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Marsh Market

WOW!: The Wonders Of Wetlands

Marsh MarketSummaryStudents construct a “living”wetland food web, then createtheir own web by tracing compo-nents of their lunches.

ObjectivesStudents will:

• appreciate the interdependenceof the organisms, includinghumans, involved in a food web.

• make the connection betweenthe importance of naturalresources and the ways weimpact them.

Materials• large ball of string or yarn• large file cards or strips of paper• students’ lunches or lists of every

item each student ate in a recentmeal

• drawing paper and markers• tape

Making ConnectionsWetland habitats provide thenecessities of life: abundant foodsource, adequate water supply,space to live and grow, safe coverfor resting and nurturing young.Without wetlands, we would nothave many of our own sources offood and income. Your studentsmay be surprised to find out howmany familiar things we derivefrom wetland resources.

This activity introduces theimportance of wetland commu-nity. This study of interactions oforganisms in a habitat leads to anunderstanding of our own rolesin, and potential effects on, theenvironment.

BackgroundA wetland is a great marketplaceof food sources. The vast number

of plants growing in a healthywetland form the basis of this foodweb. (A food web is a complexsystem of many food chains.)Resident and visiting animals canfind a wide array of food choicesin a wetland, whether they eatplants, animals, or both. A wet-land with a great diversity of plantlife will attract higher numbersand more species of animals.

Plants are called primary produc-ers because they supply food atthe lowest level of a food chain.It takes an enormous number ofindividual plants to support theother parts of the web. Wetlandhabitats are extremely productivein terms of plant life.

At the next level of a food chainare primary consumers: plant-eaters or herbivores. Primaryconsumers include rabbits, mice,deer, and certain other mammals,some insects and fish, and ducks,geese, and certain other birds.

Primary consumers are eaten bysecondary consumers, or carni-vores (meat-eaters). This groupincludes predators such as birdsof prey, some snakes, foxes, wildcats, and people. Secondaryconsumers are eaten by tertiaryconsumers, which may be preda-tors or scavengers such as turkeyvultures, crabs, and sometimespeople. Note that these categoriesare very broad and general. Manyanimals fit into more than onegroup, and there are more com-plex levels of the web.

Any of the food web componentsmentioned above can be brokendown by decomposers, organismssuch as bacteria and fungi thatreduce dead plant or animalmatter into smaller particles. Adecaying plant, for example, will

Grade Level2-8

Subject AreasEcology, Biology

DurationPart I: 40 minutes;Part II: 40-60 minutes

SettingClassroom

SkillsGathering, analyzing, andinterpreting information

Charting the CourseAdvanced students may do“Marsh Mystery,” a lesson onbioaccumulation. You mayalso play the “MarshMunchies” game to learnmore about nutrients andenergy flow.

Vocabularyherbivore, carnivore,omnivore, insectivore,predator, prey, producer,consumer, decomposer,food web

© The Watercourse and Environmental Concern Inc. 1995110

be broken down into nutrientsthat enrich the soil. This processsupports the growth of moreplants.

People are also part of the wet-land food web! Many regionaleconomies depend upon wetlandfoods. Are you a seafood lover?Oysters, shrimp, bluefish, floun-der, and other popular, commer-cially important fish and shellfishare produced in wetlands, espe-cially coastal marshes. Waterfowl,deer, and other game species thatvisit wetlands provide a source offood and income. Wetlandmammals such as beaver, mink,and muskrat are valued for theirfur—and muskrat is even becom-ing a popular gourmet dish.Cattail shoots, wild rice, andmany other wetland plants thatgrow in wetlands are edible. Nexttime you get the munchies, visit awetland for a snack!

ProcedureWarm UpHave the class discuss the conceptof a food web—what animals eatand who eats them. Introduce orreview the terms herbivore,carnivore, omnivore, insectivore,predator, prey, producer, andconsumer. Have older students

discuss the flow of energy fromprimary producers throughtertiary consumers and decom-posers (see diagram).

The ActivityPart I: Make a “Living” WetlandFood Web

1. Make a list of plants andanimals (birds, mammals,reptiles, amphibians, fish,insects, and other invertebrates)that live in or use wetlands.Assign items on the list tostudents and have them researchthe animals’ food habits andpredators. Then place the ani-mals in a chart of “carnivores,”“herbivores,” etc.

2. Write the name of each plantand animal on the list on aseparate card or strip of paper.Tape the cards or strips on theboard and ask students to selectone name. Have students sticktheir selection on their clothing.

