PennyLearnsESS is a one-person project, no team, no funding, just an IB ESS teacher building the resource ESS students kept asking for. Each subtopic page contains short interactive checks and markscheme-style practice. If you spot something wrong, feel free to send an email so I can fix it.
If you want to tell me how helpful the page is, that is also welcome!
A few things to watch for as you read
⇄Don't confuse
Flags two related ideas that get mixed up on exam scripts, and pins down exactly what separates them.
⚠Common misconception
Catches a belief that sounds right but isn't, before it costs you marks.
✎Exam-safe wording
Guidance on wording an answer precisely, since a technically-true answer can still miss what's being asked.
🛠Application of skills
The named IB skill for that content statement, practiced directly instead of just described.
🔗Linking across the course
Points to where else in ESS the same idea shows up, since the content builds on itself topic to topic.
Topic 1
Foundations of Environmental Systems and Societies
The vocabulary and mental models every later topic assumes you already have: perspectives, systems, and sustainability itself.
View outcomes & skills, straight from the syllabus
Content statements (IB Guide)
1.1.1A perspective is how a particular situation is viewed and understood by an individual.
1.1.2Perspectives are informed and justified by sociocultural norms, scientific understandings, laws, religion, economic conditions, local and global events, and lived experience, among other factors.
1.1.3Values are qualities or principles that people feel have worth and importance in life.
1.1.4The values that underpin our perspectives can be seen in our communication and actions with the wider community.
1.1.5Values surveys can be used to investigate the perspectives shown by a particular social group towards environmental issues.
1.1.6Worldviews are the lenses shared by groups of people through which they perceive, make sense of and act within their environment.
1.1.7An environmental value system is a model that shows the inputs affecting our perspectives and the outputs resulting from our perspectives.
1.1.8Environmental perspectives (worldviews) can be classified into the broad categories of technocentric, anthropocentric and ecocentric.
1.1.9Perspectives and the beliefs that underpin them change over time in all societies.
1.1.10The development of the environmental movement has been influenced by individuals, literature, the media, major environmental disasters, international agreements, new technologies and scientific discoveries.
Skills you'll practice
Design and carry out questionnaires/surveys/interviews, using online collaborative survey tools, to correlate perspectives with attitudes towards particular environmental or sustainability issues.
Interpret behavior-time graphs. Examples could include specific changes, such as smoking, littering, eating meat or how traditional lifestyles in indigenous cultures are being replaced by modern ones.
View outcomes & skills, straight from the syllabus
Content statements (IB Guide)
1.2.1Systems are sets of interacting or interdependent components.
1.2.2A systems approach is a holistic way of visualizing a complex set of interactions, and it can be applied to ecological or societal situations.
1.2.3In system diagrams, storages are usually represented as rectangular boxes and flows as arrows, with the direction of each arrow indicating the direction of each flow.
1.2.4Flows are processes that may be either transfers or transformations.
1.2.5Systems can be open or closed.
1.2.6The Earth is a single integrated system encompassing the biosphere, the hydrosphere, the cryosphere, the geosphere, the atmosphere and the anthroposphere.
1.2.7The concept of a system can be applied at a range of scales.
1.2.8Negative feedback loops occur when the output of a process inhibits or reverses the operation of the same process in such a way as to reduce change.
1.2.9As an open system, an ecosystem will normally exist in a stable equilibrium, either in a steady- state equilibrium or in one developing over time (for example, succession), and will be maintained by stabilizing negative feedback loops.
1.2.10Positive feedback loops occur when a disturbance leads to an amplification of that disturbance, destabilizing the system and driving it away from its equilibrium.
1.2.11Positive feedback loops will tend to drive the system towards a tipping point.
1.2.12Tipping points can exist within a system where a small alteration in one component can produce large overall changes, resulting in a shift in equilibrium.
1.2.13A model is a simplified representation of reality; it can be used to understand how a system works and to predict how it will respond to change.
1.2.14Simplification of a model involves approximation and, therefore, loss of accuracy.
1.2.15Interactions between components in systems can generate emergent properties.
1.2.16The resilience of a system, ecological or social, refers to its tendency to avoid tipping points and maintain stability.
1.2.17Diversity and the size of storages within systems can contribute to their resilience and affect their speed of response to change (time lags).
1.2.18Humans can affect the resilience of systems through reducing these storages and diversity.
Skills you'll practice
Create systems diagrams representing the storages and flows, inputs and outputs of systems, such as a lab-based or local natural ecosystems.
Use diagrams representing examples of negative feedback.
Use diagrams representing examples of positive feedback.
View outcomes & skills, straight from the syllabus
Content statements (IB Guide)
1.3.1Sustainability is a measure of the extent to which practices allow for the long-term viability of a system.
1.3.2Sustainability is comprised of environmental, social and economic pillars.
1.3.3Environmental sustainability is the use and management of natural resources that allows replacement of the resources, and recovery and regeneration of ecosystems.
1.3.4Social sustainability focuses on creating the structures and systems, such as health, education, equity, community, that support human well-being.
1.3.5Economic sustainability focuses on creating the economic structures and systems to support production and consumption of goods and services that will support human needs into the future.
1.3.6Sustainable development meets the needs of the present without compromising the ability of future generations to meet their own needs.
1.3.7Unsustainable use of natural resources can lead to ecosystem collapse.
1.3.8Common indicators of economic development, such as gross domestic product (GDP), neglect the value of natural systems and may lead to unsustainable development.
1.3.9Environmental justice refers to the right of all people to live in a pollution-free environment, and to have equitable access to natural resources, regardless of issues such as race, gender, socio- economic status, nationality.
1.3.10Inequalities in income, race, gender and cultural identity within and between different societies lead to disparities in access to water, food and energy.
1.3.11Sustainability and environmental justice can be applied at the individual to the global operating scale.
1.3.12Sustainability indicators include quantitative measures of biodiversity, pollution, human population, climate change, material and carbon footprints, and others.
