Activity Bank - The weakest link
Pieces of different-coloured yarn, stretching about three feet in length
Tape or safety pins
Twenty to thirty minutes
Write the names of several different animals and plants on the paper cards. There should be one card with the sun written on it. Choose animals that have different feeding habits, but that could be connected to one another in a food web.
Assign the identity of an animal to each student by fastening the cards to their shirts. Give each student two or three pieces of yarn; the sun does no t need any yarn. Make sure that there are only three pieces of black yarn (or a dark colour of your choosing) for the whole class in total.
Have students grab hold of another student's piece of yarn if they would eat that animal or plant, and ask them to hold onto someone else's string if they would be eaten by that animal. The plants should ask the sun to hold onto their strings, and then hold onto herbivores. Herbivores should be connected to carnivores, etc. The end result is that you should have one giant food web made up of members of the class.
After everyone is organized, tell the students that the people who are holding onto a black piece of yarn have ingested a toxin. Anyone holding a black piece of string must let go of it, because toxins have infected them. Then inform the students that any of them that had a connection with a contaminated animal or plant (i.e. black string) must now let go as they have either ingested the poison or lost their food source. Any students left over are probably connected to animals with broken connections, and they must also let go of the string. The end result will be that the entire web will have deteriorated, all from a little bit of poison.
Impress upon the students the snowball effect of toxins in the environment, and discuss what kind of measures can be taken to reduce, control and prevent environmental pollution.