Transcript Document

Dynamics of Ecosystems
Chapter 54-55
Biology Raven and Johnson 7th Ed
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Mimicry
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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
3
Coevolution and Symbiosis
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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
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Keystone species
– Species that have a particularly strong
effect on community composition.
 top predators
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Succession
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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
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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
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Phosphates weather from soils into water,
enter plants and animals, and are redeposited 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
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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
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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
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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
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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
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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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