1.3.13The concept of ecological footprints can be used to measure sustainability.
1.3.14The carbon footprint measures the amount of greenhouse gases (GHGs) produced, measured in carbon dioxide equivalents (in tonnes).
1.3.15Biocapacity is the capacity of a given biologically productive area to generate an ongoing supply of renewable resources and to absorb its resulting wastes.
1.3.16Citizen science plays a role in monitoring Earth systems and whether resources are being used sustainably.
1.3.17There are a range of frameworks and models that support our understanding of sustainability, each with uses and limitations.
1.3.18The UN Sustainable Development Goals (SDGs) are a set of social and environmental goals and targets to guide action on sustainability and environmental justice.
1.3.19The planetary boundaries model describes the nine processes and systems that have regulated the stability and resilience of the Earth system in the Holocene epoch.
1.3.20The doughnut economics model is a framework for creating a regenerative and distributive economy in order to meet the needs of all people within the means of the planet.
1.3.21The circular economy is a model that promotes decoupling economic activity from the consumption of finite resources.
Skills you'll practice
Use footprint calculators to establish students’ own ecological/carbon/water footprint. Present comparative data on footprints graphically, using a spreadsheet and graph-plotting software.
Topic 2
Ecosystems and Ecology
How natural systems can be modeled: the organisms and populations inside them, the energy and matter flowing through them, and the cycles, climates and change that shape them.
View outcomes & skills, straight from the syllabus
Content statements (IB Guide)
2.1.1The biosphere is an ecological system composed of individuals, populations, communities, ecosystems.
2.1.2An individual organism is a member of a species.
2.1.3Classification of organisms allows for efficient identification and prediction of characteristics.
2.1.4Taxonomists use a variety of tools to identify an organism.
2.1.5A population is a group of organisms of the same species living in the same area at the same time, and which are capable of interbreeding.
2.1.6Factors that determine the distribution of a population can be abiotic or biotic.
2.1.7Temperature, sunlight, pH, salinity, dissolved oxygen and soil texture are examples of many abiotic factors that affect species distributions in ecosystems.
2.1.8A niche describes the particular set of abiotic and biotic conditions and resources upon which an organism or a population depends.
2.1.9Populations interact in ecosystems by herbivory, predation, parasitism, mutualism, disease and competition, with ecological, behavioral and evolutionary consequences.
2.1.10Carrying capacity is the maximum size of a population determined by competition for limited resources.
2.1.11Population size is regulated by density-dependent factors and negative feedback mechanisms.
2.1.12Population growth can either be exponential or limited by carrying capacity.
2.1.13Limiting factors on the growth of human populations have increasingly been eliminated, resulting in consequences for sustainability of ecosystems.
2.1.14Carrying capacity cannot be easily assessed for human populations.
2.1.15Population abundance can be estimated using random sampling, systematic sampling or transect sampling.
2.1.16Random quadrat sampling can be used to estimate population size for non-mobile organisms.
2.1.17Capture–mark–release–recapture and the Lincoln index can be used to estimate population size for mobile organisms.
2.1.18A community is a collection of interacting populations within the ecosystem.
2.1.19Habitat is the location in which a community, species, population or organism lives.
2.1.20Ecosystems are open systems in which both energy and matter can enter and exit.
2.1.21Sustainability is a natural property of ecosystems.
2.1.22Human activity can lead to tipping points in ecosystem stability.
2.1.23Keystone species have a role in the sustainability of ecosystems.
2.1.24The planetary boundaries model indicates that changes to biosphere integrity have passed a critical threshold.
2.1.25To avoid critical tipping points, loss of biosphere integrity needs to be reversed.
2.1.26There are advantages of using a method of classification that illustrates evolutionary relationships in a clade.
2.1.27There are difficulties in classifying organisms into the traditional hierarchy of taxa.
2.1.28The niche of a species can be defined as fundamental or realized.
2.1.29Life cycles vary between species in reproductive behavior and lifespan.
2.1.30Knowledge of species’ classifications, niche requirements and life cycles help us to understand the extent of human impacts upon them.
Skills you'll practice
Know how to use dichotomous keys, applications and databases for the identification of species.
Investigate a local ecosystem.
Use methods for measuring at least three abiotic factors in an aquatic or terrestrial ecosystem, including the use of data logging.
Use models that demonstrate feeding relationships, such as predator–prey.
Use quadrat sampling estimates for abundance, population density, percentage cover and percentage frequency for non-mobile organisms and measures change along a transect.
Students should use the Lincoln index to estimate population size. Students should understand the assumptions made when using this method.
View outcomes & skills, straight from the syllabus
Content statements (IB Guide)
2.2.1Ecosystems are sustained by supplies of energy and matter.
2.2.2The first law of thermodynamics states that as energy flows through ecosystems, it can be transformed from one form to another but cannot be created or destroyed.
2.2.3Photosynthesis and cellular respiration transform energy and matter in ecosystems.
2.2.4Photosynthesis is the conversion of light energy to chemical energy in the form of glucose, some of which can be stored as biomass by autotrophs.
2.2.5Producers form the first trophic level in a food chain.
2.2.6Cellular respiration releases energy from glucose by converting it into a chemical form that can easily be used in carrying out active processes within living cells.
2.2.7Some of the chemical energy released during cellular respiration is transformed into heat.
2.2.8The second law of thermodynamics states that energy transformations in ecosystems are inefficient.
2.2.9Consumers gain chemical energy from carbon (organic) compounds obtained from other organisms.
2.2.10Because producers in ecosystems make their own carbon compounds by photosynthesis, they are at the start of food chains.
2.2.11Carbon compounds and the energy they contain are passed from one organism to the next in a food chain.
2.2.12There are losses of energy and organic matter as food is transferred along a food chain.
2.2.13Gross productivity (GP) is the total gain in biomass by an organism.
2.2.14The number of trophic levels in ecosystems is limited due to energy losses.
