Topic 1- Systems and Models (5h)
This topic may best be viewed as a theme to be used in the delivery of other topics, rather than as an isolated teaching topic.
It is essential that the systems approach is used throughout this course. This approach identifies the elements of systems and examines the relationships and processes that link these elements into a functioning entity.
The systems approach also emphasizes the similarities between environmental systems, biological systems and artificial entities such as transport and communication systems. This approach stresses that there are concepts, techniques and terms that can be transferred from one discipline (such as ecology) to another (such as engineering).
This topic identifies some of the underlying principles that can be applied to living systems, from the level of the individual up to that of the whole biosphere. It would therefore be helpful to, wherever possible, describe and analyze the systems addressed in the terms laid out in this topic.
1.1.1 Outline the concept and characteristics of a system.
1.1.2 Define the terms open system, closed system and isolated system.
1.1.3 These terms should be applied when characterizing real systems.
� An open system exchanges matter and energy with its surroundings ( eg an ecosystem).
� A closed system exchanges energy but not matter; the "Biosphere 11" experiment was an attempt to model this. Closed systems do not occur naturally on Earth
� An isolated system exchanges neither matter nor energy. No such systems exist (with the possible exception of the entire cosmos).
1.1.3 Describe how the first and second laws of thermodynamics are relevant to 2 environmental systems.
The first law concerns the conservation of energy. The second law explains the dissipation of energy that is then not available to do work, bringing about disorder. The second law is most simply stated as, "in any isolated system entropy tends to increase spontaneously". This means that energy and materials go from a concentrated to a dispersed form (the availability of energy to do work diminishes) and the system becomes increasingly disordered.
Both laws should be examined in relation to the energy transformations and maintenance of order in living systems.
1.1.4 Explain the Nature of Equilibria.
A steady-state equilibrium should be understood as the common property of most open systems in nature. A static equilibrium, in which there is no change, should be appreciated as a condition to which natural systems can be compared. (Since there is disagreement in the literature regarding the definitely of dynamic equilibrium, this term should be avoided.) Students should appreciate, however, that some systems may undergo long-term changes to their equilibrium while retaining integrity to the system (succession). The relative stability of an equilibrium-the tendency of the system to turn to that original equilibrium following disturbance rather than adopting a new one should also be understood.
1.1.5 Define and explain the principles of positive feedback and negative feedback.
The self-regulation of natural systems is achieved by the attainment of equilibrium through feedback systems. Negative feedback is a self-regulating method of contro1 leading to the maintenance of a steady stat. Equilibrium it counteracts deviation, Positive feedback leads to Increasing change In a systemit accelerates deviation. Feedback links involve time lags.
1.1.6 Describe transfer and all transformation processes.
Transfers normally flow through a system and involve change in location. Transformations lead to an Interaction within a system in the formation of a new end product, or Involve a change of state. Using water as .an example, run-off is a transfer process and evaporation is a transformation process. Dead organic matter entering a lake is an example of a transfer process; decomposition of this material is a transformation process.
1.1.7 Distinguish between flows (inputs and outputs) and storages (stock) in relation to systems.
Identify flows through systems and describe their direction and magnitude.
1.1.8 Construct and analyze quantitative models involving flows and storages in a 3 system.
Natural storages, yields and outputs should be included in the form of clearly constructed diagrammatic and graphical models.
Topic 2: The Ecosystem.
2.1 Structure (10h)
2.1.1 Distinguish between biotic and abiotic (physical) components of an ecosystem.
2.1.2 Define the term trophic level.
2.1.3 Identify and explain trophic levels in food chains and food webs selected from the local environment.
Relevant terms (eg producers. consumers. decomposers, herbivores, carnivores, top carnivores) should be applied to local, named examples and other food chains and food webs.
2.1.4 Explain the principles of pyramids of numbers, pyramids of biomass and 3 pyramids of productivity, and construct such pyramids from given data.
Pyramids are graphical models of the quantitative differences that exist between the trophic levels of a single ecosystem. A pyramid of biomass represents the standing stock of each trophic level measured in units such as grams of biomass per square meter (g m^-2).
In accordance with the second law of thermodynamics, there is a tendency for numbers and quantities of biomass and energy to decrease along food chains, therefore the pyramids become narrower as one ascends. Pyramids of numbers can sometimes display different patterns, eg when individuals at lower trophic levels are relatively large. Similarly, pyramids of biomass can show greater quantities at higher trophic levels because they represent the biomass present at a given time (there may be marked seasonal variations). Both pyramids of numbers and pyramids of biomass represent storages.
Pyramids of productivity refer to the flow of energy through a trophic level and invariably show a decrease along the food chain (see 2.2.3). For example, the turnover of two retail outlets cannot be compared by simply comparing the goods displayed on the shelves; the rate at which they are being stocked and goods sold needs to be known. Similarly, a business may have substantial assets but cash flow may be very limited. In the same way, pyramids of biomass simply represent the momentary stock, whereas pyramids of productivity show the rate at which that stock is being generated. Biomass, measured in units of mass or energy (eg J*m^-2 or g* m^-2), should be distinguished from productivity measured in units of flow ( eg J*m^-2*yr^-1 or g*m^-2*yr^-I).
