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The early atmosphere was mainly carbon dioxide and water vapour. Human activities are releasing greenhouse gases which are causing global warming, and other atmospheric pollutants.

The water cycle describes how natural processes move water between living and non-living stores. All humans rely on safe drinking water. Water is purified to remove insoluble and soluble substances. Salt can be removed from sea water to make it safe to drink. Waste water must be treated before being released into the environment.

An ecosystem is the living organisms in a particular area together with the non-living components of the environment, such as soil, air and water. An ecosystem is biodiverse if it contains many different species.

Inheritance is the process of passing genetic information to offspring. Genes are sections of DNA that code for a protein. Inheritance of genes can be shown in Punnett square diagrams.

Evolution is the change of inherited characteristics within a population over time through natural selection, which may result in the formation of a new species.

Understanding how to approach exam questions helps to boost exam performance. Question types will include multiple choice, structured, mathematical and practical questions.