2.2.15Food webs show the complexity of trophic relationships in communities.
2.2.16Biomass of a trophic level can be measured by collecting and drying samples.
2.2.17Ecological pyramids are used to represent relative numbers, biomass or energy of trophic levels in an ecosystem.
2.2.18Pollutants that are non-biodegradable, such as polychlorinated biphenyl (PCB), dichlorodiphenyltrichloroethane (DDT) and mercury, cause changes to ecosystems through the processes of bioaccumulation and biomagnification.
2.2.19Non-biodegradable pollutants are absorbed within microplastics, which increases their transmission in the food chain.
2.2.20Human activities, such as burning fossil fuels, deforestation, urbanization and agriculture, have impacts on flows of energy and transfers of matter in ecosystems.
2.2.21Autotrophs synthesize carbon compounds from inorganic sources of carbon and other elements.
2.2.22Photoautotrophs use light as an external energy source in photosynthesis.
2.2.23Primary productivity is the rate of production of biomass using an external energy source and inorganic sources of carbon and other elements.
2.2.24Secondary productivity is the gain in biomass by consumers using carbon compounds absorbed and assimilated from ingested food.
2.2.25Net primary productivity is the basis for food chains because it is the quantity of carbon compounds sustainably available to primary consumers.
2.2.26Maximum sustainable yields (MSYs) are the net primary or net secondary productivity of a system.
2.2.27Sustainable yields are higher for lower trophic levels.
2.2.28Ecological efficiency is the percentage of energy received by one trophic level that is passed on to the next level.
2.2.29The second law of thermodynamics shows how the entropy of a system increases as biomass passes through ecosystems.
Skills you'll practice
Create system diagrams from a set of data of ecosystems showing transfers and transformations of energy and matter.
Create a food chain from given data.
Work out the efficiency of transfer between trophic levels.
Create a food web from given data.
Create pyramids of numbers, biomass and energy from given data. Follow experimental procedures on how to find biomass and energy from biological samples (plant material only).
Use laboratory and field techniques for measuring primary and secondary productivity and work out GP and NP from data.
View outcomes & skills, straight from the syllabus
Content statements (IB Guide)
2.3.1Biogeochemical cycles ensure chemical elements continue to be available to living organisms.
2.3.2Biogeochemical cycles have stores, sinks and sources.
2.3.3Organisms, crude oil and natural gas contain organic stores of carbon.
2.3.4Carbon flows between stores in ecosystems by photosynthesis, feeding, defecation, cellular respiration, death and decomposition.
2.3.5Carbon sequestration is the process of capturing gaseous and atmospheric carbon dioxide and storing it in a solid or liquid form.
2.3.6Ecosystems can act as stores, sinks or sources of carbon.
2.3.7Fossil fuels are stores of carbon with unlimited residence times.
2.3.8Agricultural systems can act as carbon stores, sources and sinks, depending on the techniques used.
2.3.9Carbon dioxide is absorbed into the oceans by dissolving and is released as a gas when it comes out of a solution.
2.3.10Increases in concentrations of dissolved carbon dioxide cause ocean acidification, harming marine animals.
2.3.11Measures are required to alleviate the effects of human activities on the carbon cycle.
2.3.12The lithosphere contains carbon stores in fossil fuels and in rocks, such as limestone, that contain calcium carbonate.
2.3.13Reef-building corals and molluscs have hard parts that contain calcium carbonate that can become fossilized in limestone.
2.3.14In past geological eras, organic matter from partially decomposed plants became fossilized in coal, and partially decomposed marine organisms became fossilized in oil and natural gas held in porous rocks.
2.3.15Methane is produced from dead organic matter in anaerobic conditions by methanogenic bacteria.
2.3.16Methane has a residence time of about 10 years in the atmosphere and is eventually oxidized to carbon dioxide.
2.3.17The nitrogen cycle contains organic and inorganic stores.
2.3.18Bacteria have essential roles in the nitrogen cycle.
2.3.19Denitrification only happens in anaerobic conditions, such as soils that are waterlogged.
2.3.20Plants cannot fix nitrogen so atmospheric dinitrogen is unavailable to them unless they form mutualistic associations with nitrogen-fixing bacteria.
2.3.21Flows in the nitrogen cycle include mineral uptake by producers, photosynthesis, consumption, excretion, death, decomposition and ammonification.
2.3.22Human activities such as deforestation, agriculture, aquaculture and urbanization change the nitrogen cycle.
2.3.23The Haber process is an industrial process that produces ammonia from nitrogen and hydrogen for use as fertilizer.
2.3.24Increases in nitrates in the biosphere from human activities have led to the planetary boundary for the nitrogen cycle being crossed, making irreversible changes to Earth systems likely.
2.3.25Global collaboration is needed to address the uncontrolled use of nitrogen in industrial and agricultural processes and bring the nitrogen cycle back within planetary boundaries.
View outcomes & skills, straight from the syllabus
Content statements (IB Guide)
2.4.1Climate describes atmospheric conditions over relatively long periods of time, whereas weather describes the conditions in the atmosphere over a short period of time.
2.4.2A biome is a group of comparable ecosystems that have developed in similar climatic conditions, wherever they occur.
2.4.3Abiotic factors are the determinants of terrestrial biome distribution.
2.4.4Biomes can be categorized into groups that include freshwater, marine, forest, grassland, desert and tundra.
2.4.5The tricellular model of atmospheric circulation explains the behavior of atmospheric systems and the distribution of precipitation and temperature at different latitudes.
2.4.6The oceans absorb solar radiation and ocean currents distribute the resulting heat around the world.
2.4.7Global warming is leading to changing climates and shifts in biomes.
2.4.8There are three general patterns of climate types that are connected to biome types.
2.4.9The biome predicted by any given temperature and rainfall pattern may not develop in an area because of secondary influences or human interventions.
2.4.10The El Niño Southern Oscillation (ENSO) cycle is the fluctuation in wind and sea surface temperatures that characterizes conditions in the tropical Pacific Ocean.
