1. General: Identify habitat, animals and plants as the main parts of an ecosystem.

Transcription

1 1. General: Identify habitat, animals and plants as the main parts of an ecosystem. A habitat is a place where an organism can live. There are a wide variety of habitats within an ecosystem. Within these varied habitats there are a wide variety of plants and animals living. 2. General: Give an example of a technique, which might be used for sampling organisms, and describe its use. A quadrat is used to sample non-moving organisms like plants. A quadrat temporarily marks off a piece of ground of known area so that different plants present within the area can be identified and counted. A quadrat must be placed randomly if a representative sample is to be taken. A pitfall trap is used to obtain a sample of small invertebrates living in the ground surface. 2a. Credit: Identify a possible source of error that might accompany a sampling technique. Plants within a quadrat may be wrongly identified or wrongly counted. The quadrat sample may not be representative of the area if it is not placed randomly. Even if placed randomly, the quadrat sample may not be representative of the area from which it was taken simply because of chance. The Biosphere Summary Booklet page 1

2 Pitfall traps badly set (e.g. trap not level with the ground) will not catch many animals, making estimates inaccurate. Many animals caught in the trap initially may not be included in the final count either because they escape (in the case of flying insects) or because they get eaten in the trap by other captives. If only one or a few traps are set, then the chance of the sample collected being representative of the area, as a whole will be low. 2b. Credit: Explain how error in a sampling technique might be minimised. Quadrats should be randomly placed on the ground within the area of study, to increase the chance of the sample being representative of the area as a whole. Pitfall traps should be set carefully with the top of the trap level with the ground and the surrounding soil left as undisturbed as possible. Pitfall traps should be examined frequently and animals caught and collected. For all sampling techniques, many samples should be taken (where possible) to increase the sample size and thus increase the chance of the sample being representative of the area. 3. Can you use simple keys or checklists to identify organisms? 4a. General: Identify two abiotic factors. An abiotic factor is a physical factor (often related to weather) in the ecosystem, which can affect the lives of organisms and affect their distribution. One abiotic factor is the amount of light (light intensity) in the area. Another abiotic factor is the amount of moisture in the soil. 4b. General: Give an example of a technique which might be used to measure an abiotic factor and describe its use. A light meter can be used to estimate the light intensity at the surface of the soil (or other area). The meter is held at the soil surface and pointed in the direction of maximum light and the meter is read. Care must be taken not to shade the light when taking a reading. The Biosphere Summary Booklet page 2

3 A soil moisture meter can be used to estimate the moisture content of soil. The moisture meter is carefully pushed into the soil and the meter is read. 4c. Credit: Identify a possible source of error that might accompany a measurement technique. When measuring light intensity you may accidentally shade the meter when taking a reading. The light meter is not very accurate it is useful for making comparisons, but not for giving absolute values. When comparing light intensity in two areas errors will occur if the light intensity estimated in the two areas are not made at the same time of day and under similar weather conditions. The soil moisture meter is not very accurate it is useful for making comparisons, but not for giving absolute values. For any abiotic factor, if only one measurement is taken, then the chance of the value of the particular abiotic factor measured being representative of the area as a whole will be low. 4d. Credit: Explain how error in a measurement technique might be minimised. Use as sensitive and as accurate an instrument as possible when measuring any abiotic factor. When measuring light intensity ensure that you are not shading the meter when the reading is taken. When comparing light intensity in two areas ensure that estimates in both areas are made at the same time of day and under similar weather conditions. When measuring the value of any abiotic factor, many readings should be taken and an average obtained this will increase the chance of the estimate being representative of the area as a whole. 5. Investigation completed during class. 6a. General: State the effect an abiotic factor has on the distribution of organisms. Green plants are not found in areas where the light intensity is constantly very low. Most plant and animal types are not found in soil which is very dry. The Biosphere Summary Booklet page 3

4 Many plant and animal types are not found in soil which is very wet. 6b. Credit: Explain possible mechanisms by which abiotic factors might influence the distribution of organisms. Green plants will not be found in areas with constantly low light intensity because they will not be able to photosynthesise and grow. Green plants will not be found in soils which are very dry because they need moisture from the soil to photosynthesise and grow. Plants and animals will not be found in soil which is very wet because they will most likely drown. Note that many of the environmental factors mentioned above combine to influence the distribution of organisms in an ecosystem. The Biosphere Summary Booklet page 4

