📌 Definition Table

Term	Definition
Neuroimaging	The use of technology to view brain structure and activity non-invasively.
MRI (Magnetic Resonance Imaging)	Produces 3-D images of brain structure using magnetic fields and radio waves.
fMRI (Functional MRI)	Measures blood-oxygen levels (BOLD signal) to show brain activity during cognitive tasks.
PET (Positron Emission Tomography)	Uses a radioactive tracer to measure brain metabolism and activity.
EEG (Electroencephalogram)	Measures electrical activity across the brain’s surface using electrodes.
CT (Computed Tomography)	Combines X-ray images to show cross-sectional brain structure.
Spatial Resolution	The ability of a scan to identify precise brain locations.
Temporal Resolution	The accuracy of a scan in detecting timing of brain activity.
Triangulation	Using multiple techniques to validate findings and strengthen conclusions.

📖 Introduction

Studying the brain is fundamental to understanding the biological basis of behaviour.
Modern neuroscience employs various techniques that allow researchers to link brain structure and activity to psychological processes such as memory, emotion, and decision-making.

Each method varies in resolution, invasiveness, cost, and ethical implications, and together they help provide converging evidence for theories such as localization of function and neuroplasticity.

🧩 Overview of Major Techniques

MRI (Magnetic Resonance Imaging)

• Uses strong magnetic fields and radio waves to produce high-resolution images of brain anatomy.
  
• Provides structural data — excellent spatial resolution, but no information on activity.
  
• Safe and non-invasive (no radiation).
  
• Commonly used in localization research (e.g., Maguire et al. 2000).
  

fMRI (Functional Magnetic Resonance Imaging)

• Builds on MRI technology by measuring changes in blood oxygenation (BOLD signal) as an indirect indicator of neural activity.
  
• Excellent spatial resolution, moderate temporal resolution.
  
• Used in studies examining memory, attention, and emotion (e.g., Antonova et al. 2011).
  

PET (Positron Emission Tomography)

• Participants ingest a radioactive glucose tracer.
  
• Scanner detects where glucose is metabolized — indicates active brain areas.
  
• Good for comparing brain activity across conditions; lower spatial and temporal resolution than fMRI.
  
• Invasive and expensive — used less often today.
  

EEG (Electroencephalogram)

• Electrodes placed on the scalp measure electrical activity generated by neuron firing.
  
• Excellent temporal resolution, poor spatial resolution.
  
• Useful for sleep, attention, and reaction-time studies.
  

CT (Computed Tomography)

• Uses X-rays to form cross-sectional images of brain structure.
  
• Useful for detecting brain injury or abnormalities but provides limited detail about soft tissue.
  

🧠 Application in IB Studies

Maguire et al. (2000) – MRI

• Aim: Investigate whether taxi drivers’ spatial navigation experience altered brain structure.
  
• Method: MRI scans compared London taxi drivers to control participants.
  
• Findings: Posterior hippocampi were significantly larger in taxi drivers; correlated with years of experience.
  
• Conclusion: Spatial memory and navigation are localized to the hippocampus.
  
• Demonstrates: Localization + Structural imaging (MRI).
  

Antonova et al. (2011) – fMRI

• Aim: Examine acetylcholine’s role in memory.
  
• Method: Participants injected with scopolamine or placebo; performed spatial memory task in fMRI scanner.
  
• Findings: Scopolamine reduced hippocampal activation.
  
• Conclusion: Acetylcholine modulates hippocampal activity in memory encoding.
  
• Demonstrates: Neurotransmission + Functional imaging (fMRI).
  

Rosenzweig, Bennett & Diamond (1972) – Animal Research

• Rats placed in enriched vs. deprived environments.
  
• Post-mortem analysis showed thicker cortices in enriched group.
  
• Though not imaging, serves as historical evidence for neuroplasticity prior to modern scanning.
  

