directly linked with water availability and temp)
Sea: nutrient availability

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trophic pyramids

Back 99

a stack of rectangles is constructed each of which represents the amount of energy or biomass within on trophic level
the tendency toward inverted biomass pyramids is greatest where productivity is lowest, such as in nutrient poor regions of the open-ocean

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trophic cascade

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a change in the rate of consumption at one trophic level that results in a series of changes in species abundance or composition at lower trophic levels

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factors affecting the rate of decomposition

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more rapid in warm temps
highest at intermediate soil moistures (low at dry and wet soil)
high C:N ratio in organic matter will result in a low net release of nutrients.secondary compounds slow decomp. by inhibiting the activity of heterotrophs.
the chemistry of the carbon determines how rapidly the material can decompose.

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major biomolecules that use C, H, O, N, P, and S

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organic molecules (C, H, O)
amino acids, proteins, nucleic acids, chlorophyll (N)
nucleic acids, phospholipids (P)
amino acids, proteins (S)
everything decomposes quickly except for cellulose, and slower than that lignin.

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turnover

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the mixing of the entire water column in a stratified lake when all the layers of water reach the same temp and density.
the replacement of one species with another over time or space.

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stratification

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the layering of water in oceans and lakes due to differences in water density and temp with depth.

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oligotrophic

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nutrient-poor waters with low primary productivity

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eutrophic

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nutrient rich waters with high primary productivity

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fertilization effect hypothesis

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inc. atmospheric CO2
inc. photosynthesis rates
inc. sequestration of carbon in plant biomass
CO2 has an overall 25% increase in NPP
(inc CO2, primary productivity inc., it helps plants reduce competition. carbon is limiting)

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Carbon Cycle

Back 108

Main Reservoirs - atmosphere, oceans, land surface (soils and vegetation ) sediments and rock.
Largest - combination of sedimation and rock - makes up 99 percent of global carbon.
Processes involved - diffusion, photosynthesis, respiration, combustion and carbonification.
Net uptake of carbon from the atmosphere at the ocean surface.
Terrestial pool has the most biologically active carbon.

GPP brings down carbon (positive value).
Respiration - sending carbon back into the atmosphere.
Plants use Rubisco to change carbon dioxide into a carbohydrate.

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Thermohaline Circulation

Back 109

Gulf Stream - warm and sits on the surface of the oceans. One it is up at the North sea it cools very fast and fresh water freezes out and salt stays.
Cold and salty - much denser
As this process happens it tends to sink. The water that was the Gulf Stream sinks to the bottom of the ocean then runs along the surface of the ocean basin. Follows a path of getting deeper. Surface of Pacific Ocean is higher than the surface of the Atlantic Ocean. Takes about ten thousand years. Causes upwelling near Alaska and the Indian Ocean. Warm surface water transfers to the polar regions then is dragged down to the bottom.

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Nitrogen Cycle

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Rate of internal cycling is much greater than nitrification and biological fixation.

pools - terrestrial N2 fixation by bacteria and decomposition.
Oceanic N2 fixation.
Denitrification moves N from terrestrial and marine pool into the atmosphere.
Loss of nitrogen through burial of organic matter and burning of biomass.
anthropogenic processes dominate components of the nitrogen cycle.
recycling at ocean surfaces, internal cycling in the ocean, and internal cycling of the land through plants and human activities.
Largest pool - atmospheric N2.
Processes - denitrification, biological fixation, fixation and lightning.

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Phosphorous

Back 111

No atmospheric pool, primarily internal cycling in terrestrial soils and marine sediments.
limits primary production in some terrestrial ecosystem. C,N, and P are linked to one other through photosynthesis, NPP, and decomposition and N2 fixation.
Movement of phosphorous from terrestrial to aquatic ecosystems occurs primarily through erosion and movement of POM into streams.
Anthropogenic effects: fertilizers, sewage and industrial waste, and increase in terrestrial surface erosion.

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Sulfur

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Major Pools - rocks, sediment and the ocean.
Net movement of sulfur from the terrestrial pool to the organic pool associated with transport and rivers and in atmospheric dust.
Oceans release sulfur through wind born ocean spray.
Arthropogenic emission- burning coil and oil.

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CLAW Hypothesis

Back 113

More sun reflected on the ocean --> warms the ocean --> which then enhances phytoplankton growth -->which then enhances DMS production ---> which then there is elevated DMS concentration --> elevated SO2 concentration -->more cloud concentration nuclei --->> enhanced droplet number liquid water content cloud area.

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Thermal Expansion

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accompanies mixing of heat into the ocean long after Carbon Dioxide emissions have stopped.