-SYLLABUS DETAILS-
2.1.8 2,3 Describe and explain, with examples, population interactions, including :
competition, parasitism, mutualism, predation and herbivory.
Mutualism is an association in which both species derive benefit (Ie., a restricted type of symbiosis).
Each association should be exemplified with named species. Interactions should be understood in terms of the influences each species has on the population dynamics of the other and carrying capacity of the other's environment. Graphical representations of these influences should be interpreted.
2.2 Function (9h)
2.2.1 1,2 Explain the role of producers, consumers and decomposers in the ecosystem.
2.2.2 1,2 Describe photosynthesis and respiration simply in terms of inputs, outputs and
energy transformations.
It is important to note that biochemical details will not be required. No details of chloroplast, light dependent and independent reactions, mitochondria, carrier systems, ATP etc are necessary, nor will a knowledge of specific intermediate biochemicals be expected.
Photosynthesis should be understood as requiring carbon dioxide, water, chlorophyll and certain visible wavelengths of light producing organic matter and oxygen. The transformation of light energy into the chemical energy of organic matter should be appreciated.
Respiration should be recognized as requiring organic matter with oxygen to produce carbon dioxide and water and without oxygen to produce carbon dioxide and other waste products, involving the release of energy in a form available for use by living organisms but ultimately to be lost as heat.
2.2.3 1,3 Describe and explain the transfer and transformation of energy and material as it flows through an ecosystem.
Explain pathways of incoming solar radiation falling on the ecosystem (including losses through reflection and absorption, conversion of light to chemical energy, losses of chemical energy from one trophic level to another, efficiencies of transfer, overall conversion of light to heat energy by an ecosystem, and re-radiation of heat energy to the atmosphere).
Processes involving the transfer and transformation of carbon, nitrogen, oxygen, phosphorus and water as they cycle through an ecosystem should be described noting the inter-conversion of organic and inorganic storage where appropriate. Interpret, and construct from given data, diagrams of these cycles.
The laws of thermodynamics should be simply related to the energy and material flow through ecosystems (see also 1.1.3).
2.2.4 1 Define the terms gross productivity, net productivity, primary productivity and secondary productivity.
2.2.5 2 Calculate the values of gross and net productivity from given data.
Productivity is production per unit time. Gross productivity (GP) is the total gain in energy or biomass per unit time which could be through photosynthesis in primary producers or absorption in consumers.
Net productivity (NP) is the gain in energy or biomass per unit time remaining after allowing for respiratory losses (R). Other metabolic losses may take place, but these may be ignored in calculating and defining net productivity for the purpose of this course. Calculations can usually be made using the following equation:
NP = GP -R
In addition, for consumers only:
GP = Food eaten �Faecal losses
Students should be familiar with the terms gross primary productivity and net primary productivity.
2.2.6 3 Explain the terms negative and positive feedback mechanisms in relation to ecosystems.
Examples can be found in population dynamics and mineral cycling, for example.
2.3 Changes (8h)
2.3.1 1,3 Explain the concepts of limiting factors and carrying capacity in the context of population growth.
2.3.2 2,3 Describe and explain 'S� and 'J' population growth curves.
Explanations should be given for changes in both numbers and rates of growth in standard 'S' and 'J' population curves. Population curves should be sketched, described, interpreted and constructed from given data.
2.3.3 1,3 Describe the role of density dependent and independent, internal and external factors in the regulation of populations.
According to theory, density dependent factors operate as negative feedback mechanisms leading to the stability/regulation of the population.
Both factors may operate on a population. Many species (particularly 'r' strategists) are probably regulated by density-independent factors (weather is the most important of these factors). Also note that density dependence takes over (by definition) at high population densities.
Internal factors might include density dependent fertility or size of breeding territory and external factors might include predation or disease.
2.3.4 1,2 Describe the principles associated with survivorship curves including, 'r' and 'K' selection.
r = specific growth rate.
Species employing r-strategies achieve a high specific growth rate. By investing very little in a large number of offspring, although mortality rates tend to be high early in the lifespan, sufficient survive through to sexual maturity.
K = carrying capacity .
Species employing K -strategies have been selected for competitive superiority at or near the carrying capacity. Much parental investment in each offspring results in low numbers but ensures low mortality rates early in lifespan and so sufficient survive through to sexual maturity.
Students should be familiar with interpreting features of survivorship curves including logarithmic scales.
2.3.5 2 Describe the concept and processes of succession in a named habitat.
Named examples of a pioneer community, seral stages and climax community for a lithosere, hydrosere, psammosere or halosere should be studied.
Succession seen as one community causing changes in the physical environment such that another community can become established which then replaces the first through competition.
2.3.6 2,3 Explain the changes in energy flow, gross and net productivity, diversity and mineral cycling in different stages of succession.
As system becomes more complex energy flows also become more branching, i.e., simple food chains become complex food webs.
In early stages gross production is low due to harsh conditions and low density of producers. Proportion of energy lost through community respiration is relatively low too, so net productivity is high, i.e., system is growing. In later stages, with increased consumer community, gross productivity may be high in climax community, but this is balanced by respiration so net productivity approaches zero.
Diversity increases with succession as production base increases.
Minerals become increasingly locked up in biotic components.
2.3.7 2 Describe factors affecting the nature of climax communities.
