Reading Essentials for Biology Glencoe, страница 7

Review the terms and their definitions in the Mini Glossary above. Circle the three termsthat identify specific types of relationships between organisms that live in the same ecosystem. On the lines below, give an example of each type of relationship.____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________2.

Use the pyramid diagram below to help you review what you have read. List the four levelsthat ecologists have organized the living world into. Start with the least complex level at thebottom and work your way up.READING ESSENTIALSChapter 215NameDateClassSection2.1Organisms and Their Environment, continued3. In Column 1 are some new concepts you learned about in this section. Column 2 gives oneexample of each concept.

Use the line next to each concept to put the letter of the examplethat matches it.New ConceptColumn 1_____1. abiotic factor_____2. habitat_____3. predator-prey relationship_____4. biological community_____5. parasitismExampleColumn 2a. an owl eating a mouseb. a rain forestc. raind. a tick on a cate. millipedes, centipedes, insects, slugs, andearthworms under a logCopyright © 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 organisms and their environment.16Chapter 2READING ESSENTIALSNameDateClassSection2.2 Nutrition and Energy Flow◗ Before You ReadSC.G.1.4.2 The student understands how the flow of energy through an ecosystem madeup of producers, consumers, and decomposers carries out the processes of life and thatsome energy dissipates as heat and is not recycled. Also covers SC.B.1.4.1, SC.B.1.4.2,SC.B.1.4.7, SC.F.1.4.4, SC.G.2.4.1, SC.G.1.4.1, SC.G.1.4.3This section discusses how organisms interact with their environment to get the food and energythey need.

On the lines below, explain how a pet’s food might be different if it had to live in the wildand get its own food.______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________◗ Read to LearnHow Organisms Obtain EnergyCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.One of the most important things about a species’ niche is howthe species gets its energy.

Ecologists study the flow of energythrough communities to discover nutritional relationshipsbetween organisms.Autotrophs The ultimate source of energy for all life is the sun.Plants use the sun’s energy to make food. This process is calledphotosynthesis (foh toh SIN thuh suhs). This makes plantsautotrophs. Autotrophs (AW tuh trohfs), or producers, areorganisms that use light energy or energy stored in chemicalcompounds to make energy-rich compounds. Grass, trees, andother plants are the most familiar autotrophs, but some onecelled organisms, such as green algae, also make their own food.Heterotrophs Some organisms cannot make their own food.They must eat other organisms to get their food and energy.These organisms are called consumers, or heterotrophs(HE tuh ruh trohfs). Some heterotrophs, such as rabbits, feedonly on autotrophs. Other heterotrophs, such as lions, feed onlyon other heterotrophs.

Still other heterotrophs, such as bears andhumans, feed on both autotrophs and heterotrophs.Decomposers There are other organisms called decomposers.They break down the complex compounds of dead and decayingplants and animals. They change these compounds into simplerforms that they can use for fuel. Some protozoans, many bacteria,and most fungi are decomposers.READING ESSENTIALSMake an Outline Make anoutline of the informationyou learn about in this section. Use the headings in thereading as a starting point.Include the boldface terms.1.

What do decomposersdo?________________________________________________________________________Chapter 217NameDateClassSection2.2Nutrition and Energy Flow, continuedFlow of Matter and Energy in EcosystemsWhen you eat food, such as an apple, you consume matter.Matter, in the form of carbon, nitrogen, and other elements, flowsthrough the levels of an ecosystem from producers to consumers.Scientists call this flow of matter cycling. The apple is more thanmatter, though.

It also contains some energy from sunlight. Thisenergy was trapped in the apple as a result of photosynthesis. Asyou cycle the matter in the apple by eating it, some trapped energyis transferred from one level of the ecosystem to the next. At eachlevel, a certain amount of energy is also transferred to the environment as heat.What are food chains?2.

Interpret When energyis transferred betweentrophic levels, what isalways given off to theenvironment? (Circle yourchoice.)a. photosynthesisb. heatc. water18Chapter 2BerriesMiceBlack BearMost food chains are made up of two, three, or four transfers,or steps. Each organism in a food chain represents a feeding step,or trophic (TROH fihk) level, in the transfer of energy and matter. The amount of energy in the last transfer is only a small partof what was available at the first transfer. At each transfer, some ofthe energy is given off as heat.READING ESSENTIALSCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.Ecologists study feeding relationships and symbiotic relationships to learn how matter and energy flow in ecosystems.

