IB ESS HL — All Flashcards

A perspective is a person's point of view on an issue, based on what they believe and value.

A person's perspective is shaped by their assumptions, values, and beliefs.

An assumption is something a person accepts as true without questioning it.

A value is something a person believes is important, such as economic growth or protecting the environment.

A belief is a strong idea about what is right, wrong, or true.

Perspectives matter because different people see environmental problems differently and support different solutions.

Some people see deforestation as creating jobs and income, while others see it as habitat loss and environmental damage.

Climate change: some see it as a serious global threat, others see it as exaggerated.

Water use: farmers may value irrigation, while conservationists focus on saving water.

Building a large dam to control a river, even if ecosystems are flooded.

Setting fishing limits so fish stocks remain for the future.

Protecting a mountain because it is beautiful, not for money.

Protecting forests because they provide clean water to cities.

Taking only enough fish to feed the community and giving back to nature.

Clearing forests because they exist mainly to provide timber.

Protecting forests because damaging them also harms people.

Seeing food waste as disrespectful because of cultural values.

A person accepts climate change evidence that supports their opinion but ignores data that challenges it.

India has low emissions per person but high total emissions because of population size.

A worldview about the relationship between humans and the natural world that shapes environmental decisions.

Inputs are influences, processes are how you interpret them (values/beliefs), and outputs are the decisions/actions you take.

Examples: cultural traditions, media/social media, scientific information, economic conditions, religion, direct experiences.

How you interpret inputs: evaluating evidence, emotions, moral judgements, and identity/values.

Examples: supporting/opposing laws, lifestyle choices (diet/energy/travel), campaigning/volunteering, political choices.

Ecocentric, anthropocentric, technocentric.

Nature-centred: protect ecosystems and live in balance with the environment.

Human-centred: manage nature responsibly to meet human needs.

Technology-centred: innovation and technology can solve environmental problems.

Put nature first. Protect ecosystems even if humans must change how they live.

They think overuse of resources causes problems, so reducing use and waste stops damage before it happens.

Nature is valuable simply because it exists, not because humans use it.

Examples: protecting forests/rivers, using fewer resources, reducing waste, sustainable farming, recycling/reusing.

Because it floods habitats, blocks fish migration, alters river flow, reduces water quality, and can destroy culturally important land.

Humans are central. Nature matters mainly because it supports human life and development, so it should be managed responsibly.

Through practical management: laws and regulations, planning, education, incentives (e.g. taxes), and international agreements.

Allow controlled logging, require replanting, set limits, and fine illegal cutting to protect forests while supporting the economy.

It may still allow environmental damage if it benefits humans, and may protect ecosystems less if they have no direct human use.

Trust technology and innovation to solve environmental problems while allowing continued economic growth.

Innovation. They prefer smarter, cleaner technology rather than making people use much less.

Examples: renewable energy, electric vehicles, carbon capture, smart grids/LEDs, geoengineering.

They can ignore overconsumption, create new problems (e-waste/mining), be expensive, and give a false sense that tech will fix everything.

A research method that asks questions to a sample of people to find out what they believe, value, and prioritise.

They help identify the environmental perspective of a group (ecocentric, anthropocentric, or technocentric).

They usually rate how much they agree or disagree on a scale (e.g., 1–5 or 1–7).

Examples: environment/sustainability, technology/development, government responsibility, religion/morality, lifestyle/priorities.

Ecocentric (nature-centred; environment has priority).

Technocentric (technology-centred; innovation solves problems).

Human-centred, but supports sustainable management of resources using laws and policies.

Examples: World Values Survey (WVS), European Values Survey (EVS), Pew Global Attitudes Survey.

They reveal patterns in environmental beliefs, show which worldview is dominant, explain reactions to policies, and allow comparisons between groups/countries.

People and organisations working to protect nature, reduce pollution, and use resources sustainably.

Because people become aware that human activities damage the environment and believe action is needed to protect ecosystems and future generations.

Problem identified → awareness spreads → action or policy change follows.

Understanding — using any relevant example and clearly explaining cause → awareness → action.

It exposes hidden environmental damage, raises public concern, and can lead to new laws.

They raise awareness, mobilise public support (e.g., protests/campaigns), and increase political pressure on decision-makers.

They provide evidence of environmental damage, which supports environmental laws and policies.

They make damage visible quickly, shifting public opinion and increasing demand for regulation.

They offer solutions that reduce environmental impacts (e.g., renewable energy and cleaner technology).

They help countries cooperate on global environmental problems and encourage shared action.

Media spreads information widely, increasing awareness, influencing public opinion, and encouraging behaviour change.

A scientist and writer who exposed the harmful effects of pesticides like DDT in her book Silent Spring, helping start the modern environmental movement.

It was used as a pesticide to kill mosquitoes, helping reduce diseases such as malaria.

DDT does not break down easily, can enter soil and water, and builds up in food chains (biomagnification).

Birds received the highest DDT concentrations; eggshells became thin and broke, causing bird populations to decline.

Public awareness increased, pressure on governments grew, and DDT was banned in many countries.

Silent Spring exposed the harmful effects of DDT, increasing public awareness and leading to bans.

A climate activist known for school strikes and speaking to world leaders, increasing pressure on governments to act on climate change.

Climate change and government inaction on emissions.

She organised school strikes, joined public protests, and gave international speeches.

Greta Thunberg raised awareness of climate change and increased political pressure through protest.

A Kenyan scientist and activist who founded the Green Belt Movement, using tree planting to protect ecosystems and support local communities.

She founded the Green Belt Movement and promoted tree planting.

It reduced deforestation and soil erosion, protected water supplies, and empowered local communities.

Wangari Maathai protected ecosystems through tree planting and community action.

A model is a simplified representation of reality.

A model is a simplified representation of reality used to understand, explain, or predict how a system works.

Diagram models, mathematical models, physical models, computer models, and written models.

