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18 Cards in this Set

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Explain the importance of autotrophic organisms with respect to energy flow and nutrient cycling in ecosystems.
Autotrophic organisms covert energy(sunlight)to chemical energy,passed to heterotrophs in the organic compunds of food,and dissipated in the form of heat.
Energy flow through an ecosystem is ultimately dissipated into space as heat. Where as chemical elements are continually recycled.
List and describe the importance of the four consumer levels found in an ecosystem.
Chemical cycling and energy flow are passed through all four consumer levels giving off heat and eventually leads to detritus and the nutrients then cycle back to the primary producers.
1)Primary consumers
2)Secondary consumers
3)Tertiary consumers
4)Detritivores(decomposers)
Explain how gross primary productivity is allocated by the plants in an ecosystem.
GPP is allocated in plants by using some of the molecules as fuel in their own cellular respiration.
GPP is the amount of light energy that is converted to chemical energy by photosynthesis per unit time.
List the factors that can limit productivity of an ecosystem.
1)The extent of photosynthetic production sets the spending limit for the energy budget of the entire ecosystem.
2)In aquatic ecosystems, both light and nutrients are important in controlling the primary production.
Overall,terrestrial ecosystems contribute approximately 2/3 of global net primary production and marine ecosystems approximately 1/3.
Explain why productivity declines at each trophic level.
Trophic efficiencies must always be less in production b/c it takes into account not only the energy lost through respiration and contained in feces,but also the energy in organic material in a lower trophic level that is not consumed by the next trophic level.
Trophic efficiency- the percentage of production transferred from one trophic level to the next.
Distinguish between energy pyramids and biomass pyramids.
Energy pyramids-the size of each block is proportional to the net production, expressed in energy units,of each trophic level.
Biomass pyramids-each tier represents the standing crop (the total dry weight of all organisms) in one trophic level.
Energy pyramids are stacked in blocks,with primary producers forming the foundation of the pyramid.
Biomass pyramid-narrow sharply from primary producers at the base to top-level carnivores at the apex b/c energy transfers between trophic levels are so inefficient.
Describe the hydrologic cycle.
The main process driving the water cycle are evaporation of liquid water by solar energy,condensation of water vapor into clouds, and precipitation.Surface and groundwater flow can return water to the oceans, completeing the water cycle.
The water cycle.
Describe the carbon cycle.
Photosynthesis by plants and photoplankton removes large amounts of CO2 each year.CO2 is also added to the atmosphere through cellular respiration by producers and consumers.The burning of fossil fuels is adding significant amounts of additional CO2 to the atmosphere.
Describe how the carbon cycle differs in terrestrial and aquatic systems.
In aquatic environments carbon cycling is more complex due to interaction of CO2 with water and limestone.
During the carbon cycle, autotrophs acquire carbon dioxide (CO2) from the atmosphere by diffusion, incorporating it into their biomass. Some of this becomes a carbon source for consumers, and respiration returns CO2 to the atmosphere.
Describe the nitrogen cycle.
The major pathway for nitrogen to enter an ecosystem is via nitrogen fixation.
Ammonification is the decomposition of organic nitrogen back into ammonium. Nitrification is a metabolic process by which certain aerobic soil bacteria use ammonium (NH4+) as an energy source by first oxidizing it to nitrite (NO2) and then to nitrate(NO3).
Denitrification occurs when bacteria obtain the oxygen necessary for their metabolism from NO3- rather than O2 under anaerobic conditions. This process returns nitrogen to the atmosphere by converting NO3to N2.
Nitrogen fixation-the conversion of N2 by bacteria to forms that can be used to synthesize nitrogenous organic compounds.Some nitrogen is fixed by lightning.
Explain the importance of nitrogen fixation to all living organisms.
Can be used to synthesize nitrogenous organic compounds such as amino acids.
Explain how phosphorous is recycled locally in most ecosystems.
Organic phosphate is transferred from plants to consumers and returned to the soil through the action of decomposers or by animal excretion.
Humus and soil particles usually bind phosphate, keeping it available locally for recycling.
Explain why the soil in tropical forests contains lower levels of nutrients than soil in temperate forests.
The relatively low concentrations of some nutrients in the soil of tropical rain forests result from a fast cycling time.
Warmer temperatures and more abundant precipitation in the tropical forest speeds up the rate of decomposition.
Describe how agricultural practices can interfere with nitrogen cycling.
Agricultural practices,such as,harvesting crops, have a huge effect on nitrogen cycling. Excess soil nitrogen can contribute to global warming,ozone thinning,& acid precipitation.Nitrogen that exceeds the critical load can contaminate groundwater, degrade lakes & rivers,& drain into the ocean.
Critical load- the amount of added nutrient that can be absorbed by plants w/o damaging the ecosystem.
Describe how deforestation can affect nutrient cycling within an ecosystem.
The effect of deforestation on nutrient cycling is increased water runoff by 30-40%;net loss of minerals was large;and nitrate increased in concentration in the creek,removing this critical soil nutrient and contaminating drinking water.
Describe how "cultural eutrophication" can alter freshwater ecosystems.
Sewage & fertilizer runoff from farms and yards add large amounts of nutrients to lakes,killing off most fish species because of the nutrient phosphorus enables cyanobacteria to bloom.
Eutrophication-A process by which nutrients,partially phosphorus and nitrogen, become highly concentrated in a body of water,leading to increased growth of organisms such as algae.
Cultural eutrophication refers to situations where the nutrients added to the water body originate mainly from human sources,such as agricultural drainage or sewage.
Explain why toxic compounds usually have the greatest effect on top-level carnivores.
Magnification occurs because the biomass at any given trophic level is produced from a much larger biomass ingested from the level below.
Biological Magnification- Toxins that become more concentrated in successive trophic levels of a food web.
Describe how increased atmospheric concentrations of carbon dioxide could affect the earth.
Increased atmospheric concentrations of CO2 will increase global temperature.