A pyramid of energy may either be represented as the standing stock (biomass) measured in units of energy (J*m^-2) or as productivity measured in units of flow of energy (J*m^-2 *yr^-l), depending on the text consulted. As this is confusing, this syllabus avoids the term pyramid of energy.
2.1.5 Discuss how the pyramid structure affects the functioning of an ecosystem.
Examples: concentration of non-biodegradable toxins in food chains, limited length of food chains, vulnerability of top carnivores.
Definitions of the terms biomagnification, bioaccumulation and bio- ~ concentration are not required.) ~
2.1.6 Define the terms species', population, community, niche and habitat with reference to local Examples.
2.1.7 Define the term biome.
2.1.8 Outline the distribution and relative productivity of tropical rainforests, deserts, temperate forests, tundra and anyone other biome.
Refer to prevailing climate and limiting factors. For example, tropical rainforests are found close to the equator where there is high insulation and rainfall and where light and temperature are not limiting. The other biome may be, for example, temperate grassland or a local example.
2.1.9 Compare the biomes studied in 2.1.8 in terms of climate, productivity and structure.
Limit climate to temperature, precipitation and insulation.
2.1.10 Describe and explain population interactions using examples of named species.
Include competition, parasitism, mutualism, predation and herbivory. Mutualism is an interaction in which both species derive benefit. Interactions should be understood in terms of the influences each species has on the population dynamics of others, and upon the carrying capacity of the others' environment. Graphical representations of these influences should be interpreted.
2.2 Function (10H)
2.2.1 Explain the role of producers, consumers and decomposers in the ecosystem.
2.2.2 Describe photosynthesis and respiration in terms of inputs, outputs and 2 energy transformations.
Biochemical details are not required. Details of chloroplasts, light dependent and light-independent reactions, mitochondria, carrier systems, ATP and specific intermediate biochemicals are not expected.
Photosynthesis should be understood as requiring carbon dioxide, water, chlorophyll and certain visible wavelengths of light to produce 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 and oxygen to produce carbon dioxide and water. Without oxygen, carbon dioxide and other waste products are formed. Energy is released in a form available for use by living organisms, but is ultimately lost as heat.
2.2.3 Describe and explain the transfer and transformation of energy and material, as they flow through an ecosystem.
Explain pathways of incoming solar radiation incident on the ecosystem including:
� Loss of radiation through reflection and absorption .
� Conversion of light to chemical energy
� Loss of chemical energy from one trophic level to another
� Efficiencies of transfer
� Overall conversion of light to heat energy by an ecosystem '
� Re-radiation of heat energy to the atmosphere.
Construct and interpret simple energy flow diagrams illustrating the movement of energy through ecosystems, including the productivity of the various trophic levels.
The distinction between storages of energy illustrated by boxes in ." energy-flow diagrams (representing the various trophic levels), and the flows of energy or productivity often shown as arrows (sometimes of varying widths) needs to be emphasized. The former are measured as the amount of energy or biomass per unit area and the latter are given as rates, eg J*m^-2*day^-1.
Processes involving the transfer and transformation of carbon, nitrogen, oxygen, phosphorus and water as they cycle through an ecosystem should be described, and the conversion of organic and inorganic storage noted where appropriate. Interpret and construct diagrams of these cycles from given data. The laws of thermodynamics (see 1.1.3) should be related to the energy and material flow through ecosystems.
2.2.4 Define the terms gross productivity, net productivity, primary productivity, secondary productivity, gross primary productivity and net primary productivity.
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 when calculating and defining net productivity for the purpose of this course.
2.2.5 Calculate the values of gross and net productivity from given data.
For both producers and consumers, calculations can be made using the following equation:
NP=GP-R
In addition, the equation for consumers only is: GP = food eaten -fecal losses
The term assimilation is sometimes used instead of gross secondary productivity .
2.2.6 Explain the terms negative feedback mechanism and positive feedback mechanism in relation to ecosystems.
Examples can be found in population dynamics and mineral cycling.
2.3 Changes ( 10h)
2.3.1 Explain the concepts of limiting factors and carrying capacity in the context of population growth.
2.3.2 Describe and explain "S" and "J" population growth curves.
Explain changes in both numbers and rates of growth in standard S and J population growth curves. Population curves should be sketched, described, interpreted and constrllcted from given data.
S curve J curve
Population Population
2.3.3 Describe the role of density-dependent and density-independent factors, and internal and external factors, in the regulation of populations.
According to theory, density-dependent factors operate as negative feedback mechanisms leading to stability or regulation of the population. Both types of factors may operate on a population. Many species, particularly strategists, are probably regulated by density-independent factors, of which weather is the most Important factor. Internal factors might include density-.dependent fertility or, size of breeding territory, and external factors might include predation or disease.
2.3.4 Describe. the principles associated with survivorship curves including, K and r-strategists.
K and r-strategists represent idealized categories and many organisms occupy a place on the continuum. Students should be familiar with interpreting features of survivorship curves including logarithmic scales.
