ENVS 200 Final Exam

metapopulation

a population consisting of a collection of subpopulations, each one of which has a realistic chance both of going extinct and of appearing again through recolonization.

habitat patches

Areas of suitable habitat for a species that are separated by areas of unsuitable habitat.

disturbance

Event that opens up a Gap

Gap

patches within which many species suffer local extinction simultaneously. (In forests, high winds, elephants, or simply the death of a tree through old age)

founder-controlled communities

community where species are approximately equivalent in their ability to invade gaps and can hold the gaps against all comers during their lifetime. On each occasion that a population goes locally extinct a gap is opened up for invasion.

Priority Effect

effect between competing species in which the species that arrives first at a site is able to hold it against competing invades, whatever the outcome would be if they competed as simultaneously arriving equals.

dominance-controlled communities

communities where some species are competitively superior to others and an initial colonizer of a patch cannot necessarily maintain its presence there.

community successions

disturbances that open up gaps lead to reasonable predictable sequences of species, because different species have different strategies for exploiting resources - early species are good colonizers and fast growers, whereas later species can tolerate lower resource levels and grow to maturity in the presence of early species, eventually out-competing them.

climax stage

community reaches a point when the most efficient competitors oust there neighbors. In this sequence, if it runs its full course, then number of species first increases (because of colonization) then decreases (because of competition).

primary succession

sequence of species, where an opened-up gaps has not previously been influenced by a community

secondary succession

subsequent sequence of species where the species of an area has been partially or completely removed but seeds and spores remain.

Chronosequence

a sequence of communities that exist over time at a given location (as a glacier retreats, the first stage of the succession may be observed just beyond its tip, with later stages strung out further down the glacial valley, this series of communities currently in existence can be used to infer what the succession must have been.

food web

complex web of interactions between an organism, and other predators, parasites, food sources, and competitors within its community.

Tropic level

each of several hierarchical levels in an ecosystem, comprising organisms that share the same function in the food chain and the same nutritional relationship to the primary sources of energy.

direct effects

the direct impact of one individual on another when not mediated or transmitted through a third individual (cheetah captures a gazelle or a bee pollinate a flower, then you have observed a direct effect in action). Separated into categories such as predation, competition, mutualism, etc.

indirect effects

the impact of one organism or species on another that is mediated or transmitted by a third. In other words, A (donor) has an effect on B (transmitter), which then affects C (recipient).

super predator

a predator at the top of a food chain, with no natural predators.

trophic cascade

occurs when a predator reduces the abundance of its prey, and this cascades down to the tropic level below, such as that prey's own resources increase in abundance.

top-down control

when a consumer limits a prey population. Typically the predators controlling the abundance of the herbivores, so called top-down control.

bottom-up control

The abundance of predator populations at higher trophic levels is regulated by the abundance of prey populations at lower trophic levels

meta-analysis

structured analyses of large numbers of of data sets with a view to discerning consistent trends

Why is the world green?

the world is green because top-down control predominates: green plant biomass accumulates because predators keep herbivores in check.

typical sequence of dominant vegetation

annual weeds > herbaceous perrenials > shrubs > early successional trees > late successional trees

species richness

the number of different species in a community

diversity indices

measures that combine both species richness and the evenness or equitability of the distribution of individuals among these species

purpose of diversity indicies

a community of 10 species with equal numbers in each seems more diverse than another with 10 species in which 91% of the individuals belong to the most common species and just 1% to the other nine, although species diversity would deem both equally diverse.

Evenness

relative abundance of each species

niche breadth

The portion of resources that a species uses (n) out of the resources available to the community (R). The variation among individuals in a population in their resource use.

niche overlap

the extent of common use of a resource by two or more species denoted by o.

productivity hypothesis

Emphasizes the importance of climate in determining productivity at the lowest trophic level (plants and microbes) and the resources these then provide for herbivores and then carnivores further up the food chain

energy hypothesis

emphasizes the direct role of energy (often measured by environmental temperature) on organisms throughout the community

Eutrophication

A process by which nutrients, particularly phosphorus and nitrogen, become highly concentrated in a body of water, leading to increased growth of organisms such as algae or cyanobacteria.

paradox of enrichment

Diversity or richness and productivity have a unimodal relationship. Species richness should increase with productivity.

