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Why biodiversity matters, how people damage it through pollution, deforestation and climate change, and how it can be protected.
Specification references this topic covers: AQA 4.6.3, 4.7.3; Edexcel B9.9, B9.10.
Biodiversity means the variety of living things on Earth. This lesson looks at how people harm it, and what we can do to protect it.
It matters because we depend on healthy ecosystems for clean air, water, food and medicines. When wildlife is lost, the effects spread much further than the animals themselves.
By the end you will be able to explain what biodiversity is. You will describe pollution, deforestation and global warming. You will also weigh up ways of protecting wildlife, including their costs.
Biodiversity is the variety of all the different species in an ecosystem, or on Earth. A species is one type of living thing. An ecosystem is all the living things in an area, and the place they live in.
High biodiversity makes an ecosystem stable, because the species depend on each other. It also gives us food, medicines and materials.
The human population is growing quickly. More people use more land for building, farming and quarrying, and they make more waste. That leaves less land for other species.
Pollution means harmful substances in the environment. Water can be polluted by sewage, fertiliser and toxic chemicals. Air can be polluted by smoke and by gases such as sulfur dioxide, which causes acid rain.
Land can be polluted by landfill, which is rubbish buried in the ground, and by pesticides. Each kind harms the living things there.
Here is how fertiliser can kill fish. It runs into a river and makes algae grow very fast. When they die and decay, the decomposers use up the oxygen in the water.
Deforestation means removing large areas of forest. In tropical areas, trees are cut down to make land for cattle, rice fields and crops for biofuels. A biofuel is a fuel made from plants.
Fewer trees means less carbon dioxide taken in by photosynthesis. Burning and decaying trees also release carbon dioxide. The habitat is lost too, so biodiversity falls.
Peat bogs are drained and the peat is dug up for compost. When peat decays or burns, it releases carbon dioxide and the bog habitat is destroyed.
Carbon dioxide and methane are greenhouse gases. They trap thermal energy from the Sun in the atmosphere, and this keeps the Earth warm. Think of them as a blanket around the planet.
Human activity has added more of these gases. Methane comes from cattle, rice fields and landfill. So the average temperature of the Earth is rising. This is global warming.
It can melt ice caps, raise sea levels, and cause more floods and droughts.
Global warming and habitat loss reduce biodiversity. Some species can move to cooler places, but others cannot. They may become extinct, which means none are left.
Changes in where species live also affect food webs. The breeding season of some animals may stop matching the time when their food is available.
Habitat destruction is the main cause of species loss. This is why protecting habitats matters so much. Once a habitat is gone, the species that lived there often have nowhere else to go.
People are trying to protect biodiversity. Zoos run breeding programmes for endangered species. Rare habitats, such as heathland, can be protected so the species there survive.
Farmers can plant hedgerows and field margins, which are strips of wild habitat. Governments can cut deforestation and carbon dioxide emissions. They can also encourage recycling, so less waste goes to landfill.
Every scheme has costs. Breeding programmes are expensive, and a country may need its land for farming. Many schemes also need countries to agree, because pollution crosses borders.
Biodiversity is the variety of species, and it makes ecosystems stable.
Pollution, deforestation and the destruction of peat bogs harm wildlife. Carbon dioxide and methane cause global warming.
Breeding programmes, protected habitats and hedgerows help. In a long answer, give an advantage, a disadvantage and then a conclusion.
Name two greenhouse gases.
Answer: carbon dioxide and methane
Explain how the draining of peat bogs increases global warming.
Answer: Peat releases carbon dioxide when it decays or burns, increasing the greenhouse effect
Explain why fertiliser running into a river can kill fish.
Answer: Excess algae die and decay, and the decomposers use up the oxygen so fish die
Biodiversity and human impact on the environment practice questions for GCSE Combined Science Biology. Try each one, then open the answer. Easy questions come first.
What name is given to the variety of all the species in an ecosystem?
Answer: biodiversity
Name the gas released when peat and forests are burned.
Answer: carbon dioxide
Name the greenhouse gas that comes from cattle and rice fields.
Answer: methane
What is the removal of large areas of forest called?
Answer: deforestation
What word describes a fuel that is made from plants?
Answer: biofuel
What word describes a species that has died out completely, so none are left?
Answer: extinct
Name the gas that causes acid rain.
Answer: sulfur dioxide
What is the main cause of the loss of species?
Answer: habitat destruction
Longer questions in the style of a written paper, with the marking points. These are Yumio practice questions.
(a) Describe how deforestation increases the amount of carbon dioxide in the atmosphere. [2 marks] (b) Suggest one way of reducing the damage from deforestation. [1 mark] (c) Explain why reducing biodiversity can harm an ecosystem. [1 mark]
Answer: (a) fewer trees take in carbon dioxide for photosynthesis, and burning and decay of the trees release carbon dioxide (b) replant trees or protect forests (c) species depend on each other, so the loss of one can affect many others
Scientists want to protect an area of rainforest that contains many species. Local people want to clear the land for farming. Discuss the arguments for and against protecting the forest. [6 marks]
Answer: Protecting the forest keeps habitats and a high biodiversity, stores carbon so reduces global warming, and may provide medicines and materials in future. But local people need land to grow food and make a living, and the protection may cost the government money. A compromise such as protecting part of the forest, sustainable farming and payment for protecting the forest could help both sides.
Confusing global warming with the hole in the ozone layer
Global warming is caused by greenhouse gases such as carbon dioxide and methane.
Saying carbon dioxide causes acid rain
Sulfur dioxide causes acid rain.
Giving only the problems and not the solutions
Say how biodiversity can be protected, and the costs and benefits.
Saying deforestation only affects trees
It also removes habitats and adds carbon dioxide.
Biodiversity and human impact on the environment is on both Foundation and Higher papers for GCSE Combined Science Biology, aimed at around grade 5.
Confusing global warming with the hole in the ozone layer. Global warming is caused by greenhouse gases such as carbon dioxide and methane.
Open Show answer under each question on this page. The questions are Yumio practice questions, not past exam questions.
See how the papers are set: AQA Combined Science papers and Edexcel Combined Science papers.
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