Births and immigration are inputs to a human population.

Whether you're a current IB ESS student looking to get a deeper grasp of the syllabus or a prospective IB student weighing your Group 4 options, this post will be your guide. We'll break down the IB ESS syllabus to give you a clear understanding of what to expect in the course.

Foundation

A perspective is how a particular situation is viewed and understood by an individual.

Perspectives are informed and justified by sociocultural norms, scientific understandings, laws, religion, economic conditions, local and global events, and lived experience, among other factors.

Values are qualities or principles that people feel have worth and importance in life.

The values that underpin our perspectives can be seen in our communication and actions with the wider community.

Values surveys can be used to investigate the perspectives shown by a particular social group towards environmental issues.

Worldviews are the lenses shared by groups of people through which they perceive, make sense of and act within their environment.

An environmental value system is a model that shows the inputs affecting our perspectives and the outputs resulting from our perspectives.

Environmental perspectives (worldviews) can be classified into the broad categories of technocentric, anthropocentric and ecocentric.

Perspectives and the beliefs that underpin them change over time in all societies.

The development of the environmental movement has been influenced by individuals, literature, the media, major environmental disasters, international agreements, new technologies and scientific discoveries.

Perspectives

Systems are sets of interacting or interdependent components.

A systems approach is a holistic way of visualizing a complex set of interactions, and it can be applied to ecological or societal situations.

In 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.

Flows are processes that may be either transfers or transformations.

The Earth is a single integrated system encompassing the biosphere, the hydrosphere, the cryosphere, the geosphere, the atmosphere and the anthroposphere.

The concept of a system can be applied at a range of scales.

Negative 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.

As 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.

Positive feedback loops occur when a disturbance leads to an amplification of that disturbance, destabilizing the system and driving it away from its equilibrium.

Positive feedback loops will tend to drive the system towards a tipping point.

Tipping points can exist within a system where a small alteration in one component can produce large overall changes, resulting in a shift in equilibrium.

A 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.

Simplification of a model involves approximation and, therefore, loss of accuracy.

Interactions between components in systems can generate emergent properties.

The resilience of a system, ecological or social, refers to its tendency to avoid tipping points and maintain stability.

Diversity and the size of storages within systems can contribute to their resilience and affect their speed of response to change (time lags).

Humans can affect the resilience of systems through reducing these storages and diversity.

Systems

Sustainability is a measure of the extent to which practices allow for the long-term viability of a system.

Sustainability is comprised of environmental, social and economic pillars.

Environmental sustainability is the use and management of natural resources that allows replacement of the resources, and recovery and regeneration of ecosystems.

Social sustainability focuses on creating the structures and systems, such as health, education, equity, community, that support human well-being.

Economic 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.

Sustainable development meets the needs of the present without compromising the ability of future generations to meet their own needs.

Unsustainable use of natural resources can lead to ecosystem collapse.

Common indicators of economic development, such as gross domestic product (GDP), neglect the value of natural systems and may lead to unsustainable development.

Environmental 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.

Inequalities in income, race, gender and cultural identity within and between different societies lead to disparities in access to water, food and energy.

Sustainability and environmental justice can be applied at the individual to the global operating scale.

Sustainability indicators include quantitative measures of biodiversity, pollution, human population, climate change, material and carbon footprints, and others.

The concept of ecological footprints can be used to measure sustainability.

The carbon footprint measures the amount of greenhouse gases (GHGs) produced, measured in carbon dioxide equivalents (in tonnes).

Biocapacity is the capacity of a given biologically productive area to generate an ongoing supply of renewable resources and to absorb its resulting wastes.

Citizen science plays a role in monitoring Earth systems and whether resources are being used sustainably.

There are a range of frameworks and models that support our understanding of sustainability, each with uses and limitations.

The UN Sustainable Development Goals (SDGs) are a set of social and environmental goals and targets to guide action on sustainability and environmental justice.

The planetary boundaries model describes the nine processes and systems that have regulated the stability and resilience of the Earth system in the Holocene epoch.

The 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.

The circular economy is a model that promotes decoupling economic activity from the consumption of finite resources.

Sustainability

Ecology

The biosphere is an ecological system composed of individuals, populations, communities, ecosystems.

An individual organism is a member of a species.

Classification of organisms allows for efficient identification and prediction of characteristics.

Taxonomists use a variety of tools to identify an organism.

A 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.

Factors that determine the distribution of a population can be abiotic or biotic.

Temperature, sunlight, pH, salinity, dissolved oxygen and soil texture are examples of many abiotic factors that affect species distributions in ecosystems.

A niche describes the particular set of abiotic and biotic conditions and resources upon which an organism or a population depends.

Populations interact in ecosystems by herbivory, predation, parasitism, mutualism, disease and competition, with ecological, behavioural and evolutionary consequences.

Carrying capacity is the maximum size of a population determined by competition for limited resources.

Population size is regulated by density-dependent factors and negative feedback mechanisms.

Population growth can either be exponential or limited by carrying capacity.

Limiting factors on the growth of human populations have increasingly been eliminated, resulting in consequences for sustainability of ecosystems.

