Transcript Ecology

Inquiry into Life
Eleventh Edition
Sylvia S. Mader
Chapter 34
Lecture Outline
34-1
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34.1 The biotic components of
ecosystems
• Populations of an ecosystem
– Autotrophs- primary producers
• Require an energy source and inorganic nutrients to produce
organic food molecules
• Manufacture organic nutrients for all organisms
• Green plants and algae-photosynthesis
• Bacteria-chemoautotrophs
– Heterotrophs- consumers
• Consume organic nutrients
– Herbivores, carnivores, omnivores
• Decomposers- fungi, bacteria
– Break down decaying matter releasing nutrients
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Biotic components
• Fig. 34.1
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The biotic components of ecosystems
cont’d.
• In and Ecosystem Energy flows and Chemicals cycle
– Energy enters ecosystem in the form of sunlight absorbed by
producers
– Chemicals enter when producers absorb inorganic nutrients
– Produces then make organic nutrients for themselves and all
other organisms in the ecosystem
• Consumers (herbivores and omnivores) gain nutrients and energy
from eating producers
• Higher level consumers (carnivores) then gain nutrients and energy
from eating herbivores and omnivores
– Some energy is released at each level of the environment in the
form of heat and waste products
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Energy flow and chemical cycling
• Fig. 34.2
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Energy balances
• Fig. 34.3
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The biotic components of ecosystems
cont’d.
• The following two slides illustrate food webs
– Food webs illustrate the interrelationships between organisms in
the food chain
– Identify the producers, primary consumers, and secondary
consumers
• Laws of thermodynamics
– First law- energy is neither created nor destroyed
• Ecosystems depend on continual outside source of energy
– Second law- with every transformation, some energy is
given off as heat
• The amount of available energy at each successive trophic
level is less than the one below it
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Grazing food webs
• Fig. 34.4
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Detritis food web
• Fig. 34.5
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34.2 Energy flow
• Trophic levels
– Trophic level is composed of all organisms that feed at a
particular link in the food chain
• Primary producers- first trophic level
• Primary consumers- second trophic level
• Secondary consumers- third trophic level
• Ecological pyramids
– Represent amount of available energy in each trophic level
– Producers are at the base- the most available energy
• Energy is given off in less usable forms as producers are eaten by
primary consumers, etc.
– Biomass- the number of organisms at each level multiplied by
their weight
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Ecological pyramid
• Fig. 34.6
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34.3 Global biogeochemical cycles
• Biogeochemical cycles
– Pathways involve both biotic and abiotic components
• Reservoir-source unavailable to producers
• Exchange pool-source from which organisms take chemicals
• Biotic community-chemicals move through community along food chains
– 2 main types of cycles
• Gaseous cycle-drawn from and returns to the
atmosphere
• Sedimentary cycle-element is drawn from soil by plant
roots, eaten by consumers, returned to soil by
decomposers
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Model for chemical cycling
• Fig. 34.7
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Global biogeochemical cycles cont’d.
• The water cycle
– Freshwater evaporates from bodies of water
– Precipitation over land enters ground, surface waters,
aquifers
– Eventually returns to oceans over time
– Hydrologic cycle is illustrated on the following slide
• Note that size of arrow is proportional to rate of transfer
– Human impact
• In arid southwest and southern Florida, water mining is
occurring
– Aquifers are being drained faster than they can be
naturally replenished
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The hydrologic cycle
• Fig. 34.8
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Global biogeochemical cycles cont’d.
• The phosphorus cycle
– Phosphate enters soil as rocks undergo weathering process
– Picked up by producers and cycles through consumers and
finally decomposers
– Human impact
• Accelerated transfer rate due to phosphate mining,
supplementation on farm fields, detergents
– Cultural eutrophication- over-enrichment
» Can lead to increased algal bloom
» As algae die off, decomposers consume high levels of
oxygen in the water
» Results in massive fish kills
– Phosphorus cycle is illustrated on the following slide
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The phosphorus cycle
• Fig. 34.9
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Global biogeochemical cycles cont’d.
• The nitrogen cycle
– Nitrogen fixation-conversion of nitrogen gas N2 to ammonium
NH4+ by bacteria
– 78% of atmosphere is nitrogen gas, but unusable by
plants
– Root nodules of legumes house nitrogen-fixing bacteria
– Nitrification-production of nitrates which plants can also use
• Nitrogen gas converted to nitrate in atmosphere by lighting, meteor
trails, cosmic radiation
• Ammonium in soil converted to nitrate by nitrifying bacteria
– Denitrification-conversion of nitrate back to nitrogen gas by
denitrifying bacteria
– Human activities- N2 from fertilizers increases transfer rates
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The nitrogen cycle
• Fig. 34.10
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Global biogeochemical cycles cont’d.
• The carbon cycle
– Photosynthesis takes up carbon dioxide from the atmosphere
– Cell respiration returns it to the atmosphere
– Reservoirs of carbon
• Dead organisms- fossil fuels
• Forests
– Human activities
• More carbon dioxide is being deposited in atmosphere
than is being removed
– Due to deforestation and burning of fossil fuels
• Increased carbon dioxide in atmosphere contributes to
global warming, which is caused by an increase in
Greenhouse Gasses and can lead to a rise in sea levels
affecting coastal cities and can cause changes in global
climate patters with disastrous effects.
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The carbon cycle
• Fig. 34.11
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Nitrogen and Air Pollution
• Human activities convert atmospheric nitrogen to
fertilizer which when broken down by soil bacteria adds
nitrogen oxides to the atmosphere at three times the
normal rate.
• Humans also burn fossil fuels which put
nitrogen oxides (NOx) and sulfur dioxide
(SO2) in the atmosphere.
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• Nitrogen oxides and sulfur dioxide react with
water vapor to form acids that contribute to
acid deposition (Acid Rain).
• Acid deposition is killing lakes and forests and also
corrodes marble, metal, and stonework.
• Nitrogen oxides and hydrocarbons (HC) react to form
photochemical smog, which contains ozone and PAN
(peroxyacetylnitrate), oxidants harmful to animal and
plant life.
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Acid deposition
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• A thermal inversion, where these pollutants
are trapped under warm, stagnant air
concentrates pollutants to dangerous levels.
• Nitrous oxide is not only a greenhouse gas, but
contributes to the breakdown of the ozone shield that
protects surface life from harmful levels of solar
radiation.
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Thermal inversion
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