DefinitionsDefinitions• Ecology Ecology defined by interactions and interconnections – with defined by interactions and interconnections – with

own species, other species, environment; organisms affect own species, other species, environment; organisms affect each other, environment; environmental factors affect each other, environment; environmental factors affect organisms and activities. organisms and activities.

• Organisms and envt. factors: Organisms and envt. factors: SpeciesSpecies - group of actively or potentially interbreeding - group of actively or potentially interbreeding

individuals reproductively isolated from other such groupsindividuals reproductively isolated from other such groupsPopulationPopulation - all individuals of a species in a discrete area - all individuals of a species in a discrete areaCommunityCommunity – a group of populations of species that occur – a group of populations of species that occur

together and interacttogether and interactEcosystemEcosystem – functional unit; community and surrounding – functional unit; community and surrounding

physical and chemical environment.physical and chemical environment.– Large, complex, component studiesLarge, complex, component studies– Ocean ecosystems – different physico-cemical factors, different Ocean ecosystems – different physico-cemical factors, different

biotic effects, biotic effects, – Drives adaptation, changing compositionDrives adaptation, changing composition

Energy - Trophic StructureEnergy - Trophic Structure

AutotrophsAutotrophs

standing crop/biomassstanding crop/biomass

productivityproductivity

HeterotrophsHeterotrophs

DecomposersDecomposers

Food chainFood chain

Trophic levelsTrophic levels

Food webFood web

Biogeochemical cyclesBiogeochemical cycles

Carbon CycleCarbon Cycle

• SourceSource

• SinkSink

• Self limiting feedback Self limiting feedback

Limiting factorsLimiting factors

• Energy – how it enters, how it moves, Energy – how it enters, how it moves, where is it storedwhere is it stored

• Abiotic factors – tolerance range for Abiotic factors – tolerance range for physical, chemicalphysical, chemical

• Interactions with other organisms Interactions with other organisms

NicheNiche - ecological role of a species in the community - ecological role of a species in the community

Fundamental nicheFundamental niche – all the ecological conditions – all the ecological conditions where an organism could exist, roles it could playwhere an organism could exist, roles it could play

Realized nicheRealized niche – actual conditions where organism – actual conditions where organism does exist, roles it does play (real world distribution)does exist, roles it does play (real world distribution) Niche BreadthNiche Breadth - range of conditions tolerated or - range of conditions tolerated or resources used by an organismresources used by an organism

• Specialist – narrow range of conditions tolerated, Specialist – narrow range of conditions tolerated, resources usedresources used• Generalist – broad range of conditions tolerated, Generalist – broad range of conditions tolerated, resources usedresources used

– – place where an organism is found (more general)place where an organism is found (more general)

EnvironmentEnvironment

NicheNiche

Realized nicheRealized niche

Fundamental nicheFundamental nicheSalinitySalinity

TemperatureTemperature

InteractionInteraction

Reproductive potential >> natural Reproductive potential >> natural population. population.

Limits to explosive growth?Limits to explosive growth?

• CompetitionCompetition

• PredationPredation

• Parasitism and diseaseParasitism and disease

CompetitionCompetition – interaction among organisms – interaction among organisms for a necessary resource that exists in short for a necessary resource that exists in short supplysupply

- Interspecific- Interspecific - Intraspecific- Intraspecific

• InterferenceInterference - one individual exerts negative - one individual exerts negative effects/actively prevents another from getting effects/actively prevents another from getting resourcesresources

• ExploitationExploitation - one individual exploits a resource - one individual exploits a resource at a higher rate than another (less direct)at a higher rate than another (less direct)

Competitive exclusion principleCompetitive exclusion principle (Gause’s principle 1934) – no 2 species (Gause’s principle 1934) – no 2 species with the same requirements can exist with the same requirements can exist in the same space at the same timein the same space at the same time

Niche overlap Niche overlap competition competition outcomes. outcomes.