2.4.11El Niño is due to a weakening or reversal of the normal east–west (Walker) circulation, which increases surface stratification and decreases upwelling of cold, nutrient-rich water near the coast of north-western South America.
2.4.12Tropical cyclones are rapidly circulating storm systems with a low-pressure center that originate in the tropics and are characterized by strong winds.
2.4.13Rises in ocean temperatures resulting from global warming are increasing the intensity and frequency of hurricanes and typhoons because warmer water and air have more energy.
Skills you'll practice
Create climate graphs showing annual precipitation/average temperature for different biomes.
Use the tricellular model of atmospheric circulation and link it to the planetary distribution of heat and biomes.
View outcomes & skills, straight from the syllabus
Content statements (IB Guide)
2.5.1Zonation refers to changes in community along an environmental gradient.
2.5.2Transects can be used to measure biotic and abiotic factors along an environmental gradient in order to determine the variables that affect the distribution of species.
2.5.3Succession is the replacement of one community by another in an area over time due to changes in biotic and abiotic variables.
2.5.4Each seral community (sere) in a succession causes changes in environmental conditions that allow the next community to replace it through competition until a stable climax community is reached.
2.5.5Primary successions happen on newly formed substratum where there is no soil or pre- existing community, such as rock newly formed by volcanism, moraines revealed by retreating glaciers, wind-blown sand or waterborne silt.
2.5.6Secondary successions happen on bare soil where there has been a pre-existing community, such as a field where agriculture has ceased or a forest after an intense firestorm.
2.5.7Energy flow, productivity, species diversity, soil depth and nutrient cycling change over time during succession.
2.5.8An ecosystem’s capacity to tolerate disturbances and maintain equilibrium depends on its diversity and resilience.
2.5.9The type of community that develops in a succession is influenced by climatic factors, the properties of the local bedrock and soil, geomorphology, together with fire and weather-related events that can occur.
2.5.10Patterns of net productivity (NP) and gross productivity (GP) change over time in a community undergoing succession.
2.5.11r- and K-strategist species have reproductive strategies that are better adapted to pioneer and climax communities, respectively.
2.5.12The concept of a climax community has been challenged, and there is uncertainty over what ecosystems would develop naturally were there no human influences.
2.5.13Human activity can divert and change the progression of succession leading to a plagioclimax.
Skills you'll practice
Investigate zonation along an environmental gradient using a transect sampling technique and a range of relevant abiotic measurements. Create kite diagrams to show distribution.
Use secondary data and a mapping database to recreate or map the changes through succession in a given area.
Topic 3
Biodiversity and Conservation
How diversity is explained, measured, lost and, where possible, restored.
View outcomes & skills, straight from the syllabus
Content statements (IB Guide)
3.1.1Biodiversity is the total diversity of living systems and it exists at several levels.
3.1.2The components of diversity contribute to the resilience of ecological systems.
3.1.3Biodiversity arises from evolutionary processes.
3.1.4Natural selection is the mechanism driving evolutionary change.
3.1.5Evolution by natural selection involves variation, overproduction, competition for limited resources, and differences in adaptation that affect rates of survival and reproduction.
3.1.6Speciation is the generation of new species through evolution.
3.1.7Species diversity in communities is a product of richness and evenness.
3.1.8Simpson’s reciprocal index is used to provide a quantitative measure of species diversity, allowing different ecosystems to be compared and for change in a specific ecosystem over time to be monitored.
3.1.9Knowledge of global and regional biodiversity is needed for the development of effective management strategies to conserve biodiversity.
3.1.10Mutation and sexual reproduction increase genetic diversity.
3.1.11Reproductive isolation can be achieved by geographical separation or, for populations living in the same area, by ecological or behavioral differences.
3.1.12Biodiversity is spread unevenly across the planet, and certain areas contain a particularly large proportion of species, especially species that are rare and endangered.
3.1.13Human activities have impacted the selective forces acting on species within ecosystems, resulting in evolutionary change in these species.
3.1.14Artificial selection reduces genetic diversity and, consequently, species resilience.
3.1.15Earth history extends over a period of 4.5 billion years.
3.1.16Earth history is divided up into geological epochs according to the fossil record.
3.1.17Mass extinctions are followed by rapid rates of speciation due to increased niche availability.
3.1.18The Anthropocene is a proposed geological epoch characterized by rapid environmental change and species extinction due to human activity.
3.1.19Human impacts are having a planetary effect, which will be detectable in the geological record.
Skills you'll practice
Collect data in order to work out Simpson’s reciprocal index for diversity.
View outcomes & skills, straight from the syllabus
Content statements (IB Guide)
3.2.1Biological diversity is being adversely affected by both direct and indirect influences.
3.2.2Most ecosystems are subject to multiple human impacts.
3.2.3Invasive alien species can reduce local biodiversity by competing for limited resources, predation and introduction of diseases or parasites.
3.2.4The global conservation status of species is assessed by the International Union for Conservation of Nature (IUCN) and is published as the IUCN Red List.
3.2.5Assigning a global conservation status publicizes the vulnerability of species and allows governments, non-governmental agencies and individual citizens to select appropriate conservation priorities and management strategies.
3.2.6Investigate three different named species: a species that has become extinct due to human activity; a species that is critically endangered; and a species whose conservation status has been improved by intervention.
3.2.7The tragedy of the commons describes possible outcomes of the shared unrestricted use of a resource, with implications for sustainability and the impacts on biodiversity.
3.2.8Biodiversity hotspots are under threat from habitat destruction, which could lead to a significant loss of biological diversity, especially in tropical biomes.
3.2.9Key areas that should be prioritized for biodiversity conservation have been identified on the basis of the international importance of their species and habitats.
3.2.10In KBAs, there is conflict between exploitation, sustainable development and conservation.
3.2.11Traditional indigenous approaches to land management can be seen as more sustainable but are facing challenges of population growth, economic development, climate change and a lack of governmental support and protection.