2.3.5 Describe the concept and processes of succession in a named habitat.
Study named examples of organisms from a pioneer community, seral stages and climax community.
The concept of succession, occurring over time, should be carefully distinguished from the concept of zonation which refers to a spatial pattern.
2.3.6 Explain the changes in energy flow, gross and net productivity, diversity and mineral cycling in different stages of succession.
In early stages gross productivity is low due to the initial conditions and low density of producers. The proportion of energy lost through community respiration is relatively low too, so net productivity is high, ie the system is growing and biomass is accumulating. in later stages, with an increased consumer community, gross productivity may be high in a climax community. However, this is balanced by respiration, so net productivity approaches zero and the production: respiration (P:R) ratio approaches I.
2.3.7 Describe factors affecting the nature of climax communities.
Climatic and edaphic factors determine the nature of a climax community, unless human or other factors maintain an equilibrium at a sub-climax community.
Topic 3: Global Cycles and Physical Systems
3.1 The Atmosphere (4h)
3.1.1 Describe the overall structure and composition of tile atmosphere and outline the concept of lapse rate.
Lapse rate is the rate at which temperature declines with increasing altitude in the troposphere.
3.1.2 Describe and explain tile global atmospheric energy budget.
There should be a qualitative understanding of latent and sensible heat flux and how water can absorb or release heat as It changes state. Interpret and produce 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 actual figures is not required.
3.1.3 Explain the role of atmospheric circulation in redistributing heat from the equator to polar regions.
Consider reasons for the differences in insolation per unit area between the equator and poles. Examination of the global energy budget should lead an awareness of the global imbalances of solar energy inputs and outputs.
3.1.4 Describe major patterns of atmospheric circulation including the tricellular model, tropical cyclones and depressions.
The function of these circulation mechanisms in the redistribution of energy should be understood.
3.1.5 Explain how atmospheric circulation gives rise to broad climatic regions and, consequently, biomes.
Consider the location of broad climatic belts, ie tropical, arid, temperate and polar, as a natural consequence of air circulation patterns (eg falling and drying air flow causes arid belts at approximately 30 degrees. North and South). There should be a clear understanding of the relationship between latitude, precipitation and temperature as they influence the distribution of biomes (see -.J .8).
3.2 Depletion of Stratospheric Ozone (3h)
3.2.1 Describe the role of ozone in tile absorption of ultraviolet radiation.
Ultraviolet radiation is absorbed during the formation and destruction of ozone from oxygen. Memorization of chemical equations is not required.
3.2.2 Explain the interaction between ozone and halogenated organic gases.
Halogenated organic gases are very stable under normal conditions but can liberate halogen atoms when exposed to ultraviolet radiation in the stratosphere. These atoms react with monatomic oxygen and slow the rate of ozone reformation. Pollutants enhance the destruction of ozone thereby disturbing the equilibrium of the ozone production system (see I. 1.4).
3.2.3 State the effects of ultraviolet radiation on living tissues and biological 1 productivity.
The effects include mutation and subsequent effects on health and damage to photosynthetic organisms, especially phytoplankton and their consumers such as zooplankton.
3.2.4 Describe three methods of reducing the manufacture and release of ozone-depleting substances.
For example, recycling refrigerants, alternatives to gas-blown plastics, alternative propellants and alternatives to methyl bromide.
3.2.5 Describe and evaluate the role of national and international organizations in reducing the emissions of ozone-depleting substances.
Examine the role of the United Nations Environmental Programme (UNEP) in forging international agreements on the use of ozone-depleting substances, and study the relative effectiveness of these agreements and the difficulties in implementing and enforcing them. In addition, students should be familiar with what steps national governments are taking to comply with these agreements, and what named local organizations are doing to persuade governments to comply.
3.3 Tropospheric Ozone (Ih)
3.3.1 State the source and outline the effect of tropospheric ozone.
When fossil fuels are burned, two of the pollutants emitted are hydrocarbons (from unburned fuel) and nitrogen oxide (NO). Nitrogen oxide reacts with oxygen to form nitrogen dioxide (NO2), a brown gas which contributes to urban haze. Nitrogen dioxide can also absorb sunlight and break up to release oxygen atoms that combine with oxygen in the air to form ozone.
Ozone is a toxic gas and an oxidizing agent. It damages crops and forests, irritates eyes, can cause breathing difficulties in humans and may increase susceptibility to infection. It is highly reactive and can attack fabrics and rubber materials.
3.3.2 Outline the formation of photochemical smog.
Photochemical smog is a mixture of about one hundred primary and secondary pollutants formed under the influence of sunlight. Ozone is the main pollutant.
The frequency and severity of photochemical smogs in an area depends on local topography, climate, population density and fossil] fuel use.
Precipitation cleans the air and winds disperse the smog. Thermal inversions trap the smogs in valleys ( eg Los Angeles, Santiago, Mexico City, Rio de Janeiro, Sao Paulo, Beijing) and concentrations of air pollutants can build to harmful and even lethal levels.
The Issue to Global Warming (4h)
3.4.1 Describe the role of greenhouse gases in maintaining mean global temperature.
The greenhouse effect is a normal and necessary condition for life on Earth. Consider carbon dioxide (CO2) levels in geological times.