Climatic and edaphic factors determine the nature of a climax community unless human or other activities maintain an equilibrium at a subclimax community .
Topic 3 -Global cycles and physical systems
3.1 The ecosphere (0h)
3.1.1 2 Describe how the atmosphere, lithosphere and hydrosphere interact to form the ecosphere.
See also 2.2.3
3.2 The atmosphere (4h)
3.2.1 1 Describe the overall structure of the atmosphere.
Temperature and pressure profiles of the troposphere and stratosphere and its gaseous composition. The location of the ozone layer should be known and there should be a clear differentiation between stratospheric and tropospheric ozone. Knowledge of tropospheric ozone's role as a pollutant is expected.
3.2.2 2,3 Describe and explain the global atmospheric energy budget.
Reasons for the differences in insolation per unit area between the equator and poles. There should be a qualitative understanding of latent and sensible heat flux, and the manner in which water can absorb or release heat as it changes state. Interpret and generate diagrams of the global energy budget, including flows and storage of energy.
Analyze the global energy budget from a systems point of view, examining inputs and outputs of energy.
Memorization of figures or percentages is not required.
3.2.3 2,3 Explain the role of atmospheric circulation in redistributing heat from the equator to polar regions. Examination of the global energy budget should produce awareness of the global imbalances of solar energy inputs and outputs.
3.2.4 2 Describe major patterns of atmospheric circulation including the Hadley cell, tropical and temperate cyclones and Rossby waves.
Students should understand the mechanisms by which circulation achieves the redistribution of heat. This objective is descriptive and does not require knowledge of the physics involved (i.e., knowledge of what Rossby waves are and their role in transferring hot air north and cold air south in the northern hemisphere is required, but an understanding of how Rossby waves form is not.)
3.2.5 2,3 Explain how atmospheric circulation gives rise to broad climatic regions and, subsequently, biomes.
The location of broad climatic belts, i.e., tropical, desert, temperate and polar, as a natural consequence of air circulation patterns, e.g., how falling and drying air flow causes desert belts at approximately 30 degrees North and South. There should be a clear understanding of the relationship between latitude, wind direction, precipitation and temperature, in the formation of the following biomes: tropical rainforests, deserts, temperate forests and tundra.
3.3 The depletion of stratospheric ozone (2h)
3.3.1 2 Describe the role of ozone in absorbing ultraviolet radiation.
Knowledge of the interactions between diatomic oxygen and high energy radiation leading to the formation of ozone is required (memorization of chemical equations is not required).
3.3.2 1 State the effects of ultraviolet radiation on living tissues and biological productivity.
Mutation and subsequent effects on health. Damage to photosynthetic organisms, especially phytoplankton, and their consumers (e.g., zooplankton).
3.3.3 2,3 Explain the interaction between ozone and halogenated organic gases.
Halogenated organic gases, although very stable under normal conditions, can, when exposed to ultraviolet radiation in the stratosphere, liberate halogen ions, which are then free to react with monatomic oxygen, thus slowing the rate of ozone reformation. There should be some knowledge of the relative destructiveness of different halogenated organic gases.
3.3.4 1,2 Describe three methods of reducing the manufacture and release of ozone depleting substances.
Recycling refrigerants, developing new refrigerants, reduction of gas blown plastics, reduction of some propellants. Examine alternatives relevant to the students' locale as the relative importance of one or another ozone-depleting substance is likely to vary with location. Students should be aware of products they use which contain these compounds, and what changes they can make in their lifestyle to limit their use of these compounds.
3.3.5 1,3 Describe and evaluate the role of national and international organizations in reducing the emissions of ozone-depleting substances.
The role of the United Nations (UNEP) in forging international agreements on the use of ozone-depleting substances should be examined. Also the relative effectiveness of these agreements and the difficulties in implementing and enforcing them should be studied. In addition, students should be familiar with what local governments are doing to comply with these agreements, and what local organizations are doing to persuade governments to comply.
3.4 The issue of global warming (3h)
3.4.1 2 Describe the role of greenhouse gases in maintaining mean global temperature.
The 'greenhouse effect is a normal and necessary condition for life on Earth. There is a fundamental difference between the short wave energy entering and the long wave energy leaving the planet. The absorption of long wave radiation by water, carbon dioxide, methane and CFCs should be understood. A change in the amount of these gases present in the atmosphere will result in more or less heat being retained. No knowledge of the chemistry involved is required.
3.4.2 1,3 Describe four ways in which human activities add to greenhouse gases, and discuss four ways in which global emission of greenhouse gases can be reduced.
Consider deforestation, burning fossil fuels, rice and cattle farming, and use of CFCs. Methods of reduction should include conservation of energy (including carbon tax), use of alternative energy sources.
3.4.3 3 Discuss qualitatively the effects of increased mean global temperature on the planetary distribution of biomes and consequently on global agriculture.
The variety of, and sometimes conflicting, arguments surrounding this issue. Students should be able to discuss:
� thermal expansion of the oceans;
� melting of the polar ice caps;
� increased evaporation in tropical latitudes leading to increased snow fall on the polar ice caps, triggering a new ice age;
� the effect of air pollutants (aerosols) in reflecting radiation, thus offsetting the warming trends.
Note the complexity of the problem and the uncertainty of global climate models.
