Ecology Exam 4

Intraspecific competition

competition among members of the same species

Interspecific competition

competition among individuals of different species

Resource

* Any substance or factor that is both consumed by an organism and supports increased population growth rates as its availability increases​
* Consumed, availability decreases​
* Used for maintenance and growth​
* Reduced availability reduces population growth​

\

Renewable resource

resources that are constantly regenerated (seeds, sunlight)

Nonrenewable resources

resources that are not regenerated(space)

Leibig’s law of the minimum:

 law stating ​that a population increases until the supply ​of the most limiting resource prevents it ​from increasing further.​

Competitive exclusion principle

 two species cannot coexist indefinitely when they are both limited by the same resource.​

​

When two species are limited by the same resource, one species is often a better competitor survives better when resources are scarce.​ (Grocery store ham example)

Possible outcomes of competition

* coexistence​
* Species 1 Wins (Drives Species 2 to local extinction)​
* Species 2 Wins (Drives Species 1 to local extinction)​
* Winning species depends on starting conditions​

Asymmetric competition

A competitive relationship between two species in which each has a competitive advantage with respect to different limiting factors in the environment​

Exploitive competition

 competition in which individuals consume and drive down the abundance of a resource to a point that other individuals cannot persist.​ (the sister in the milk example)

Interference competition

when competitors do not immediately consume resources but defend them; considered direct competition.​ (the brother in the milk example)

Apparent competition

 when two species have a negative effect on each other through an enemy—including a predator, parasite, or herbiviore.​

Allelopathy

 a type of interference competition that occurs when organisms use chemicals to harm their competitors.​ (effective strategy for invasive plants)

Lotka Volterra Competition model

r1N1(1-N1+aN2/K1) = N1

r2N2(1-N2+BN2/K2)= N2

\
α = competition coefficient for species 1, which converts individuals of species 2 into the equivalent number of individuals of species 1.​

​

β = competition coefficient for species 2, which converts individuals of species 1 into the equivalent number of individuals of species 2.​

​

Competitive interactions

* # of individuals using resources of species 1 ​= N1 + α • N2​
* # of individuals using resources of species 2 ​= N2 + β • N1​

Species 1 outcompetes species two

Species two outcompetes one

Competitive exclusion

Coexistance

community

An assemblage of species that occur together in the same place​

Historical debate in community ecology

1. Superorganism – Holistic concept​

\- (Frederick) Clements​

2\. Individualistic concept​

\-(Henry) Gleason​

Holistic concept(clement)

Communities are a distinct ecological unit or organization having recognizable boundaries and whose structure and functioning are regulated by interaction among its component species​

requires that communities be discrete entities and distinguishable from one another

Individualistic concept (gleason)

a loose assemblage of species that can tolerate the conditions of a particular habitat​

Does not require boundaries

Closed community

distributions of species sets closely coincide and are separated from other sets of species

Open community

species are independently distributed along environmental conditions​

Species richness

 the number of species in a community.​

Relative abundance

 the proportion of individuals in a  community represented by each species.​

Log-normal distribution

a normal, or bell-shaped, distribution that uses a logarithmic scale on the x-axis.​

U-shaped productivity curve

Negative productivity

None productivity

Positive productivity

Hump shaped productivity

Keystone species

a species that substantially affects the structure of communities, although species might not be particularly numerous.​

Intermediate disturbance hypothesis:

 the hypothesis that more species are present in a community that experiences occasional disturbances than in a community with either frequent or rare disturbances.​

Food chain

a linear representation of how different species in a community feed on each other.​

Food web

a complex and realistic representation of how species feed on each other in a community.​

Trophic level

a level in a food chain or food web of an ecosystem.​

Primary consumer

Species that eats producer

Secondary consumer

a species that eats primary consumers.​

​

Tertiary consumer

a species that eats secondary consumers.​

Omnivore

 a species that feeds at several trophic levels.​

Guild

 within a given trophic level, a group of species that feeds on similar items; members of the group are not necessarily related.​

Problems with trophic levels

Informality of construction​

Lumping species into guilds or categories​

Ignore changing roles (catfish: detritivore/predator)​

All links equal, although may vary in strength​

\

General conclusions of trophic levels

Most are fairly short (average = 4 links in previous)​

Most are open (receive significant input from and export to adjoining systems)​

Bottom-up control

**:** when the abundances of trophic groups are determined by the amount of energy available from producers.​

top down control

 when the abundances of trophic groups are determined by the existence of predators at the top of the food web.​

Community stability

the ability of a community to maintain a particular structure.​

Community resistance

 the amount a community changes when acted upon by a disturbance (e.g., addition or removal of a species).​

Community resilience

 the time it takes after a disturbance for a community to return to its original state.​ (diversity improves this)

Succession

the process by which the species composition of a community changes over time.​

​

Seral stage

each step of community change during succession

Pioneer species

 the earliest species to arrive at a site; typically are able to disperse long distances and arrive quickly at disturbed sites.​

\

Climax community

the final seral stage in the process of succession; generally composed of organisms that dominate in a given biome.​

​

Chrono sequence

 a sequence of communities that exist over time at a given location.​

Primary succession

 the development of communities in habitats that are initially devoid of plants and organic soil, such as such dunes, lava flows, and bare rock.​

Secondary Succession

 the development of communities in disturbed habitats that contain no plants but still contain organic soil (e.g., plowed fields, forests uprooted by a hurricane).​