3.4.2 Describe how human activities add to greenhouse gases.
Water, CO2, methane and CFCs are the main greenhouse gases. Human activities are increasing levels ofCO2, methane and CFCs in the atmosphere.
3.4.3 Outline three global and three local ways that emissions of greenhouse gases can be reduced.
� Global-intergovernmental and international agreements, carbon tax, alternative energy sources.
� Local-allow students to explore their own lifestyle in the context of local greenhouse gas emissions.
3.4.4 Discuss qualitatively the effects of increased mean global temperature on the distribution of biomes, and consequently on global agriculture.
Students should know the variety of sometimes conflicting arguments still surrounding this issue. They should be able to discuss.
� Thermal expansion of the oceans .
� Melting of the polar ice caps
� Increased evaporation in tropical latitudes leading to increased snowfall on the polar ice cap, which reduces the mean global temperature (an example of negative feedback)
� The effect of air pollutants (aerosols) in reflecting radiation, thus offsetting the warming trends.
Any feedback mechanisms associated with global warming may involve very long time lags. Note the complexity of the problem and the uncertainty of global climate models. Cross reference with 2.1.8 and 3.2.5.
3.5 Acid Deposition (2h)
3.5.1 Outline the chemistry leading to the formation of acidified precipitations.
Refer to the conversion of sulfur dioxide and nitrogen dioxide into the sulfates and nitrates of dry deposition and the sulfuric and nitric acids of wet deposition. Knowledge of chemical equations is not required.
3.5.2 Describe three possible effects of acid deposition on soil, water and living organisms.
Include:
� one direct effect, eg acid on aquatic organisms and coniferous forests
� one toxic effect, eg aluminum ions on fish
� one nutrient effect, eg leaching of calcium.
3.5.3 Explain why the effect of acid deposition is regional rather than global.
Refer to areas downwind of major industrial regions which are adversely. affected by acid rain and link them to sources of sulfur dioxide and nitrogen dioxide emissions. Consider the effect of geology (rocks and soils) on water acidity through buffering.
3.5.4 Outline and evaluate methods to reduce emissions of the principal causal agents of acid deposition.
Measures to reduce fossil fuel combustion should be considered, eg reducing demand for electricity and private cars and switching to renewable energy. 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 Outline methods for restoring acidified soils and waters, and evaluate their efficacy.
Consider liming. The cost-effectiveness of spreading ground limestone in Swedish lakes in the early 1980s provides a good case study.
3.6 The Hydrosphere (5h)
3.6.1 Describe the Earth's water budget.
Only a small fraction (2.6% by volume) of the Earth's water supply is fresh water. Of this fresh water, over 80% is in the form of ice caps and glaciers, 0.59% is groundwater and the rest is made up of lakes, soil water, atmospheric water vapour, rivers and biota in decreasing order of storage size. Precise figures are not required.
3.6.2 Describe and evaluate the sustainability of freshwater resource usage.
Irrigation, industrialization and population increase all make demands on the supplies of fresh water. Global warming may disrupt rainfall patterns and disrupt water supplies. The hydrological cycle supplies humans with fresh water but we are withdrawing water from underground aquifers and degrading it with wastes at a greater rate than it can be replenished. Consider the increased demand for fresh water, inequity of usage, methods of reducing use and increasing supplies.
3.6.3 Outline the role of ocean currents in the global transfer of energy.
The global atmospheric energy model cannot be understood without reference to the role of ocean currents in the transfer of energy. Students 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 should be noted.
3.6.4 Outline the role of ocean currents in the regulation of climate.
The rate at which water absorbs and releases heat relative to the land, and. the consequent moderating effect on climate, should be understood. The transport of heat by ocean currents and the influence on climate should also be understood, eg the North Atlantic Drift moderating the climate of north-western Europe which, in the absence of this current, would otherwise have a sub-arctic climate: the Humbolt current off Peru and the Benguela current off Namibia.
3.6.5 Describe the El Nino Southern Oscillation (ENSO) phenomenon and its impacts.
Students should make reference to relationships among trade winds, ocean surface currents, nutrient upwelling, productivity of fish stocks ( eg those off the Peruvian coast) and more distant climatic effects.
Periodic disruption of tropical easterly trade winds results in a mass of warm water in the Pacific expanding eastwards towards South America. This raises the surface temperature of the ocean and prevents nutrient-laden waters from upwelling, thus limiting productivity. Reasons for the disruption in trade winds are not required. Descriptions of climatic effects elsewhere should. Be limited to correlations between El Nino and atypica1 � weather patterns In, for example, the western USA, Australia, and southern Africa.
3.7 The Lithosphere (3h)
3.7.1 Describe the structure of tile Earth's internal zones and the theory of plate tectonics.
Include the crust, mantle and core, as well as convection cells and mantle plumes in the asthenosphere. The terms constructive margins, destructive margins subduction and mid-oceanic ridge should be understood. Students will be expected to draw and label diagrams showing the interactions between plates, and the formation and destruction of crust.
