1. Which gases can cause acid rain ?
Answer
Sulfur dioxide and nitrogen oxides.
2. What is "deforestation" and why does it occur ?
Answer
Cutting down trees (on a large scale) to provide land for cattle and rice fields, and to grow crops for biofuels.
3. What are the main greenhouse gases ?
Answer
Carbon dioxide, methane and water vapour.
4. Give two reasons why humans are using more resources and producing more waste.
Answer
Rapid growth in the population and an increase in the standard of living.
5. Explain why a greater biodiversity results in a more stable ecosystem.
Answer
It reduces the dependence of one species on another for food, shelter or maintenance of the physical environment.
6. In the past, farmers used peat to produce compost that improves the quality of soil, as peat was cheap and readily available. Explain the advantages and disadvantages of using peat in this way.
Answer
Improved soil quality increases crop yield, thereby increasing the amount of food produced. Using peat destroys peat bogs or reduces the area of their habitat, which in turn reduces biodiversity and the variety of plant, animal, and microorganism species that live there. When peat decays, carbon dioxide is released into the atmosphere, contributing to global warming.
7. Describe some negative effects that deforestation can have on ecosystems.
Answer
Deforestation can increase the greenhouse effect. It destroys habitats and therefore reduces biodiversity. It affects the water cycle, as there is less transpiration by trees, which leads to a drier climate. It also removes the roots that hold soil together, which can cause soil erosion, landslides, and flooding. Reduced water and the loss of roots can eventually cause soil to turn into desert.
8. Explain how human activities can increase the proportion of greenhouse gases in the atmosphere.
Answer
Greenhouse gases in the atmosphere can increase due to deforestation. Combustion or burning of fossil fuels and wood increases carbon dioxide. Burning or decay of peat also increases carbon dioxide. Rice fields and cattle release methane.
9. Describe some ways of reducing the negative effects of humans on ecosystems and biodiversity.
Answer
Reducing deforestation and carbon dioxide emissions; Breeding programmes for endangered species; Protection and regeneration of rare habitats; Reintroduction of field margins and hedgerows in agricultural areas where farmers grow only one type of crop; Recycling resources rather than dumping waste in landfill.