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30 Cards in this Set
- Front
- Back
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• Ecosystem
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o Consists of all organisms living in a community as well as all the abiotic factors with which they interact
o Involves two processes: energy flow and chemical cycling • Energy enters ecosystems as sunlight and leaves in the form of heat • Energy flows through ecosystems (cannot be recycled) • Without the sun, ecosystems wouldn’t have a source of energy- need a constant source of energy • Matter cycles through ecosystems (can be recycled) |
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• Primary producers
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o Autotrophs
o Trophic level that supports all other levels o Convert light energy into chemical energy o Can be ANY autotrophic organism (plants, amoeba, algae) |
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• Primary consumers
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o Organisms that eat primary producers
o Often herbivores |
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• Secondary consumers
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o Eat primary producers
o Carnivores that eat herbivores |
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• Tertiary consumers
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o Carnivores that eat carnivores
o Eat secondary consumers |
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• Detritivores
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o Aka decomposers (prokaryotes and fungi)
o Consumers that get energy from detritus (nonliving organic material) o Ex: feces, dead organisms, fallen leaves, wood o Link primary producers and consumers o Contribute to chemical cycling by breaking down organic material and turning it into other forms |
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• Primary production
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o Amount of light energy converted to chemical energy by autotrophs
o The extent of photosynthetic production determines how much energy goes into an ecosystem |
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• Gross primary production (GPP)
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o Total primary production
o Amount of light energy converted to chemical energy by photosynthesis per unit time |
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• Net primary production (NPP)
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o Gross primary production minus the energy used by the primary producers for respiration
o NPP=GPP-R o Represents the amount of chemical energy available to consumers in an ecosystem o Estuaries, coral reefs, and rainforests have high net primary production |
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• Biomass
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→ the total mass of all the organisms in an ecosystem (minus the weight of the water in each organism)
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• Standing crop
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total biomass of photosynthetic autotrophs present at a given time
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• Why are oceans unproductive?
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o Light limitation
• Decreased light decreases primary production • For oceans, much of the radiation is absorbed in the first meter of water o Nutrient limitation • Limiting nutrient→ element that must be added for production to increase in an area (often nitrogen or phosphorus) • Nutrient availability determines marine primary production |
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• Eutrophication
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o Ecosystem response to the addition of artificial or natural substances like nitrates and phosphates through fertilizer or sewage to an aquatic system
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• Actual evapotranspiration
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o Annual amount of water transpired by plants and evaporated from a landscape
o Increases with the amount of precipitation in a region and the amount of solar energy available to drive evaporation/transpiration o More actual evapotranspiration=higher net primary production |
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• Secondary production
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o Amount of chemical energy in consumers’ food that is converted to their own new biomass during a given time period
o Production of consumers |
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• Inefficient transfer of energy
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o Transfer of energy is inefficient→ if a caterpillar eats 200 J of energy it only gets 33 J of energy
• Energy in feces and in respiration is lost o only chemical energy stored as biomass is available as energy to the ecosystem o most net primary production is not consumed by herbivores o Production efficiency=energy stored in biomass/total energy eaten • Warm blooded animals have low production efficiencies |
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• Trophic efficiency
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o Percentage of production transferred from one trophic level to the next
o 80-95% of energy available at one trophic level is not transferred to the next o 10% of energy at one trophic level is transferred to the next |
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• Pyramid of net production
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o When the trophic levels are stacked in blocks with primary producers forming the foundation of the pyramid
o Size of each block is proportional to amount of energy at each trophic level |
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• Pyramid of Biomass
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o When each tier represents the total dry weight of all organisms in each trophic level
o Biomass dramatically decreases as you move up trophic levels b/c energy transfer is so inefficient o Some aquatic ecosystems have inverted pyramids of biomass • Primary consumers outweigh producers • Happens when producers (phytoplankton) grow and reproduce and are consumed by zooplankton so fast that they never develop a large population size • Phytoplankton have short turnover time • Turnover time=biomass/production • Phytoplankton can reproduce fast enough to support a big population of zooplankton (primary consumers) |
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• Pyramid of numbers
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o 0.1% of chemical energy fixed by photosynthesis flows all the way to the top trophic levels
• that’s why food webs only have 4-5 trophic levels o top level consumers are bigger in size • So the limited biomass at the top of a pyramid is concentrated in a small number of large individuals o Size of each block is proportional to number of individuals in each tier |
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• Green world hypothesis
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o Terrestrial herbivores consume relatively little plant biomass because they are held in check by factors like predators, parasites, and disease
o That’s why there’s still a lot of plants- herbivores don’t eat it all o Herbivores consume less than 17% of total net primary production by plants o Parts of the hypothesis • Plants have defenses against herbivores (so herbivores can’t eat all plants) • Nutrients, not energy supply, usually limit herbivores • Lack of nutrients hurt herbivores (not lack of energy) • Abiotic factors limit herbivores • Unfavorable temperatures, moisture etc. hurt herbivore survival so they don’t eat all the plants • Intraspecific competition can limit herbivore numbers • Competition limits herbivore population • Interspecific interactions keep herbivore densities in check • Predators, parasites, disease limit herbivore population growth • Application of top down model |
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• Biogeochemical cycles
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another name for nutrient circuits (chemical cycling)
o Global cycles deal with gases (b/c the atmosphere cycles everywhere) o Local cycles deal with solids (like phosphorus and calcium) |
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• Water Cycle
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o Evaporation of liquid water by solar energy
o Condensation of water vapor into clouds and precipitation o It rains o Transpiration of water by terrestrial plants o Some water runs off into the ocean |
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• Carbon cycle
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o CO2 is released into the atmosphere
• Burning of fossil fuels and wood • Cellular respiration • Decomposition o CO2 is absorbed from the atmosphere • Through photosynthesis o Animals eat plants and obtain carbon |
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• Nitrogen cycle
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o N2 is absorbed from the atmosphere
• Nitrogen fixation→ converts N2 to NH3 • Ammonification→ converts NH3 to NH4+ (ammonia) • Nitrification→ NH4+ is converted to NO3- by nitrifying bacteria • NO3- gets sucked up by plants o Nitrogen is assimilated by organisms • Plants suck up NO3- • Consumers eat plants and pee • Decomposers decompose dead tissue and urine into NH4+ o N2 is released into the atmosphere • Denitrification→ anaerobic denitrifying bacteria use NO3- instead of O2 and release N2 |
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• Phosphorus cycle
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o Phosphorus stuck in a rocky mountain
o Rain weathers the rock and causes sediment to wash into a river o River adds phosphorus to the soil o Plants take up phosphorus through their roots o Consumers eat the plants o Consumers and plants die or poop o they decompose and add the phosphorus back into the soil |
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• Rate of decomposition increases with actual evapotranspiration
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o more decomposition increases rate of nutrient cycles
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biological magnification
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toxins become more concentrated in successive trophic levels of a food web
b/c biomass at any given trophic level is produced from a larger biomass ingested from the level below ex: PCBs and DDTs concentration of PCB in herring gull eggs was 5000 times greater than in the phytoplankton |
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greenhouse effect
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atmosphere traps some infrared rays within the earth, keeping it warm (which is a good thing as long as it's not trapping too much heat)
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depletion of atmospheric ozone
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Ozone layer (O3) protects the earth from absorbing too many UV rays
Ozone layer absorbs UV radiation, preventing much of it from reaching the organisms on earth the ozone layer is currently thinning and holes are being discovered more UV rays will enter the atmosphere which is bad depletion of ozone layer is due to accumulation of CFCs |