3.7.2 Explain how plate activity has influenced evolution and biodiversity.
The consequences of plate tectonics on speciation should be understood (ie the separation of gene pools, formation of physical barriers and land bridges) together with the implications these consequences have for evolution. Also focus on the role of plate activity in generating new and diverse habitats, thus promoting biodiversity.
3.8 The Soil System (5h)
3.8.1 Outline how soil systems integrate aspects of living systems.
Emphasize a systems approach. Students should draw diagrams that show links between the soil, lithosphere, atmosphere and living organisms. The soil as a living system should be considered with reference to the soil profile.
Transfers of material (including deposition) result in reorganization of the soil. There are inputs of organic and parent material, precipitation, infiltration and energy. Outputs include leaching, uptake by plants and mass movement. transformations include decomposition, weathering and nutrient cycling.
3.8.2 Describe three stages of soil formation. 2
Consider:
� .initial mechanical and chemical weathering processes resulting in the inorganic component
� introduction of living organisms-the biotic component
� decomposition and the formation of an organic component.
Note the time required for soil formation (hence, soil is a non-renewable resource).
3.8.3 Compare the structure and properties of sand, clay and loam soils, including their relevance to primary productivity.
Consider mineral content, drainage, water-holding capacity, air spaces, biota and potential to hold organic matter, and link these to primary productivity.
3.8.4 Outline the processes that cause soil degradation.
Human activities such as overgrazing, deforestation, unsustainable agriculture and irrigation cause processes of degradation. These include soil erosion, toxification and salinization. Desertification (enlargement of deserts through human activities) can be associated with this degradation. Each year about 11 million hectares of arable land is lost from production through soil degradation processes.
3.8.5 Evaluate soil conservation measures.
Explore:
� soil conditioners (lime to increase pH, organic materials)
� wind reduction techniques (wind breaks, shelter belts, strip cultivation)
� cultivation techniques (terracing, contour-plowing)
� efforts to stop plowing of marginal lands.
Topic 4: Human Population and Carrying Capacity
4.1 Population Dynamics (7h)
4.1.1 Describe the nature and explain the implications of exponential growth in human populations.
4.1.2 Calculate and explain, from given data, the values of crude birth rate, crude death rate, fertility, doubling time and natural increase rate.
4.1.3 Analyze age/sex pyramids and diagrams showing demographic transition models.
4.1.4 Discuss the use of models in predicting the growth of human populations.
This might include computer simulations, 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 Explain the concept of resources in terms of natural capital.
Ecologically minded economists describe resources as "natural capital". If properly managed, renewable and replenishable resources are forms of wealth that can produce "natural income" indefinitely in the form of valuable goods and services. This income may consist of marketable commodities such as timber and grain (goods) or may be in the form of ecological or life-support services such as the flood and erosion protection provided by forests (services). Similarly, non-renewable resources can be considered in parallel to those forms of economic capital that cannot generate wealth without liquidation of the estate.
4.2.2 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 and uses solar energy and photosynthesis. This natural capital can yield marketable goods such as wood fiber, but may also provide unaccounted essential services when left in place, eg 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 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 the sustainable yields or harvests from such stocks are natural income.
4.2.4 explain the concept of sustainability in terms of natural capital and natural Income.
The term "sustainability" has been given a precise meaning in this syllabus. The term "sustainable development", however, is not used because of the wide variation in the way that it is defined in different disciplines, by the public and in the media. Furthermore, the concept of sustainable development involves value judgments which fall outside the scope of a science course such as this.
Students 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 Calculate and explain sustainable yields from given data.
Sustainable yield (sy) may be calculated as the rate of increase in natural capital, ie 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 Identify various values associated with natural capital and evaluate how these values influence this capital's appraisal and use.
Examples include ecological, economic and aesthetic values. In industrial societies people tend to emphasize monetary or economic valuations of nature. In some cases the economic value of a natural capital stock can be determined from the market price of the goods or services it produces. However, there are no formal markets for many valuable ecological processes such as waste assimilation, flood and erosion control, nitrogen-fixation, photosynthesis, etc. These ecological services may be essential for human existence, but we have tended to take them for granted.
Furthermore, organisms or ecosystems that are valued on aesthetic or intrinsic grounds may not provide commodities identifiable as either goods or services, and so remain unpriced or undervalued from an economic viewpoint. Organisms or ecosystems regarded as having intrinsic value, for instance from an ethical, spiritual or philosophical perspective, are valued regardless of their potential use to humans. Therefore diverse perspectives may underlie the evaluation of natural capital.
Attempts are being made to acknowledge diverse valuations of nature so that they may be weighed more rigorously against more common economic values. However, some argue that these valuations are impossible to quantify and price realistically. Not surprisingly, much of the sustainability d: 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 Explain the difficulties in applying the concept of carrying capacity to local human populations.
By examining carefully the requirements of a given species and the resources available, it might be possible to estimate the carrying capacity of that environment for the species. This is problematic in the case of human populations for a number of reasons. The range of resources used by humans is usually much greater than for any other species. Furthermore, when one resource becomes limiting, humans show great ingenuity in substituting one resource for another. Resource requirements vary according to lifestyles, which differ from time to time and from population to population. Technological developments give rise to continual changes in the resources required and available for consumption. Human populations also regularly import resources from outside their immediate environment which enables them to grow beyond the boundaries set by their local resources and increases their carrying capacity. While importing resources in this way increases the carrying capacity for the local population, it has no influence on global carrying capacity. All these variables make it practically impossible to make reliable estimates of carrying capacities for human populations.
