What is an ecosystem? -- What organisms form an ecosystem? -- How many organisms are there? -- Why is biodiversity important? -- What are the basic needs for survival? -- Where on earth do organisms live? -- How big are ecosystems? -- What is a suitable environment? -- How does a balanced ecosystem work? -- What happens when an ecosystem changes? -- What is a food chain? -- What is a population cycle? -- What is a keystone species? -- How long can a species survive? -- Can endangered species be saved? -- What impact do humans have on nature? -- What is ecotourism? -- Are national parks for wildlife or people? -- How does human activity affect the environment? -- What is a rain forest without rain? -- Eco-careers -- Young scientists at work -- Take an eco-survey.