1 dynamics of ecosystems chapter 57. 2 flow of energy in ecosystems first law of thermodynamics:...
TRANSCRIPT
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Dynamics of Ecosystems
Chapter 57
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Flow of Energy in Ecosystems
• First Law of Thermodynamics: energy is neither created nor destroyed; it changes forms
• Second Law of Thermodynamics: whenever organisms use chemical-bond or light energy some is converted to heat (entropy)
• Sun our major source of energy (E)
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• Trophic levels: level an organism “feeds” at
• Producers (autotrophs): “self-feeders” make organic compounds (photosynthesis)
• Consumers (heterotrophs): must take in food
Flow of Energy in Ecosystems
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• Consumers are classified by their diet
• Herbivores: first consumer level, eat plants• Primary carnivores: eat herbivores• Secondary carnivores: eat primary
carnivores or herbivores• Detritivores: eat decaying matter–Decomposers: microbes that break up
dead matter – “CHONPS”
Flow of Energy in Ecosystems
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Trophic levels within an ecosystem
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• Productivity: the rate at which the organisms in the trophic level collectively synthesize new organic matter
• Primary productivity: producers• Respiration: rate producers use org. compounds• Net primary productivity (NPP) = PP – respiration
• Secondary productivity: productivity of a heterotroph trophic level
Flow of Energy in Ecosystems
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• biomass: the amount of organic matter present at a particular time
• Only small fraction of incoming solar energy is captured by producers ~ 1%/year– Used to make chemical-bond energy– As energy passes up the food chain, most is
lost as heat and waste– Less biomass/fewer individuals at each
trophic level
Flow of Energy in Ecosystems
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• 50% of chemical-bond energy is not assimilated and is egested in feces
• 33% of ingested energy is used for cellular respiration
• 17% ingested energy is converted into insect biomass
Flow of Energy in Ecosystems
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Flow of energy through the trophic levels of Cayuga Lake
Flow of Energy in Ecosystems
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• Biomagnification: becomes more concentrated at higher trophic levels
• predatory bird species’ eggshells so thin that the shells broke during incubation
Human Impacts: Pollution
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Ecosystem productivity per year
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• Trophic level interactions– Trophic cascade: process by which effects
exerted at an upper level flow down to influence two or more lower levels
– Top-down effects: when effects flow down– Bottom-up effects: when effect flows up through
a trophic chain
Flow of Energy in Ecosystems
15Trophic cascade in a large-scale ecosystem
Flow of Energy in Ecosystems
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• Human removal of carnivores produces top-down effects– Over fishing of cod - 10% their previous numbers– Jaguars and mountain lions absent on Barro
Colorado Island– Smaller predators become abundant
Example: Top-down
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• When primary productivity is low, producer populations cannot support herbivore populations
• As primary productivity increases, herbivore populations increase
• Increased herbivore populations lead to carnivore populations increasing
Example: bottom-up
18Bottom up effects
Flow of Energy in Ecosystems
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• Species richness is influenced by ecosystem characteristics–Primary productivity–Habitat heterogeneity• Accommodate more species
–Climatic factors
Biodiversity and Stability
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Factors that affect species richness
Biodiversity and Stability
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• Tropical regions have the highest diversity–Species diversity cline: biogeographic
gradient in number of species correlated with latitude – Evolutionary age of tropical regions– Increased productivity– Stability/constancy of conditions–Predation– Spatial heterogeneity
Biodiversity and Stability
22Latitudinal cline in species richness
Biodiversity and Stability