⚖️ Evaluation of Techniques

Technique	Strengths	Limitations	Ethical Issues
MRI	High spatial resolution, non-invasive, reliable structural data	Expensive, movement can distort image, cannot infer causation	Minimal — requires consent and screening for metal implants
fMRI	Maps active brain areas in real time, no radiation	Poor temporal resolution, indirect measure of neural activity	Claustrophobia, motion restriction
PET	Measures metabolic activity, useful in clinical diagnosis	Invasive (radioactive tracer), expensive	Radiation exposure — limited use in minors
EEG	High temporal precision, inexpensive, non-invasive	Poor spatial localization	None significant beyond consent
CT	Detects structural damage quickly	Radiation exposure, low soft-tissue detail	Radiation — caution required

🧩 Theoretical Links

• Supports Localization of Function — by showing which areas activate during specific behaviors.
  
• Enhances understanding of Neuroplasticity — longitudinal studies show structural changes over time.
  
• Encourages Methodological Triangulation — using multiple methods strengthens validity of findings.
  

💡 TOK ConnectionKnowledge Question: How reliable is indirect evidence (e.g., fMRI signals) in representing mental processes? Perspective: Cognitive processes like memory are inferred from physical brain activity — raises epistemological questions about inference and correlation. Link: Encourages discussion on correlation vs. causation in knowledge claims.

🧪 IA / Internal Assessment ConnectionBrain imaging techniques inspire IA experiments on cognitive processes (e.g., memory, attention). Students can simulate design considerations — independent variables might mimic cognitive load or task complexity. Important to discuss ecological validity and ethical procedures modeled after real imaging research.

🌍 Real-World ConnectionMRI and fMRI are used in diagnosing Alzheimer’s, brain tumors, and traumatic injuries. PET scans are applied in neurological disorders like Parkinson’s and schizophrenia. EEG informs medical monitoring for epilepsy and sleep disorders. Understanding neuroplasticity informs rehabilitation after stroke or brain trauma.

❤️ CAS / Community LinksCAS project ideas: Creating an educational awareness campaign on mental health and brain imaging. Partnering with local clinics to explain neuroimaging’s ethical side. Designing workshops illustrating how neuroplasticity can support learning and recovery.

🧠 Examiner TipsClearly differentiate structural vs. functional techniques in responses. Always mention strengths, limitations, and ethics. Avoid overclaiming causation — imaging shows correlation, not direct proof of behavior. In Paper 1 SAQs, refer to specific studies (Maguire, Antonova). Use concise definitions: “Localization refers to specific brain areas controlling specific behaviors.”

📘 Definition Table

Term	Definition
Neurotransmitter	A chemical messenger that transmits signals across the synaptic gap from one neuron to another.
Synapse	The junction between two neurons where neurotransmission occurs.
Action Potential	An electrical impulse that travels down the neuron, triggering neurotransmitter release.
Excitatory Neurotransmitter	Increases the likelihood that the receiving neuron will fire an action potential (e.g., glutamate).
Inhibitory Neurotransmitter	Decreases the likelihood that the receiving neuron will fire (e.g., GABA).
Reuptake	The reabsorption of neurotransmitters by the presynaptic neuron after signal transmission.
Agonist	A chemical or drug that enhances the effect of a neurotransmitter.
Antagonist	A chemical or drug that blocks or reduces the effect of a neurotransmitter.
Serotonin	A neurotransmitter involved in mood regulation, sleep, and arousal.
Dopamine	A neurotransmitter linked with reward, motivation, and movement.
Acetylcholine (ACh)	A neurotransmitter involved in muscle contraction, learning, and memory.

📌 Introduction

Neurotransmission is the process of communication between neurons through chemical messengers known as neurotransmitters.
When an electrical impulse reaches the end of an axon (the presynaptic terminal), it triggers the release of neurotransmitters into the synaptic cleft, where they bind to receptors on the postsynaptic neuron.

This process allows for rapid, targeted communication, influencing perception, emotion, cognition, and behavior.
Different neurotransmitters have distinct roles: dopamine in reward and motivation, serotonin in emotion and sleep, acetylcholine in memory, and GABA in anxiety regulation.

Understanding neurotransmission provides a biological explanation for behavior and insight into treatments for psychological disorders.