Thesescientists sometimes use a simple model called a food chain. Foodchains show how matter and energy move through an ecosystem.In a food chain, nutrients and energy move from autotrophs toheterotrophs to, in the end, decomposers. A food chain is drawnusing arrows. The arrows show the direction in which energy istransferred. An example of a simple food chain in a forest ecosystem is shown below.NameDateClassSection2.2Nutrition and Energy Flow, continuedWhat is a food web?A food chain shows only one possible path for the transfer ofmatter and energy through an ecosystem. Many other paths mayexist because many different species can be on each trophic level.For instance, in the food chain example on the previous page,there are many animals in the forest other than mice that eatberries. Also, many different kinds of organisms eat more thanone type of food.

This means that a single species may feed atseveral different trophic levels. The black bear, for instance, doesnot eat only mice. It also eats berries. There also are other animals in the forest that eat berries and mice. For these reasons,ecologists also use food webs. Food webs are models that showall possible feeding relationships at each trophic level in a community. A food web is a more realistic model than a food chainbecause most organisms depend on more than one type of organism for food.Copyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.How does energy flow through an ecosystem?Food chains and food webs deal with both matter and energy.When ecologists want to focus only on energy, they use anothertype of model—an ecological pyramid.

An ecological pyramidshows how energy flows through an ecosystem. There are different types of ecological pyramids. Each pyramid has the autotrophs,or first trophic layer, at the bottom. Higher trophic layers are thenlayered on top of one another.The pyramid of energy shows that the amount of availableenergy becomes less from one trophic level to the next. The totalenergy transfer from one trophic level to the next is only aboutten percent because organisms do not use all the food energy inthe trophic level below them. An organism uses energy to do allthe things necessary for life.

Organisms use energy to move, tointeract with their environment, and to digest their food. Theyalso use energy to build body tissue. Some of this energy is givenoff as heat. The law of conservation of energy states that energy isneither lost nor gained. Even though some of the energy transferred at each trophic level enters the environment as heat, it isstill energy. It is just in a different form.A pyramid of numbers shows the number of organisms eatenby the level above it. In most cases, the number of organismsdecreases at each higher trophic level.READING ESSENTIALS3. What type of organismsappear at the bottom ofthe ecological pyramid?________________________________________________________________________Fox (1)Birds (25)Grasshoppers(250)Grasses(3000)Chapter 219NameDateClassSection2.2Nutrition and Energy Flow, continued4.

What is biomass?Biomass is the total weight of living matter at each trophiclevel. A pyramid of biomass shows the total dry weight of livingmaterial at each trophic level.________________________________________________________________________Cycles in NatureMatter, in the form of food, moves through every organism. Inthis way, matter is found at every trophic level. Matter is nevermade or destroyed.

It just changes form as it cycles through thedifferent trophic levels. There is the same amount of matter todayas there was when life on Earth began.CondensationPrecipitationWater also cycles through different stages. It is always movingbetween the atmosphere and Earth. For instance, when you leavea glass of water out for a few days, some of it seems to disappear.It has evaporated or changed into water vapor in the air.

Similarly,water from lakes and oceans evaporates. At some point, this watervapor condenses, or comes together, and makes clouds. After evenmore condensation, drops of water form. This water then fallsback to Earth as rain, ice, or snow.Plants and animals needwater to live.

When the waterfalls to Earth, plants and animals use it. Plants pull waterEvaporationfrom the ground and losewater from their leaves. Losingwater this way puts watervapor back into the air. Thiscontinues the water cycle.LakeAnimals also take in water.They breathe out water vaporin every breath. When animalsIn the water cycle, water isurinate, they return water toconstantly moving betweenthe atmosphere and Earth.the environment. This waterthen continues in the cycle.What is the carbon cycle?Carbon has its own cycle.

All life on Earth is based on carbon,and all living organisms need carbon.The carbon cycle starts with autotrophs. In photosynthesis,autotrophs use the sun’s energy to change carbon dioxide gas intoenergy-rich forms of carbon.20Chapter 2READING ESSENTIALSCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.What is the water cycle?NameDateClassSection2.2Nutrition and Energy Flow, continuedAutotrophs use this carbon for growth and energy. Heterotrophsthen feed on autotrophs or feed on other animals that have alreadyfed on autotrophs. The heterotrophs then use the carbon forgrowth and energy.