Water Pollution and Food Chains

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Water Pollution and Food ChainsEdit

Student worthinessEdit

This lesson was never tested with a group of sixth graders but the "flower coloring" experiment was performed to make sure that it would work as expected.

Primary biological content area coveredEdit

There are two key concepts covered in this lesson: first, how pollution can affect plants, and, second, how polluted plants affect the rest of the food cycle. In sum, this lesson teaches students about "Bioaccumulation".


Materials required for the teacher's use:

  • Food coloring
  • Easel paper
  • white board/markers

Materials required for each student group:

  • 2 plastic cups
  • water

Materials that each individual student would need:

  • 1 carnation
  • graphic organizer (see handout section)


This graphic organizer is meant to help students understand the idea of bioaccumulationin food chain triangles. This handout will be completed as a class and then the students will write a small paragraph explaining the pyramid for the final assessment. The blanks in the title stand for "Bioaccumulation". The blanks near the arrow stand for "amount", these will be filled in throughout the lesson.


Bioaccumulation Handout

Description of activityEdit

This activity has two parts: dyeing the flowers, and talking about the experiment. The flowers should be given about four days to change colors (especially for lighter colors, like red or yellow). This lesson plan is more a direction for the discussion rather than the experiment but the experiment is given, as well.

Lesson planEdit


Start of the experiment

  • Experiment: (about 15 min)

1. Give two plastic cups to every group of four students. Have the students place their initials on the cups

2. Ask the group to decide what 2 colors they want to try, mark the cups to show which color is being tested

3. Have the students fill the cup about two-thirds of the way up with water

4. Drop three to five drops of food coloring in each cup of water (the water should be dark version of the dye)

5. Have the students carefully mix the dye and water and then have them place their flowers in the water/dye

6. Have students set aside the cups in a given place (during the first trial, the plants were left on a window sill). (Zoom Science Activities).


Final Lab Pic.

End of Experiment

  • Hook: (5 min.)

1. Have students collect their flowers.

2. Ask the students to explain what happened to their flowers: The color of the flower has changed.

3. Ask students if they remember when they were taught about plants absorbing water. Ask them to guess why the flowers changed colors: The dye changed the color of the water so when the water was absorbed, some of it went into the flowers. As the water evaporated or was used up by the plant, the dye remained behind. (Oregon State)

4. Explain to students that the idea of plants absorbing water can be applied to pollution; tell students this is the idea we are going to explore.

  • Activity: How are humans affected? (20 min.)

Ask students, what types of pollution affect water? Record answers on easel paper (connection to background knowledge)

1. Pass out the Bioaccumulation triangles

2. Ask the students if they see anything different about the sections of the triangle: the sections get smaller as they progress upwards.

3. Explain to the students that the bottom of the triangle is the start of the food chain. Have them write "algae" in the bottom section of the triangle. Tell the students that there are a bunch of algae that can absorb the pollutants. Tell the students that like the flowers, the algae is flowing in the water and absorbing the water and pollution. Each day the algae absorb more pollutants, until it gets eaten by an insect. Show this by drawing a circle on the board (the alga) then add an "X" (pollutants) to the alga (preface each action with "on day one", "on day two", ect.) draw two or three of these circles, possibly varying the "X"'s

4. Have students write "insects" in the next section. Explain to students that the insects eat the algae. Draw an arrow from the circle to an insect on the board, add the initial "X"'s to the insect from the alga. Then draw another arrow from the insect to another alga, add those "X"'s to the insect. Ask the students if the insects will have more or less pollution than the algae. Explain the same process happens in every section of the triangle

5. Have student write "Trout" in the next section up. Ask the student to predict if the trout will have more pollutants than the insect. (If needed draw the pictures again)

6. Have the students write "Human" in the top section of the triangle. Ask the students, if a fisherman fishes in polluted water and catches our trout and eats it, will the fisherman eat the pollutants? Answer: Yes, because like the aquatic organisms the fisherman will take in all of the pollutants that the fish had in its body. (Again, if needed, draw representations of this on the board). (Prentice-Hall, ch.8, section 3)

7. Tell the students that this idea is called Bioaccumulation by scientists. Write the word on the board, so the students can copy it onto their handout. Then write a definition for them: the increasing amount of toxic substances within each increasing link in the food chain ( Tell students to fill in amount in the blank near the arrow.

  • Closing: (5 min.)

Explain to the students that bioaccumulation is one of the biggest problems with pollution. If we hurt animals by polluting, eventually those pollutants can work themselves up the food chain and into humans. By helping the animals and not polluting, then we are actually helping ourselves. Each layer of the food chain passes on their pollutants to the next layer as it gets eaten (Closs, et al. pg. 162).

  • Assessment: (homework)

Ask students to write a paragraph of at least 3 to 5 sentences explaining their triangles. Tell the students to hand in their triangles with their paragraphs.

Potential pitfallsEdit

  • For many students this lesson should be placed into an unit on Pollution or, more specifically, Water Pollution. In this manner, the question about how much background knowledge students have can be answered because it was just taught
  • Depending on the students, the activity may wind up taking longer than 30 mintues due to the subject matter
  • Having students write a paragraph explaining the triangle maybe difficult depending on the writing abilities of the students. If this is an issue perhaps having students draw the explanation might be easier.
  • It might be hard to keep students engaged in the activity. If this is an issue, have students come up and draw the pictures on the board.

Math connectionsEdit

This activity would be really easy to link with a math lesson on multiplication. By showing the students that each level had more pollutants than the level before it, students to see the idea of exponential growth, without using those terms. The idea would be that if an insect ate two algae (each with four day of pollution) then the insect will ingest 8 days worth of pollution (2*4=8). If this is done though, it must be explained to the students that 8 days worth of pollution in algae, won't immediately be harmful to humans, the build-up and repeated ingestion is the issue.

Connections to educational standardsEdit

This lesson addresses the Vermont Standards and Grade Level Expectations:

  • Standard 7.13: Organisms, Evolution and Interdependence: Students understand the characteristics of organisms, and recognize the interdependence of all systems that support life.

cc.Describe, model and explain the principle of the interdependence of all systems that support life (eg. Food chains, and webs) and apply them to local, regional, and global systems

  • GE S5-6:35: Students demonstrate their understanding of Food Webs in an Ecosystem by developing a model for a food web of a local aquatic environment. Science Concept: Food webs model the interdependent relationships that organisms engage in as they acquire their food and energy needs. Aquatic food webs (fresh water and marine) are supported by microscopic ocean plants.

Next stepsEdit

My next major step with this lesson would be to test it out with a group of sixth graders. Also I think that it is interesting "end-of-the-unit" activity. This lesson therefore can be used to wrap-up the ideas taught throughout a unit on pollution, or water pollution.

Citations and linksEdit

Along with the seven cited sources throughout my lesson I used three scientific articles to gain background knowledge on this topic:

  • Berglund, Olof, et al. The Effect of Lake Trophy on Lipid Content and PCB Concentrations in Planktonic Food Webs. Ecology, Apr. 2001, Vol. 82.4, pg. 1078-1088.
  • Mazak, Edward John, et al. Influence of Feeding Habits on Organochlorine Contaminant Accumulation in Waterfowl on the Great Lakes. Ecological Applications, Nov. 1997, Vol. 7.4, pg. 1133-1143.
  • Stow, Craig A., et al. Evidence That PCBs Are Approaching Stable Concentrations In Lake Michigan Fishes. Ecological Applications, Feb. 1995, Vol. 5.1, pg. 248-260.

Works Cited:

(accessed 4-29-07).

--Kcallahan 01:28, 29 April 2007 (UTC)K. Callahan

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