3.2.12Environmental justice must be considered when undertaking conservation efforts to address biodiversity loss.
3.2.13The planetary boundary “loss of biosphere integrity” indicates that species extinctions have already crossed a critical threshold.
Skills you'll practice
Investigate the impact of human activity on biodiversity in an ecosystem by studying change in species diversity along a transect laid perpendicular to a site of human interference or by randomly sampling within transects before and after the human activity.
View outcomes & skills, straight from the syllabus
Content statements (IB Guide)
3.3.1Arguments for species and habitat preservation can be based on aesthetic, ecological, economic, ethical and social justifications.
3.3.2Species-based conservation tends to involve ex situ strategies, and habitat-based conservation tends to involve in situ strategies.
3.3.3Sometimes a mixed conservation approach is adopted, where both habitat and particular species are considered.
3.3.4The Convention on Biological Diversity (CBD) is a UN treaty addressing both species-based and habitat-based conservation.
3.3.5Habitat conservation strategies protect species by conservation of their natural environment.
3.3.6Effective conservation of biodiversity in nature reserves and national parks depends on an understanding of the biology of target species and on the effect of the size and shape of conservation areas.
3.3.7Natural processes in ecosystems can be regenerated by rewilding.
3.3.8Conservation and regeneration measures can be used to reverse the decline in biodiversity to ensure a safe operating space for humanity within the biodiversity planetary boundary.
3.3.9Environmental perspectives and value systems can impact the choice of conservation strategies selected by a society.
3.3.10Success in conserving and restoring biodiversity by international, governmental and non- governmental organizations depends on their use of media, speed of response, diplomatic constraints, financial resources and political influence.
3.3.11Positive feedback loops that enhance biodiversity and promote ecosystem equilibrium can be triggered by rewilding and habitat restoration efforts.
3.3.12Rewilding projects have both benefits and limitations.
3.3.13The success of conservation or regeneration measures needs to be assessed.
3.3.14Ecotourism can increase interdependence of local communities and increase biodiversity by generating income and providing funds for protecting areas, but there can also be negative societal and ecological impacts.
Skills you'll practice
Use secondary data from databases to assess the success of a rewilding project. Use questionnaires to assess the impact of ecotourism or the values that it promotes.
Topic 4
Water and Aquatic Food Production Systems and Societies
How water systems support life on Earth, and what happens when their inputs and outputs stop balancing.
View outcomes & skills, straight from the syllabus
Content statements (IB Guide)
4.1.1Movements of water in the hydrosphere are driven by solar radiation and gravity.
4.1.2The global hydrological cycle operates as a system with stores and flows.
4.1.3The main stores in the hydrological cycle are the oceans (96.5%), glaciers and ice caps (1.7%), groundwater (1.7%), surface freshwater (0.02%), atmosphere (0.001%), organisms (0.0001%).
4.1.4Flows in the hydrological cycle include transpiration, sublimation, evaporation, condensation, advection, precipitation, melting, freezing, surface run-off, infiltration, percolation, streamflow and groundwater flow.
4.1.5Human activities, such as agriculture, deforestation and urbanization, can alter these flows and stores.
4.1.6The steady state of any water body can be demonstrated through flow diagrams of inputs and outputs.
4.1.7Water has unique physical and chemical properties that support and sustain life.
4.1.8The oceans act as a carbon sink by absorbing carbon dioxide from the atmosphere and sequestering it.
4.1.9Carbon sequestered in oceans over the short term as dissolved carbon dioxide causes ocean acidification; over the longer term, carbon is taken up into living organisms as biomass that accumulates on the seabed.
4.1.10The temperature of water varies with depth, with cold water below and warmer water above.
4.1.11Stratification occurs in deeper lakes, coastal areas, enclosed seas and open ocean, with a thermocline forming a transition layer between the warmer mixed layer at the surface and the cooler water below.
4.1.12Global warming and salinity changes have increased the intensity of ocean stratification.
4.1.13Upwellings in oceans and freshwater bodies can bring cold, nutrient-rich waters to the surface.
4.1.14Thermohaline circulation systems are driven by differences in temperature and salinity.
Skills you'll practice
Create and use a systems diagram showing the transfers and transformations of the hydrological cycle.
Extract data from a database and analyze data on water temperatures with oxygen and salinity concentrations using an appropriate statistical test.
View outcomes & skills, straight from the syllabus
Content statements (IB Guide)
4.2.1Water security is having access to sufficient amounts of safe drinking water.
4.2.2Social, cultural, economic and political factors all have an impact on the availability of, and equitable access to, freshwater.
4.2.3Human societies undergoing population growth or economic development must increase the supply of water or the efficiency of its utilization.
4.2.4Water supplies can be increased by constructing dams, reservoirs, rainwater catchment systems, desalination plants and enhancement of natural wetlands.
4.2.5Water scarcity refers to the limited availability of water to human societies.
4.2.6Water conservation techniques can be applied at a domestic level.
4.2.7Water conservation strategies can be applied at an industrial level in food production systems.
4.2.8Mitigation strategies exist to address water scarcity.
4.2.9Freshwater use is a planetary boundary, with increasing demand causing increased water stress.
4.2.10Local and global governance is needed to maintain freshwater use at sustainable levels.
4.2.11Water footprints can serve as a measure of sustainable use by societies.
4.2.12Citizen science is playing an increasing role in monitoring and managing water resources.
4.2.13“Water stress,” like “water scarcity,” is another measure of the limitation of water supply.
4.2.14Water stress is defined as a clean, accessible water supply of less than 1,700 cubic meters per year per capita.
4.2.15The causes of increasing water stress may depend on the socio-economic context.
4.2.16Water stress can arise from transboundary disputes when water sources cross regional boundaries.
4.2.17Water stress can be addressed at an industrial level.
4.2.18Industrial freshwater production has negative environmental impacts that can be minimized but not usually eliminated.