3.4.4 3 Evaluate five ways in which emissions of greenhouse gases can be reduced in your local community.
Students can explore their own lifestyle in the context of local greenhouse gas emissions.
3.5 Acid deposition (2h)
3.5.1 2 Describe, in outline, the chemistry leading to the formation of acidified precipitations.
Conversions of sulphur dioxide and nitrogen dioxide into the sulphates and nitrates of dry deposition and the sulphuric and nitric acids of wet deposition. Knowledge of chemical equations is not required.
3.5.2 3 Describe the possible effects of acid deposition on soil, water and living organisms.
Leaching of aluminium, calcium, magnesium, lead and hydrogen ions from soils and discharging them into lakes and rivers. Problems of aluminium ions affecting the gills of fish, becoming concentrated up the food chain and contaminating human water supply and their effect on plants. Possible effects of acid on aquatic organisms and coniferous forests.
3.5.3 2 Explain why the effect of acid deposition is regional rather than global.
Refer to areas downward of major industrial areas, which are adversely affected by acid rain and link them to sources of sulphur dioxide and nitrogen dioxide emissions. Consider regions unaffected and discuss reasons for this.
3.5.4 2,3 Briefly describe and evaluate means of reducing emissions of the principal causal agents of acid deposition.
Debate measures to reduce fossil fuel combustion. Think of reducing demand for electricity and private cars and switching to renewable energy. Secondly refer to clean up measures at 'end of pipe' locations (points of emission). Consider the role of international agreements in effecting change.
3.5.5 2,3 Briefly describe methods for restoring acidified soils and waters, and evaluate their efficacy.
Discuss liming. The cost effectiveness of spreading ground limestone in Swedish lakes in the early 1980s provides a good case study.
3.6 The hydrosphere (2h)
3.6.1 1 State the major components of the hydrosphere.
Relative proportions of water in seas, lakes, rivers, atmosphere, ice caps and ground water. Precise figures are not required.
3.6.2 2 Describe the role of ocean currents in the planetary transfer of energy.
The global atmospheric energy model cannot be understood without reference to ocean currents' role in the transfer of energy. Candidates should know that cold currents flow from poles to the equator, and that warm currents driven by wind and the Earth's rotation flow away from the equator. Naming all the individual currents is not required, although examples may be noted.
3.6.3 1,3 Explain briefly the role of ocean currents in the regulation of climate.
The rate at which water absorbs and releases heat relative to land and the consequent moderating effect on climate should be understood. The transport of heat by ocean currents and the influence on climate should be understood, e.g., the North Atlantic Drift moderating the climate of north-western Europe, which, in the absence of this current, would have a sub-arctic climate.
3.7 The lithosphere (3h)
3.7.1 2,3 Describe the structure of the Earth's internal zones and give an explanation of plate tectonics.
This should include knowledge of the Earth's internal zones (crust, mantle and core). Knowledge of convection cells and mantle plumes in the asthenosphere is required. The terms constructive and destructive margins, subduction and mid-oceanic ridge should be understood. Candidates will be expected to draw and label models showing the interactions between plates, and the formation and destruction of crust.
3.7.2 2,3 Explain how plate activity has influenced evolution and biodiversity.
The consequences of plate tectonics on speciation should be understood, i.e., the separation of gene pools, formation of physical barriers or land bridges, giving rise to new species. Also, its role in generating new and diverse habitats, thus promoting biodiversity .
Topic 4 Human population and carrying capacity
Because of the unfamiliar nature of some of the material in this topic, more background information has been given than for the other topics.
4.1 Population dynamics (7h)
4.1.1 2,3 Describe the nature, and explain the implications, of exponential growth in human populations.
4.1.2 2 Explain and calculate from data the values of crude birth rate, crude death rate, fertility, doubling time and natural increase rate.
4.1.3 2,3 Construct and analyze age/sex pyramids and demographic transition models.
4.1.4 3 Explain and exemplify the use of models in predicting the growth of human populations.
Include computer simulation, statistical/demographic tables for developing and developed, countries, age/sex pyramids and graphical extrapolation of population curves.
4.2 Resources (natural capital) (5h)
4.2.1 1 Explain the concept of resources in terms of natural capital.
Ecologically-minded economists describe resources as 'natural capital' because, if properly managed, they are forms of wealth that can produce 'natural income' in the form of valuable goods and services indefinitely. This income may consist of marketable commodities such as timber and grain or in the form of ecological or life-support services such as the flood and erosion protection provided by forests.
4.2.2 1 Define the terms renewable, replenishable and non-renewable natural capital.
There are three broad classes of natural capital:
* Renewable natural capital, such as living species and ecosystems, is self- producing and self-maintaining, using solar energy and photosynthesis. These forms can yield marketable goods such as wood fiber, but may also provide unaccounted essential services when left in place (e.g., climate regulation).
� Replenishable natural capital, such as groundwater and the ozone layer, is non-living but is also often dependent on the solar 'engine' for renewal.
� Non-renewable forms of natural capital such as fossil fuel and minerals, are analogous to inventories - any use implies liquidating part of the stock.
4.2.3 1 Distinguish between natural capital and natural income.
Natural capital can be explained in terms of standing stocks and income flows. The stock is the present accumulated quantity of natural capital and the income is any sustainable rate of harvest. For example, forests and fish stocks are forms of natural capital and sustainable yields or harvests from such stocks is natural income.
