What is ecology?

The study of interactions between The study of interactions between organisms and their environment.organisms and their environment.

Ecology? Biology?

Biology is simply the “study of life.”Biology is simply the “study of life.” Ecology involves the interactions of living Ecology involves the interactions of living

and nonliving aspects of the environment. and nonliving aspects of the environment.

Both biotic and abiotic factors are Both biotic and abiotic factors are interconnected – a change in one, interconnected – a change in one, changes all the others over time.changes all the others over time.

Factors

Biotic FactorsBiotic Factors Living factorsLiving factors Humans, plants, insectsHumans, plants, insects

Abiotic FactorsAbiotic Factors Nonliving factorsNonliving factors Physical & chemical characteristics Physical & chemical characteristics Temperature, pH, OTemperature, pH, O22 concentration, concentration,

sunlight, Hsunlight, H22O, soilO, soil

Abiotic? Biotic?

Exploding human populationExploding human population BioticBiotic

Species endangerment/extinctionSpecies endangerment/extinction BioticBiotic

Thinning of the ozone layerThinning of the ozone layer AbioticAbiotic

Greenhouse effectGreenhouse effect AbioticAbiotic

Interactions at Levels

OrganismOrganism A single speciesA single species Example: one blue gillExample: one blue gill Note: Since no organism is isolated, Note: Since no organism is isolated,

ecologists must use ecologists must use MODELSMODELS to study to study the environment and to make the environment and to make predictions about the futurepredictions about the future

Interactions at Levels

PopulationPopulation Members of a single speciesMembers of a single species Example: population of blue gills in a Example: population of blue gills in a

lakelake

Interactions at Levels

CommunityCommunity A group of different populations that A group of different populations that

live in the same arealive in the same area Only living factors in an area interacting Only living factors in an area interacting

with each otherwith each other Example: fish, turtles, algaeExample: fish, turtles, algae

Interactions at Levels

EcosystemEcosystem The interactions among living things The interactions among living things

and the nonliving things in an areaand the nonliving things in an area Example: lakeExample: lake NOTE: Biomes are large ecosystemsNOTE: Biomes are large ecosystems

Interactions at Levels

BiosphereBiosphere Broadest categoryBroadest category The part of Earth The part of Earth

where living things where living things existexist

Example: Example: atmosphere, atmosphere, lithospherelithosphere

Organisms

HabitatHabitat Where an organism livesWhere an organism lives

NicheNiche What an organism does (its job or role) in its What an organism does (its job or role) in its

environmentenvironmentRole in the food chain & nutrient cyclingRole in the food chain & nutrient cycling Interactions with other speciesInteractions with other species

Two types of nichesTwo types of nichesFundamental nicheFundamental nicheRealized nicheRealized niche

Fundamental Niche

The potential range of conditions and The potential range of conditions and resources that an organism can assumeresources that an organism can assume

Total range of environmental conditions Total range of environmental conditions that are suitable for a species existencethat are suitable for a species existence

Example:Example: We can live anywhere in U.S. (tolerance)We can live anywhere in U.S. (tolerance)

Realized Niche

The actual range of conditions and The actual range of conditions and resources that an organism assumesresources that an organism assumes

Example:Example: We live and do our “jobs” in We live and do our “jobs” in

Northbrook.Northbrook.

Ecological Roles

GeneralistsGeneralists Organisms with very broad nichesOrganisms with very broad niches Can live in many habitats, many conditionsCan live in many habitats, many conditions ““Jack of all trades, master of none”Jack of all trades, master of none” Example:Example:

OpossumOpossumCockroachesCockroachesMiceMiceHumansHumans

Ecological Roles

SpecialistsSpecialists Organisms with very narrow and specific Organisms with very narrow and specific

nichesniches Live in one or few habitats, narrow range Live in one or few habitats, narrow range

of conditionsof conditions Out compete generalists in preferred Out compete generalists in preferred

habitatshabitats Example: Example:

Koala can only live and survive on Koala can only live and survive on Eucalyptus trees in AustraliaEucalyptus trees in Australia

Ecological Roles

In a changing environment, it is better to In a changing environment, it is better to be a generalist.be a generalist.

In a stable environment, it is better to be a In a stable environment, it is better to be a specialist.specialist.

What is a population?

All the individuals of a single All the individuals of a single species living in an areaspecies living in an area

Rabbits in Australia

Population Size? Density?

Population SizePopulation Size Number of individualsNumber of individuals

Population DensityPopulation Density Number of individuals in an areaNumber of individuals in an area Persons/square milePersons/square mile

Limiting Factors

Density dependent limiting factorsDensity dependent limiting factors Factors that limit a population only Factors that limit a population only

when a population reaches a certain when a population reaches a certain densitydensity

Examples:Examples:Competition, predation, parasitism, Competition, predation, parasitism,

disease, water availabilitydisease, water availability

Limiting Factors

Density independent limiting factorsDensity independent limiting factors Factors that affect all population in the Factors that affect all population in the

same way regardless of densitysame way regardless of density Examples:Examples:

Weather, natural disasters, seasonal Weather, natural disasters, seasonal cycles, pollutioncycles, pollution

Growth Rate

Change in population size over timeChange in population size over time Depends on births, deaths, immigration Depends on births, deaths, immigration

(in), and emigration(out).(in), and emigration(out).

Growth Rate

Populations grow exponentially until they Populations grow exponentially until they reach carrying capacity (the maximum reach carrying capacity (the maximum number of organisms that an area can number of organisms that an area can support)support)

Example:Example: 1, 2, 4, 8, 16, 32….1, 2, 4, 8, 16, 32….

Population Growth Models

Exponential (J-shaped) Growth CurveExponential (J-shaped) Growth Curve Logistic (S-shaped) ModelLogistic (S-shaped) Model Boom and Bust ModelBoom and Bust Model

Exponential (J-shaped) Growth Curve

Ideal ModelIdeal Model Under ideal conditions: Under ideal conditions:

plenty of resources, no plenty of resources, no competition, no parasites, competition, no parasites, no predators, etc.no predators, etc.

Because of limiting Because of limiting factors, populations rarely factors, populations rarely exhibit J-shaped growth exhibit J-shaped growth curvescurves

Logistic (S-shaped) Model

Realistic modelRealistic model Rapid growth, then slowing of growth and Rapid growth, then slowing of growth and

leveling offleveling off Regulated by carrying capacity (# of individuals Regulated by carrying capacity (# of individuals

which can be supported by resources of which can be supported by resources of environment without damage to environment)environment without damage to environment)

Generally density dependentGenerally density dependent Growth is affected by the density of Growth is affected by the density of

individualsindividuals

Boom and Bust Model

Example:Example: 26 reindeer were introduced onto an 26 reindeer were introduced onto an

island off the coast of Alaska in 1910.island off the coast of Alaska in 1910. Within 30 years the herd increased to Within 30 years the herd increased to

2,000. 2,000. However, overgrazing reduced the food However, overgrazing reduced the food

supply and the population crashed to 8 supply and the population crashed to 8 animals by 1950.animals by 1950.

Boom and Bust Model

Realistic ModelRealistic Model Growth occur exponentially, but crash due Growth occur exponentially, but crash due

to…to… Disturbance, such as weatherDisturbance, such as weather Overexploitation of environmentOverexploitation of environment