Goals:

• Define interspecific competition & explain how it has an impact on evolution.

• Define coevolution.

• List the 4 major types of interspecific interactions & explain their effects on population density . (ex: parasitism, neg population impact on host, positive on parasite)

• Define cryptic coloration, aposematic coloration, Mullerian mimicry, Batesian mimicry.

• Explain brood parasitism & why it increases the fitness of the parasite (think in terms of energy… what species is expending energy & which is conserving it?).

• Define niche.

• Define keystone species & keystone predator.

• Discuss how predators can affect community structure by moderating competition among prey.

• Explain how exotic species can alter community structure.

• Define ecological succession & distinguish between primary & secondary succession.

• Explain how disturbance causes succession & give examples.

• Define trophic levels, primary producers, used for food are herbivores.

• primary consumers, secondary consumers, tertiary consumers, detritivores, ecological efficiency, food chain & food web.

• Explain why much energy is lost as it flows through an ecosystem.

• Based on ecological efficiency being so low, explain why nearly all domestic animals

Ch 37 Community Ecology

Ch 37 Community Ecology• Community –• Interspecific interactions can be strong selection factors in

evolution• Coevolution – when 2 species develop evolutionary adaptation in

response to each other.• Interspecific interactions may have +, - , or neutral effects on a

pops density:– Predation & parasitism (+/-)– Competition (-/-)– Commensalism (+/0)– Mutualism (+/+)

Predation

• predators - adaptations to locate & catch prey.

• Prey - developed evolutionary adaptations in defense

• Plant defenses:– thorns, hooks, chemicals

– Ex: morphine from poppy, nicotine from tobacco, cinnamon, peppermint

• counter adaptations by herbivores:– absorb or detox chemicals, Ex: monarch butterfly

Predation• animal defenses

– can be passive –hiding – or active - fleeing or fighting (less common)– alarm calls to cause mobbing Ex: sparrows mobbing hawks– distraction– adaptive coloration – cryptic coloration (camouflage)– deceptive markings – eyes– shape– smells– aposemetic coloration – brightly colored to warn predators of toxicity– mimicry – look like something else

• batesian mimicry – a harmless species looks like a harmful one. Ex: catapillar looking like a snake, wiggling head & hissing!

• Mullerian mimicry – 2 or more dangerous brightly colored species look like each other

viceroy & monarch butterflies

Parasitism (+/-)• interesting type of parasitism – brood parasitism

– host is not eaten, just taken advantage of– Ex: cowbirds lay eggs in nests of other species, newly hatched

brood parasite kicks out native eggs, – Evolutionary adaptation to this by hosts being able to detect

parasite eggs & kick them out• Counter adaptation to this is the development of egg mimicry

Commensalism (+/0) & Mutalism (+/+)• Commensalism:

– Ex: cowbirds feeding on insects the grazing cows kick up

– Ex: barnacles hitching a ride on a whale

• Mutualism – both benefit

– Ex: nitrogen fixation by bacteria in roots of legumes

– Ex: digestion of cellulose by microorganisms in cows & termites

– Ex: flowers & pollinators

Interspecific competitions (-/-)• Interspecific competition – when pops of 2 or more species in a

community rely on similar limiting resources• Ecological niche – all biotic & abiotic resources an org uses in its env,

its “occupation”• Ex: tree lizards niche is temp is lives at, size of trees it lives in,

time its active, size & type of food it eats

INTERSPECIFIC INTERACTIONS & COMMUNITY STRUCTURE

• keystone species – a species that makes an unusually strong impact on the community structure.

• Ex: beavers with dams, elephants with uprooting trees• keystone predator – a predator species that moderates competition

among its prey, keeps the strongest competitor in check so it doesn’t destroy community structure

• Ex: sea stars eat special type of mussel which then took over when the sea stars were removed

Mutualism & parasitism can have community-wide effects

• Ex: nitrogen fixing bacteria & roots of legumes

Interspecific competition influences pops of many species & can affect community structure.

• Exotic species - can outcompete native species & alter community structure.

– Ex: zebra mussels – clogged reservoir intake pipes in great lakes. no natural enemies.

• the more varied a habitat, the more ecological niches available.

Disturbance & Nonequalibrium• Stability – tendency of a community to reach & maintain an

equilibrium in the face of disturbance• Nonequalibrium resulting from disturbance is a prominent feature of

most communities • Ex: storms, fire, drought, human activities•• Humans - most widespread agents of disturbance

– Ex: logging, mining, farming, overgrazing – are all bad– Ex: fires – sometimes good cause some species need them

Succession• Succession - process of change that results from disturbance in

communities.• Ecological succession – transitions in species composition over time.

– 2 types:– primary – begins lifeless such as new volcanic island or rubble

from retreating glacier– secondary – existing community cleared & soil is intact. Ex:

logged areas• What determines who grows / lives there? Competition for resources

Matter & energy flow through an ecosystem.

They are never created or destroyed!

NEVER! EVER!

EVER!The energy just gets transformed into other types of

energy.

The matter just gets passed on to other organisms.

Ch 54

Matter &

Energy

Flow

Through

Ecosystems

It’s like this, baby…

Food Chain – the transfer of energy from one organism to another.

• As each org is eaten, the energy is transferred.

Only 10% of the energy gets transferred from one organism to the next!Why so little? What happens to all the energy?

Much of it gets transformed into heat energy when the organism performs cellular respiration.

Energy

pyramid –

shows trophic

levels & the

amt of energy

that moves up

from one level

to next.

Food Web – shows many connected food chains.

Trophic level – contains organisms that are the same number of steps away from

the sun.

Quaternary consumers – eat tertiary consumers (carns that eat carns that eat carns)

Tertiary consumers – eat secondary consumers (carnivores that eat carnivores)

secondary consumers – eat primary consumers (carnivores)

primary consumers – eat producers (herbivores)

primary producers – make food from sun’s energy

1. What trophic level is the grasshopper at?

2. What trophic level is the great horned owl at?

3. The sparrow?

4. The grass?