4.2.4 1,2 Explain the concept of sustainability in terms of natural capital and natural income.
Candidates should understand that any society that supports itself in part by depleting essential forms of natural capital is unsustainable. If human well-being is dependent on the goods and services provided by certain forms of natural capital then long-term harvest (or pollution) rates should not exceed rates of capital renewal. Sustainability means living within the means of nature, on the 'interest' or sustainable income generated by natural capital.
4.2.5 1,2 Explain and calculate sustainable yields from given data.
Sustainable yield may be calculated as the rate of increase in natural capital, i.e., that which can be exploited without depleting the original stock or its potential for replenishment. For example, the annual sustainable yield for a given crop may be estimated simply as the annual gain in biomass or energy through growth and recruitment. Thus,
SY = (Total biomass/energy at time t + 1) - (Total biomass/energy at time t)
SY = (Annual growth and recruitment) -(Annual death and emigration)
4.2.6 2,3 Identify and give examples of various values ( e.g. ecological, scientific, economic and aesthetic values) associated with nature and natural capital, and describe the way these values influence the appraisal and use of natural capital in industrial societies.
In industrial societies, people tend to put the most weight on monetary or economic values. In some cases, the economic value of a natural capital stock can be determined from the market price of the goods it produces. However, there are no formal markets for many valuable ecological goods and services such as waste assimilation, flood and erosion control, nitrogen-fixation, photosynthesis, etc. The same is true for curiosity or scientific values and most of the aesthetic benefits associated with nature. All these functions and values therefore usually remain unpriced and undervalued. Thus, even though certain ecological services may be essential for human existence, we have tended to take them for granted.
Methods are being developed better to price the ecological, scientific, and
aesthetic/recreational values of the environment so that they may be weighted more rigorously against more common economic (development) values. However, some argue that they are impossible to quantify and price realistically. Not surprisingly, therefore, much of the sustainability debate hinges around the problem of how to weigh conflicting values in our treatment of natural capital.
4.3 Limits to growth ( 6h)
4.3.1 2,3 Explain the concept of carrying capacity and how it must be modified when applied to local human populations.
Carrying capacity is usually defined as the maximum population of a given species that can be supported indefinitely in a defined habitat without permanently damaging that habitat. However, human ingenuity is often capable of substituting one resource for another or substituting manufactured capital for some form of natural capital that might run out. People are able to trade with other regions so that an energy-poor agricultural country can trade food for petroleum from another country with lots of oil but little domestic agriculture. This means that both can grow beyond the boundaries set by their local resources. Some economists therefore argue that there are no practical limits to economic growth and the carrying capacity concept does not apply to human beings. A technically attainable carrying capacity for a local population may therefore not be sustainable in the long term. Also it may not be possible to extrapolate any density to the global population.
4.3.2 1 Explain how reuse, recycling, remanufacturing and absolute reductions in energy and material use can affect human carrying capacity.
Human carrying capacity is determined not by population per se but rather by the rate of energy and material consumption, the level of pollution, and the extent of human interference in global life support systems. To the extent that recycling, reuse, and remanufacturing reduce these impacts, they can increase human carrying capacity .
4.3.3 2,3 Discuss how national and international development policies (e.g., population Ipolicy) and cultural influences (e.g, the changing roles of women) can affect human population dynamics and growth.
Many policy factors influence human population growth. Domestic and international development policies that attack the death rate through agricultural development, improved public health and sanitation, better service infrastructure, etc., may stimulate rapid population growth by lowering mortality without significantly affecting fertility. Some analysts believe that birth rates will come down by themselves as economic welfare improves and that the population problem is therefore better solved through policies to stimulate economic growth. Education about birth control encourages family planning. Parents may be dependent on their children for support in their later years and this may create an incentive to have many children. Urbanization may also be a factor in reducing crude birth rates. Policies directed toward the education of women, and enabling women to have greater personal and economic independence, may be the most effective in reducing fertility and therefore population pressure.
4.3.4 2,3 Describe and explain the relationship between population, resource consumption and technological development and their influence on carrying capacity and material economic growth.
Because technology plays such a large role, many economists and technological optimists argue that human carrying capacity can be expanded continuously through technological innovation. For example, if we learn to use energy and material twice as efficiently, we can double the population or the use of energy without necessarily increasing the impact ('load') imposed on the ecosphere. However to compensate for foreseeable population growth (doubled by the year 2040?) and the economic growth that is deemed necessary, especially in developing countries, various estimates have suggested that efficiency would have to be raised by a factor of 4 to 10 to remain within global carrying capacity.
Option A -Analysing marine ecosystems
The objectives of this option can only be achieved satisfactorily if it is taught by means of a substantial amount of field work.
A.l Measuring physical components of the system (lh) .
A.l.l 1 List the variable physical factors of a marine ecosystem.
A.l.2 2,3 Describe and evaluate methods for measuring at least 3 physical variables within a marine system.
Methods for measuring any three significant physical variables such as salinity, pH, temperature, dissolved oxygen and wave action, and how these may vary in a given ecosystem with depth, time or distance.
As a practical, this may be carried out effectively in conjunction with an examination of related biotic components.