As primary productivity increases the richness first increases, hits some maximum level and then decreases. (Eutrophication)

particulate organic matter

the rain of chemical energy falling as dead organic matter from the sea surface (fecal matter, food wastes, toilet paper).

α-diversity(alpha diversity)

the mean species diversity in sites or habitats at a local scale. Number of species in a local (small) area of homogeneous habitat.

β-diversity (beta diversity)

refers to the differences among communities within a region, so it is high when different communities in a region differ in the species they contain

γ-diversity (gamma diversity)

refers to diversity at the whole regional scale (collections of communities). It therefore combines a and b diversity and is highest when both individual communities are diverse and the communities in a region differ.

potential evapotranspiration

the amount of water that would evaporate or be transpired from a saturated surface and hence a measure of atmospheric energy

net primary productivity

the rate at which biomass accumulates in an ecosystem / The energy captured by producers in an ecosystem minus the energy producers respire

Benthic

bottom dwelling

intermediate disturbance hypothesis

communities are expected to contain most species when the frequency of disturbance is neither too high nor too low

4 Predictions of Island Bio geography

1. The number of species on an island should eventually become roughly constant through time

2. This should be a result of a continual turnover of species, that is the result of some becoming locally extinct and others immigrating.

3. Large islands should support more species than small islands.

4. Species number should decline with the increasing remoteness of an island.

standing crop

the bodies of the living organisms within a unit area constitute a standing crop of biomass

biomass

the mass of organisms per unit area of ground (or water), usually expressed in unites of energy (such as joules per square meter), dry organic matter (grams per square meter), or mass of carbon (grams of carbon per square meter).

primary productivity

the rate at which biomass is produced per unit area or volume through photosynthesis.

Gross Primary Productivity (GPP)

the total fixation of energy by photosynthesis. A proportion of this, however, is respired away by the primary producer organisms (the autotrophs) themselves and is lost from the ecosystem as respiratory heat.

respiratory heat

a proprotion of the total fixation of energy by photosynthesis

Net Primary Productivity (NPP)

the difference between Gross Primary Productivity and respiratory heat. It represents the actual rate of production of new biomass that is available for consumption by heterotrophic organisms (bacteria, fungi, and animals)

secondary productivity

the rate of production of biomass by heterotrophs

net ecosystem productivity (NEP)

the difference between gross primary productivity and the respiration of all organisms in an ecosystem (Rtotal). It measures the net rate of accumulation or loss of organic matter, energy, or organic carbon from the ecosystem and is equivalent to the rate of Net Primary Productivity minus the respiration of all heterotrophic organisms.

live consumer system

a proportion of production consumed by herbivores, which, in turn, are consumed by carnivores.

decomposer system

the fraction of Net Primary Productivity that is not eaten by herbivores

Decomposer

An organism that breaks down wastes and dead organisms (ex. fungi, and bacteria).

Detrivores

animals that consume dead matter

Where do the highest rates of net primary productivity occur?

tropical rain forests

What kind of rates net primary productivity occur in wetlands, estuaries, and giant kelp beds?

rates equal to the tropical rain forests, but the spatial area of these ecosystems is too small for them to be apparent.

Where do the lowest rates of net primary productivity occur?

deserts, and subtropical gyres of the world's oceans

Where do medium rates of net primary productivity occur?

temperate forests, grasslands, tropical savannas, up-welling zones, and much of the North Atlantic Ocean.

What regulates terrestrial primary productivity?

solar radiation, carbon dioxide, water and soil nutrients.

3 ways that precipitation and temperature work together to structure the distribution of terrestrial biomes across the Earth and their influence on Net primary productivity

1. temperature has a direct effect on the physiological processes of photosynthesis, which tends to lead to higher rates of net primary productivity as temperature increases

2. the relationship between temperature and evaporation: evaporation increases greatly with increased temperature, and this can lead to lower water availability to plants, greatly reducing net primary productivity.

3. the rate of decomposition of dead organic matter increases as temperature rises.

Liebig's Law of the Minimum states that

the growth of a plant is limited primarily by the one nutrient that is in relatively short supply (usually, nitrogen or phosphorus) - relative, that is, to the needs of the plant.

colimation

phenomenon in which nitrogen and phosphorus are limiting to production in an ecosystem.

What regions is Phosphorus the most limiting in?

The tropics

What region is Nitrogen the most limiting in?