4.2.19Inequitable access to drinkable water and sanitation negatively impacts human health and sustainable development.
Skills you'll practice
Use secondary data sources to investigate the causes of water stress within a given society.
View outcomes & skills, straight from the syllabus
Content statements (IB Guide)
4.3.1Phytoplankton and macrophytes provide energy for freshwater and marine food webs.
4.3.2Humans consume organisms from freshwater and marine environments.
4.3.3Demand for foods from freshwater and marine environments is increasing due to population growth and changes in dietary preferences.
4.3.4The increasing global demand for seafood has encouraged use of unsustainable harvesting practices and overexploitation.
4.3.5Overexploitation has led to the collapse of fisheries.
4.3.6The maximum sustainable yield (MSY) is the highest possible annual catch that can be sustained over time.
4.3.7Climate change and ocean acidification are having impacts on ecosystems and may cause collapse of some populations.
4.3.8Unsustainable exploitation of freshwater and marine ecosystems can be mitigated through policy legislation and changes in consumer behavior.
4.3.9Marine protected areas (MPAs) can be used to support aquatic food chains and maintain sustainable yields.
4.3.10Aquaculture is the farming of aquatic organisms; the industry is expanding but has associated environmental impacts.
4.3.11Productivity, thermal stratification, nutrient mixing and nutrient loading are interconnected in water systems.
4.3.12Accurate assessment of fish stocks and monitoring of harvest rates are required for conservation and sustainable use.
4.3.13There are risks in harvesting fish at the maximum sustainable yield (MSY) rate that need to be managed carefully.
4.3.14Species that have been overexploited may recover with cooperation between governments, industry and other stakeholders.
4.3.15Under UNCLOS, coastal states have an exclusive economic zone within which they can regulate fishing; most of the ocean is high seas with limited regulation.
4.3.16Harvesting of seals, whales and dolphins raises ethical issues relating to the rights of animals and of indigenous groups.
Skills you'll practice
Plan an experiment to investigate the impact of acidification on shelled organisms.
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Content statements (IB Guide)
5.1.1Soil is a dynamic system within the larger ecosystem that has its own inputs, outputs, storages and flows.
5.1.2Soil is made up of inorganic and organic components, water and air.
5.1.3Soils develop a stable, layered structure known as a profile made up of several horizons, produced by interactions within the system over long periods of time.
5.1.4Soil system inputs include those from dead organic matter and inorganic minerals.
5.1.5Soil system outputs include losses of dead organic matter due to decomposition, losses of mineral components and loss of energy due to heat loss.
5.1.6Transfers occur across soil horizons, into and out of soils.
5.1.7Transformations within soils can change the components or the whole soil system.
5.1.8Systems flow diagrams show flows into, out of and within the soil ecosystem.
5.1.9Soils provide the foundation of terrestrial ecosystems as a medium for plant growth (a seed bank, a store of water and almost all essential plant nutrients).
5.1.10Soils contribute to biodiversity by providing a habitat and a niche for many species.
5.1.11Soils have an important role in the recycling of elements as a part of biogeochemical cycles.
5.1.12Soil texture defines the physical make-up of the mineral soil.
5.1.13Soil texture affects primary productivity through the differing influences of sand, silt, clay and dead organic matter, including humus.
5.1.14Soils can act as carbon sinks, stores or sources, depending on the relative rates of input of dead organic matter and decomposition.
5.1.15Soils are classified and mapped by appearance of the whole soil profile.
5.1.16Horizons are horizontal strata that are distinctive to the soil type.
5.1.17The A horizon is the layer of soil just beneath the uppermost organic humus layer, where present.
5.1.18Factors that influence soil formation include climate, organisms, geomorphology (landscape), geology (parent material) and time.
5.1.19Differences between soils rich in sand, silt or clay include particle size and chemical properties.
5.1.20Soil properties can be determined from analyzing the sand, silt and clay percentages, percentage organic matter, percentage water, infiltration, bulk density, color and pH.
5.1.21Carbon is released from soils as methane or carbon dioxide.
Skills you'll practice
Create a systems flow diagram representing the soil system.
Use soil profile diagrams to classify examples of soils that can be linked to the biomes studied, for example, brown earths to temperate deciduous forests, or oxisols to rainforests.
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Content statements (IB Guide)
5.2.1Land is a finite resource, and the human population continues to increase and require feeding.
5.2.2Marginalized groups are more vulnerable if their needs are not taken into account in land-use decisions.
5.2.3World agriculture produces enough food to feed eight billion people, but the food is not equitably distributed and much is wasted or lost in distribution.
5.2.4Agriculture systems across the world vary considerably due to the different nature of the soils and climates.
5.2.5Agricultural systems are varied, with different factors influencing the farmers’ choices.
5.2.6Nomadic pastoralism and slash-and-burn agriculture are traditional techniques that have sustained low-density populations in some regions of the world.
5.2.7The Green Revolution (also known as the Third Agricultural Revolution in the 1950s and 1960s) used breeding of high-yielding crop plants, combined with increased and improved irrigation systems, synthetic fertilizer and application of pesticides, to increase food security.
5.2.8Synthetic fertilizers are needed in many intensive systems to maintain high commercial productivity at the expense of sustainability.
5.2.9A variety of techniques can be used to conserve soil, with widespread environmental, economic and sociocultural benefits.
5.2.10Humans are omnivorous, and diets include fungi, plants, meat and fish.
5.2.11Current global strategies to achieve sustainable food supply include reducing demand and food waste, reducing greenhouse gas emissions from food production and increasing productivity without increasing the area of land used for agriculture.
5.2.12Food security is the physical and economic availability of food, allowing all individuals to get the balanced diet they need for an active and healthy life.
5.2.13Contrasting agricultural choices will often be the result of differences in the local soils and climate.
5.2.14Numerous alternative farming approaches have been developed in relation to the current ecological crisis.
5.2.15Regenerative farming systems and permaculture use mixed farming techniques to improve and diversify productivity.