5 7. General: Describe what is meant by habitat, population, community and ecosystem. A habitat is the place where an animal or plant lives. All the living things of one kind of plant or animal are called a population. All the living things in an ecosystem are called a community. Ecosystem = Living things + Habitat. All ecosystems contain the components habitat, population, and community. Examples of ecosystems include; woodland, fresh water, marine (sea or ocean), moorland. 8. General: Describe what is meant by producer and consumer. Producers make their own food by photosynthesis. Green plants are producers. Producers use the energy of sunlight to produce their own food. The sun is the source of energy for all living things. Consumers obtain their food from other living things. Animals are consumers. Herbivores are animals which eat plants. Carnivores are animals which eat other animals. Omnivores are animals which eat plants and animals. 9a. General: Give an example of both a food chain and food web. A food chain is a diagram showing feeding relationships between several living things. Arrow in a food chain point from food to feeder. The Biosphere Summary Booklet page 5

6 Consumers which eat producers are called primary consumers. Consumers which eat primary consumers are called secondary consumers. Predators are animals which feed on other animals. Victims of predators are called prey. More complicated diagrams showing inter-connected food chains are called food webs. 9b. Credit: Explain the possible effects of the removal of one species on the remaining organisms in a food web. Sheep affect the number of seedlings growing in a woodland. Fishermen can upset the balance of organisms in a marine food web. Myxomatosis (a disease that occurs in rabbits) not only affects the number of rabbits, but also the other organisms in the food web. 10a. General: State that the arrows in a food web diagram indicate the direction of energy flow. The arrows in a food web show the direction of energy flow. In a food web, energy is transferred from food to feeder. Living things can use this energy to move and grow. 10b. General: State two ways in which energy can be lost from a food web. There is an energy loss at each step in the food chain. Only about 10% of the available energy is passed on in a food chain. Living things are not efficient at food into body material. Few links in a food chain mean less energy loss. 10c. Credit: Explain what is meant by the terms pyramid of numbers/biomass. The organism size increases as you move along the food chain. The number of organisms decreases as you move along the food chain. The mass of organisms decreases as you move along the food chain. A pyramid of biomass is a diagram showing the mass of organisms in a food chain. The Biosphere Summary Booklet page 6

7 A pyramid of numbers is a diagram showing the number of organisms in a food chain. 11a. General: State that the growth rate of a population depends on birth and death rates. Population size depends on birth rate and death rate. In the present human population birth rate is exceeding death rate. 11b. Credit: Describe the growth curve of a population under ideal conditions. Under ideal conditions the growth of a yeast population: i. initially shows little or no growth ii. followed by a period of rapid growth iii. eventual slowing down of growth 12a. General: State 3 factors which can limit the growth of a population. A population explosion results when there is no check on population numbers. Predators, disease, food supply and space can limit the population size. Predators limit the population by eating individuals in the population. Disease can lead to the death of organisms. Limited food supply can lead to starvation. Limited space e.g. no nesting site may prevent breeding. 12b. Credit: Explain the growth curve of a population under ideal conditions. An example is the yeast growth curve. Initially there is little or no increase in population size as the yeast cells are preparing to divide. Large population increase is caused by yeast multiplication using available food. Growth eventually declines due to : i. food running out ii. waste substances accumulating The Biosphere Summary Booklet page 7