⚙️ Mechanism of Neurotransmission

1. Action Potential Generation:
   
   • An electrical signal travels down the axon due to depolarization.
     
2. Vesicle Release:
   
   • Neurotransmitters stored in vesicles are released into the synaptic cleft.
     
3. Receptor Binding:
   
   • Neurotransmitters bind to receptor sites on the postsynaptic membrane.
     
4. Signal Transmission:
   
   • Excitatory neurotransmitters (e.g., glutamate) increase neuron firing; inhibitory neurotransmitters (e.g., GABA) reduce it.
     
5. Reuptake/Degradation:
   
   • Enzymes break down neurotransmitters or they are reabsorbed for reuse (e.g., serotonin reuptake).
     

🧪 Key Studies

1. Rogers and Kesner (2003)

• Aim: To determine the role of acetylcholine (ACh) in memory formation.
  
• Method: Rats were trained to run a maze to find food. They were then injected with either scopolamine (ACh blocker) or saline (control).
  
• Findings: The scopolamine group took longer and made more mistakes in maze learning.
  
• Conclusion: ACh plays a key role in the formation of spatial memories.
  

2. Antonova et al. (2011)

• Aim: To investigate the effect of blocking acetylcholine receptors on spatial memory in humans.
  
• Method: Double-blind, repeated measures fMRI study with 20 healthy males. Each participant received either scopolamine (ACh antagonist) or a placebo before performing a spatial memory task in an fMRI scanner.
  
• Findings: Participants under scopolamine showed reduced hippocampal activation.
  
• Conclusion: Acetylcholine is essential for encoding spatial memories; fMRI provides neural evidence for this mechanism.
  

3. Fisher, Aron & Brown (2005)

• Aim: To examine dopamine’s role in romantic love.
  
• Method: fMRI scans of individuals “intensely in love” shown photos of their partners versus neutral acquaintances.
  
• Findings: Activation in dopamine-rich areas (ventral tegmental area, caudate nucleus) associated with reward and motivation.
  
• Conclusion: Romantic love involves dopamine pathways similar to addiction and reward circuits.
  

4. Crockett et al. (2010)

• Aim: To investigate the role of serotonin in prosocial behavior.
  
• Method: Participants were given citalopram (a selective serotonin reuptake inhibitor, SSRI) or a placebo. They completed moral dilemmas involving harm to others.
  
• Findings: Participants on citalopram were less likely to inflict harm, showing increased prosocial responses.
  
• Conclusion: Increased serotonin levels promote prosocial and cooperative behavior by modulating emotional processing.
  

5. Martinez & Kesner (1991)

• Aim: To study the role of acetylcholine in memory retrieval.
  
• Method: Rats injected with scopolamine (blocks ACh), physostigmine (enhances ACh), or saline before running a maze.
  
• Findings: Scopolamine impaired memory; physostigmine improved it.
  
• Conclusion: ACh directly facilitates memory encoding and retrieval—critical for learning processes.
  

🧩 Evaluation

Strengths

• Triangulation of evidence: Both animal and human studies show consistent findings.
  
• Use of fMRI and controlled lab conditions enhances reliability.
  
• Demonstrates biological basis of learning, emotion, and memory.
  

Limitations

• Reductionist: Focuses narrowly on neurotransmitters, ignoring psychological and social influences.
  
• Ethical issues in animal research (injections, induced stress).
  
• Drug studies may have side effects that confound results.
  

Ethical Considerations

• Human studies (Antonova, Crockett) used double-blind designs and informed consent.
  
• Animal studies (Rogers & Kesner) minimized suffering but must justify the use of invasive techniques.
  

🔍 Theory of Knowledge (TOK) Connection

Knowledge Question: How can we know that neurotransmitters cause behavior rather than merely correlate with it?
This highlights the epistemological challenge of correlation vs. causation in biological psychology.
TOK links include debates on determinism vs. free will, and the extent to which chemical processes define emotions like love or morality.

❤️ CAS LinkStudents could create awareness campaigns or workshops about how sleep, diet, and stress affect brain chemistry. Projects promoting mental health can emphasize serotonin balance through mindfulness, exercise, and positive lifestyle habits.