A food web showing feeding relationships in an ecosystem (e.g., coral reef or pond).

Real environmental systems are too complex to study in full. Models help us focus on the most important features so we can test ideas and make predictions.

Simplification is focusing on the important features of a system while leaving out less relevant details.

An equation predicting population growth, such as N = N0 e^(rt), used to model how population size changes over time.

Simpler models are easier to understand and use, but they are usually less accurate and can miss important details.

A trade-off is a balance between competing factors: simpler models are easier to use, but may be less accurate.

Models rely on assumptions and may miss important information. Results depend on data quality, so predictions can be inaccurate.

A food chain is a model that shows feeding relationships and energy transfer between organisms in an ecosystem.

Examples include diagram models and computer models (also mathematical, physical, and written).

As new evidence and knowledge appear (and values may change), assumptions can become outdated, so models must be revised to stay useful.

Name the model and state what it shows (e.g., food chain shows feeding relationships).

Always include simplification and purpose: a model simplifies reality to understand, explain, or predict a system.

The boundary decides what is included and excluded. If it is too small, important influences are missed; if it is too large, the system becomes too complex to analyse.

A method of studying how parts of a system are connected and interact, rather than examining parts in isolation.

A system is interacting parts forming a whole.

A system is a group of interacting parts that form a whole, with components, connections, a function, and emergent properties.

Emergent properties: new characteristics arise from interactions between parts.

Studying a lake’s water quality without including upstream farmland can miss fertiliser runoff as the cause of eutrophication.

An imaginary line that defines what is included in the system and what is outside it.

Characteristics that appear only when parts of a system interact, not in the parts on their own.

The system includes too many variables and interactions, making it hard to identify key drivers or explain cause and effect clearly.

State what you included and excluded, and explain why that boundary is useful for answering the question (focuses on the key influences).

Boundaries affect what factors you include, so they change how you understand the problem and what conclusions you reach.

Predator-prey cycles: population patterns emerge only when predator and prey interact.

Connections, interactions, and boundaries.

Small scale (e.g., pond), medium scale (e.g., rainforest), large scale (e.g., Earth system).

Ask: Does it include the key inputs, outputs, and interactions that control the system behaviour for this question?

A closed system exchanges energy with its surroundings but does not exchange matter (matter stays inside and is recycled).

An open system exchanges both matter and energy with its surroundings across the system boundary.

Both matter and energy cross the system boundary (enter and leave).

A pond is an open system: sunlight and rain enter, while water (evaporation/runoff) and organisms/heat can leave.

Energy crosses the system boundary, but matter stays inside and is recycled.

Energy enters as sunlight and leaves as heat, but almost no matter enters or leaves Earth, so matter is recycled within the system.

Earth (at the global scale) is the classic closed system example because matter is retained but energy is exchanged.

Matter is physical stuff with mass (water, nutrients, organisms). Energy is not physical stuff (sunlight, heat) that drives change.

Open: a pond (matter + energy exchange). Closed: Earth (energy exchange, matter retained).

Because you can clearly identify inputs (sunlight, rain, nutrients) and outputs (evaporation, runoff, organisms leaving), showing matter and energy exchange.

They are closed systems at the global scale because the matter (atoms) is recycled within Earth, while energy enters and leaves.

Input: sunlight or rainfall or nutrients. Output: heat loss, oxygen release, runoff water, or organisms leaving.

State what crosses the boundary: energy crosses (sunlight in, heat out) but matter does not cross (it stays and is recycled).

Because inputs and outputs happen continuously, so storages and conditions can change over time.

Open: exchanges matter and energy. Closed: exchanges energy but not matter. Always state what enters and what leaves.

An input is the thing that moves (e.g., water). An inflow is the process moving it into a storage (e.g., rainfall).

Boxes represent storages (stocks) where matter, energy, or information accumulates over time.

A storage is a place where matter, energy, or information builds up over time (e.g., water in a reservoir, CO2 in the atmosphere).

Arrows represent flows moving matter, energy, or information into or out of storages.

A flow is the movement of matter, energy, or information into or out of a storage, changing the amount stored.

“Rainfall is an inflow.” The water is the input; rainfall is the flow process.

Dynamic equilibrium occurs when inflows equal outflows, keeping the storage constant.

An inflow is a flow that enters a storage and increases the amount stored (e.g., rainfall filling a reservoir).

Dynamic equilibrium occurs when inflows equal outflows, so the storage stays constant even though flows continue.

An outflow is a flow that leaves a storage and decreases the amount stored (e.g., dam release reducing reservoir water).

A buffer is a storage that absorbs sudden changes in flows, slowing system response and creating time delays.

The storage increases because more enters than leaves (e.g., reservoir fills when rainfall exceeds evaporation).

A system boundary is an imaginary line separating the system from its surroundings; choosing it affects what inputs/outputs are included and how useful the model is.

Storages are shown as boxes and flows are shown as arrows; thicker arrows often represent larger flows.

Movement of matter or energy without changing its form.

A chain where a change causes effects that feed back to influence the original change.

A positive feedback loop where tourism growth generates more income and investment, attracting even more tourism.

Wealth enables investment and influence, producing more wealth, widening the gap unless interrupted.

A diagram showing cause-and-effect links between variables, forming feedback loops over time.

A condition where inputs and outputs are balanced so the system stays roughly the same over time.

A positive relationship: the variables change in the same direction.

A mature forest: growth and death balance so overall biomass stays similar.

Start change → chain of effects → show the loop closes → state if reinforcing or balancing.

A change in form, state, or chemical nature of matter or energy.

Negative feedback reduces change and helps stabilise a system.

Creates jobs and income, and can fund infrastructure or conservation.

It stabilises systems by reducing change and helping maintain equilibrium.

A negative relationship: the variables change in opposite directions.

A time gap between a change and when its effects are seen in the system.

Positive feedback amplifies change; negative feedback counteracts change and stabilises the system.