Carrying capacity cannot be easily assessed for human populations.

Population abundance can be estimated using random sampling, systematic sampling or transect sampling.

Random quadrat sampling can be used to estimate population size for non-mobile organisms.

Capture–mark–release–recapture and the Lincoln index can be used to estimate population size for mobile organisms.

A community is a collection of interacting populations within the ecosystem.

Habitat is the location in which a community, species, population or organism lives.

Ecosystems are open systems in which both energy and matter can enter and exit.

Sustainability is a natural property of ecosystems.

Human activity can lead to tipping points in ecosystem stability.

Keystone species have a role in the sustainability of ecosystems.

The planetary boundaries model indicates that changes to biosphere integrity have passed a critical threshold.

To avoid critical tipping points, loss of biosphere integrity needs to be reversed.

There are advantages of using a method of classification that illustrates evolutionary relationships in a clade.

There are difficulties in classifying organisms into the traditional hierarchy of taxa.

The niche of a species can be defined as fundamental or realized.

Life cycles vary between species in reproductive behaviour and lifespan.

Knowledge of species’ classifications, niche requirements and life cycles help us to understand the extent of human impacts upon them.

Individuals, populations, communities, and ecosystems

Ecosystems are sustained by supplies of energy and matter.

The 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.

Photosynthesis and cellular respiration transform energy and matter in ecosystems.

Photosynthesis is the conversion of light energy to chemical energy in the form of glucose, some of which can be stored as biomass by autotrophs.

Producers form the first trophic level in a food chain.

Cellular 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.

Some of the chemical energy released during cellular respiration is transformed into heat.

The second law of thermodynamics states that energy transformations in ecosystems are inefficient.

Consumers gain chemical energy from carbon (organic) compounds obtained from other organisms.

Because producers in ecosystems make their own carbon compounds by photosynthesis, they are at the start of food chains.

Carbon compounds and the energy they contain are passed from one organism to the next in a food chain.

There are losses of energy and organic matter as food is transferred along a food chain.

Gross productivity (GP) is the total gain in biomass by an organism.

The number of trophic levels in ecosystems is limited due to energy losses.

Food webs show the complexity of trophic relationships in communities.

Biomass of a trophic level can be measured by collecting and drying samples.

Ecological pyramids are used to represent relative numbers, biomass or energy of trophic levels in an ecosystem.

Pollutants that are non-biodegradable, such as polychlorinated biphenyl (PCB), dichlorodiphenyltrichloroethane (DDT) and mercury, cause changes to ecosystems through the processes of bioaccumulation and biomagnification.

Non-biodegradable pollutants are absorbed within microplastics, which increases their transmission in the food chain.

Human activities, such as burning fossil fuels, deforestation, urbanization and agriculture, have impacts on flows of energy and transfers of matter in ecosystems.

Autotrophs synthesize carbon compounds from inorganic sources of carbon and other elements.

Photoautotrophs use light as an external energy source in photosynthesis.

Primary productivity is the rate of production of biomass using an external energy source and inorganic sources of carbon and other elements.

Secondary productivity is the gain in biomass by consumers using carbon compounds absorbed and assimilated from ingested food.

Net primary productivity is the basis for food chains because it is the quantity of carbon compounds sustainably available to primary consumers.

Maximum sustainable yields (MSYs) are the net primary or net secondary productivity of a system.

Sustainable yields are higher for lower trophic levels.

Ecological efficiency is the percentage of energy received by one trophic level that is passed on to the next level.

The second law of thermodynamics shows how the entropy of a system increases as biomass passes through ecosystems.

Energy and biomass in ecosystems

Biogeochemical cycles ensure chemical elements continue to be available to living organisms.

Biogeochemical cycles have stores, sinks and sources.

Organisms, crude oil and natural gas contain organic stores of carbon.

Carbon flows between stores in ecosystems by photosynthesis, feeding, defecation, cellular respiration, death and decomposition.

Carbon sequestration is the process of capturing gaseous and atmospheric carbon dioxide and storing it in a solid or liquid form.

Ecosystems can act as stores, sinks or sources of carbon.

Fossil fuels are stores of carbon with unlimited residence times.

Agricultural systems can act as carbon stores, sources and sinks, depending on the techniques used.

Carbon dioxide is absorbed into the oceans by dissolving and is released as a gas when it comes out of a solution.

Increases in concentrations of dissolved carbon dioxide cause ocean acidification, harming marine animals.

Measures are required to alleviate the effects of human activities on the carbon cycle.

The lithosphere contains carbon stores in fossil fuels and in rocks, such as limestone, that contain calcium carbonate.

Reef-building corals and molluscs have hard parts that contain calcium carbonate that can become fossilized in limestone.

In 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.

Methane is produced from dead organic matter in anaerobic conditions by methanogenic bacteria.

Methane has a residence time of about 10 years in the atmosphere and is eventually oxidized to carbon dioxide.

The nitrogen cycle contains organic and inorganic stores.

Bacteria have essential roles in the nitrogen cycle.

