Ch. 20

Community Ecology

What is predation?• Predator eats prey

What are three adaptations of predators?

• What makes them good at finding, capturing, and consuming prey?– acute smell– heat sensing pits– venom – sticky webs– teeth/mouthparts– camouflage– speed

List three adaptations of prey?

• What makes them good at escaping, avoiding, or warding off predators?– fleeing– hiding – warning coloration– resembling something inedible– deceptive markings– chemical defenses

What is mimicry?• One species resembles another

What are the two types of mimicry?

• Batesian – harmless species resembles a harmful one

• Mullerian – 2 or more dangerous or distasteful species look similar

What are some plant prey adaptations?

• Thorns, spines, sticky hairs, tough leaves, chemical defenses

Define interspecific competition

• Two or more species using the same limited resource

Intraspecific – same species competing

Interspecific – different species competing

Competitive Exclusion• A species is eliminated from a

community because of competition

What is symbiosis?• Close long-term relationship between

two organisms.

• 3 types:– Parasitism (-/+)– Mutualism (+/+)– Commensalism (+/0)

• Parasitism : one benefits (parasite), one is harmed (host)

• Exp. fleas, ticks, tapeworms

• Mutualism: both benefit• Exp. ants and acacia trees

• Commensalism: one benefits, other is neither helped nor harmed

• Exp. cattle egrets and cape buffalos, sharks and remoras

Patterns in Communities

Succession

What is succession?• Gradual sequential re-growth of a

community.

Ecological succession• Gradual, sequential regrowth of a

community• years or decades• usually after a disturbance

Mt. St. Helens

What’s the difference between primary and secondary

succession?• Primary – no soil previously; area

previously did not support life• Secondary – soil already intact; follows

disruption of a pre-existing community

Primary succession• Begins with virtually lifeless area

without soil, then…– bacteria– lichens & mosses

Once there’s soil, other plants can grow:

– grasses– shrubs– trees

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When is primary succession likely to occur?

• On bare rock• Sand dunes• After volcanic eruption• On concrete (like an abandoned

parking lot)

What is a pioneer species?• First species in an area• Predominate early succession• Characteristics: small, grow quickly,

reproduce quickly, disperse seed easily

What organisms are typically found in the early stages of

primary succession?• Lichens – form soil → Grasses/weeds → Mosses → Eventually larger plants

and finally trees

• Large conifers may be found in the end stage of primary succession in northern latitudes (pines, balsams, spruces)

Secondary succession• Existing community cleared,

but base soil is still intactburning releases nutrients formerly locked up in the tissues of tree

the disturbance starts the process of succession over again

When is secondary succession likely to occur?

• After forest fires, strong storms, farming, logging, mining

Organisms found in early stages of secondary

succession?• Weeds → Perennial grasses and

shrubs → Hardwood trees eventually (deciduous forest)

Climax Community• Plant community dominated by trees • Representing final stage of natural

succession for specific location – stable plant community– remains essentially unchanged in species composition

as long as site remains undisturbed• birch, beech, maple,

hemlock• oak, hickory, pine