🧪 IA LinkA possible IA could investigate the effect of caffeine or music on memory recall, connecting cognitive performance to neurotransmitter activity (dopamine and norepinephrine pathways). The IA should discuss ethical considerations and avoid biological interventions.

🌍 Real-World ConnectionDepression treatment: SSRIs increase serotonin to regulate mood. Parkinson’s disease: Linked to dopamine deficits; treated with L-DOPA. Addiction research: Overactivation of dopamine pathways underlies dependency. Alzheimer’s disease: Linked to loss of acetylcholine-producing neurons. These findings underscore how understanding neurotransmitters translates into medical and psychological interventions that improve quality of life.

🧠 Examiner TipIn Paper 1 SAQs:Define neurotransmission clearly. Explain how one neurotransmitter affects behavior (ACh or serotonin are most common). Support with one study (Rogers & Kesner or Antonova). Include one evaluation point or ethical issue for top marks. Avoid describing brain structure changes — those belong under neuroplasticity.

📘 Definition Table

Term	Definition
Neuroplasticity	The brain’s ability to reorganize itself by forming new neural connections throughout life.
Synaptic Plasticity	The process by which synaptic connections strengthen or weaken over time in response to increases or decreases in activity.
Cortical Remapping	When functions previously performed by a damaged area of the brain are taken over by undamaged regions.
Long-Term Potentiation (LTP)	A long-lasting increase in synaptic strength resulting from repeated stimulation.
Dendritic Branching	Growth of new dendritic spines that create additional synaptic connections.
Neurogenesis	The formation of new neurons, especially in the hippocampus and olfactory bulb.
Experience-Dependent Plasticity	Brain structural and functional changes in response to environmental demands and learning.

📌 Introduction

Neuroplasticity describes the dynamic nature of the brain—its capacity to adapt structurally and functionally in response to learning, environmental changes, and injury. Once thought to be fixed after childhood, modern neuroscience has shown that plasticity persists throughout life, enabling recovery from trauma and supporting lifelong learning.

It involves both functional plasticity (the brain’s ability to move functions from damaged to undamaged areas) and structural plasticity (the brain’s ability to change its physical structure through new connections and dendritic growth).

Plasticity is influenced by environmental enrichment, learning, stress, and trauma, and is mediated by neurochemical and molecular changes like LTP and neurotrophin release (e.g., BDNF).

🧩 Mechanisms of Neuroplasticity

Mechanism	Description	Biological Process
LTP (Long-Term Potentiation)	Repeated activation of synapses strengthens synaptic transmission.	Increased neurotransmitter release and receptor sensitivity.
Dendritic Branching	Formation of new dendritic spines, increasing synaptic networks.	Promotes information storage and learning.
Cortical Remapping	Brain reallocates functional areas after injury or experience.	Neighboring regions take over lost functions.
Environmental Enrichment	Stimulating surroundings promote neuron growth.	Increased neurogenesis and synaptic density.
Neurogenesis	Growth of new neurons, primarily in hippocampus.	Linked to memory, learning, and mood regulation.

🧠 Key Studies

1. Maguire et al. (2000)

• Aim: To investigate whether structural changes occur in the hippocampus of London taxi drivers in response to spatial navigation experience.
  
• Method: MRI scans of 16 male London taxi drivers compared with 50 matched controls.
  
• Findings: Increased grey matter volume in the posterior hippocampus of taxi drivers, positively correlated with years of experience.
  
• Conclusion: Experience (navigation) causes structural plasticity; the hippocampus adapts to spatial demands.
  

2. Draganski et al. (2004)

• Aim: To investigate whether learning a new skill (juggling) induces structural changes in the brain.
  
• Method: MRI scans before, during, and after participants learned to juggle over three months.
  
• Findings: Increased grey matter in mid-temporal areas involved in visual motion; decreases after training stopped.
  
• Conclusion: Learning new skills leads to temporary structural brain changes—evidence of experience-dependent plasticity.
  

3. Rosenzweig, Bennett & Diamond (1972)

• Aim: To study the effects of environmental enrichment and deprivation on neuroplasticity in rats.
  
