Methods of preventing species extinctions include: zz
Nature reserves.
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Zoo breeding programmes. Seed banks (the storage of seeds to protect biodiversity).
The careful management of the Earth’s natural resources to prevent species from becoming extinct is called conservation.
Human population and species extinction
In maths, two factors are said to be ‘correlated’ if the changes in both factors are related. Correlation can be positive or negative. As scientists, it is important to remember that correlation does not always mean causation.
1. Consider the following statements. Which statement has merit? zz
‘I am good at basketball because I am tall.’ zz
‘I am tall because I am good at basketball.’
2. Research the relationship between the growth of the human population and species extinctions. Is there a correlation? Is it a causal relationship? Explain your answer.
Pollution Pollution happens when harmful substances are added to the environment. The three main sources of pollution are: 1. Agricultural
2. Industrial 3. Domestic All three sources can pollute air, water and soil.
1. Agricultural Pollution As the human population grows, more food is needed. This causes a number of problems.
Growing too many crops can damage the soil. This can lead to desertification.
Desertification means that the land becomes more arid (dry) and the species that once lived there are lost.
Fertilisers are used to boost the growth of crops. The spreading of fertilisers on farmland can lead to the pollution of soil and water. Fertilisers may also contain chemicals that can poison organisms.
If too much fertiliser is spread, nutrients can be washed off the soil and into nearby rivers and lakes. This is known as enrichment.
Enrichment causes a sudden rise in algae (algal bloom): zz
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The algae stop light entering the water and aquatic plants cannot photosynthesise.
When the algae die, decomposing bacteria use up the oxygen in the water. As a result, fish and other aquatic plants and animals cannot respire and so die.
