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Dynamics of EcosystemsChapter 54-55

Biology Raven and Johnson 7th Ed

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Mimicry

• Batesian mimicry– Palatable insects resemble brightly

colored, distasteful species.• Mullerian mimicry

– Unrelated protected species resemble one another.

predators learn more quickly

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Mimicry

• Batesian mimicry– Palatable insects resemble brightly

colored, distasteful species.• Mullerian mimicry

– Unrelated protected species resemble one another.

predators learn more quickly

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Coevolution and Symbiosis

• Coevolution involves long-term mutual evolutionary character adjustments of two or more species.

– predator-prey interactions– symbiotic relationships

two or more kinds of organisms live together in permanent relationships

commensalism, mutualism, and parasitism

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Interactions Among Ecological Processes

• Keystone species– Species that have a particularly strong

effect on community composition. top predators

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Succession

• Succession is the process of ecosystems changing from a simple to a more complex structure.

– primary succession - occurs in bare or open areas

eutrophication of oligotrophic lakes Lichens first, then mosses, then larger

plants.– secondary succession - occurs following

only when soil is already present

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Carbon Cycle

CO2 is formed in many ways, but only photosynthesis can break it down.

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The Nitrogen Cycle

• Relatively few types of organisms can fix nitrogen into forms that can be used for biological processes.

• Nitrogen fixation: N2+ 3H2 2NH3

– Only symbiotic bacteria fix enough nitrogen to be of major significance in nitrogen production.

– ammonification– denitrification

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Nitrogen Cycle

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The Phosphorus Cycle

• Phosphates weather from soils into water, enter plants and animals, and are re-deposited in the soil when plants and animals decompose.

– Millions of tons are added to agricultural land annually to increase crop production.

Superphosphate- can cause oligotrophication of water sources by “choking”.

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Phosphorus Cycle

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Trophic Levels

• Autotrophs - capture light energy and manufacture own chemical energy

– primary producers• Heterotrophs - must obtain organic

molecules that have been synthesized by autotrophs

– consumers

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Trophic Levels

– Primary consumers - herbivores– Secondary consumers - organisms that

feed on herbivores– Decomposers - break down complex

organic material into simpler compounds– Detritivores - live on refuse of an

ecosystem

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Trophic Levels

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Trophic Levels

• Trophic level refers to the feeding level of an organism.

– Organisms from each trophic level constitute a food chain.

Interconnected food chains constitute a food web.

• On average, 10% of the organic matter (energy) transfers from one trophic level to the next.

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Primary Productivity

• Primary productivity refers to the amount of organic matter produced from solar energy in a given area during a given period of time.

– Gross primary productivity is the total organic matter produced.

– Net primary productivity is the amount of organic matter produced that is available to heterotrophs.

• Secondary productivity - rate of production by heterotrophs

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The Energy in Food Chains

• Due to the Second Law of Thermodynamics, food chains are generally limited to three or four steps (trophic levels).

– A community’s productivity is ultimately determined by the amount of sunlight it receives.

– In northern climates, net primary productivity often increases as the growing season lengthens.

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