Body temperature control: too hot → sweating → cooling → back to normal.

Higher water/energy demand, more waste/pollution, and habitat loss from development.

Positive feedback amplifies the original change and pushes the system further from balance.

It amplifies change and can push systems towards tipping points.

Eutrophication: more nutrients → more algae → plant death/decomposition → more available nutrients.

People or processes overcorrect because the system responds slowly, leading to repeated over- and under-shooting.

Reinforcing loops amplify change; balancing loops resist change and stabilise the system.

Because the output (tourism income/infrastructure) feeds back to increase the input (tourist attraction).

Crossing a tipping point can shift a system into a new equilibrium that may be difficult to reverse.

Predator–prey: prey increases → predators increase → prey decreases → predators decrease.

Name variables, follow arrows, explain +/− links, and state whether the loop is reinforcing or balancing.

Use limits such as visitor caps, zoning, pricing/taxes, and protected areas to reduce growth pressure.

Ice-albedo: ice melts → darker surface → more heat absorbed → more melting.

A threshold where a small change triggers a large, often hard-to-reverse shift to a new equilibrium.

Resilience is a system’s ability to absorb disturbance and keep functioning (or recover) without collapsing.

Excess nitrates and phosphates from agriculture runoff or sewage discharge.

It reduces biodiversity and biomass storage, weakening buffers and increasing tipping point risk.

Strong negative feedback loops usually support resilience because they counteract change.

Loss of biodiversity, repeated disturbances, removal of storages, or strong human pressures (pollution/deforestation).

Ability to recover from disturbance and keep functioning over time.

Rapid growth of algae due to high nutrient levels, often turning water green and reducing light.

Strong positive feedback amplifies change and can reduce resilience by pushing systems toward tipping points.

High biodiversity and large/multiple storages (buffers).

More species/roles create redundancy; if one fails, others can replace its function.

A sudden event that disrupts a system (e.g., fire, flood, disease, pollution).

It reduces biodiversity and functional redundancy, making ecosystems less able to recover from disturbance.

Protect habitats, restore mixed native species, improve soil management, or restore wetlands.

Decomposition of dead algae/plants uses dissolved oxygen, causing hypoxia and fish kills.

They can change in the short term after disturbance but remain stable in the long term.

Loss of diversity, shrinking storages, and strong human pressures (pollution/deforestation/overuse).

Clear lake + nutrient input → algal bloom → murky, low-oxygen lake state.

Large/multiple storages buffer change and slow system response, reducing collapse risk.

Soil nutrients, forest biomass, water in lakes/reservoirs, or carbon in vegetation.

Feedback delays mean impacts appear later, so humans may respond only when collapse is near.

Nutrients stored in sediments can keep feeding algal growth even after inputs are reduced.

A diverse forest that can regrow after fire and continue functioning.

The system settles into a new equilibrium, often difficult to reverse.

Crossing tipping points and shifting to a new equilibrium.

Yes: more nutrients → more algae → more death/decomposition → conditions that can release/retain nutrients, driving more algae.

Reduce pressures, protect diversity, and strengthen storages/buffers to support stabilising feedback.

Human actions can raise or lower resilience by changing biodiversity and storages, affecting tipping point risk.

With weaker buffers and fewer stabilising processes, disturbances push the system past thresholds more easily.

The system is more likely to cross a tipping point and shift to a new equilibrium.

Actions that increase diversity and storages usually increase resilience.

Using natural resources and producing waste at rates that stay within ecosystem regeneration and absorption limits.

Meeting current needs without reducing future generations’ ability to meet their needs.

Building societies where people can live healthy, fair, meaningful lives now and in the future.

Meeting needs now without reducing future generations’ ability to meet theirs.

Organising the economy so people’s needs are met over time without the system breaking down.

How raw materials and energy are turned into goods and services that people use.

Access to healthcare and education (also equality, safety, strong communities, culture).

Can the ecosystem recover within its natural limits after use/disturbance?

Environmental, social, and economic sustainability (all interconnected).

Do not use resources faster than they are replaced (also reduce pollution, protect biodiversity, allow recovery).

Strong: natural capital is irreplaceable; weak: technology can substitute for natural capital.

Trust, cooperation, and supportive connections between people that increase community resilience.

Biodiversity supports ecosystem functioning and resilience, helping systems recover from disturbance.

Prices can make essentials unaffordable for vulnerable groups, so support/regulation may be needed.

Trust and supportive connections that help communities function and cope with crises.

How raw materials and energy become goods and services people use.

Ask if ecosystems can recover naturally after resource use or disturbance. If not, it is unsustainable.

Unpaid care and domestic work supports health and social stability; stressed households weaken system sustainability.

Overfishing can exceed reproduction rates and cause fishery collapse.

Communities with high trust/support cope better and recover faster, improving resilience.

Not just growth; it is meeting basic needs reliably and fairly over time.

It can harm health, reduce livelihoods, increase inequality, and weaken community stability.

Environmental damage can reduce livelihoods and health, increasing inequality and harming economies.

Link environment → society → economy as a chain of dependence; damage in one spreads to others.

Healthy ecosystems are sustainable because resources are used within limits and materials can be recycled or absorbed naturally.

Right to a safe environment plus fair access to resources and fair distribution of harms/benefits.

High consumption in one region can cause extraction, pollution, and waste in another region.

Fair access to a safe environment and resources, and fair distribution of environmental benefits and harms.

Fairness: who benefits from resource use and who bears the costs/risks.

Profits and power are often concentrated elsewhere, while local communities bear pollution and health costs.

Who consumes, who profits, and who cleans up or suffers the damage?

Reinforcing loop: wealth → influence/opportunity → more wealth; harms concentrate in vulnerable groups.

Reinforcing feedback: wealth → more influence/opportunity → more wealth; vulnerable groups face higher exposure.

Lower labour costs and weaker environmental regulation can reduce costs, but increase local environmental damage.