4.3.2 Explain how reuse, recycling, remanufacturing and absolute reductions in energy and material use can affect human carrying capacity.
Human carrying capacity is determined by the rate of energy and material consumption, the level of pollution and the extent of human interference in global life support systems. While recycling, reuse and remanufacturing reduce these impacts, they can also increase human carrying capacity.
4.3.3 Discuss how national and international development policies and cultural influences can affect human population dynamics and growth.
Many policy factors influence human population growth. Domestic and international development policies that target the death rate through agricultural development, improved public health and sanitation, and better service infrastructure 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, enabling women to have greater personal and economic independence, may be the most effective method for reducing population pressure.
4.3.4 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 in human life, many economists 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 environment. However, to compensate for foreseeable population growth (possibly doubling between the years 2000 and 2040) and the economic growth that is deemed necessary, especially in developing countries, it is suggested that efficiency would have to be raised by a factor of 4 to 10 to remain within global carrying capacity.
Option A: Analyzing Ecosystems
Note: The objectives for this option can only be achieved satisfactorily if it is ~ taught by means of a substantial amount of fieldwork.
The techniques required in this option may be exemplified through practical work in marine, terrestrial, freshwater or urban ecosystems, or any combination of these. The selection of environments call be made according to the local systems available to the students, and the most convenient systems for demonstrating the techniques in question. However, there is an advantage in using the various practical measurements to quantify different aspects of the same ecosystem, where possible. In this way the techniques are not simply rehearsed in isolation, but can be used to build up a holistic model of that system.
A.1 Measuring Physical Components of the System (2h)
A.1.1 List the significant abiotic (physical) factors of an ecosystem.
A.1.2 Describe and evaluate methods for measuring at least three abiotic factors within an ecosystem.
Students should know methods for measuring any three significant abiotic factors and how these may vary in a given ecosystem with depth, time or distance. For example:
� marine-salinity, pH, temperature, dissolved oxygen, wave action
� freshwater-turbidity, flow velocity, pH. temperature, dissolved oxygen
� terrestrial-temperature, light intensity, wind speed, particle size, slope, soil moisture, drainage, mineral content.
This activity may be carried out effectively in conjunction with an examination of related biotic components.
A.2 Measuring Biotic Components of the System (5h)
A.2.1 Construct simple keys and use published keys for the identification of organisms
Students could practice with keys supplied and then construct their own keys for up to eight species.
A.2.2 Describe and evaluate methods for estimating abundance of organisms.
Methods should include capture/mark/release/recapture (Lincoln index)and quadrats for measuring population density, percentage frequency and percentage cover.
A.2.3 Describe and evaluate methods for estimating the biomass of trophic levels in a community.
Dry weight measurements of quantitative samples could be extrapolated to estimate total biomass.
A.2.4 Define the term diversity
Diversity is often considered as a function of two components: the number of different species and the relative numbers of individuals of each species.
A.2.5 Apply Simpson's diversity index and outline its significance.
D = (N(N-1))/Summation(n(n-1))
where D = diversity index
N = total number of organisms of all species found
n = number of individuals of a particular species
D is a measure of species richness. A high value of D suggests a stable and ancient site and a low value of D could suggest pollution, recent colonization or agricultural management. The index is normally used in studies of vegetation but can also be applied to comparisons of animal (or even all species) diversity.
A.3 Measuring Productivity of the System (4h)
A.3.1 Describe and evaluate a method for measuring gross and net primary productivity in an ecosystem.
For marine and freshwater ecosystems, the light and dark bottle technique should be used for measuring gross and net productivity of aquatic plants. While methods for measuring primary productivity in vegetation for terrestrial ecosystems might not be feasibly carried out as student investigations, possible methods should be described and evaluated (eg measuring changes in biomass of covered and uncovered quadrats of grassland, and measuring absorption of CO2 in enclosed communities).
A.3.2 Describe and evaluate a method for measuring gross and net secondary productivity in an ecosystem.
Gross secondary productivity might be simply estimated as food eaten minus feces produced.
As a laboratory investigation, an aquarium population of invertebrate herbivores ( eg brine shrimps) or a terrarium population of invertebrate herbivores (eg silkworms) might be fed on a known producer biomass for a
period of time. The remaining food material and feces are 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 investigation, biomass might be estimated as a fixed percentage of wet weight to avoid the killing of organisms for dry weight measurements. Alternatively, secondary data could be used
A.4 Measuring Changes in the System (4h)
A.4.1 Describe and evaluate methods for measuring changes in abiotic and biotic components of an ecosystem along an environmental gradient or over time.
A.4.2 Outline methods for assessing changes in abiotic and biotic components of 2 an ecosystem due to a specific human activity.
Methods and changes should be selected appropriately for the human activity chosen. Suitable human impacts for study might include toxins from mining activity, landfills, eutrophication, effluent, oil spills and overexploitation.
