1. The Biosphere Credit Objectives

2. Sub-topic (a) Investigating an Ecosystem Identify possible errors that may arise when using techniques for sampling and measurement. Pit fall trap Possible errors: The numbers and types of organisms may not be typical of the whole ecosystem. Birds may eat trapped animals. Some animals may eat others.

3. Quadrats: numbers and types of plant may not be representative of the whole area. Light Intensity: Observer may stand in shadow, in the way of the light. Light intensity may change from one moment to the next. Moisture content: Moisture from previous measurement may be left on the probe. Explain how errors can be minimised when using techniques for sampling and measurement. Pit fall trap: Set up several traps. Disguise the opening. Check traps regularly Or put preservative liquid at the bottom of traps.

4. Quadrats: Take large numbers of random samples. Light intensity: Ensure all observers are standing to one side of the light meter. Take all the measurements as near to the same time as possible or take several readings at one site and take an average. Moisture content: Wipe the probe before each reading.

5. Explain how an abiotic factor has an effect on the distribution of organisms. Light Intensity: Green plants make their food by photosynthesis using light energy. In conditions of low light intensity, it is possible that they are unable to obtain sufficient solar energy to produce food. They are therefore unable to survive in the dimly lit conditions. For example daisies would be unable to grow within an oak wood. Therefore light intensity plays a part in determining the distribution of daisies.

6. Sub-topic (b) How it Works Explain the effects of the removal of one species from a food web. When explaining the effects use the terms INCREASE, DEACREASE or STAY THE SAME. Fully explain the effect given. Explain what is meant by pyramid of numbers/biomass. Pyramid of numbers Shows the relative numbers of organisms at each stage of a food chain; the further from the producer the smaller the number.

7. Pyramid of Biomass This represents the relative biomass possessed by the organisms at each stage of a food chain. Describe and explain population growth under ideal conditions. The growth of a population under ideal conditions continues to rise indefinitely because the birth rate is high and the death rate is low and therefore the population continues to increase and realise its full reproductive potential without being controlled by factors such as disease.

8. Describe the sequences or processes in the nitrogen cycle. All living things need nitrogen to make protein. Plants and animals cannot make use of nitrogen gas directly. Plants absorb nitrogen from the soil in the form of NITRATE. Animals must eat plant or animal protein to obtain their supply of nitrogen. Study and learn the nitrogen cycle in your notes.

9. Sub-topic (c) Control and Management Explain the possible problems related to the use of fossil fuels and nuclear power. The burning of fossil fuels can have an adverse effect on the environment because the sulphur dioxide and other poisonous gases released pollute the atmosphere and may even be converted into acid rain. Nuclear power is used instead of fossil fuels in some power stations. Many of the radioactive wastes produced are extremely dangerous since they continue to give out harmful radiation for many years.

10. Explain the relationship between level of pollution with organic waste, numbers of micro-organisms, oxygen concentration and numbers of species. As the level of pollution increases so will the level of organic waste. The number of micro-organisms will also increase as they have a rich food supply and will multiply. As the bacteria multiply they will use up available oxygen causing the oxygen concentration to decrease. This will cause surrounding species to decrease as their oxygen supply will be depleted.

11. Explain what is meant by an indicator species. Some types of living things only thrive well under certain environmental conditions. Such organisms are called INDICATOR SPECIES because their presence shows that these conditions are present in the environment. Mayfly nymph thrive in rivers with a high oxygen concentration. Rat-tailed maggots thrive in rivers with low oxygen concentrations.

12. Explain how the parts of an ecosystem are controlled in either agriculture or forestry. Agriculture By employing agricultural practices, people deliberately interfere with an ecosystem in order to produce vast numbers of a useful species (eg. crops). Parts of the ecosystem are controlled. Nutrient supply: fertilisers (natural and unnatural). Crop habitat: clearing the land of other possible competitors (herbicides, weed killers, fences and maintains water).