When powerful businesses/individuals influence regulators so rules serve them rather than the public/environment.

When regulators act in the interests of powerful groups rather than environmental protection/public good.

High consumption creates textile waste; disposal/export can pollute land/water and burden low-income communities.

From individual and community to national and global scales.

Fair decision-making, fair outcomes, and shared responsibility for costs and benefits.

Define justice → explain unequal impacts/power → apply to a real context (trade/waste/pollution/climate).

It ignores inequality and environmental impacts, so it cannot show whether development is sustainable.

Improving lives today while ensuring future generations can also meet their needs, within environmental limits.

It does not show inequality, environmental damage, or well-being beyond income.

Measuring income inequality (lower value means more equal).

A measure of one specific aspect of development or sustainability (social, economic, or environmental).

No single indicator shows the full picture, so we combine social, economic, and environmental measures.

Life expectancy, education (years of schooling), and income per person.

0 to 1, where higher values indicate higher human development.

It adjusts for planetary pressures using CO2 emissions and material footprint, showing environmental cost of development.

Lower is usually better (pollution, emissions, extinction rate).

Global hectares (gha).

How much pressure human activities place on Earth’s systems.

The ability of ecosystems to regenerate resources and absorb wastes.

Land/sea area needed to provide resources used and absorb waste produced by a population (in global hectares).

Earth’s ability to regenerate resources and absorb waste.

Greenhouse gas emissions (often expressed as tonnes CO2 per person per year).

Embedded/virtual water used to produce goods and services you consume.

A biocapacity deficit: resource use is unsustainable (often relies on imports or overexploitation).

The date when humanity has used the resources Earth can regenerate in that year; after it we use future resources.

Collecting large-scale environmental data (biodiversity, climate, migration) with help from non-scientists.

17 UN goals adopted in 2015 to address global social and environmental challenges by 2030.

17 goals aiming for progress by 2030 (adopted in 2015).

They provide a common global framework and shared language for goals, targets, and indicators.

Goal = big aim, Target = specific objective, Indicator = data used to measure progress.

They provide measurable data to track progress and compare changes over time.

Nested dependencies: environment supports society; society supports the economy.

Environment supports society; society supports the economy (planet first).

They can be treated as silos rather than as connected systems.

Goal → Target → Indicator (indicator = data used to measure progress).

Countries differ in resources and global shocks (conflict, disasters, pandemics) can slow progress.

Use: shared global framework for action. Limitation: can oversimplify or be treated as silos with data gaps.

The same goals can reflect different local priorities and constraints across countries.

Data gaps make progress hard to measure, manage, and improve.

Lower-income countries may need funding/technology support, despite contributing least to some global problems.

State one clear use + one clear limitation and link to systems thinking (goals are connected).

An organism is one individual living thing. Example: one dog, one sunflower, or one bacterium.

No. A herd is many organisms. One elephant is one organism.

A species is a group of organisms that can breed together and produce fertile offspring.

Fertile offspring means the babies can grow up and have babies of their own.

Yes. They can breed and produce fertile puppies, so they are the same species.

No. They do not normally produce fertile offspring, so they are different species.

Classification helps scientists identify organisms and organise the huge variety of life.

If you know the group an organism belongs to, you can predict features. Example: if it is a mammal, it likely has hair and feeds milk to young.

A binomial name is a two-part scientific name: Genus then species. Example: Homo sapiens.

Write Genus with a capital letter and species in lower case, and put both in italics (or underline). Example: Homo sapiens.

A genus is a group of closely related species. Example: Canis includes dogs, wolves, and coyotes.

Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.

Some organisms have mixed features. Example: a platypus has fur like a mammal but lays eggs.

New evidence, especially DNA evidence, can show organisms are more or less related than we thought.

Can they breed and produce fertile offspring? If yes, they are the same species.

Homo sapiens.

It makes biodiversity and population data accurate, so scientists can make correct conclusions and conservation decisions.

Examples include leaf shape, flower colour, number of petals, or presence of thorns.

Examples include number of legs, wings, antennae, or body segments.

A dichotomous key is an identification tool that uses a series of paired choices to identify an organism.

It means “two choices”. At each step you must choose between two contrasting options.

1 Read both choices. 2 Pick the choice that matches your organism. 3 Follow to the next step until you reach a name.

It is quick and low cost, and it can be used in fieldwork without lab equipment.

If the organism is damaged, very young, or looks similar to other species, you may choose the wrong path and get the wrong identification.

A caterpillar is an immature stage and may not have the adult features the key expects, so it can be misidentified.

Always read both choices carefully before deciding.

A population is a group of the same species living in the same area at the same time. Example: wolves in one national park.

A species is all organisms of that type worldwide. A population is one local group of that species in one place.

Births and immigration increase population size. Deaths and emigration decrease population size.

An abiotic factor is a non-living condition. Examples: temperature, light, water, pH, or salinity.

A biotic factor is a living influence. Examples: predation, competition, disease, or availability of food.

Low water can limit plant populations because photosynthesis and growth slow down.

An increase in predators can reduce prey population size by increasing deaths.

A limiting factor is something that restricts the size, growth, or distribution of a population.

A tolerance curve shows how well a species survives as one abiotic factor changes, such as temperature.

The optimum is the best condition where the species does best (highest survival or growth).

The zone of stress is near the limits: the species may survive but grows or reproduces poorly.

A fish may grow best at about 22°C. It may survive from about 10°C to 35°C. Outside that range it may die.

Abiotic factors are non-living conditions. Biotic factors are living interactions.

A community is all the different species living together in the same place.

A community is all the populations of different species living and interacting in the same area.

A community is all the different species living together in the same area. For example, fish, plants, insects, and bacteria living in a pond.

An ecosystem is a community of organisms interacting with the abiotic environment.

An ecosystem is a community of living things and the non-living environment they interact with.