A.2 Measuring biotic components of the system (3H)
A.2.1 2 Construct simple keys and use published keys for the identification of marine organisms.
Students could practice with keys supplied and construct their own key for up to 12 species.
A.2.2 2,3 Describe and use methods for estimating abundance of marine organisms (including mark/release/recapture, quadrat and percentage frequency, population density and percentage cover), and state the limitations of the, methods.
A.2.3 2,3 Describe and evaluate methods for estimating biomass of trophic levels in a marine community.
Dry weight measurements of quantitative samples could be extrapolated to estimate total biomasses.
A.2.4 1 Define the term diversity .
A.2.5 2 Describe how a named diversity index is used.
Diversity as a function of two components: the number of different species and the relative numbers of individuals of each species. Mathematical methods that take both these components into account in producing an index of diversity should be used by students, but will not be required for examination.
A.3 Measuring productivity of the system (3h).
A.3.1 2,3 Describe and evaluate a method for measuring gross and net primary productivity in a marine ecosystem.
The use of the light and dark bottle technique might be an ideal method to select for measuring gross and net productivity of phytoplankton.
A.3.2 2,3 Describe and evaluate a method for measuring gross and net secondary productivity in a marine ecosystem.
Gross productivity might be simply estimated as food eaten minus faeces produced. As a laboratory practical, an aquarium population of invertebrate herbivores (e.g., brine shrimps) might be fed on a known algal biomass for a period of time and remaining algae and faeces collected, dried and weighed. Net productivity might be measured as the increase in biomass of a consumer population over time. As a laboratory or field practical investigation, biomass might be estimated as a fixed % of wet weight to avoid the killing of organisms for dry weight measurements. Alternatively, 'second hand data' could be used.
A.4 Measuring changes in the system (3h)
A.4.1 2,3 Describe and evaluate methods for measuring changes in abiotic and biotic components of a marine system along an environmental gradient or over time.
A.4.2 2 Describe methods for assessing changes in abiotic and biotic components of a marine system due to a specific human activity.
Methods and changes should be selected appropriately for the human activity chosen. Suitable human impacts might include effluent, oil spills and over-exploitation.
A.4.3 3 Describe and explain changes that might be found by these studies.
A.5 Comparative study of ecosystems (5h)
A.5.1 1 State the physical characteristics of two different marine ecosystems.
Marine systems to be selected from: pelagic, neritic, bathyal, littoral, mangroves and coral reefs.
A.5.2 2 Describe the inter-relationships of these physical characteristics.
The inter-relationships of their main physical characteristics, such as the salinity, depth, pressure, temperature, insulation or wave action as appropriate, should be explained.
A.5.3 2 Describe the overall community structure and functioning of each of the two marine ecosystems.
A.5.4 3 Compare the community structure and functioning of each of the two systems, relating differences to the physical characteristics.
Characteristic species, dominant communities, diversity, productivity, food chains etc. should be described.
Option B -Analysing terrestrial ecosystems
The objectives of this option can only be achieved satisfactorily if it is taught by means of a substantial amount of field work.
B.l Measuring physical components of the system (lh)
B.I.I 1 List the variable physical factors of a terrestrial ecosystem.
Methods for measuring any three significant physical variables such as temperature, light intensity, wind speed, particle size, slope, soil moisture, drainage and mineral content, and how these may vary in a given ecosystem vertically or with time or distance. As a practical, this may be carried out effectively in conjunction with an examination of related biotic components.
B.1.2 2,3 Describe and evaluate methods for measuring at least 3 physical variables within a terrestrial system.
B.2 Measuring biotic components of the system (3h)
B.2.1 2 Construct simple keys and use published keys for the identification of terrestrial organisms.
Students could practise with keys supplied and construct their own key for up to 12 species
B.2.2 2,3 Describe and use methods for estimating abundance of terrestrial organisms (including mark/release/recapture, quadrat and percentage frequency, population density and percentage cover) and state the limitations of the methods.
B.2.3 2,3 Describe and evaluate a method for estimating biomass of trophic levels in a terrestrial community.
Dry weight measurements of quantitative samples could be extrapolated to estimate total biomasses.
B.2.4 1 Define the term diversity .
B.2.5 2 Describe how a named diversity index is used.
Diversity as a function of two components: the number of different species and the relative numbers of individuals of each species. Mathematical methods that take both these components into account in producing an index of diversity should be used by students, but will not be required for examination.
B.3 Measuring productivity of the system (3h)
B.3.1 2,3 Describe and evaluate a method for measuring gross and net primary
productivity in a terrestrial ecosystem.
While methods for measuring primary productivity in terrestrial vegetation might not be feasibly carried out as student practicals, possible methods should be described and criticized, e.g., measuring changes in biomass of covered and uncovered quadrats of grassland, measuring absorption of CO2 in enclosed communities.
B.3.2 2,3 Describe and evaluate a method for measuring gross and net secondary productivity in a terrestrial ecosystem.
Gross productivity might be simply estimated as food eaten minus faeces produced.
As a laboratory practical, a terrarium population of invertebrate herbivores (e.g., silkwonns) might be fed on a known plant biomass for a period of time and remaining plant material and faeces collected, dried and weighed.
Net productivity might be measured as the increase in biomass of a consumer population over time.