• Method: Rats placed in either enriched (toys, social interaction) or deprived environments.
  
• Findings: Enriched rats developed thicker cerebral cortices and higher acetylcholine activity.
• Conclusion: Enriched environments enhance brain growth and synaptic complexity—environment affects neural development.
  
  
  

4. Merzenich et al. (1984)

• Aim: To examine cortical remapping in the somatosensory cortex after sensory deprivation in monkeys.
  
• Method: Fingers of monkeys were amputated; cortical responses were measured using microelectrodes.
  
• Findings: Adjacent cortical areas took over the region previously responsible for the amputated finger.
  
• Conclusion: The brain reorganizes functional mapping following injury—demonstrating cortical plasticity.
  

🔍 Evaluation

Strengths

• Empirical evidence from MRI and animal studies supports both structural and functional plasticity.
  
• Cross-species consistency (rats, monkeys, humans) enhances theoretical reliability.
  
• Applications to rehabilitation and education are significant.
  

Limitations

• Causation cannot always be inferred (e.g., taxi drivers may have had larger hippocampi to begin with).
  
• MRI studies show correlation, not process.
  
• Animal research raises ethical concerns regarding deprivation and harm.
  

Ethical Considerations

• Use of animals (Rosenzweig, Merzenich) must adhere to minimization of harm and proper housing.
  
• Human studies like Maguire are non-invasive and low-risk, aligning with IB ethical guidelines.
  

💬 Theory of Knowledge (TOK) ConnectionNeuroplasticity challenges the deterministic view of the brain.Knowledge Question: To what extent can scientific evidence of brain plasticity support the idea of free will? If the brain changes with experience, are behavior and personality truly fixed? This raises TOK debates between biological determinism and personal agency—bridging neuroscience with philosophy.

❤️ CAS LinkStudents can engage in service projects promoting neurorehabilitation or mental agility in aging populations — such as organizing “Brain Fitness” workshops that involve memory games, puzzles, or mindfulness sessions to demonstrate neuroplastic change through experience.

🧪 IA LinkAn IA could explore memory recall improvement through practice, linking behavioral changes to potential neural adaptation. For example, replicating aspects of Maguire or Draganski by testing participants on spatial or skill-based tasks over time.

🌍 Real-World ConnectionStroke Recovery: Therapies like constraint-induced movement therapy rely on cortical remapping to restore motor control. Education: Learning techniques that encourage repeated practice and spaced recall stimulate long-term potentiation. Mental Health: Cognitive-behavioral therapy (CBT) physically alters neural pathways involved in emotion regulation. Technology: Neurofeedback and brain-computer interfaces harness plasticity to enhance rehabilitation.

🧠 Examiner TipIn Paper 1 SAQs, focus on:Define neuroplasticity. Explain how it occurs (LTP, dendritic branching). Support with one study (Draganski or Maguire). Discuss one strength or limitation. Avoid confusing neuroplasticity with localization — emphasize change over time rather than fixed structure-function mapping.

A1.1.1 – LOCALIZATION OF FUNCTION

📘 Definition Table

Term	Definition
Localization of Function	The theory that specific brain areas are responsible for specific psychological functions or behaviors.
Cortical Specialization	The distribution of different functions across distinct areas of the cerebral cortex.
Broca’s Area	Brain region in the left frontal lobe responsible for speech production.
Wernicke’s Area	Region in the left temporal lobe essential for speech comprehension.
Hippocampus	A structure in the limbic system associated with memory consolidation and spatial navigation.
Amygdala	Part of the limbic system involved in processing emotions, particularly fear and aggression.
Corpus Callosum	Bundle of neural fibers connecting the left and right hemispheres, enabling interhemispheric communication.

📌 Introduction

Localization of function refers to the concept that different parts of the brain perform distinct roles in behavior and cognition. This principle emerged from 19th-century neurology, evolving through studies of brain injury, neuroimaging, and animal research.
While early theorists like Gall (phrenology) oversimplified this idea, modern neuroscience shows that although specific brain regions are specialized, most behaviors arise from the interaction between localized areas.