An ecosystem includes living organisms and the non-living environment. For example, a forest with trees, animals, soil, sunlight, and rain.

A community includes only living things. An ecosystem includes living things plus abiotic (non-living) factors such as water, soil, light, and temperature.

No. A community includes only living organisms.

All the animals and plants in a coral reef community, without including the water or sunlight.

Abiotic means non-living parts of the environment, such as sunlight, temperature, water, soil, and rocks.

Sunlight warming a lake, soil nutrients in a forest, or water temperature in the ocean.

Yes. An ecosystem includes non-living factors such as water, sunlight, soil, and temperature.

Trees in a forest, fish in a lake, grass in a field, or bacteria in soil.

Biotic means living components of an environment, such as plants, animals, fungi, and microorganisms.

Abiotic means non-living parts of the environment.

Biotic means living parts of the environment.

A population is a group of individuals of the same species living in the same area at the same time.

A habitat is where an organism lives. For example, a frog living in a pond or a bird nesting in a tree.

A habitat is the place where an organism lives.

A lake ecosystem where sunlight enters, rain adds water, and fish and nutrients move in and out.

Examples include predation, competition, parasitism, mutualism, or herbivory between different species in the same area.

Energy enters as sunlight, moves to plants, then to animals, and is lost as heat. For example, Sun → grass → rabbit → fox.

Ecosystem, because temperature and rainfall are abiotic (non-living) factors.

Because energy and matter can move in and out of the ecosystem.

A habitat is the place where an organism lives and finds the resources it needs to survive.

Dead plants and animals decompose and nutrients return to the soil, where plants reuse them.

Energy enters ecosystems mainly as sunlight.

No. Energy flows through ecosystems and is lost as heat.

A habitat is where a particular species lives. An ecosystem includes many species plus abiotic factors and their interactions.

Ecosystem, because it includes living organisms plus non-living factors like soil, air, and sunlight.

An open system is a system where both energy and matter can enter and leave across the system boundary.

Yes. Matter such as nutrients and water is recycled.

Because energy (sunlight, heat) and matter (water, nutrients, organisms) move in and out of the ecosystem.

Scale is the size or level at which a system is studied, such as a pond, a forest, a biome, or the whole planet.

At small scale you see local interactions. At large scale you see wider patterns and flows across regions.

Community = only living things (different populations of different species in the same area).

Ecosystem = community + abiotic environment interacting together.

A disturbance is an event that disrupts ecosystem structure or function and changes populations or resource flows.

Redundancy is when multiple species perform similar roles, so ecosystem functions continue if one species is lost.

A storage is a place where energy or matter is held for a period of time within a system.

Sustainability means using resources at a rate they can be replaced, so the ecosystem can keep going in the future.

Sustainability is long-term continued functioning; resilience is ability to recover after disturbance.

Sustainability is using resources at a rate that allows them to be replaced so the system can continue long term.

Low biodiversity and small storages reduce the ability to recover after disturbance.

Natural: wildfire, storm, flood, drought. Human: deforestation, pollution, overfishing, oil spill.

Sustainable fishing means catching only as many fish as can be replaced by reproduction each year.

Resilience is the ability of an ecosystem to resist disturbance and recover after it.

Large storages buffer change by releasing resources slowly, reducing extremes after disturbance.

If one species declines, others can replace its role, reducing the chance of function collapse.

With little buffering and few backups, disturbances push the system past thresholds more easily.

High biodiversity, large storages, and redundancy (multiple species doing similar roles).

Bees, flies, butterflies and beetles can all pollinate; if one declines, others may still pollinate many plants.

Disturbance causes change; resilience determines recovery; recovery shows how fast the system returns towards its previous state.

Changes are more extreme because there is little buffering; recovery is slower and collapse risk is higher.

Coral reefs under repeated heat stress can shift to algal-dominated states and recover slowly or not at all.

Forests and soils store carbon in biomass and organic matter, reducing rapid carbon release to the atmosphere.

More biodiversity creates more pathways and backup species, so ecosystem functions continue even if one species declines.

Cutting down forest faster than it can regrow is unsustainable because the resource gets depleted.

Wetlands and lakes store water, reducing floods and providing water during dry periods.

Resilience is how well an ecosystem can recover after a disturbance and keep functioning.

Resource use does not exceed renewal, so ecosystem functions and services continue over time.

After a disturbance, a resilient ecosystem recovers faster and is more likely to maintain key functions and services.

High biodiversity often increases redundancy because more species means more chances that roles overlap.

Habitat destruction, pollution, overexploitation, and invasive species can reduce resilience by simplifying the ecosystem.

Redundancy.

Maintaining storages prevents rapid depletion, keeping ecosystem services available for the long term.

No. Redundancy protects function, but losing species still reduces biodiversity and can weaken the system over time.

A tipping point is a threshold where small extra change causes a large shift to a new state that may be hard to reverse.

Increase biodiversity, protect or restore storages (forests, wetlands, soils), and reduce chronic human pressures.

Sustainability is long-term continued functioning; resilience is short-term ability to recover after disturbance.

Resilience.

After a fire, plants regrow and animals return over time. The ecosystem returns to a working state.

A disturbance is an event that disrupts an ecosystem. Natural: hurricane or fire. Human: oil spill or deforestation.

More species means more “backup” organisms. If one species declines, others can still keep ecosystem jobs going.

If bees decline, other pollinators like butterflies, flies, and beetles can still pollinate many plants.

A storage is a place where a resource is kept in an ecosystem, like water in a wetland or carbon in a forest.

Wetlands store extra water during heavy rain, so less water rushes downstream at once.

Forests store carbon in tree biomass and in soils, which slows how fast carbon enters the atmosphere.

Redundancy means several species do the same job, so the system still works if one species is lost.

Dead leaves can be broken down by fungi, bacteria, earthworms, and beetles. If one is missing, others still decompose.