As a laboratory or field practical investigation, biomass might be estimated as a fixed % of wet weight to avoid the killing of organisms for dry weight measurements. Alternatively, 'second hand data' could be used.
Obj B.4 Measuring changes in the system (3h)
B.4.1 2,3 Describe and evaluate methods for measuring changes in abiotic and biotic components of a terrestrial system along an environmental gradient or over time.
B.4.2 2 Describe methods for assessing changes in abiotic and biotic components of a terrestrial system due to a specific human activity.
Methods and changes should be selected appropriately for the human activity chosen. Suitable human impacts might include toxins from mining activity, landfills and over-exploitation.
B.4.3 3 Describe and explain changes that might be found by these studies.
B.5 Comparative study of ecosystems (5h)
B.5.1 1 State the physical characteristics of two different terrestrial ecosystems.
Terrestrial systems to be selected from: tropical forest, temperate forest, tropical grassland, temperate grassland, desert and tundra.
B.5.2 2 Describe the inter-relationships of these physical characteristics. The inter-relationships of their main physical characteristics, such as the insulation, rainfall, altitude, temperature, soil water or mineral content as appropriate, should be explained.
B.5.3 2 Describe the overall community structure and functioning of each of the two terrestrial ecosystems.
B.5.4 3 Compare the community structure and functioning of each of the two systems, relating differences to the physical characteristics.
Characteristic species, dominant communities, diversity, productivity, food chains, etc. should be described.
Option C -Analyzing freshwater ecosystems
The objectives of this option can only be achieved satisfactorily if it is taught by means of a substantial amount of fieldwork.
C.l Measuring physical components of the system (lh)
C.l.l 1 List the variable physical factors of a freshwater ecosystem.
Methods for measuring any three significant physical variables such as turbidity, pH, temperature, dissolved oxygen and flow velocity, and how these may vary in a given ecosystem with depth, time or distance.
As a practical, this may be carried out effectively in conjunction with an examination of related biotic components.
C.l.2 2,3 Describe and evaluate methods for measuring at least 3 physical variables within a freshwater system.
C.2 Measuring biotic components of the system (3h)
C.2.1 2 Construct simple keys and use published keys for the identification of freshwater organisms.
Students could practice with keys supplied and construct their own key for up to 12 species.
C.2.2 2,3 Describe and use methods for estimating abundance of freshwater organisms (including mark/release/recapture, quadrat and percentage frequency, population density and percentage cover), and state the limitations of the methods.
C.2.3 2,3 Describe and evaluate methods for estimating biomass of trophic levels in a freshwater community.
Dry weight measurements of quantitative samples could be extrapolated to estimate total biomasses.
C.2.4 1 Define the term diversity.
C,2.5 2 Describe how a named diversity index is used.
Diversity as a function of two components: the number of different species and the relative numbers of individuals of each species. Mathematical methods that take both these components into account in producing an index of diversity should be used by students, but will not be required for examination.
C.3 Measuring productivity of the system (3h)
C.3.1 2,3 Describe and evaluate a method for measuring gross and net primary productivity in a freshwater ecosystem.
The use of the light and dark bottle technique might be an ideal method to select for measuring gross and net productivity of phytoplankton.
C.3.2 2,3 Describe and evaluate a method for measuring gross and net secondary productivity in a freshwater ecosystem.
Gross productivity might be simply estimated as food eaten minus faeces produced. As a laboratory practical, an aquarium population of invertebrate herbivores (e.g.,Asellus) might be fed on a known plant biomass for a period of time and remaining plant material and faeces collected, dried and weighed.
Net productivity might be measured as the increase in biomass of a consumer population over time. As a laboratory or field practical investigation, biomass might be estimated as a fixed % of wet weight to avoid the killing of organisms for dry weight measurements. Alternatively, 'second hand data' could be used.
C.4 Measuring changes in the system (3h)
C.4.1 2,3 Describe and evaluate methods for measuring changes in abiotic and biotic components of a freshwater system along an environmental gradient or over time.
C.4.2 2 Describe methods for assessing changes in abiotic and biotic components of a freshwater system due to a specific human activity.
Methods and changes should be selected appropriately for the human activity chosen.
Suitable human impacts might include effluent, eutrophication and over-exploitation.
C.4.3 3 Describe and explain changes that might be found by these studies.
C.5 Comparative study of ecosystems (5h)
C.5.1 1 State the physical characteristics of two different freshwater ecosystems.
Freshwater systems to be selected from: lakes, rivers, bogs, swamps, marshes and, estuaries.
C.5.2 2 Describe the inter-relationships of these physical characteristics.
The inter-relationships of their main physical characteristics, such as the flow, depth, turbidity, temperature, dissolved oxygen or minerals as appropriate, should be explained.
C.5.3 2 Describe the overall community structure and functioning of each of the two freshwater ecosystems.
C.5.4 3 Compare the community structure and functioning of each of the two systems, relating differences to the physical characteristics.
Characteristic species, dominant communities, diversity, productivity, food chains, etc. should be described.
Option D -Impacts of resource exploitation
D.l Exploitation of energy resources (4h)
D.1.1 1,3 Evaluate the advantages and disadvantages of five sources of energy.
Consider fossil fuels, nuclear, solar, hydroelectric and one other source. These sources should be compared for efficiency (i.e., cost of extraction, conversion, transport and safety), sustainability and adverse effects.