Denitrification only happens in anaerobic conditions, such as soils that are waterlogged.

Plants cannot fix nitrogen so atmospheric dinitrogen is unavailable to them unless they form mutualistic associations with nitrogen-fixing bacteria.

Flows in the nitrogen cycle include mineral uptake by producers, photosynthesis, consumption, excretion, death, decomposition and ammonification.

Human activities such as deforestation, agriculture, aquaculture and urbanization change the nitrogen cycle.

The Haber process is an industrial process that produces ammonia from nitrogen and hydrogen for use as fertilizer.

Increases 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.

Global collaboration is needed to address the uncontrolled use of nitrogen in industrial and agricultural processes and bring the nitrogen cycle back within planetary boundaries.

Biogeochemical cycles

Climate describes atmospheric conditions over relatively long periods of time, whereas weather describes the conditions in the atmosphere over a short period of time.

A biome is a group of comparable ecosystems that have developed in similar climatic conditions, wherever they occur.

Abiotic factors are the determinants of terrestrial biome distribution.

Biomes can be categorized into groups that include freshwater, marine, forest, grassland, desert and tundra.

The tricellular model of atmospheric circulation explains the behaviour of atmospheric systems and the distribution of precipitation and temperature at different latitudes.

The oceans absorb solar radiation and ocean currents distribute the resulting heat around the world.

Global warming is leading to changing climates and shifts in biomes.

There are three general patterns of climate types that are connected to biome types.

The biome predicted by any given temperature and rainfall pattern may not develop in an area because of secondary influences or human interventions.

The El Niño Southern Oscillation (ENSO) cycle is the fluctuation in wind and sea surface temperatures that characterizes conditions in the tropical Pacific Ocean.

El 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.

Tropical cyclones are rapidly circulating storm systems with a low-pressure centre that originate in the tropics and are characterized by strong winds.

Rises 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.

Climate and biomes

Zonation refers to changes in community along an environmental gradient.

Transects 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.

Succession is the replacement of one community by another in an area over time due to changes in biotic and abiotic variables.

Each 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.

Primary 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.

Secondary 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.

Energy flow, productivity, species diversity, soil depth and nutrient cycling change over time during succession.

An ecosystem’s capacity to tolerate disturbances and maintain equilibrium depends on its diversity and resilience.

The 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.

Patterns of net productivity (NP) and gross productivity (GP) change over time in a community undergoing succession.

r- and K-strategist species have reproductive strategies that are better adapted to pioneer and climax communities, respectively.

The concept of a climax community has been challenged, and there is uncertainty over what ecosystems would develop naturally were there no human influences.

Human activity can divert and change the progression of succession leading to a plagioclimax.

Zonation, succession and change in ecosystems

Biodiversity and conservation

Biodiversity is the total diversity of living systems and it exists at several levels.

The components of diversity contribute to the resilience of ecological systems.

Biodiversity arises from evolutionary processes.

Natural selection is the mechanism driving evolutionary change.

Evolution by natural selection involves variation, overproduction, competition for limited resources, and differences in adaptation that affect rates of survival and reproduction.

Speciation is the generation of new species through evolution.

Species diversity in communities is a product of richness and evenness.

Simpson’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.

Knowledge of global and regional biodiversity is needed for the development of effective management strategies to conserve biodiversity.

Mutation and sexual reproduction increase genetic diversity.

Reproductive isolation can be achieved by geographical separation or, for populations living in the same area, by ecological or behavioural differences.

Biodiversity is spread unevenly across the planet, and certain areas contain a particularly large proportion of species, especially species that are rare and endangered.

Human activities have impacted the selective forces acting on species within ecosystems, resulting in evolutionary change in these species.

Artificial selection reduces genetic diversity and, consequently, species resilience.

Earth history extends over a period of 4.5 billion years.

Earth history is divided up into geological epochs according to the fossil record.

Mass extinctions are followed by rapid rates of speciation due to increased niche availability.

The Anthropocene is a proposed geological epoch characterized by rapid environmental change and species extinction due to human activity.

Human impacts are having a planetary effect, which will be detectable in the geological record.

Biodiversity and evolution

Biological diversity is being adversely affected by both direct and indirect influences.

Most ecosystems are subject to multiple human impacts.

Invasive alien species can reduce local biodiversity by competing for limited resources, predation and introduction of diseases or parasites.

The global conservation status of species is assessed by the International Union for

Assigning 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.

Investigate 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.

The tragedy of the commons describes possible outcomes of the shared unrestricted use of a resource, with implications for sustainability and the impacts on biodiversity.

Biodiversity hotspots are under threat from habitat destruction, which could lead to a significant loss of biological diversity, especially in tropical biomes.

Key areas that should be prioritized for biodiversity conservation have been identified on the basis of the international importance of their species and habitats.

In KBAs, there is conflict between exploitation, sustainable development and conservation.

Collections

Physics

Biology

Chemistry

Human populations

Syllabus concepts to know

Study & practice 8.1 Human populations

Practice 8.1 in Question Bank

Read Notes for 8.1

Review 8.1 Flashcards