Low biodiversity and small storages reduce resilience. Heavy human pressure (pollution, habitat loss) also lowers resilience.

A tipping point is a point where a small extra change causes a big shift, and the ecosystem may not return to the old state.

Biodiversity gives more species. Redundancy gives backup species doing the same job. Storages provide reserves (water/carbon/nutrients). Together they help the ecosystem recover after disturbance.

Keystone species.

A trophic cascade is a chain reaction of population changes through a food web after a species is added or removed.

An ecosystem engineer is a species that modifies the physical environment and creates or maintains habitats for other species.

A keystone species is a species with a disproportionately large effect on ecosystem structure or function relative to its abundance.

Trophic cascade.

Because habitat changes can affect many other populations, increasing biodiversity and altering community structure.

They help maintain food-web balance by controlling populations or supporting key interactions, which keeps biodiversity higher.

Herbivore numbers can increase, plant biomass can decrease, and biodiversity may fall as habitats become simplified.

If removing one species causes major changes across many other species (food web shifts, biodiversity drops), it is likely a keystone species.

They control dominant populations and maintain habitat/food-web structure, allowing more species to coexist.

Food-web links weaken and key functions fail, so the ecosystem is less able to recover after disturbance.

Beavers build dams that create wetlands, increasing habitat for fish, birds, insects and plants.

A top predator can prevent one prey species from becoming too abundant, protecting plant communities and keeping habitats diverse.

They can change water flow, soil moisture, light levels or sedimentation, which reshapes the habitat.

State the keystone has a large effect, then describe knock-on impacts on other populations and biodiversity/food-web stability.

Step 1: remove keystone → immediate population change. Step 2: knock-on effects spread → community structure and biodiversity change.

Protecting a keystone species can protect many other species and maintain ecosystem services by keeping the system stable.

Keystone species increase resilience by keeping key ecosystem functions and food-web relationships stable after disturbance.

Keystone species maintain stability, supporting faster recovery after disturbance.

Look for “creates habitat”, “builds”, “digs”, “modifies environment”, or “changes water flow/soil structure”.

True. It includes role, resource use and interactions, not just location.

A niche is the role of a species in an ecosystem, including how it uses resources and interacts with other species.

Resources are things organisms need to survive, such as food, water, light, space or shelter.

True. Habitat is the place or physical environment where a species lives.

Niche overlap is when two species use the same resources in the same way and place/time.

Habitat is where a species lives; niche is how it lives (its role and resource use).

Food type and feeding method; activity time; abiotic tolerances; interactions (predator, competitor, pollinator).

If resources are limited, both species demand the same resource, reducing growth, survival or reproduction for at least one.

Competition (often caused by niche overlap).

One species may be outcompeted and decline locally, reducing biodiversity.

By resource partitioning: using different food types, locations, or activity times (different niches).

State feeding role, key interactions, and the abiotic conditions needed for survival.

Their niches overlap, so competition is likely unless resources are abundant or they separate by time/place.

More available niches allow species to specialise and coexist with less direct competition.

More niches usually allow more species to coexist, increasing biodiversity.

Carrying capacity is the maximum population size an environment can support sustainably over time.

Predation is an interaction where a predator hunts, kills and eats a prey organism.

Because counting every individual is usually impossible; sampling estimates population size from a representative subset.

Births, deaths, immigration and emigration.

The maximum population size the environment can support sustainably over time.

Quadrats are used to sample non-mobile organisms (mainly plants) to estimate density, frequency or percentage cover.

Prey peaks first; predator peaks later due to time lag.

The prey population peaks first; the predator peak usually lags behind.

A limiting factor is an environmental factor that restricts population growth, size or distribution.

Competition is the demand by two or more organisms for the same limited resource.

Negative feedback is a process that reduces change and returns a population towards balance (for example predators increase when prey increase).

Mutualism benefits both species; parasitism benefits the parasite while harming the host.

A transect is used to show how species or abundance change across an environmental gradient (for example shore to land).

Population growth is limited by the factor in shortest supply, even if other resources are abundant.

Liebig’s Law of the minimum.

N = (n1 × n2) / m, where n1 is marked first, n2 is caught second, and m is recaptured marked.

Non-mobile organisms, mainly plants (and very slow animals).

A time lag is a delay between a change in one population and the response of another population.

Pathogens spread faster when population density is high because individuals contact each other more often.

Density-dependent: competition, disease, predation. Density-independent: drought, flood, fire, storm.

The population is closed (no immigration/emigration) and marks are not lost and do not affect survival or capture.

N = (n1 × n2) / m.

Describe the pattern (rise, fall, oscillation, time lag) before explaining the cause.

Name the interaction and state who benefits and who is harmed (or how resources are affected).

Identify the lowest bar and state it is the limiting factor because it caps population size.

Herbivores eat producers, carnivores eat animals, and omnivores eat both producers and animals.

Sunlight captured by producers through photosynthesis.

A food chain is a linear sequence showing how energy is transferred from one organism to another through feeding.

A producer is an organism that makes its own organic food from inorganic substances using an energy source, usually sunlight.

Decomposers break down dead organic matter and waste, releasing mineral nutrients back into the environment.

A scavenger is a consumer that feeds on dead animals and helps begin nutrient recycling.

A trophic level is the feeding position an organism occupies in a food chain.

Biomass is the mass of living material in organisms (energy stored in organic matter).

Nutrients are reused when decomposers release them for producers, but energy is dissipated as heat at each transfer and cannot be recycled.

A consumer is an organism that gains energy and nutrients by feeding on other organisms.

Photosynthesis converts light energy into chemical energy stored in glucose (biomass).

Mineral nutrients are inorganic nutrients such as nitrates and phosphates that plants can absorb to build biomass.

Both break down dead organic matter; detritivores digest inside the body, while saprotrophs digest outside using enzymes and then absorb nutrients.

Detritivores ingest dead material and digest it inside the body; saprotrophs digest outside the body using enzymes and then absorb nutrients.