D.2 Exploitation of food resources (6h)
D.2.1 1 Review world food production.
The relative proportions and importance of different food sources (fish, meat, cereals, dairy products, fruit, root crops). Precise figures are not required.
D.2.2 1 Compare the efficiency of terrestrial and aquatic food production systems.
Compare in terms of their trophic levels, efficiency of energy conversion and ease of harvesting. There is no need to consider individual production systems in detail.
D.2.3 1,3 Describe and evaluate the efficiency and environmental impact of a named commercial farming system in either a terrestrial or an aquatic environment.
An example should be chosen that demonstrates use of pesticides, fertilizers, monoculture, artificial breeding and reduction of competitors.
D.2.4 1,3 Describe and evaluate the efficiency and environmental impact of a traditional (subsistence) system of food production in a comparable environment to that of D.2.3.
An example should be chosen that demonstrates polyculture, sustainable harvesting, natural productivity.
D.2.5 3 Compare the efficiency and environmental impacts of the systems described in D.2.3 and D.2.4.
The pair of examples could be, e.g., North American cereal farming and subsistence farming in some parts of South East Asia, intensive beef production in the developed, world and the Masai tribal use of livestock, or commercial salmon farming in Norway/Scotland and rice-fish farming in Thailand. Other local/global examples are equally valid.
D.2.6 3 Evaluate the implications for future global food supply of changes in the management of food production systems.
Consider maximizing yield and improving storage and distribution methods of food production systems. Also, how humans can change dietary habits, e.g., eat less meat.
D.3 The environmental demands ofhuman populations (5h)
D.3.1 1 Explain the concept of an ecological footprint as a model for assessing the demands human populations make on their environment.
The ecological footprint of a population is the area of land in the same vicinity as the population that would be required to provide all its resources and assimilate all its wastes. As a model, it is able to provide some understanding and quantitative estimate of human carrying capacity. It is, in fact, the inverse of carrying capacity, i.e., it refers to the area required to sustainably support a given population rather than the population that a given area can sustainably support.
D.3.2 1,2,3 Calculate from appropriate data the ecological footprint of given populations, stating the approximations and assumptions involved.
Although the accurate calculation of an ecological footprint might be very complex, an approximation can be achieved through the following steps:
Per capita land requirement for food production (ha) = Per capita food consumption (Kg yr^-1)
Mean food production per hectare of local arable land (kg ha-l yr-l)
Per capita land requirement for absorbing waste CO2 from fossil fuels (ha) = per capita CO2 emission (kg C yr6-1) Net carbon fixation per hectare of fuels local natural vegetation (kg C ha-l yr-l)
The total land requirement (ecological footprint) can then be calculated as the sum of these two per capita requirements, multiplied by the total population.
This calculation clearly ignores other elements of a 'footprint' arising from the land or water required to: provide any aquatic and atmospheric resources; assimilate wastes other than CO2; produce the energy and material subsidies imported to the arable land for increasing yields; replace loss of productive land through urbanization, etc.
D.3.3 2,3 Describe and explain the differences found between the ecological footprints of two human populations, one from a developing and one from a developed region.
Data for food consumption are often given in grain equivalents, so that a population with a meat-rich diet would tend to consume a higher grain equivalent than a population that fed directly on grain. Grain production will be higher with intensive farming strategies. Populations more dependent on fossil fuels will have higher CO2 emissions. Fixation of CO2 is clearly dependent on climatic region and vegetation type. These, and other factors, will often explain the differences in the ecological footprints of developing and developed populations.
Option E -Conservation and biodiversity
E.l The species concept (3h)
E.l.l 1 Define the terms biodiversity, and genetic, species and habitat diversity
E.1.2 1,3 Discuss the mechanism of natural selection as a possible driving force for speciation.
The mechanism by which change occurs, i.e., change in the frequency of an allele in the population in response to environmental pressure. The concept of fitness should be understood. The history of the development of modern theory of evolution is not expected.
E.l.3 1 State that isolation can lead to different species being produced, which are unable to interbreed to yield fertile offspring.
Isolation of a gene pool, behavioral differences that preclude reproduction, and the inability to produce fertile offspring (leading to speciation) should all be examined.
E.l.4 2,3 Explain the relationship between ecosystem stability, diversity, succession and habitat.
How diversity changes through succession. How habitat diversity leads to greater species and genetic diversity . How diversity contributes to ecosystem stability .How habitat type relates to species diversity .
E.2 Vulnerability and extinction (6h)
E.2.1 2,3 Describe the relative value of tropical rainforests in contributing to global biodiversity, and their vulnerability.
Tropical rain forest should be compared with other major ecosystems. Take particular note of agriculture when considering vulnerability.
E.2.2 3 Discuss current estimates of numbers of species and past and present rates of species extinction.
Students should compare and contrast by examining the fossil record to look at mass extinctions in the past, and compare the hypothetical causes of these to the present day.
The time frame of these periods of extinction should be examined.
E.2.3 2,3 Describe and explain the factors that may make species more or less prone to extinction.
The following factors (among others) will affect the propensity to extinction: degree of specialization, distribution, reproductive potential and behavior, and trophic level. An ecosystem's ability to survive change may depend on diversity, resilience and inertia.
