Reading Essentials for Biology Glencoe, страница 8

As autotrophs and heterotrophs use this carbon, they release carbon dioxide into the air. The carbon cyclecontinues very slowly. How rapidly it cycles depends upon whetherthe carbon is found in soil, leaves, roots, in oil or coal, in animalfossils, or in calcium carbonate reserves.What is the nitrogen cycle?Copyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.Nitrogen is another element important to living things.Although 78 percent of air is nitrogen, plants cannot use thisform well.

There are bacteria, though, that change the nitrogenfrom air to a form plants can better use. This form is found in thesoil. Plants use this nitrogen to make proteins. Animals eat theplants and change the plant proteins into animal proteins. Theseproteins are used in building muscle and blood cells. Urine is ananimal waste that lets animals get rid of nitrogen they do notneed.

This urine returns nitrogen to the soil. When organismsdie and decay, nitrogen returns to the soil. Plants then reuse thisnitrogen. Soil bacteria also act on these dead organisms and putnitrogen back into the air. In this way, nitrogen is always cyclingthrough the system.5. What type of organismschange nitrogen in theair into a form plants canbetter use?________________________________________________________________________What is the phosphorous cycle?Phosphorus also cycles through ecosystems. It is another elementthat all organisms need. It cycles in two ways.

In the short-termcycle, plants get phosphorus from the soil. Animals get phosphorus from eating plants. When these animals die, their decayingbodies release phosphorus back into the soil to be used again.In the long-term cycle, materials containing phosphorus arewashed into rivers and oceans. As millions of years pass, the phosphorus becomes locked in rocks. Millions of years later, as theenvironment changes, some of the rock is no longer covered.As this rock wears away, the phosphorus is released back intothe environment.READING ESSENTIALSChapter 221NameDateClassSection2.2Nutrition and Energy Flow, continued◗ After You ReadMini Glossaryautotrophs (AW tuh trohfs): organisms thatuse energy from the sun or energy storedin chemical compounds to make theirown nutrientsfood web: a model that shows all the possiblefeeding relationships at each trophic level ina communitybiomass: the total mass or weight of all livingmatter in a given areaheterotrophs (HE tuh ruh trohfs): organisms thatcannot make their own food and must feedon other organisms for energy and nutrientsdecomposers: organisms, such as fungi andbacteria, which break down and absorbnutrients from dead organismstrophic (TROH fihk) level: an organism that represents a feeding step in the movement ofenergy and materials through an ecosystemfood chain: a simple model that shows how matter and energy move through an ecosystem1.

Review the terms and their definitions in the Mini Glossary above. Define autotrophs andheterotrophs in your own words. Give an example of an autotroph and a heterotroph.________________________________________________________________________________________________________________________________________________________________________2. Use the table below to help you review what you have read.

For each of the organismsshown in the food chain, choose three facts from the list below the table that are true. Thenwrite the facts in the table under the correct organism.Grass→Rabbit→performs photosynthesisheterotrophheterotrophon lowest trophic leveleats other heterotrophsautotrophon highest trophic leveleats autotrophsWolfprovides energy for other heterotrophs22Chapter 2READING ESSENTIALSCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.____________________________________________________________________________________NameDateClassSection2.2Nutrition and Energy Flow, continued3. Next to each of the statements below, place a T if the statement is true or an F if the statement is false._____a.

Although 78 percent of air is nitrogen, plants cannot use this form well._____b. Heterotrophs can get the energy they need directly from the sun._____c. During part of its cycle, phosphorus falls back to Earth as rain, ice, or snow._____d. All life on Earth is based on carbon.Copyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.Visit the Glencoe Science Web site at science.glencoe.com to findyour biology book and learn more about nutrition and energy flow.READING ESSENTIALSChapter 223NameDateClassSection3.1 CommunitiesSC.G.2.4.4 The student knows that the world ecosystems are shaped by physical factors that limit their productivity.Also covers SC.G.1.4.1, SC.G.2.4.2◗ Before You ReadThis section discusses organisms and how they are affected by where they live.

Think about thekinds of plants and animals you see around you. On the lines below, list as many types of plants andanimals you can think of that live in your community. Think of an organism that would have troublesurviving where you live. Write its name below, too.____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________◗ Read to LearnIdentify theMain Point Highlight themain point in each paragraph.Highlight in a different coloran example that helps explainthe main point.A community is made up of populations of organisms that livein a common area.

For example, weeds, beetles, worms, and bacteria might live in someone’s lawn. In that same lawn, there wouldalso be moisture and soil. This lawn community is made up ofpopulations of organisms and abiotic factors. They all contributeto the life of the lawn. The factors these populations share createtheir environment.Different combinations of living and nonliving factors interactin different places around the world.

They form communitieswhere conditions may be good for one form of life but notfor another.What is a limiting factor?1. Anything that limits anorganism’s ability to livein an environment iscalled a________________________________________________________________________24Chapter 3Anything that limits an organism’s ability to live in a particularenvironment is known as a limiting factor. For example, in mostmountain areas, there is a timberline.

Trees cannot grow abovethe timberline. It is too high, too cold, too windy, and the soil istoo thin.Something that limits one population in a community canhave an indirect effect on another life form. A lack of water couldcause grass to die in an area. If an animal group living in that areadepends on grass for food, its population could decrease asa result.READING ESSENTIALSCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.Life in a CommunityNameDateClassSection3.1Communities, continuedWhat is the range oftolerance?Limits of TolerancePopulationThe ability of living thingsto survive the changes in theirOrganismsenvironment is called tolerabsentOrganismsance. An organism reachesinfrequentits limits of tolerance when itGreatest numberof organismsgets too much or too little ofan environmental factor. Forexample, corn plants needZone ofZone ofwarm, sunny weather and aphysiologicalintoleranceOptimum rangestressregular supply of water.

Ifthese conditions do not existRange of toleranceover a long period of time,Lower limitthe plants may survive, butthey will not produce a crop.The figure above shows the range of tolerance for organisms.Notice that in the zones of intolerance, the corn plants would notgrow. In the zones of stress, the crop would be poor.

The cornplants grow the best in the optimum range.Copyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.Succession: Changes over TimeSuccession (suk SE shun) is the process of gradual, naturalchange and species replacement that takes place in the communities of an ecosystem over time. There are two types of succession—primary and secondary.OrganismsabsentOrganismsinfrequentZone ofphysiologicalstressZone ofintoleranceUpper limit2. What is succession?________________________________________________________________________What is primary succession?Primary succession takes place on land where there are noliving organisms. For example, when lava flows from a volcano,it destroys everything around it.