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- All students to understand that organisms are dependent on each other
- Most students to understand why protection of all aspects of habitats is important to maintain them
- Some students to understand the concept of bioaccumulation
- Poster materials
Illustrate interrelationships on the board: start with a human, ask what organisms they use / affect during the day e.g. use milk from a cow, step on an ant. All organisms which are mentioned should be shown on the board. Ask then what affects / needs the cow has etc. A final web should be built up. Conclude that they depend on each other.
- State that most interrelationships are predation or competition. Identify examples from the web drawn and write them down.
- Give 3 organisms and ask students to arrange them into a feeding chain (e.g. rabbit, fox, grass becomes grass * rabbit * fox). Give numbers of organisms to show how numbers decrease up the chain. Show how these can be interpreted as pyramids of number (use printable Ecology worksheet) Explain how a food web is built up when other organisms are added (e.g. add cows, humans). Identify clearly competition and predation in the food web, and decreasing numbers up the web. Students draw out their own food chains, and then link them into food webs. Use the printable Populations worksheet to reinforce.
- 2 environmental issues are raised by food web interrelationships.POISONS ACCUMULATE: if each grass blade has a portion of insecticide on it, how many grass plants and insecticide portions will the rabbit eat? How many insecticide portions will the fox then eat if it stayed in the rabbit?
ENVIRONMENTS NEED TO BE PROTECTED: if one organism in a food chain reduces in numbers, what affects will it have on those eating it and those being eaten by it? Their population numbers can change significantly and have a knock on effect. Reducing numbers of an organism at the start of a food chain can have an effect on many other organisms further up the food web.
- Individual students to draw an advertising poster for one of these issues, highlighting their importance to the general public
- List in a table what changes occur daily and seasonally in a habitat. Complete the table describing how different organisms change / are adapted to live with these changes.