Encourage children to identify things that are needed for humans to survive. Prompt them to stray away from store-bought items and luxuries and instead encourage them to focus on items that are found in the natural world: food, air, water, shelter. Record the information that children supply on chart paper.
Ask students to identify things that other organisms -- dogs, cats, bears, chickens -- need to survive. Record this information on chart paper, as well.
Compare and contrast the lists that are generated. After comparing and contrasting, deduce that both humans and animals need the same basic things for survival.
Explain to students that though animals and humans may differ, they all share common basic needs. Inform them that these basic needs are supplied by the earth, creating a large ecosystem. Discuss the definition of the word ecosystem with children to drive home the point that all organisms rely on one another for survival.
Encourage children to think about what would happen if all of the plants on earth were destroyed. Discuss the impact that the loss of plant life would have on ecosystems. Talk about ways in which humans can ensure that such a loss does not happen.
Arrange to take children to a nearby setting that is relatively unaltered: a beach, a park or a forest, for example.
Provide children with magnifying glasses, paper and pencils. Encourage them to explore the setting, using their magnifying glasses to get a closer look at some of the organisms found within the ecosystem.
Instruct students to record what they observe within the ecosystem: the types of plants and animals they see and how the organisms interact with one another. Encourage children to draw pictures to illustrate these interactions.
Discuss what students observe and invite them to share the pictures they have created. Talk about how all of the elements within the ecosystem work and explain how one organism is necessary for the survival of another organism.