E.2.4 1 State and explain the criteria used to determine a species' conservation status.
Students should know how species are placed in the Unknown, Rare, Vulnerable, Endangered and Extinct categories in the Red Data Books. (These are available for each country).
E.2.5 1,2 Describe the case histories of three species, one that has become extinct, another that is currently endangered, and a third that was endangered and has now been removed from the endangered list.
Students should know the ecological, socio-political and economic pressures that caused or are causing the chosen species' extinction. The species' ecological roles and the consequences of their disappearance should be understood.
E.2.6 1,2 Describe the case history of a natural area of biological significance that is threatened by human activities.
Students should know the ecological, socio-political and economic pressures that caused or are causing the degradation of the chosen area, and the consequent threat to biodiversity.
E.3 Reasons for preserving biodiversity (lh)
E.3.1 1,2 State the arguments for preserving species and habitats.
Students should appreciate arguments based on ethical, aesthetic, genetic resource and commercial (including opportunity cost) considerations, and life support/ecosystem support functions.
E.4 Methods for preserving biodiversity (5h)
E.4.1 1,3 Compare the role and activities of UNEP with WFN and Greenpeace in preserving and restoring ecosystems and biodiversity.
Bring out the differences between governmental (UNEP) and non-governmental organizations in terms of use of the media, speed of response, diplomatic constraints and enforceability.
E.4.2 1 Outline the World Conservation Strategy proposed by IUCN, UNEP and WFN
E.4.3 1,2 State and describe the criteria used to design reserves.
In effect, protected areas may become 'islands' within a country and as such will normally lose some of their diversity .So there will be a need to apply principles of island biogeography to the design of reserves. Appropriate criteria are discussed in the World Conservation Strategy.
E.4.4 3 Evaluate the success of a named protected area.
The granting of protected status to a species or ecosystem is no guarantor of protection without community support, adequate funding and proper research. Consider a local specific example.
E.4.5 2,3 Discuss and evaluate the strengths and weaknesses of the species-based approach to conservation.
Students should consider the relative strengths and weaknesses of the following:
1)CITES and other international treaties governing trade in endangered species.
2)Captive breeding and reintroduction programs, and zoos
3)Aesthetic versus ecological value.
Option F -Pollution
F.1 Environmental impact assessments and monitoring (3h)
F.1.1 1 Define the terms pollution, point and non -point sources.
F.1.2 1 State that pollution can be measured either directly or indirectly (by its effects).
Repeat over time and throughout the region.
F.1.3 1,2 Describe three methods of monitoring levels of pollution directly.
The methods will be one for each of air, water and soil pollution.
F.1.4 1,2 Describe one method of measuring pollution levels indirectly by a biotic index.
This will involve levels of tolerance, diversity and abundance of organisms and should compare a polluted and an unpolluted site (e.g., upstream and downstream of a point source).
F.1.5 1,2 Describe the form and use of environmental impact assessments (EIAs).
Students should have the opportunity to see an actual EIA study. They should realize that an EIA involves production of a baseline study before any environmental development, assessment of possible impacts, and monitoring of change during and after the development.
F.2 Transport sources (3h) ~ :
F.2.1 1 Compare the output from diesel and petrol engines.
F.2.2 1 Compare the output from engines using leaded and unleaded petrol.
Effect of lead on children.
F.2.3 2,3 Evaluate the use of the different forms of fuel.
PM10 particles (under 10 nanometers diameter, from diesel engines), benzene, Carbon dioxide and carbon monoxide - unburned hydrocarbons.
J.2.4 2,3 Discuss methods of reducing harmful emissions.
Catalytic converters. Electric vehicles in towns. LPG (liquid petroleum gas) and alcohol.
F.3 Domestic waste sources (3h)
F.3.1 1,2 State and describe types and sources of domestic waste.
Detergents (phosphates), sewage, metal, paper and organic waste. Biodegradable and recyclable materials.
F.3.2 1,2 Describe the impact of domestic waste on ecosystems.
Untreated sewage in freshwater and the sea. Refuse in land-fill sites.
F.3.3 2,3 Describe and evaluate methods of treatment of domestic waste.
-Sewage treatment
-Salvaging and recycling
-Composting
-biogas generation.
Leachates and methane production (methane to heat factories, run sewage works).
F.4 Agricultural sources (3h)
F.4.1 1,2 State and describe types and sources of agricultural pollution.
Run-off, fertilizers, slurry, pesticides.
F.4.2 1,2 Describe the impact of agricultural waste on ecosystems.
Eutrophication (see also F.3.2). Concentration of pesticides along food chains. Contamination of drinking water by nitrates, nitrites and other toxins.
F.4.3 2,3 Describe and evaluate methods of control of agricultural waste.
Reduced fertilizer use, and use of fertilizer mainly when plants are growing quickly. Reduced pesticide use. Education/economics.
F .5 Industrial sources (3h)
F.5.1 1,2 State and describe types and sources of industrial waste.
Gaseous, solid, liquid; heavy metals, organic, radioactive.
F.5.2 1,2 Describe the impact of one heavy metal and one organic industrial waste on ecosystems.
Include effects on food chains and people.
F.5.3 2,3 Describe and evaluate methods of control of industrial waste.
A case study of a real or simulated industry -designing a scheme for the control of waste.