Trophic level 2 (primary consumer).

Scavenger.

The arrows show the direction of energy flow, from the organism eaten to the organism that eats it.

Energy enters as sunlight, is transformed into biomass, and is lost as heat at each transfer, so it cannot be recycled back down the chain.

Energy flows one-way through food chains, and nutrients are recycled when decomposers release them back to soil or water for producers.

From the food source to the consumer (direction of energy flow).

Trophic level 2 is the primary consumer level (herbivores that feed on producers).

They are the main entry point of energy into ecosystems and form the base of food chains and food webs.

Producers (TL1) → primary consumers (TL2) → secondary consumers (TL3) → tertiary consumers/top predators (TL4+).

Consumers transfer energy through food chains and help control population sizes; many also recycle nutrients by feeding on dead matter and waste.

They prevent dead matter build-up and recycle nutrients so producers can grow and make new biomass.

A food web is a network of interconnected food chains.

A food web is a network of interconnected food chains showing multiple feeding relationships in an ecosystem.

Energy transfer is inefficient; much energy is lost as heat and waste at each step, leaving too little to support many higher levels.

Alternative feeding pathways allow organisms to switch prey if one species declines, helping maintain energy flow.

Most organisms feed on more than one species and have multiple predators, so energy can move through several pathways.

Available energy decreases at each trophic transfer, so higher trophic levels have less energy and biomass.

If one prey species declines, consumers may switch to alternative prey, allowing energy flow to continue.

There is less energy and biomass available at higher trophic levels, so fewer large consumers can be supported and they often require large territories.

Energy decreases at each trophic transfer due to inefficient transfer and heat loss, limiting the number of levels.

The direction of energy flow from the organism eaten to the consumer.

Energy transfers are inefficient with heat loss, and less energy/biomass is available at higher trophic levels to support additional levels.

Arrows represent the direction of energy flow from the organism eaten to the consumer.

Food webs may not show population sizes, strength of interactions, or seasonal changes, so they simplify real ecosystems.

Often 4 to 5 trophic levels from producers to top predators.

Biomass and numbers generally decrease at higher trophic levels because less energy is available to build new biomass.

Energy does not cycle; it flows through ecosystems and is lost as heat.

Energy cannot be created or destroyed; it can only be transformed from one form to another.

An open system exchanges both energy and matter with its surroundings.

Main input is sunlight; main output is heat.

Every energy transfer is inefficient; some energy is dissipated as heat, so less usable energy remains.

Energy cannot be created or destroyed, only transformed.

Energy flows through ecosystems and is eventually lost as heat, so it cannot be recycled.

Energy is used for respiration, movement and maintenance and much is lost as heat, so only a small proportion becomes new biomass.

Energy transfers are inefficient and some energy becomes heat.

Sunlight is captured by producers, transferred by feeding through consumers, and leaves the system as heat at each step.

An open system exchanges energy and matter with its surroundings.

Use “energy is transformed” for the first law and “transfers are inefficient with heat loss” for the second law.

Energy is lost as heat at each transfer so less usable energy remains to build biomass at higher levels.

Fewer energy transfers means less heat loss, so more of the original energy supports food production.

Heat loss at each transfer reduces usable energy at higher trophic levels, limiting the number of trophic levels supported.

Photosynthesis is the conversion of light energy into chemical energy stored in glucose.

Cellular respiration is the process that releases energy from glucose in cells, usually using oxygen.

Energy is lost as heat from respiration and in waste/uneaten material (faeces, bones, plant fibre).

Energy efficiency is the percentage of energy transferred from one trophic level to the next.

Photosynthesis.

Incomplete consumption is when not all parts of an organism are eaten, so energy in those parts is not transferred.

Some energy is transferred to ATP for life processes and a significant amount is released as heat.

On average, about 10% of energy at one trophic level becomes biomass available to the next level.

Inputs: carbon dioxide and water. Outputs: glucose and oxygen.

Cellular respiration.

Heat loss from respiration and losses in waste/uneaten material.

Photosynthesis occurs in chloroplasts.

Yes. Plants respire continuously to release energy for life processes.

Inefficient digestion is when not all ingested food is absorbed; energy leaves the body as faeces.

Energy is used for respiration, movement and maintenance and is lost as heat and waste rather than becoming new biomass.

Energy leaves mainly as heat released during respiration.

About 10% (order-of-magnitude).

It traps solar energy and stores it as chemical energy in biomass that can be transferred through food chains.

Low transfer efficiency leaves too little energy at higher trophic levels to support many levels, so chains are short.

Organisms use energy for metabolism and release much of it as heat, so less becomes new biomass available to the next level.

Less energy becomes new biomass at each transfer because most is lost as heat and waste, so biomass decreases at higher levels.

Fewer trophic transfers means less energy is lost as heat before reaching humans.

Because only a small proportion of energy becomes new biomass at each trophic transfer; most is lost as heat and waste.

Respiration releases heat, showing that energy transfers are inefficient and usable energy decreases.

Energy enters mainly as sunlight and is captured by producers via photosynthesis.

Biomass is the total dry mass of living organisms in a given area, representing stored chemical energy at a trophic level.

A pyramid of energy shows energy flow per unit area per unit time at each trophic level.

A pyramid of biomass shows the total dry mass of organisms at each trophic level.

A pyramid of numbers shows the number of individual organisms at each trophic level.

Ecological pyramids are diagrams that represent trophic levels using numbers, biomass, or energy, with producers at the base.

One large producer, such as a tree, can support many consumers like insects, making the level above wider.

Water content varies widely and does not contain usable chemical energy, so drying allows fair comparison of stored energy between organisms and trophic levels.

Energy is lost as heat at every trophic transfer, so less energy is available at higher levels.

Producers like phytoplankton have low standing biomass but reproduce rapidly, supporting larger consumer biomass.