8 13a. General: State that competition occurs when organisms have a need for the same resources. In nature, animals will compete for water, food, shelter, nesting sites and mate, since these resources are in limited supply. In nature, plants will compete for light, water and soil nutrients, since these resources are in limited supply. 13b. General: Describe some of the effects of competition. Weaker individuals will be unable to compete and may die before they reproduce. Stronger individuals will thrive and go onto reproduce. 14a. General: Explain the importance of nutrient cycles to the organisms of an ecosystem. Bacteria and fungi are two important groups of decomposers. Decomposers release nutrients (from dead plants and animals) into the soil. Released nutrients are absorbed by plants. 14b. Credit: Describe the sequence of processes in the nitrogen cycle. Nitrogen is a chemical element necessary for protein formation. Bacteria and fungi in the soil release ammonia from the bodies of dead plants and animals. Bacteria convert Ammonia Nitrites Bacteria convert Nitrites Nitrates Plants absorb nitrates from the soil Plants use the nitrates to make protein Denitrifying bacteria release atmospheric nitrogen from nitrates. Leguminous plants use atmospheric nitrogen to make nitrate. Fertiliser is an artificial method of adding nitrogen to the soil. Lightening is a natural method of adding nitrogen to the soil. The Biosphere Summary Booklet page 8

9 15a. General: State that pollution affects air, freshwater, sea and land. Pollution causes harm to living things, looks unsightly or causes damage to buildings. Pollution can affect the following ecosystems: air, freshwater, sea and land. 15b. General: State that the main sources of pollution are domestic, agricultural and industrial, giving an example of a pollutant from each. The main sources of pollution are agriculture (e.g. excess pesticides and fertilisers cause run off into nearby rivers), industry (carbon particles, sulphur dioxide, nitrogen oxides, oil, heavy metals, detergents, radiation, paper fibres) and the home (e.g. sewage, house hold rubbish). 15c. Credit: Explain an adverse effect of using fossil fuels and nuclear power as energy sources. Problems of burning fossil fuels: blocks light for photosynthesis, makes buildings dirty, acid rain, depletion of non-renewable resources. Problems of using nuclear energy: release of low level radiation with cooling water, danger of leaks of high radiation into the atmosphere, disposal of highly radioactive spent fuel, unknown long term effects. The Biosphere Summary Booklet page 9

10 16. General: Give one way in which pollution may be controlled. Legislation European agreements to reduce the emission of sulphur dioxide. Removal of sulphur component in coal before it is burnt. Removal of sulphur dioxide from flu gases. Fit catalytic converters to car exhausts. Research to produce new car engines which produce less oxides of nitrogen. Use of lead free petrol. Inland towns must treat sewage before it is released into rivers. 17a. General: State that organic waste is a food source for micro-organisms. Organic material is material which is living or was once living. Bacteria feed on organic wastes such as sewage and paper fibres. 17b. General: Describe the effect of increased numbers of micro-organisms on the oxygen available to other organisms. With a plentiful supply of food, bacteria multiply rapidly. Bacteria take up oxygen from the surrounding water. A reduction in the amount of oxygen will result in less being available for other aquatic organisms such as invertebrates and fish. Organisms that require a lot of oxygen will disappear. 17c. Credit: Explain the relationship between level of pollution with organic waste, numbers of micro-organisms, oxygen concentration and number of species. With an increase in the amount of organic pollution there is an increase in the number of bacteria. With an increase in the number of bacteria less oxygen will be available to other aquatic organisms. The Biosphere Summary Booklet page 10

11 A stretch of water which contains a lot of oxygen will support a greater diversity and different community of aquatic organisms compared to a stretch of water which contains little oxygen. 17d. Credit: Explain what is meant by indicator species. The occurrence of organisms in a stretch of water is determined by the amount of oxygen available. Some organisms are able to tolerate less oxygen than others. The presence or absence of particular species of organisms can be used to assess the degree of pollution. Such organisms are called indicator species. 18a. General: Give two examples of poor management of natural resources and suggest possible improvements. Fish stocks are dwindling because of over-fishing. Stocks can be improved by setting limits on numbers of fish caught E.U. has done this. Overgrazing of grasslands. Plant more resilient grasses and plant shelter beds. 18b. General: Describe how the effect of poor management of natural resources can produce problems. Erosion of soil in third world countries and lack of technology and education in farming has resulted in crop failure and famine. This problem can be reduced by educating third world farmers and providing modern technology. 18c. Credit: Explain how components of an ecosystem are controlled in either agriculture or forestry. In crop farming soil must be kept fertile. Artificial environment must be maintained. Pests must be kept at bay. Weeds must be controlled. The Biosphere Summary Booklet page 11