MonthDayTopic Nov.8Individuals to populations 10Holiday! 13Populations to communities 15Community patterns 17Ecosystems 20Film-1 st showing 22Film-2 nd showing 24Holiday! 27Ecosystem services

A population is:

A group of individuals of the same species living in a given area at a given time.

What controls where a population lives?

It has to get there –Evolution –Dispersal

What controls where a population lives? It has to get there –Evolution –Dispersal Its ecological niche

Key concept in ecology: the niche

Fundamental niche –Abiotic conditions that the species can live within

Key concept in ecology: the niche Fundamental niche –Abiotic conditions that the species can live within Realized niche –Biotic interactions that reduce or enhance the fundamental niche

Barnacle story Balanus’ fundamental niche: upper, middle and lower zone Balanus’ realized niche: middle zone, limited from upper by competition, lower by predation

Interactions among populations determine a species’ realized niche...

A community is:

Populations of different species that live together in a given area at a given time.

Communities are... Defined by abiotic factors –Populations in a community have similar fundamental niches

Communities are... Defined by abiotic factors –Populations in a community have similar fundamental niches Defined by biotic interactions –Some are weak –Some are strong

Types of community interactions POP. 2 HarmNo effectBenefit HarmCompetitionAmensalismPredation or Parasitism POP. 1No effectAmensalismCommensalism BenefitPredation or Parasitism CommensalismMutualism

Types of community interactions POP. 2 HarmNo effectBenefit HarmCompetitionAmensalismPredation or Parasitism POP. 1No effectAmensalismCommensalism BenefitPredation or Parasitism CommensalismMutualism

Types of community interactions POP. 2 HarmNo effectBenefit HarmCompetitionAmensalismPredation or Parasitism POP. 1No effectAmensalismCommensalism BenefitPredation or Parasitism CommensalismMutualism

Keys to competition (-/-) Organisms compete for limited resources

Can be: –Intraspecific Keys to competition (-/-)

Time Population size

Organisms compete for limited resources Can be: –Intraspecific –Interspecific Keys to competition (-/-)

Competition can: Restrict species ranges

Competition can: Restrict species ranges Reduce species abundances

Competition can: Restrict species ranges Reduce species abundances Cause the local extinction or competitive exclusion of species from an area

The ghost of competition past...

Predator-prey interactions (+/-) Predators are generally larger than their prey (but many exceptions...)

Predator-prey interactions (+/-) Predators are generally larger than their prey (but many exceptions...) Predators live outside of the body of their prey

Predator-prey interactions (+/-) Predators are generally larger than their prey (but many exceptions...) Predators live outside of the body of their prey Predators generally kill their prey

Predator-prey interactions Dynamics of predator and prey populations may be:

Predator-prey interactions Dynamics of predator and prey populations may be: Loosely coupled –predator “switches” when prey is scarce Tightly coupled –predator starves when prey is scarce

Tightly coupled predator-prey interactions change over time An evolutionary “arms race”

Mimicry Tightly coupled predator-prey interactions change over time

Batesian mimicry

Predator-prey interactions change over time An evolutionary “arms race” Mimicry Plant defenses against herbivores

Host-parasite interactions (+/-) Parasites are generally smaller than their hosts Parasites live inside or on the body of their host Parasites generally kill their hosts more slowly than predators

Amensalism (0/-)

Commensalism (0/+)

Mutualisms (+/+) Mutualisms can be loose or tight

Acacia with antsAcacia without ants

Communities are... Defined by abiotic factors –Populations in a community have similar fundamental niches Defined by biotic interactions –Weak and strong interactions determine a population’s realized niche Dynamic –Vary in time and in space

Why do communities vary in time?

Communities are... Comprised of populations that respond individualistically to change

Communities vary in time Ecological succession: a sequence of change in the species composition of a community

Succession 1.Primary –establishment of communities on new sites that previously had no organisms

Succession 1.Primary –establishment of communities on new sites that previously had no organisms 2.Secondary –re-establishment of communities following disturbance

Why do communities vary in space?

Communities vary in space Time Relief/aspect Parent material Climate Organisms

Terrestrial biome

A major community type that differs from other types in the structure of its dominant vegetation.

Terrestrial biome A major community type that differs from other types in the structure of its dominant vegetation. Primarily controlled by climate. –Relationship between rainfall and temperature

The vegetation of a biome has a similar appearance wherever on Earth that biome is found. In many cases, this is due to convergent evolution. Biomes

EuphorbiaceaeCactaceae

Tundra

-severe winters -short growing season, cool summer -arctic or alpine Tundra

Temperate Forest Temperate forest

-distinct winter season, frost a defining feature -summer season usually moist Temperate Forest

Desert

-hot or cold deserts exist -low precipitation

Desert

-found near the equator -temperature varies little from approximately 23°C -Over 2 m of rainfall Tropical Rain Forest

-canopy trees up to 55 m tall -largest biome, on an area basis -soils are generally unfertile -nutrients and carbon stored in plant biomass, not soils