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| Question | Answer |
| Changes in the environment - caused by various factors such as a lack of a usual food source - may affect the distribution and behaviour of organisms. | Animals and plants are exposed to environmental change. These changes may be caused by living factors, such as a change in a predator, a food source or a competitor. Environmental changes may also be caused by non-living factors, such as a change in temperature or rainfall. |
| Changes in the environment affect the distribution and behaviour of living organisms. For example, humans have been cutting down trees for thousands of years. We do this to clear land for farming and building, and for wood to use as a fuel or building material. This deforestation can have local effects, such as a reduction in food and shelter for animals. It can also have more widespread effects, such as changes in rainfall and temperature. These changes may change the distribution of bird species, for example. | If the prey population grows, predator numbers will respond to the increased food supply by increasing as well. Growing predator numbers will eventually reduce the food supply to the point where it can no longer sustain the predator population, and the number of predators will go down. |
| The animation shows how the numbers of predators (ladybirds) and their prey (aphids) can change over time. The graph would look fairly similar for any two populations of predators and prey. | Human activities can pollute the air and water. The presence or absence of certain living organisms acts as an indicator of the amount of pollution. |
| The most common source of air pollution is the combustion of fossil fuels. This usually happens in vehicle engines and power stations. Sulfur dioxide is released if the fuel contains sulfur compounds. This gas contributes to acid rain. Lichens can be used as air pollution indicators, especially of the concentration of sulfur dioxide in the atmosphere. | Lichens are plants that grow in exposed places such as rocks or tree bark. They need to be very good at absorbing water and nutrients to grow there. Rainwater contains just enough nutrients to keep them alive. Air pollutants dissolved in rainwater, especially sulfur dioxide, can damage lichens, and prevent them from growing. This makes lichens natural indicators of air pollution. For example: bushy lichens need really clean air leafy lichens can survive a small amount of air pollution crusty lichens can survive in more polluted air. |
| In places where no lichens are growing, it is often a sign that the air is heavily polluted with sulfur dioxide. | Water pollution is caused by the discharge of harmful substances into rivers, lakes and seas. Many aquatic invertebrate animals cannot survive in polluted water, so their presence or absence indicates the extent to which a body of water is polluted. |
| clean -mayfly larva low- freshwater shrimp high- water louse very high- rat-tailed maggot, sludgeworm | Living organisms can be used to indicate environmental changes, such as pollution, but scientists can also use equipment to measure environmental changes. For example, oxygen levels in water can be measured using oxygen probes. These are often connected to a data logger. |
| Rainfall is measured using a rain gauge. The depth of rain is usually measured daily, for example at the same time every morning. A simple rain gauge consists of a funnel that empties into bottle. The daily contents of the bottle are poured into a measuring cylinder. This is calibrated so that it reads the depth of rainfall in millimetres. | An ordinary thermometer can be used to measure the temperature in an environment. Traditional maximum and minimum thermometers have a U-shaped tube. Each side contains a pin which moves inside with the liquid: one pin records the maximum temperature; and the other pin records the minimum temperature. After readings have been taken, the pins are reset using a magnet. A digital thermometer connected to a data logger allows an almost continuous measurement of temperature over time. It also has the advantage that no one needs to be there to take a reading. |
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