5.2.16Technological improvements can lead to very high levels of productivity, as seen in the modern high-tech greenhouse and vertical farming techniques that are increasingly important for supplying food to urban areas.
5.2.17The sustainability of different diets varies.
5.2.18Harvesting wild species from ecosystems by traditional methods may be more sustainable than land conversion and cultivation.
5.2.19Claims that low-productivity, indigenous, traditional or alternative food systems are sustainable should be evaluated against the need to produce enough food to feed the wider global population.
5.2.20Food distribution patterns and food quality variations reflect functioning of the global food supply industry and can lead to all forms of malnutrition (diseases of undernourishment and overnourishment).
Skills you'll practice
Make a detailed study of one example of a pair of named contrasting systems.
Create a survey to investigate food preferences and the worldviews of various groups.
Topic 6
Atmospheric Systems and Societies
What the atmosphere is made of, how it moves heat, and why a handful of trace gases keep the whole system livable.
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Content statements (IB Guide)
6.1.1The atmosphere forms the boundary between Earth and space.
6.1.2Differential heating of the atmosphere creates the tricellular model of atmospheric circulation that redistributes the heat from the equator to the poles.
6.1.3GHGs and aerosols in the atmosphere absorb and re-emit some of the infrared (long-wave) radiation emitted from the Earth’s surface, preventing it from being radiated out into space.
6.1.4The greenhouse effect keeps the Earth warmer than it otherwise would be due to the broad spectrum of the Sun’s radiation reaching the Earth’s surface and infrared radiation emitted by the warmed surface then being trapped and re-radiated by GHGs.
6.1.5The atmosphere is a dynamic system, and the components and layers are the result of continuous physical and chemical processes.
6.1.6Molecules in the atmosphere are pulled towards the Earth’s surface by gravity.
6.1.7Milankovitch cycles affect how much solar radiation reaches the Earth and lead to cycles in the Earth’s climate over tens to hundreds of thousands of years.
6.1.8Global warming is moving the Earth away from the glacial–interglacial cycle that has characterized the Quaternary period, toward new, hotter climatic conditions.
6.1.9The evolution of life on Earth changed the composition of the atmosphere, which in turn influences the evolution of life on Earth.
Skills you'll practice
Create system diagrams to represent the atmospheric system.
Investigate the impact of albedo or different GHGs on the temperature of a closed system.
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Content statements (IB Guide)
6.2.1Climate describes the typical conditions that result from physical processes in the atmosphere.
6.2.2Anthropogenic carbon dioxide emissions have caused concentrations of atmospheric carbon dioxide to rise significantly.
6.2.3Analysis of ice cores, tree rings and deposited sediments indicates a positive correlation between atmospheric carbon dioxide and global temperatures.
6.2.4The greenhouse effect has been enhanced by anthropogenic emissions of GHGs, leading to global warming and climate change.
6.2.5Climate change impacts ecosystems at a variety of scales and affects the resilience of ecosystems, leading to biome shifts.
6.2.6Climate change has an impact on human societies at a variety of scales and socio-economic conditions.
6.2.7Systems diagrams and models can be used to represent cause and effect of climate change with feedback loops.
6.2.8Evidence suggests that the Earth has already passed the planetary boundary for climate change.
6.2.9Perspectives on climate change for both individuals and societies are influenced by many factors.
6.2.10Data collected over time by weather stations, observatories, radar and satellites provides opportunity for the study of climate change.
6.2.11Global climate models manipulate inputs to climate systems to predict possible outputs, tested via hindcasting.
6.2.12Climate models use different scenarios to predict possible impacts of climate change.
6.2.13Climate models show the Earth may approach a critical threshold with changes to a new equilibrium.
6.2.14Individual tipping points of the climate system may interact to create tipping cascades.
6.2.15Countries vary in their responsibility for climate change and also in vulnerability, with political and economic implications and issues of equity.
Skills you'll practice
Investigate graphs of ice-core data spanning 800,000 years of glacial cycles.
Investigate climate graphs for different global locations.
Use databases to explore the impact of temperature change on a specific ecosystem.
6.4.7Ozone depletion allows increasing amounts of UVB radiation to reach the Earth's surface, impacting ecosystems and human health.
6.4.8The Montreal Protocol is an international treaty regulating CFCs and other ODSs, regarded as the most successful example of international cooperation on an environmental issue.
6.4.9Actions taken in response to the Montreal Protocol have prevented the planetary boundary for stratospheric ozone depletion being crossed.
6.4.10ODSs release halogens, such as chlorine and fluorine, into the stratosphere, which break down ozone.
6.4.11Polar stratospheric ozone depletion occurs in the spring due to unique chemical and atmospheric conditions.
6.4.12Hydrofluorocarbons (HFCs) were developed to replace CFCs, but are potent GHGs, now controlled by the Kigali Amendment.
6.4.13Air conditioning units are energy-intensive, contribute to GHG emissions and traditionally have contained ODSs.
Skills you'll practice
Review alternatives to air conditioning units.
Use databases to compare air conditioning use per capita across societies and present the data graphically.
Topic 7
Natural Resources
How the renewability of natural capital shapes how sustainably it can be used.
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Content statements (IB Guide)
7.1.1Natural resources are the raw materials and sources of energy used and consumed by society.
7.1.2Natural capital is the stock of natural resources available on Earth.
7.1.3Natural capital provides natural income in terms of goods and services.
7.1.4The terms “natural capital” and “natural income” imply a particular perspective on nature.
7.1.5Ecosystems provide life-supporting ecosystem services.
7.1.6All resources are finite.
7.1.7Natural capital has aesthetic, cultural, economic, environmental, health, intrinsic, social, spiritual and technological value.
7.1.8The value of natural capital is dynamic in that it can change over time.
7.1.9The use of natural capital needs to be managed in order to ensure sustainability.
7.1.10Resource security depends on the ability of societies to ensure the long-term availability of sufficient natural resources to meet demand.