​

Lake succession (1/2)

1.   After a lake or pond is created, the edge of the water body is initially colonized by plants.​
2. The plants expand laterally across open water and begin accumulating dead plant matter (i.e., peat).​
3. Plants continue to expand and the peat layer becomes thicker.​
4.   Lateral expansion of plants eventually covers the lake surface and peat sediments fill in the basin.​

Lake succession (2/2 )

1.  An open lake or pond experiences a drought of one or more decades and the water level falls.​
2. Plants colonize the newly exposed lake sediments.​
3.   As the drought ends, the lake fills and living plants detach from lake sediments and float on the lake’s surface.​
4. Peat sediments eventually fill the basin.​

Facilitation

a mechanism in which one species increases the probability that a second species can become established.​

Inhibition

a mechanism in which one species decreases the probability that a second species will become established (e.g., by competition, predation, or parasitism).​

Priority effect

when the arrival of species at a site affects the colonization of other species; often occurs through inhibition.​

Tolerance

when the arrival of species at a site affects the colonization of other species; often occurs through inhibition.​

Transient Climax

A climax community that develops in an ephemeral habitat (ex. seasonal ponds)

Transient climax communities

a climax community that is not persistent; occurs when a site is frequently disturbed so a climax community cannot persist.​

Cyclic Climax

A repeating sequence of stages of succession, none of which by itself is stable, but together represent a persistent pattern​

Fire maintained climax community

 a successional stage that persists as the final seral stage due to periodic fires.​

​

Grazer maintained climax community

 when a successional stage persists as the final seral stage due to intense grazing.​

Ecosystem

**the assemblage of organisms together with their physical and chemical environments​**

Charles Elton (1920’s)

**introduced idea of food web and energy transfer within the web​**

A.G Tansley (1935)

Introduced the term “ecosystem” as the fundamental unit of ecological organization

Ecosystem Ecology

the study of natural systems from the standpoint of energy flow and cycling of matter​

Ecosystem thermodynamic principles

* Conservation of Energy​
* Entropy increases due to inefficiency​
* Treats ecosystems (and the Earth) as giant thermodynamic machines​

Primary productivity

 the rate at which solar or chemical energy is captured and converted into chemical bonds by photosynthesis or chemosynthesis.​

Standing Crop

 the biomass of producers present in a given area of an ecosystem at a particular moment in time.​

Gross primary productivity (GPP)

 the rate at which energy is captured and assimilated by producers in an area.​

Net primary productivity (NPP)

 the rate of energy that is assimilated by producers and converted into producer biomass in an area; includes all energy that is not respired:

Remote sensing

 a technique that allows measurement of conditions on Earth from a distant location, typically using satellites or airplanes that take photographs of large areas of the globe.​

Inefficiency of energy transfer

* 5-20% of energy passes to next trophic level (\~10%)​
* Why?

\- Assimilated energy​= ingested – egested energy​

\-Production​= assimilated energy – respiration - excretion​

Ecological Efficiency (Food chain efficiency)

 the percentage of net production from one trophic level compared to the next lower trophic level.​

Energy Transformations

* Chemical elements reused constantly​

\-Cycle between biologically usable and un-usable states (organic and inorganic)​

* Energy is gained or lost during transformations​

\-Oxidation—gives up electrons (loses energy)​

\-Reduction—accepts electrons (gains energy)​

* Assimilatory Processes—inorganic→organic​

\-Requires energy (Photosynthesis)​

* Dissimilatory Processes—organic→inorganic​

\-Releases energy (Respiration)​

Greenhouse effect

the process of solar radiation striking Earth, being converted to infrared radiation, and being absorbed and​ re-emitted by atmospheric gases.​

Solar equator

the latitude receiving the most direct rays of the Sun.​

Albedo

 the fraction of solar energy reflected by an object.​

Atmospheric Convection currents

 the circulation of air between the surface of Earth and the atmosphere; caused by properties of air.​

Saturation

the limit of the amount of water vapor that air can contain.​

Adiabatic cooling

 the cooling effect of reduced pressure on air as it rises higher in the atmosphere and expands.​

**Adiabatic heating**

the heating effect of increased pressure on air as it sinks toward the surface of Earth and decreases in volume.​

Latent heat release

 when water vapor is converted back to liquid, water releases energy in the form of heat and warms air.​

Hadley cells

the two circulation cells of air between the equator and 30N and 30S latitudes.​

Intertropical convergence zone (ITCZ)

the area where the two Hadley cells converge and cause large amounts of precipitation.​

Polar Cells

atmospheric convection currents between 60 and 90 latitudes that are similar to Hadley cells. ​

Coriolis effect

the deflection of an object’s path due to the rotation of the Earth.​ (wind isnisn’tt air moving against earth, it is earth moving against air)

Gyre

a large-scale water circulation pattern between continents.​

Upwelling

and upward movement of ocean water

Rain shadow

 a region with dry conditions found on the leeward side of a mountain range as a result of humid winds from the ocean causing precipitation on the windward side.​

Tropical climate

 characterized by warm temperatures and high precipitation, occurring in regions near the equator.​

Dry climate

characterized by low precipitation and a wide range of temperatures; found at approximately 30N and 30S latitudes.​

Moist subtropical mid-latitude climate

characterized by warm, dry summers and cold, wet winters.​

​

Moist continental mid-latitude climate:

exists in the interior of continents and is characterized by warm summers, cold winters, and moderate amounts of precipitation.​

​