•Competitors coexistCompetitors coexist

•Stronger competitor Stronger competitor displaces weakerdisplaces weaker

Conditions for Coexistence:Conditions for Coexistence:

– – magnitude of competitive effect on both is magnitude of competitive effect on both is low (food supply, abiotic conditions) low (food supply, abiotic conditions)

– – superior competitor is kept at low densitiessuperior competitor is kept at low densities

Competitive relationships: Competitive relationships:

hierarchical hierarchical A > B > CA > B > C

networknetwork A > B, B > C, but C > A > B, B > C, but C > AA

Community structure – make-up of species in a Community structure – make-up of species in a communitycommunity

Species richness – number of speciesSpecies richness – number of species

Species evenness – distribution of individuals among the Species evenness – distribution of individuals among the speciesspecies

““Diversity” combines richness and evennessDiversity” combines richness and evenness

Dominant species – species with greatest number of individuals or biomassDominant species – species with greatest number of individuals or biomass

Species Species

Number

Number

Population limiting factors – biological and Population limiting factors – biological and physicalphysical

• Density-dependentDensity-dependent

• Density-independentDensity-independent

Leibig’s Law of the MinimumLeibig’s Law of the Minimum – that life – that life requirement or essential resource that is first requirement or essential resource that is first reduced below the minimum (in shortest supply) reduced below the minimum (in shortest supply) will limit growth and survivalwill limit growth and survival

Resource renewal – can be active or passive, rate Resource renewal – can be active or passive, rate affects population growthaffects population growth

Exponential growth – growth without limitsExponential growth – growth without limits

Logistic growth – density-dependent Logistic growth – density-dependent growthgrowth

Predation – Predation –

Predators can prevent competitive exclusion, Predators can prevent competitive exclusion, allow coexistenceallow coexistence

Predator avoidance strategiesPredator avoidance strategies

• rapid reproductionrapid reproduction• refugesrefuges

Optimal foraging theory – predators select Optimal foraging theory – predators select prey to maximize rate of food intakeprey to maximize rate of food intake

Predation : consumption of Predation : consumption of one organism by another one organism by another

• Effect can varyEffect can vary– Large change in prey density = Large change in prey density =

predatory control (Paine’s starfish)predatory control (Paine’s starfish)– Little/no change = little control effect Little/no change = little control effect

(least tern)(least tern)

• Keystone speciesKeystone species

• Trophic cascadeTrophic cascade

Figure 5: CPUE per lunar month of Stolothrissa and Lates stappersii (mukeke)

Predation: a force to structure communities --         Pisaster, a starfish, keystone predator.  in the absence of Pisaster, a few competitive dominants (barnacles and mussels) can usurp all the space in the intertidal. Pisaster predation can free up areas of rock that can then be used by other species such as anemones.

                        2)  Sea otters reduce sea urchins and increase kelp -- The kelp "forests", in turn, provide habitat complexity, prey refuges and spawning sites (e.g., for herring) that seems to increase the diversity of species that can exist.

Population life history strategiesPopulation life history strategies• A continuum; two types (MacArthur) define A continuum; two types (MacArthur) define

extremes. extremes.

• Opportunistic or R-strategy Opportunistic or R-strategy – short life, rapid – short life, rapid maturity, many reproductions/yr., high death maturity, many reproductions/yr., high death rates, larvae usually present. Usually, small, rates, larvae usually present. Usually, small, sedentary and inefficiently use resources, poorer sedentary and inefficiently use resources, poorer competitors. Highly variable numberscompetitors. Highly variable numbers

• Equilibrium or K-strategy Equilibrium or K-strategy – long life, long – long life, long development time to maturity, proliferate slowly, development time to maturity, proliferate slowly, ne or few reproductions/yr., low death rates. ne or few reproductions/yr., low death rates. Usually larger than opportunists, mobile, Usually larger than opportunists, mobile, efficiently use resources, better competitors. efficiently use resources, better competitors. Fairly constant numbers.Fairly constant numbers.

• Opportunists favored where Opportunists favored where disturbance is frequent (waves, disturbance is frequent (waves, sedimentation, predators). Why?sedimentation, predators). Why?

• Why do bottom samples usually Why do bottom samples usually contain both types? contain both types?

• Why do proportions change over an Why do proportions change over an area?area?

• Why do the change with depth?Why do the change with depth?

Password is wfb279Password is wfb279

• For Thursday read For Thursday read

• Strathman “Why does a larva swim Strathman “Why does a larva swim so long?” and so long?” and

• Vance “Reproductive strategies in Vance “Reproductive strategies in mrien benthic invertebrates”mrien benthic invertebrates”