7.1.11The choices a society makes in using given natural resources are affected by many factors and reflect diverse perspectives.
7.1.12A range of different management and intervention strategies can be used to directly influence society’s use of natural capital.
7.1.13The SDGs provide a framework for action by all countries in global partnership for natural resources use and management.
7.1.14Sustainable resource management in development projects is addressed in an environmental impact assessment (EIA).
7.1.15Countries and regions have different guidance on the use of EIAs.
7.1.16Making EIAs public allows local citizens to have a role as stakeholders in decision-making.
7.1.17While a given resource may be renewable, the associated means of extracting, harvesting, transporting and processing it may be unsustainable.
7.1.18Economic interests often favor short-term responses in production and consumption which undermine long-term sustainability.
7.1.19Natural resource insecurity hinders socio-economic development and can lead to environmental degradation and geopolitical tensions and conflicts.
7.1.20Resource security can be brought about by reductions in demand, increases in supply or changing technologies.
7.1.21Economic globalization can increase supply, making countries increasingly interdependent, but it may reduce national resource security.
Skills you'll practice
Create a survey to investigate the value that members of the school community place on different ecosystem services.
Use secondary data sources, such as Gapminder, Our World in Data and World Bank to investigate the use of a named resource (for example, steel, concrete or inorganic fertilizer) by two different societies.
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Content statements (IB Guide)
7.2.1Energy sources are both renewable and non-renewable.
7.2.2Global energy consumption is rising with increasing population and per capita demand.
7.2.3The sustainability of energy sources varies significantly.
7.2.4A variety of factors will affect the energy choices that a country makes.
7.2.5Intermittent energy production from some renewable sources creates the need for energy storage systems.
7.2.6Energy conservation and energy efficiency may allow a country to be less dependent on importing a resource.
7.2.7Energy security for a country means access to affordable and reliable sources of energy.
7.2.8The global economy mostly depends on finite reserves of fossil fuels as energy sources.
7.2.9Nuclear power is a non-renewable, low-carbon means of electricity production.
7.2.10Battery storage is required on a large scale to meet global requirements for reduction of carbon emissions, but carries its own environmental and social costs.
Skills you'll practice
Investigate graphical representations of how energy source use changes over time, globally and by country, using statistical tests.
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Content statements (IB Guide)
7.3.1Use of natural resources generates waste that can be classified by source or type.
7.3.2Solid domestic waste (SDW) typically has diverse content.
7.3.3The volume and composition of waste varies over time and between societies due to socio-economic, political, environmental and technological factors.
7.3.4The production, treatment and management of waste has environmental and social impacts, which may be experienced in a different location from where the waste was generated.
7.3.5Ecosystems can absorb some waste, but pollution occurs when harmful substances are added faster than they can be transformed.
7.3.6Preventative strategies for waste management are more sustainable than restorative strategies.
7.3.7Different waste disposal options have different advantages and disadvantages for societies and ecosystems.
7.3.8Sustainable options for management of SDW can be promoted in societies.
7.3.9The principles of a circular economy provide a holistic perspective on sustainable waste management.
Skills you'll practice
Interpret real waste-generation data across income levels.
Trace the path of a resource through a circular economy, from manufacture to recovery.
Topic 8
Human Populations and Urban Systems
How human population dynamics are measured, compared, and predicted.
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Content statements (IB Guide)
8.1.1Births and immigration are inputs to a human population.
8.1.2Deaths and emigration are outputs from a human population.
8.1.3Population dynamics can be quantified and analyzed by calculating total fertility rate, life expectancy, doubling time and natural increase.
8.1.4The global human population has followed a rapid growth curve.
8.1.5Population and migration policies can be employed to directly manage growth rates of human populations.
8.1.6Human population growth can also be managed indirectly through economic, social, health, development and other policies that have an impact on births, deaths or migration.
8.1.7The composition of human populations can be modeled and compared using age–sex pyramids.
8.1.8The demographic transition model (DTM) describes the changing levels of births and deaths in a human population through different stages of development over time.
8.1.9Rapid human population growth has increased stress on the Earth’s systems.
8.1.10Age–sex pyramids can be used to determine the dependency ratio and population momentum.
8.1.11The reasons for patterns and trends in population structure and growth can be understood using examples of two countries in different stages of the DTM.
8.1.12Environmental issues such as climate change, drought and land degradation are causing environmental migration.
Skills you'll practice
Work out natural increase rates and doubling times from given data.
Use secondary data from sources such as Gapminder, World Bank and Our World in Data to test a hypothesis about the relationship between a socio-economic indicator and a demographic factor using a suitable statistical tool.
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Content statements (IB Guide)
8.3.1Urban air pollution is caused by inputs from human activities to atmospheric systems, including NOx, sulfur dioxide, carbon monoxide and particulate matter.
8.3.2Sources of primary pollutants are both natural and anthropogenic.
8.3.3Most common air pollutants in the urban environment are derived directly or indirectly from combustion of fossil fuels.
8.3.4A range of different management and intervention strategies can be used to reduce urban air pollution.
8.3.5NOx and sulfur dioxide react with water and oxygen in the air to produce nitric and sulfuric acid, resulting in acid rain.
8.3.6Acid rain has impacts on ecology, humans and buildings.
8.3.7Management and intervention strategies are used to reduce the impact of sulfur dioxide and NOx on ecosystems.
8.3.8Photochemical smog is formed when sunlight acts on primary pollutants, causing their transformation into secondary pollutants.
8.3.9Meteorological and topographical factors can intensify processes that cause photochemical smog formation.
8.3.10Direct impacts of tropospheric ozone are both biological and physical.
8.3.11Indirect impacts of tropospheric ozone include societal costs and lost economic output.
Skills you'll practice
Plan an experiment using an indicator species as a correlate for pollution.
Use graphs showing diurnal changes in urban air pollutants, and secondary databases with a statistical tool to study change over time.
