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WORKSHEET: ECOSYSTEMS

1. The Nature of EcosystemsA. Overview of the Participants

1. Regions on the earth function as systems running on energy from the______ processed through various organisms.2. __________________ are autotrophs that can capture sunlight energy and incorporate it into organic compounds.3. __________________ are heterotrophs that feed on tissues of other organisms.

a. ___________eat plants.b. ____________eat animals.c. ________________ reside in or on living hosts and extract energy from them.d. ___________________ eat a variety of organisms.

4. ___________include small invertebrates that feed on partly decomposed particles of organic matter (detritus).5. ________________ are also heterotrophs and include fungi and bacteria that extract energy from the remains or products of organisms.6. An _______________ is a complex of organisms interacting with one another and with the physical environment.

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a. Ecosystems are open systems through which energy _____________and materials are cycled.b. Ecosystems require energy and __________input; they generate energy (usually as heat) and nutrient output.

B. Structure of Ecosystems1. _________ (“feeding”) levels are a hierarchy of energy transfers, or bluntly stated, “Who eats whom?”

a. Level 1 (closest to the energy source) consists of ___________________; level 2 comprises _______________; and levels 3 and above are_________________.b. _______________feed on organisms from all levels.

2. Food chains cross-connect to form food webs.a. A sequence of who eats whom is called a food chain; for example, plant ——> cutworm ——> garter snake ——> sandpiper ——> marsh hawk.b. Interconnected food chains comprise ________________ in which the same food resource is often part of more than one food chain.

2. The Nature of Food WebsA. How many energy transfers are there?

1. Energy that producers initially capture passes through no more than four or five transfers.2. Energy is ____________ at each transfer.

B. There are ___________ categories of food webs.1. Energy flows into ecosystems from the______________.

a. Energy ____________ through ecosystems by way of grazing food webs, in which energy flows from plants to herbivores and then to carnivores.b. In____________ food webs, it flows mainly from plants through decomposers and detritivores.

2. Energy leaves ecosystems through ________________ generated by metabolism.

3. DDT in Food WebsA. DDT, which was an effective chemical to kill mosquitoes,

______________________ in fatty tissues and results in biological magnification and unexpected nontarget effects.

B. Even though DDT has been ___________________since the 1970s, the chemical is very persistent in certain sections of the environment, namely sediments.

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4. Studying Energy Flow Through EcosystemsA. What Is Primary Productivity?

1. ________________________ is the rate at which producers get and store energy in their tissues.

a. ____________ productivity is the total rate of photosynthesis for the ecosystem during a specified interval.b. ________ ecosystem production is the energy left over after that which is used by the plants and soil organisms is subtracted from the gross primary production.

2. Many _________ impact net production, including body size, mineral availability, temperature range, sunlight, and rainfall.

B. Ecological Pyramids1. __________________ can be diagrammed as a pyramid in which producers form a base for successive tiers of consumers above them.2. Pyramids can be of two basic types.

a. A __________________ makes provision for differences in size of organisms by using the weight of the members in each trophic level.b. An _____________________ reflects the trophic structure most accurately because it is based on energy losses at each level.

5. Energy Flow Through Silver SpringsA. To construct an energy pyramid for a freshwater spring,

you must measure the _______________________ in each organism and then multiply that by the ____________________.

B. Only about ____________________ of the energy entering one level becomes available to organisms at the next level.

6. Overview of Biogeochemical CyclesA. ______________________ cycles influence the availability of

essential elements in ecosystems.1. ______________ are available to producers as ions.2. ______________________ are maintained by environmental inputs and recycling activities.

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3. The amount of nutrients being ______________ is greater than the amount entering or leaving.4. Environment _____________ are by precipitation, metabolism, and weathering. Outputs are by runoff and evaporation.

B. There are three categories of _______________ cycles.1. In the ____________________, oxygen and hydrogen move as water molecules.2. In the ________________________, elements can move in the gaseous phase; examples include carbon and nitrogen.3. In ____________________, the element does not have a gaseous phase; an example is phosphorus.

7. Global Cycling of WaterA. Water is moved or stored by evaporation, precipitation,

retention, and transportation.1. A __________________ rain or snow into a single river.2. Nutrients are _______________ by plants to prevent their loss by leaching.

B. The Water Crisis1. Large-scale ________________________ accounts for nearly two-thirds of the human population’s use of freshwater.

a. Salt buildup (_______________) of the soil and waterlogging can result.b. Withdrawal of underground water causes water _________________ to drop.

2. About ___________________ of the world’s population depends on groundwater for drinking water, but groundwater is being polluted by _________________ chemicals leached from landfills and waste dumps.3. Human waste, insecticides, herbicides, chemicals, radioactive materials, and heat can _____________ water.4. In the past decade, thirty-three nations have engaged in ________________ over reductions in water flow, pollution, and silt buildup.5. Most of the earth’s water is too ____________ for human consumption or for agriculture.

a. _____________________ processes are available and can be used when absolutely necessary.

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b. However, desalinization is not cost effective in most locales, and it uses valuable _______________ reserves to provide the energy for the desalination equipment.

8. Carbon CycleA._______________ enters the atmosphere (where it exists as

carbon dioxide) by aerobic respiration, fossil-fuel burning, and volcanic eruptions.

1. Carbon is ________________ from the atmosphere (and bodies of water) by photosynthesizers and shelled organisms.2. _________________ of buried carbon compounds millions of years ago caused the formation of fossil fuels.3. Burning of _______________ puts extra amounts of carbon dioxide into the atmosphere, an occurrence that may lead to global warming—the greenhouse effect.

B. Most researchers think the _______________ buildup in the atmosphere is amplifying the greenhouse effect.

9. Greenhouse Gases, Global WarmingA. _________________ effect is the name for the warming

action of the earth.1. The greenhouse gases (carbon dioxide, water vapor, ozone, methane, nitrous oxide, and CFCs) trap _____________as they escape from the earth back into space.2. Heat builds in the lower atmosphere—the greenhouse effect.

B. Evidence of Global Warming1. _______________ have risen by one degree F since 1861.2. Nine of the ten hottest years have occurred since ____________.

10. Nitrogen CycleA. Nitrogen is a part of several steps in a cycling process.

1. In _________________ bacteria convert N2 to NH3, which is then used in the synthesis of proteins and nucleic acids.2. By _____________________ bacteria and fungi breakdown nitrogenous compounds, forming ammonium.

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3. _________________is a type of chemosynthesis where NH3 or NH4+ is converted to NO2–; other nitrifying bacteria use the nitrite for energy and release NO3–.4. __________________ is the release of nitrogen gas to the atmosphere by the action of bacteria (NO2– and NO3– N2).

B. Human Impact on the Nitrogen Cycle1. Although the soil is enriched by nitrogen-fixing bacteria, soil nitrogen is still scarce due to leaching, denitrification, and farming methods that emphasize synthetic fertilizers.2. Air pollutants, including oxides of nitrogen, contribute to soil acidity.3. Heavy _______________ applications not only are costly but also are lost in runoff and harvested crops.

11. Phosphorus CycleA. _________________________ moves from land, to sediments

in the seas, and back to the land in its long-term geochemical phase of the cycle.

1. In the ecosystem phase, plants take up the phosphorus from the soil; it is then transferred to herbivores and carnivores, which ________________. Of all minerals, _________________is the most limiting factor in all natural ecosystems.

B. Runoff from agricultural applications of fertilizers adds large amounts of phosphorus to aquatic ecosystems; this is called ___________________________.

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