Polar and Boreal Regions

limiting factors of primary productivity in temperate grass lands

1. winters are too cold

2. frozen soils, and low-intensity radiation

3. summers are too dry

4. nitrogen supply is too low

5. heavy grazing reduces the stand crop of photosynthesis

6. much of the incident radiation falls on bare ground

role of phosphorus and nitrogen limtiation in subtropical ocean gyres, freshwater lakes, and estuaries

There is a colimitation in subtropical ocean gyres, phosphorus is limiting in many lakes, Nitrogen is limiting in many estuaries and coastal marine ecosystems.

Eutrophication

A process by which nutrients, particularly phosphorus and nitrogen, become highly concentrated in a body of water, leading to increased growth of organisms such as algae or cyanobacteria.

central culprit nutrient in Eutrophication

phosphorus

where is primary production is regulated more by nitrogen then phosphorus?

estuaries and coastal marine systems, and eutrophication in these systems is worsened as nitrogen and the resulting net primary productivity grows

Limiting nutrients in the world's oceans

nitrogen, phosphorus, and iron.

positive feedback

Feedback that tends to magnify a process or increase its output.

transfer efficiency

the efficiency with which energy is transferred from one trophic level to the next.

Consumption Efficiency

the percentage of total productivity available at one trophic level that is consumed by the trophic level above.

assimilation efficiency

the percentage of food energy taken into the guts of consumers in a trophic level that is assimilated across the gut wall and becomes available for incorporation into growth or to do work. AE's are highest in carnivores and bacteria, lower in aquatic herbivores, and lowest in terrestrial herbivores, detrivores and microbivores

Production Efficiency

the percentage of assimilated energy incorporated into new biomass; the remainder is entirely lost to the community as respiratory heat.

Species efficiencies of Production Efficiency

1. Invertebrates have high efficiencies

2. vertebrates have medium efficiency

3. endotherms have low efficiency

4. Microorganisms have very high efficiencies

trophic transfer efficiency

CE x AE x PE

immobilization

occurs when an inorganic element is incorporated into organic form, often during primary production (ex. when carbon dioxide becomes incorporated into a plant's carbohydrates)

mineralization

the conversion of elements from organic back to an inorganic form

decomposition

the gradual disintegration of dead organic matter

Microbivores

a group of animals that operate alongside the detrivores and can be difficult to distinguish from them.

shredder

detrivores that feed on coarse particulate organic matter, such as tree leaves fallen into a river

collector-filterers

detrivores that consume fine particulate organic matter left from shredders.

Cellulase

enzyme that breaks down cellulose

nitrogen cycle

the continuing transformation of nitrogen including assimilation into biomass and mineralization back to ammonium

Nitrogen fixation is carried out primarily by

cyanobacteria in lakes and ocean gyres, and rhizobium symboints of plants

nitrogen fixation

Process of converting nitrogen gas into ammonia.

Nitrification

bacteria convert ammonium to nitrate

Denitrification

Conversion of nitrates into nitrogen gas (N2)

Closed Ecosystem vs. Open

Closed: Has sharp boundary between one ecosystem to another. No blending
Open: Shady boundary between ecosystem, blending of species and plants

Weathering

The breaking down of rocks and other materials on the Earth's surface.

Deposition

the net flux of materials from the atmosphere to the ecosystem

Biogeochemistry

the science that addresses the "biotic controls on chemistry of the environment and the geochemical control of the structure and function of ecosystems" (Horwath 1984)

Source-Sink

sites of storage of an element, or to the mechanism for loss of a material

radiative forcing

"The Earth's surface temperature is determined by the balance between incoming solar radiation and outgoing infrared radiation. Radiative Forcing (RF) is the measurement of the capacity of a gas or other forcing agents to affect that energy balance, thereby contributing to climate change. Put more simply, RF expresses the change in energy in the atmosphere due to GHG emissions."

residence time

The average time a given particle will stay in a given system

Methanogenesis

the production of methane by bacteria in the absence of oxygen.

Conservation

is the collective name we give to the various actions we can take to slow down or even reverse the loss of species and biodiversity

Biodiveristy

the variety of life in an area that is determined by the number of different species in that area

restoration

the practice of renewing and restoring degraded, damaged, or destroyed ecosystems and habitats in the environment by active human intervention and action.