Ecosystem Ecosystem Relationships & Relationships &

Population GrowthPopulation GrowthHow do relationships impact a population growth?

VocabularyVocabulary SpeciesSpecies-- a group of individuals that can a group of individuals that can

freely interbreed and freely interbreed and produce fertile produce fertile offspringoffspring..

A A populationpopulation is just is just one species one species living in living in one area.one area.

CommunityCommunity -Several different -Several different populations (species) living in a given populations (species) living in a given area.area.

EcosystemEcosystem-- The community ( The community (all all populationspopulations) and how they interact with ) and how they interact with the environment (the environment (abioticabiotic).).

Biotic factor Biotic factor a a livingliving thing, as an thing, as an animal or plant, that animal or plant, that influencesinfluences or or affects an ecosystemaffects an ecosystem

Abiotic factorAbiotic factor a a nonlivingnonliving condition condition or thing, as or thing, as climate or habitatclimate or habitat, that , that influences or affects an ecosystem influences or affects an ecosystem and the organisms in it. Examples:and the organisms in it. Examples:

Sun, temperature, rainfall, rocksSun, temperature, rainfall, rocks

Abiotic factors can determine Abiotic factors can determine which species of organisms which species of organisms willwill survive in a given  survive in a given environmentenvironment. .

Habitats and Habitats and NicheNiche

HabitatHabitat is the is the locationlocation where a where a species lives.species lives. It’s their It’s their addressaddress..

NicheNiche includes the includes the habitat and the habitat and the relationships relationships – both – both biotic and abiotic that biotic and abiotic that the species requires. the species requires. It’s their “It’s their “JobJob””

CommunityCommunity Because one species Because one species cannot live alonecannot live alone. They . They

must must interactinteract with their community. with their community. Symbiotic RelationshipsSymbiotic Relationships

a)a) Mutualism:Mutualism: Both species benefit Both species benefit

b)b) Parasitism:Parasitism: One benefits the other is One benefits the other is harmedharmed

c)c) Commensalism:Commensalism: One benefits and the One benefits and the other is not affected.other is not affected.

d)d) Predation:Predation: predator benefits, the prey predator benefits, the prey individual dies but the prey species individual dies but the prey species benefitsbenefits

Mutualism

Commensalism

Parasitism

Parasitism

PredationPredation

CommunityCommunity

Because of the relationships in a Because of the relationships in a community, one population (species) community, one population (species) will always affect will always affect the population size the population size of its of its symbiotic partnersymbiotic partner. .

Examples: Examples: Wolf – Wolf – ElkElk Fish- Fish- Eagle Eagle Aspen Tree – Aspen Tree – Deer Deer Sage Brush – Sage Brush – RabbitRabbit

Symbiotic Symbiotic PopulationsPopulations

GrowthGrowth Exponential Growth:Exponential Growth: The The raterate

of population growth in each of population growth in each new generation is a new generation is a multiplemultiple of of the previous.the previous. Few die and most Few die and most survive to survive to

reproduce reproduce J-shapedJ-shaped curve curve

Growth RateGrowth Rate Natural Growth rate is Natural Growth rate is not as not as

simplesimple Equation: Equation:

Growth rateGrowth rate = = Change in # of Change in # of individualsindividuals Time Period Time Period

Growth RateGrowth Rate

Factors Influencing Factors Influencing GrowthGrowth

a)a) Birth RateBirth Rate

b)b) Death RateDeath Rate

c)c) MigrationMigration

1. 1. ImmigrationImmigration- - movement into a movement into a populationpopulation

2. 2. EmigrationEmigration- movement - movement out of a populationout of a population

Human PopulationHuman Population

Histograms indicate the population’s distribution & overall status

Population GrowthPopulation Growth Most population growth is in Most population growth is in the developing the developing

countries countries (Latin America, Asia & Africa) (Latin America, Asia & Africa) Some countries are actually Some countries are actually droppingdropping

dramatically (many European countries & dramatically (many European countries & Japan)Japan)

The total population in the USA would have The total population in the USA would have dropping without dropping without immigrationimmigration. The . The immigrant population has increased immigrant population has increased 57%57% since 1990.since 1990.

The economic system of a country needs The economic system of a country needs ““consumersconsumers” and now they must consider ” and now they must consider the “quality of life” and long term the “quality of life” and long term sustainability. sustainability.

Limiting FactorsLimiting Factors Anything Anything bioticbiotic or or abioticabiotic in in

the environment that the environment that limitslimits the size of a populationthe size of a population Causes an Causes an increaseincrease in death rate in death rate

or or decreasedecrease in birth rate in birth rate Effects of these factors depends Effects of these factors depends

upon the upon the size and density size and density (individuals per area) of the (individuals per area) of the population and community.population and community.

Population Density Population Density PatternsPatterns

These are species specific distributions

Density Density IndependentIndependent

Affects Affects ALLALL populationspopulations regardless of regardless of sizesize (mostly (mostly abioticabiotic)) WeatherWeather Seasonal Seasonal CyclesCycles Natural DisastersNatural Disasters

Density Density DependentDependent

Factors limit size Factors limit size ONLYONLY when the when the population reaches population reaches capacitycapacity for a for a certain area – mostly certain area – mostly bioticbiotic.. DiseaseDisease Competition for Competition for limited resourceslimited resources ParasitismParasitism PredationPredation

Population Population CapacityCapacity Carrying Capacity =Carrying Capacity = the number of the number of

individuals (of a species) that an individuals (of a species) that an environment can environment can support indefinitelysupport indefinitely

This results in a This results in a levelingleveling off of the off of the growth curvegrowth curve S-shapedS-shaped curve curve

Overpopulation = Overpopulation = SharpSharp DeclineDecline

“Boom & bust” pattern follows climatic fluctuations.

Ecosystems & Ecosystems & PopulationsPopulations

Demography-Demography- the study of the study of populationspopulations

There is an on-going tendency to find There is an on-going tendency to find a a balance within systems balance within systems (both living (both living and non-living). and non-living).

This is not an intentional act. If This is not an intentional act. If organisms can’t maintain organisms can’t maintain homeostasishomeostasis their populations will their populations will declinedecline and they may become and they may become extinctextinct..