Option B: Impacts of Resource Exploitation
B.1 Exploitation of Energy Resources (5h)
B.1.1 Evaluate the advantages and disadvantages of five sources of energy
Consider fossil fuels, nuclear, solar and hydroelectric power and one other source. These sources should be evaluated for efficiency (ie cost of extraction, conversion, transport and safety), sustainability and adverse effects.
B.2 Exploitation of Food Resources (5h)
B.2.1 State the relative proportions of fish, meat and cereals consumed in developed and developing countries.
B.2.2 Compare the efficiency of terrestrial and aquatic food production systems.
Compare these in terms of their trophic levels and efficiency of energy conversion. There is no need to consider individual production systems in detail. In terrestrial systems, most food is harvested from relatively low trophic levels (producers and herbivores). However, in aquatic systems, perhaps largely due to human tastes, most food is harvested from higher trophic levels where the total storages are much smaller. Although energy conversions along the food chain may be more efficient in aquatic systems, the initial fixing of available solar energy by primary producers tends to be less efficient due to the absorption and reflection of light by water.
B.2.3 Compare the inputs and outputs of materials and energy (energy efficiency), the system characteristics and the environmental impacts for two named food production systems.
The systems selected should both be terrestrial or both aquatic. In addition, the inputs and outputs of the two systems should differ qualitatively and quantitatively (not all systems will be different ill all aspects). The pair of examples could be 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 or global examples are equally valid.
Factors to be considered might include:
� inputs-fertilizers (artificial and natural), irrigation water, pesticides, fossil fuels, food distribution, human labor, seed, breeding stock
� system characteristics-selective breeding, genetically engineered organisms, monoculture versus polyculture, sustainability
� environmental impact-pollution, habitat loss, reduction in biodiversity, soil erosion
� outputs-food (quality and quantity), pollutants, soil erosion.
B.2.4 Evaluate the implications for future global food supply of changes in the 3 management of food produciont systems.
Consider maximizing yield and improving storage and distribution methods of food production systems. Consider also how humans could change dietary habits, eg eat less meat.
B.3 Environmental Demands of Human Populations (5h)
B.3.1 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 the population's resources and assimilate all its wastes. As a model, it is able to provide a quantitative estimate of human carrying capacity. It is, in fact, the inverse of carrying capacity. It refers to the area required to sustainably support a given population rather than the population that a given area can sustainably support.
B.3.2 Calculate from appropriate data the ecological footprint of a given population, 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^-1 yr^-1)
Per capita land requirement for absorbing wastes CO2 from fossil fuels (ha) = Per capita CO2 emission (kg C yr^-l)/Net Carbon fixation per hectare of local natural vegetation (kg C ha^-1 yr^-1)
The total land requirements (ecological footprint) can then be calculated the sum of these two per capita requirements, multiplied by the total population.
This calculation clearly ignores 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.
B.3.3 Describe and explain the differences between the ecological footprints of two human populations; one from a developing region 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 of a population that feeds 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 populations in developing and developed countries.
Option C: Conservation and Biodiversity:
C1 Biodiversity in Ecosystems (3h)
C.1.1 Define the terms biodiversity, genetic diversity ( species diversity and habitat diversity.)
C.1.2 Outline the mechanism of natural selection as a possible driving force for speciation.
Speciation is the process by which change in the frequency of genetic traits in the population occurs in response to environmental pressure. The concept of fitness should be understood. The history of the development of the modern theory of evolution is not expected, neither is a detailed knowledge of genetics (including allele frequency).
C.1.3 State that isolation can lead to different species being produced that are unable to interbreed to yield fertile offspring.
Isolation of populations, behavioral differences that preclude reproduction and the inability to produce fertile offspring (leading to speciation) should all be examined, with examples.
C.1.4 Explain the relationships among ecosystem stability, diversity, succession and habitat.
Consider how:
� Diversity changes through succession
� Habitat diversity and type lead to greater species and genetic diversity
� A complex ecosystem, with its variety of nutrient and energy pathways, provides stability
� Human activities modify succession, eg logging, grazing, burning
� Human activities often simplify ecosystems, rendering them unstable, eg North American wheat farming versus tall grass prairie.
C.2 Evaluating Biodiversity and Vulnerability (6h)
C.2.1 Identify factors that lead to loss of diversity.
These include:
� Natural hazard events ( eg volcanoes, drought)
� Global catastrophic events (eg ice age, meteor impact) habitat degradation, fragmentation and loss
� Introduction/escape of non-native and genetically modified species, and monoculture
� Pollution
� Hunting, collecting and harvesting.
C.2.2 Describe the vulnerability of tropical rainforests and their relative value in contributing to global biodiversity.
Tropical rainforests should be compared with other major ecosystems. Take particular note of agriculture when considering vulnerability.
C.2.3 Discus current estimates of numbers of species and past and present rates of species extinction.
Examine the fossil record for evidence of mass extinctions in the past, and compare the possible causes of these to present day extinctions. The time frame of these periods of extinction should be considered.