3. Have the class stand in a circle.Select a “plant” to begin the weband give that student a ball ofstring. Ask him to wrap the endonce around his hand, then passthe ball to an organism that eatshis plant, connecting the onewho is consumed to the con-sumer. This student should wrap

the string around her hand andpass the ball either to an organ-ism that eats her organism or toher own organism’s food source.Remember that many of theplants and animals should beconnected to several others; if astudent receives the ball of stringa second time (or more), heshould pass it to a student hehasn’t already passed it to. As theactivity progresses, those whoresearched the organisms in-volved can help decide where topass the string. Continue in thismanner to create a “living”wetland food web.

4. Once the web has been com-pleted (all possible connectionshave been made), have thestudents shift around until theweb is taut. Have studentsdiscuss the fact that sometimes aplant or animal’s role in the webmay change, or disappear en-tirely. What effect would thishave on the web?

Use the following scenarios todescribe what can happen to partsof the web when the wetlandhabitat is disturbed. With eachdescription, have the studentsdecide which organism wouldbe affected by the change first(suggested answers appear inparentheses). Have the studentwearing this sign tug on thestring. Anyone who feels the tugshould raise her or his free hand.Have each of these students tugon the string, and so on. When thethird scenario has been covered,have the class sit down anddiscuss the web.

Scenarios:• It is raining. A lawn-carecompany’s truck skids andcrashes near the wetland, spillinghundreds of gallons of weedkiller. The rain washes the chemi-cals into the wetland (plants).

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Marsh Market

WOW!: The Wonders Of Wetlands

• A stream is blocked by a hugepile of dumped garbage. The partof the stream that usually flowsthrough the wetland dries up(fish).

• The wetland is destroyed whensomeone buys the land and buildsa shopping mall there (every-thing).

Part II: What’s For Lunch?

1. Ask the students to take outtheir lunches (don’t eat themnow!) or list foods eaten at arecent meal. Have students drawself-portraits at the top of a pieceof paper. Below this, have themdraw and label pictures of eachitem in their meal and label eachone (or draw a circle for eachitem and write the item’s nameinside). Be sure to include allitems; i.e., instead of “sandwich,”list or draw “ham,” “cheese,”“mayonnaise,” “whole wheatbread,” and so forth.

2. Decide what each item is madefrom. What is cheese? Where dofrozen peas come from? Whatwent into the can of soup? Breakdown each component of themeal, tracing each ingredient to itsmost fundamental sources. Forexample, mayonnaise is made ofeggs and vinegar. Eggs come fromchickens, which eat grain, whichgrows in the soil. Chickens comefrom eggs which come fromchickens . . . let’s not get into that.Vinegar can be made from apples,which grow on trees, which needair, soil, sun, and water.

3. Students should label theconsumers and the producers inthe diagram. Ask which categoryshows up most. There should bemore primary producers, since thefoods were probably made fromor raised on primary producers.Explain that it takes a lot of grainto raise one cow, and many

primary producers to support thehigher levels of a food web!

4. Ask students to imagine thatone of the natural resources inthe diagram has been depleted.Have them choose one and putan X beside it. Then go throughthe food web and put an Xbeside each item they would nothave without that resource.Would their meals have been thesame? Would they lose thingsthey need, things they just liketo have, or both?

Wrap Up and ActionAsk students to describe waysthat the food web might beaffected by a change in one of itslinks. Help students understandthat a change in the availability ofeven one food source could affectmany wetland residents. Stressthat parts of an ecosystem areinterconnected and interdepen-dent, and every link is vital tothe health of the whole.

AssessmentHave students:

• identify animals and plants in awetland food web and describetheir role (carnivores, herbi-vores, omnivores, insectivores,etc.).

• describe interrelationshipsamong wetland organisms(consumers, producers, decom-posers, predator, prey).

• demonstrate how severalcomponents in a wetland foodweb can be affected when evenone is disturbed.

• draw a diagram identifying howtheir own lunches fit in a foodchain.

ExtensionsNature in YourNeighborhoodTake a trip to a nearby wetland orother natural area. Observe, list,and diagram the components ofthe area’s food web. You may notsee many animals, but look forsigns that they were there—droppings, footprints, feathers,nibbled leaves and twigs, rem-nants of a meal (bones, fur, etc.),even a tunnel or other pathway.

You may find signs that peopleare part of this food chain. Fishingline caught in trees or shrubs andempty shotgun shells on theground can be signs of humanpredation. Does this area offerother natural resources thatpeople need, use, or want? Arethere signs that resources here arebeing misused, or cared for? Doyou see ways in which the foodweb in this area might beharmed? What can you do to helppreserve the resources and thefood web? See chapter 6, or“Helping Wetland Habitats,”p. 288, for some ideas.