Producers capture incoming energy, usually sunlight, and convert it into biomass that supports all higher trophic levels.

They show that numbers, biomass, and available energy usually decrease at higher trophic levels.

Productivity is the rate at which new biomass is produced in an ecosystem.

Productivity measures a rate: how quickly new biomass is produced.

Productivity is the rate at which new biomass is produced in an ecosystem, usually by producers through photosynthesis.

Net productivity equals gross productivity minus respiration: NP = GP − R.

Gross productivity is total energy captured; net productivity is what remains after respiration losses.

Gross productivity is the total biomass or energy gained by producers through photosynthesis before losses to respiration.

Net productivity is the biomass or energy remaining after respiration losses, available for growth, reproduction, and transfer to the next trophic level.

NP = GP − R.

Net productivity equals gross productivity minus respiration: NP = GP − R.

Respiration represents energy used by organisms for metabolism and life processes, released mainly as heat.

Energy is lost as heat through respiration at each transfer, so less energy remains to form new biomass at higher levels.

Net productivity is available to consumers because it is the biomass remaining after producers use energy for respiration.

Producers such as plants and algae are responsible for most productivity because they convert sunlight into chemical energy through photosynthesis.

Productivity measures how quickly new biomass is produced over time, not the total amount present.

Energy used in respiration is released as heat to the environment and cannot be passed to the next trophic level.

Net productivity is transferred because it represents biomass remaining after respiration.

Energy is lost at each trophic transfer, so progressively less energy is available to support higher trophic levels.

More energy is used for life processes and released as heat, leaving less energy available to form new biomass.

High light availability, suitable temperature, and sufficient nutrients can all increase productivity.

Human population growth and high resource consumption, combined with technology and global trade, allow rapid and large-scale environmental change.

It removes producers and habitat, reducing energy entry into the food web and lowering the number of consumers the system can support.

Human activities often change ecosystems rapidly and commonly reduce biodiversity.

Humans can change environments over years using machinery and infrastructure, act across regions via global supply chains, and cause damage that takes decades or centuries to recover.

Removing organisms faster than they can be replaced breaks feeding links, reduces prey availability, and can trigger trophic cascades.

Link the activity to the ecosystem change, then state the effect on biodiversity and/or energy flow in food webs.

By reducing producer biomass and habitat, less energy enters food webs and fewer consumers can be supported.

Pollution can reduce survival, growth, or reproduction of organisms, so less usable energy is passed to higher trophic levels.

Biodiversity is the variety of life, including diversity of species, habitats, and genetic diversity within species.

Direct impacts remove organisms or energy entry (e.g., habitat loss, overharvesting, pollution); indirect impacts change conditions or interactions (e.g., invasive species, climate change).

Human activities often reduce biodiversity and simplify food webs, which lowers resilience and makes ecosystems less able to recover from disturbances.

Removing key species can alter population sizes of other trophic levels and trigger trophic cascades, changing food web structure.

Global trade can introduce invasive species and spread pollutants rapidly, altering species interactions and energy flow in food webs.

Habitat destruction, overexploitation, and pollution.

Toxins can bioaccumulate in organisms and biomagnify up food chains, increasing exposure and health risk for humans as top consumers.

Habitat fragmentation is when one large habitat is broken into smaller, isolated patches. The habitat still exists, but populations become separated.

Habitat destruction is the removal or severe damage of a habitat so it can no longer support its original species.

Destruction removes the habitat completely or makes it unusable. Fragmentation splits habitat into smaller, isolated patches.

Fragmentation creates smaller, isolated populations, increasing extinction risk and making it harder to find mates.

Examples include deforestation for agriculture, draining wetlands for development, and clearing grassland for crops.

Edges are often hotter and windier (and can be drier), and may have more predators or invasive species.

It removes producers and habitat, so less energy enters the food web and fewer consumers can be supported, reducing stability.

Smaller, isolated populations have fewer mates, lower gene flow, and are more vulnerable to random events.

Isolation reduces gene flow. Smaller populations are more likely to inbreed, lowering genetic diversity and adaptability.

It reduces species richness and can cause local extinctions as populations lose space, food, and shelter.

Use buffer zones or increase reserve size to reduce the proportion of habitat near edges.

Edge effects are changes at habitat boundaries, such as higher temperature and wind, lower humidity, and more predators or invasive species.

Wildlife corridors connect isolated patches, allowing movement, gene flow, and breeding between populations.

Amazon rainforest cleared for cattle ranching removes habitat for many species and reduces ecosystem resilience.

Fragmentation reduces gene flow and increases edge effects, which lowers population viability and biodiversity.

Overfishing can cause stock collapse and alter food webs, e.g. Atlantic cod declined dramatically due to heavy fishing.

Overexploitation is using a natural resource faster than it can be replaced by reproduction or regrowth.

Overexploitation means unsustainable use: take more than can be replaced.

Poaching often removes breeding adults, so birth rates fall and populations decline quickly.

Overfishing, poaching, and logging of old-growth forests are common examples.

If removal exceeds reproduction, population size declines. Once numbers drop too low, recovery becomes difficult.

Fewer individuals and species remain, so the ecosystem has less functional diversity and recovers less well after disturbance.

Removing organisms breaks feeding links, reduces energy transfer, and can trigger trophic cascades.

Removing top predators or key species can cause trophic cascades and change community structure.

Declining population size or catch per unit effort (more effort needed to get the same catch).

Old-growth forests may be cut faster than they regrow, reducing habitat and biodiversity for decades.

Use quotas or regulated harvesting so removal stays below replacement rate.

Overexploitation removes organisms faster than they reproduce, reducing population size and disrupting energy transfer in food webs.

Overexploitation reduces population sizes, which can reduce species richness and lower ecosystem resilience.

Sustainable management such as quotas, seasonal bans, protected areas, or selective gear reduces removal rates.

Pollution is the introduction of harmful substances or harmful energy into the environment.