Creating A Visual Relationship of Organisms:
Food Webs and Trophic Levels

Type of Entry: Class Activity (to be done in one class period).

Type of Activity:

• Cooperative Group Activity
• Student-centered

Target Audience:

• Life Science (grades 6-8)
• Biology
• Ecology

The inter-connection of organisms in the environment is extremely complex. There are multitudes of plants and animals in our world. Many of these organisms need to relate and react to each other in order to survive and maintain homeostasis. This natural balance of organisms is due in part to their feeding habits. Due to the extreme importance of feeding behaviors in the scientific world, most life science and biology courses require students to be able to analyze food webs and be able to assign the various trophic levels (producer, primary consumer, secondary consumers, tertiary consumer) to them.

In this activity, students will become introduced to the creation and interpretation of food webs. Students are also responsible for the assignment of the organisms in the food web to the various trophic levels they belong to ( in some cases, organisms can belong to more than one trophic level). The activity works well for all types of learners, as it includes visual, kinesthetic, and auditory components. It also works well in providing a lesson which is student-centered and keeps students active for a 45-minute period.

Preparation:

There is a considerable amount of preparation that the teacher needs to do before the activity can be done in class. However, the preparation is a one-time event. That is, once the preparation is done, the same activity can be repeated each year without any preparation.

The following is a list of materials which will be needed to prepare the lesson board used:

1. A 36" x 48" cardboard presentation board (usually is folded in 3 sections, and can be found in any craft store).

2. Velcro tape (also available at any craft store).

3. Glue and Scissors

4. 3 X 5 index cards: 4 green cards, 8 blue cards, 8 red cards, 2 purple cards, 8 white cards.

5. Pictures of hay, trees, shrubs, grass, rabbits, mice, giraffe, cows, lion, humans, snakes, hawks, owls (I cut mine out from National Geographic magazines).

• Obtain 4 green index cards, and glue to each, one of the following pictures: grass, hay, shrubs, trees.

• Obtain 8 blue index cards, and leave 4 blank. On the other 4 cards, glue to each, one of the following pictures: rabbit, mouse, giraffe, cows.

• On the back of the cow card write "Cow-tipping is a load of fun, but let's hope they land on the hay" (or anything that indicates to students what is eaten by cows). On the back of the mouse card, write "The teeth of a mouse are not sharp enough for meat, so they eat small shrubs." On the back of the rabbit card, write " Bugs tends to eat carrots, but many of his relatives simply like grass." On the back of the giraffe card, write "The giraffe's long neck allows it to eat leaves from trees."

• Obtain 8 red index cards, and leave 4 blank. On the other 4 cards, glue to each one of the following pictures: lion, humans, snakes, hawks.

• On the back of the human card, write "many humans still love a good steak!" On the back of the lion card, write "the lion loves to munch on meaty giraffe necks." On the back of the hawk card, write "the hawk is a fierce creature whose teeth, beak and claws can tear apart a rabbit." On the back of the snake card, write "snakes can swallow a mouse whole."

• Obtain the 2 purple cards. Leave one blank. On the other card, glue the picture of the owl. On the back of the card, write "the superb night vision of the owl allows it to see hidden snakes crawling in the brush."

• Obtain the 8 white index cards. Label four of them with the word "sign". To the following four cards, write one of each of the following words: producers, primary consumers (herbivores), secondary consumers (omnivore or carnivore), tertiary consumers (carnivore).

• On the back of each and every card, you will need to put a small piece of velcro, since these cards will be fixed onto the presentation board.

• You will only need to use the middle (main) section of the presentation board. You will want to arrange it as shown. Use the glue (rubber cement glue works well) to attach the cards to the board.

• There will be 4 rows. The bottom row will contain the four green index cards for the producers. The next row above will have the 4 BLANK blue cards, spaced directly above the green row. The third row will contain the 4 BLANK red cards, spaced directly above the blue cards. The last row is really only the one BLANK purple card which is to be placed as the top card of the third row.

• Beside each row place the white index cards which had the words "sign" on them. Again, see example.

• Put a piece of velcro on each card on the board so that students will be able to affix index cards onto the board ( I have placed small boxes onto the chart to guide you).

Obtain 4 office envelopes. Into each, place one of each of the following:
1. One of the blue animal index cards
2. One of the red animal index cards
3. a 10-inch long paper arrow which has a piece of velcro on the back.
4. One of the white index cards indicating feeding levels.
5. One group will also have in their packet the purple "owl" card.

I have included the actual two-page packet I give to the students. It describes the implementation of the lesson.

Method of Assessment/Evaluation

When students have completed the presentation board, they receive credit for answering the questions given at the end of the assignment. You can decide what kind of credit that will be. There is then a 10 minute discussion where all terms and concepts are reinforced vocally for the auditory learner, and all questions are answered by students to check for comprehension.

Extension/Reinforcement/Additional Ideas

I find it valuable to have index cards for other animals and spaces for students to place them their position in the food web given the trophic level of the organism. Students can also vocally be given descriptions of animals and be tested on their ability to classify them into the proper trophic level. One last follow-up activity would be to give groups one more "arrow:" and have them make more connections between organisms.

This activity is meant to be a basic one-day introduction to the study of the relationships between organisms. It should be followed up by more activities/sponge activities that develop more higher-order thinking skills.

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