C.2.4 Describe and explain the factors that may make species more or less prone to extinction.
The following factors (among others) will affect the risk of extinction:
Numbers, degree of specialization, distribution, reproductive potential and behavior, and trophic level. An ecosystem's capacity to survive change may depend on diversity, resilience and inertia.
C.2.5 State and explain the criteria used to determine a species' conservation status.
Students should know criteria by which species are placed in the unknown, rare, vulnerable, endangered and extinct categories in the red data books. (These are available for each country.) Use evolutionary and ecological significance of species as criteria for determining conservation status. Taxonomic details are not required.
C.2.6 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 possible consequences of their disappearance should be understood.
C.2.7 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.
C.3 Conservation of Biodiversity (6h)
C.3.1 State the arguments for preserving species and habitats.
Students should appreciate arguments based on ethical, aesthetic, genetic resource and commercial (including opportunity cost) considerations. They should also appreciate life support/ecosystem support functions (see 4.2.6).
C.3.2 Compare the role and activities of governmental and non-governmental organizations in preserving and restoring ecosystems and biodiversity.
Consider the United Nations Environment Programme (UNEP) as a governmental organization and the Worldwide Fund for Nature (WWF) and Greenpeace as non-governmental organizations. Compare them in terms of use to- the media, speed of response, diplomatic constraints and enforceability.
C.3.3 Outline the World Conservation Strategy.
This is proposed by the International Union for the Conservation of Nature (IUCN), UNEP and WWF.
C.3.4 State and explain the criteria used to design reserves.
In effect, protected areas may become "islands" within a country and will normally lose some of their diversity. The principles of island biogeography might be applied to the design of reserves. Appropriate criteria are discussed in the World Conservation Strategy.
C.3.5 Evaluate the success of a named protected area.
The granting of protected status to a species or ecosystem is no guarantee of protection without community support, adequate funding and proper research. Consider a specific local example.
C.3.6 Discuss and evaluate the strengths and weaknesses of the species-based 3 approach to conservation.
Students should consider the relative strengths and weaknesses of the
following:
� The Convention on International Trade in Endangered Species (CITES)
� Captive breeding and reintroduction programmes, and zoos
� Aesthetic versus ecological value.
Option D: Pollution Management
Note: Not all pollutants are considered here, some are considered in topic.
D.1 Nature of Pollution (1h)
D.1.1 Define pollution.
D.1.2 Distinguish between the terms point ,source pollution and non-point ,source pollution and the challenges they present for management.
Point source pollution is generally more easily managed because its impact is more localized making it easier to control emission, attribute responsibility and take legal action.
D.1.3 State the major sources of pollutants.
Sources of pollutants are combustion of fossil fuels, domestic waste, industrial waste, manufacturing and agricultural systems.
D.2 Detection and Monitoring of Pollution (5h)
D.2.1 Describe two direct methods of monitoring pollution.
Students should describe one method for air and one for soil or water.
D.2.2 Define the term biochemical oxygen demand (BOD) and explain how it is used to assess pollution levels in water.
D.2.3 Describe and explain one indirect method of measuring pollution levels using a biotic index.
This will involve levels of tolerance, diversity and abundance of organisms. A polluted and an unpolluted site (eg upstream and downstream of a point source) should be compared.
D.2.4 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.
D.3 Impacts of Pollution (2h)
This section explores the widespread impacts of inorganic nutrients as one type of pollutant.
D.3.1 Outline the processes of eutrophication.
Include increase in nitrates and phosphates leading to rapid growth of algae, accumulation of dead organic matter, high rate of decomposition and lack of oxygen. The role of positive feedback should be noted in these processes.
D.3.2 Evaluate the impacts of eutrophication.
Include death of aerobic organisms, increased turbidity, loss of macrophytes, reduction in length of food chains and loss of species diversity.
D.4 Approaches to Pollution Management (7h)
Pollutants are produced through human activities and .create long-term effects when released into ecosystems. Strategies for reducing these impacts can be directed at three different levels in the process: altering the human activity, regulating and reducing quantities of pollutant released at the point of emission and cleaning up the pollutant and restoring ecosystems after i pollution has occurred (see diagram below). Students should be able to illustrate the value and limitations of each of the three different levels of intervention, and appreciate the advantages of employing the earlier strategies over the later ones.
D.4.1 Explain and evaluate pollution management strategies for eutrophication.
"Altering the human activity producing pollution" can be exemplified by switching to alternative fertilizers, alternative methods of enhancing crop growth, alternative detergents, etc.
� "Regulating and reducing pollutants at the point of emission" can be illustrated by sewage treatment processes that remove nitrates and phosphates from the waste.
� "Clean up and restoration" can be exemplified by pumping mud from eutrophic lakes and reintroducing plant and fish species.
D.4.2 Explain and evaluate pollution management strategies for solid domestic (municipal) waste.
Students should consider their own and their community's generation of waste. Consider total volume, paper, glass, metal, plastics, organic waste (kitchen or garden), packaging, etc.
D.4.3 Explain and evaluate pollution management strategies for a named example of industrial waste.
Appropriate examples include radioactive waste, oil spills, heavy metals from mining or a named local example.