Localization forms the foundation of biological psychology, connecting mental processes like memory, language, and emotion to observable neural structures. Modern neuroimaging techniques (fMRI, PET) have refined our understanding, showing that while certain functions are concentrated, they remain integrated within brain networks.

🧩 Mechanisms and Functional Areas

Brain Region	Function	Associated Behavior / Process
Frontal Lobe	Decision-making, impulse control, planning	Executive function, moral reasoning
Parietal Lobe	Sensory integration, spatial processing	Touch, spatial orientation
Temporal Lobe	Auditory processing, memory	Speech comprehension, facial recognition
Occipital Lobe	Visual processing	Visual recognition and perception
Hippocampus	Memory formation	Long-term memory, spatial navigation
Amygdala	Emotional processing	Fear, aggression
Broca’s Area	Speech production	Language expression
Wernicke’s Area	Speech comprehension	Language understanding
Corpus Callosum	Inter-hemispheric communication	Coordination between hemispheres

🧠 Key Studies

1. Broca (1861) – “Tan” Study

• Aim: Investigate speech loss in patient “Tan” who could only utter one syllable.
  
• Findings: Postmortem examination revealed a lesion in the left frontal lobe (now called Broca’s area).
  
• Conclusion: Speech production localized in the left frontal region.
  

2. Wernicke (1874)

• Aim: Examine patients with speech comprehension deficits but intact speech production.
  
• Findings: Lesions in the left posterior temporal lobe caused impaired understanding.
  
• Conclusion: Language comprehension localized in Wernicke’s area.
  

3. Maguire et al. (2000)

• Aim: Investigate whether London taxi drivers show structural brain differences related to spatial memory.
  
• Method: MRI scans compared taxi drivers to control participants.
  
• Findings: Taxi drivers had increased grey matter in the posterior hippocampus, correlated with years of navigation experience.
  
• Conclusion: The hippocampus is involved in spatial memory and demonstrates experience-dependent plasticity.
  

4. HM Case Study (Scoville & Milner, 1957)

• Aim: Explore the effects of hippocampal removal on memory.
  
• Findings: HM developed anterograde amnesia — inability to form new long-term memories.
  
• Conclusion: The hippocampus is essential for memory consolidation.
  

🔍 Evaluation

Strengths:

• Neuroimaging (MRI/fMRI) provides empirical support through correlational evidence.
  
• Case studies offer detailed insights into specific brain-behavior relationships.
  
• Consistent replication across studies (Broca, Wernicke, Maguire) supports general reliability.
  

Limitations:

• Reductionist – oversimplifies behavior as arising from one area, ignoring network interaction.
  
• Individual variation – not all functions are identically localized across individuals.
  
• Case studies lack generalizability and sometimes rely on postmortem analysis.
  

Ethical Considerations:

• Brain-injury studies often use patients with limited consent capacity.
  
• Modern neuroimaging resolves many ethical issues through non-invasive techniques.
  

💬 Theory of Knowledge (TOK) ConnectionLocalization relies on inference, not direct observation — we cannot see “memory” or “language,” only brain activation patterns.Knowledge Question: To what extent can we rely on indirect evidence (neuroimaging) to claim causation in psychology? This challenges how scientific knowledge is built: Does brain activation cause a behavior or merely correlate with it?

❤️ CAS LinkStudents could design a neuroscience outreach project—for example, creating informational posters or workshops explaining brain regions to younger students or communities. This encourages awareness of brain health, stroke, or trauma recovery, linking CAS service and creativity.

🧪 IA LinkIB Psychology Internal Assessments can replicate localization studies using memory recall or language tasks (e.g., Stroop test) to explore cognitive performance related to hemispheric processing. Students can relate cognitive outcomes to underlying brain functions.

🌍 Real-World ConnectionUnderstanding localization aids neurorehabilitation, education, and mental health treatment.In stroke therapy, knowing which hemisphere controls speech or motor movement helps target recovery strategies. Neurosurgery planning uses localization to avoid damaging critical regions.

📝 Examiner TipIn Paper 1 SAQs, structure your response using:