IGCSE Biology / Human influences on the environment

Fertiliser, algae and dead water revision notes

Edexcel International GCSE Biology (4BI1), chapter 15: Human influences on the environment, specification point 4.17. Part of the full course.

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Eutrophication is the process where excess nutrients enter water and lead to a fall in dissolved oxygen. Knowing the full chain explains why fish suffocate and how oxygen and bacteria levels change downstream.

More lessons in Human influences on the environment

• Glasshouses and polythene tunnels, and why they raise yield
• How fertilisers increase crop yield
• Pesticides and biological control
• Feeding people without emptying the sea
• Greenhouse gases and global warming
• How acid rain forms and what it does
• Sewage, carbon monoxide and sulfur dioxide
• The effects of cutting down forests
• Sustainable resources and conservation