The Effects of Pesticides on the Food Chain

Betty Conley                   Byrd Academy
                               363 W. Hill St.
                               Chicago, Ill.60610
                               312-280-4000

Objective:

Grade Level 4   
     Students will be able to generalize that all animals, including 
      people, depend on plants as a food source.
     Students will describe and construct a food chain.
     Students will tell how pesticides enter the food chain.
     Students will discuss possible consequences of pesticides entering        
      the food chain.
                                    
Materials needed:                                                          
   
     Ecology box showing examples of pollutants harmful to wildlife.
     Pictures of plants and animals.
     Overhead and transparency "Let's Look at a Food Chain".
     5 strips of paper.
     Identity cards for game (1-2 hawks, 3-4 shrews, and 9-18 grasshoppers).
     50-100 pictures of corn (2/3 yellow, 1/3 another color).
     A stapler.
     Colored chalk.
      
Strategy:

Activity 1.
     Students will walk around and study the pictures hanging on the walls.  
Teacher will give some facts about an animal or plant using important vocabulary 
words, ending each statement with, "Who am I?"  The students will find the 
picture of the organism and identify it.  
     Example: My rep has me stalking deer, cattle, and man.  I have been 
trapped, shot, and poisoned by both farmers and bounty hunters.  Everyone has 
forgotten that I am grandparent to man's best friend.  They even accused me of 
eating a grandmother.  Who am I? 
     Example: I am a carnivore but I'm not an animal.  Who am I?

Activity 2.
     Students will write the correct vocabulary word on the board next to it's 
definition.

Activity 3.
     Students will look at and discuss the transparency "Let's Look at a Food 
Chain."  They will identify the seen and unseen organisms and discuss their 
relationships.  They will tell what eats what.  They will describe the food 
chain as the teacher makes a chain with strips of paper. 

Activity 4.
     Students will put the following organisms in order, making a food chain: 
shrew, hawk, corn plant, and grasshopper.  They will then discuss the 
relationship of these organisms.    


Activity 5. 
     Students will play a game that will help them understand how pesticides 
affect a food chain.  After the pictures of corn have been scattered around the 
room or field, the grasshoppers will have 15 seconds to hunt for food.  Whatever 
corn they find, they will put in their "stomach" (a brown paper bag).  After 15 
seconds the shrew will start to hunt the grasshoppers.  After another 15 seconds 
it is time for the hawks to hunt the shrews.  Whoever is tagged by the animal 
hunting it, must give that animal their "stomach" and sit down.  They have been 
eaten. 
     Anyone remaining alive will come to the front of the room and empty the 
contents of their stomachs.  The contents will be divided into two groups, 
yellow and other colors, and counted.  Students will record the results on a 
chart on the board. 
     Teacher will then inform the students that the colored corn was sprayed 
with a pesticide.  Class will discuss what pesticides are, what they do to 
plants and animals, and why they are used. 
     If a grasshopper's "stomach" contained any other colored corn, that 
grasshopper is considered dead from pesticide poisoning.  Any shrews for which 
half or more of their food supply was other colors would also be considered 
dead.  The hawk may not die at this time, however a large accumulation of 
pesticide in the hawk's body may result in damage to the reproductive system.  
The eggs produced may have shells too thin to survive the nesting process. 
  
Conclusions:

     This unit should cause students to think about man's responsibilities to 
wildlife and the possible consequences of their actions.  It should cause 
students to investigate and create ways of living that will enhance the 
environment for all living creatures. 

Evaluation:

     Students will construct a food chain of what they ate for dinner.
     Students will give two examples of ways in which pesticides could enter 
      the food chain.

References:
     
Feather, Ralph M.and Ortleb, Edward P.  Science Connections.  Columbus, 
Ohio:Merrell, 1990.

Koestner, E.J.  Ecology and Energy Action Pack.  Dayton:Mc Donald Corporation, 
1977. 
               
Project Wild.  Boulder, Colorado:Western Regional Environmental Education 
Council, 1983.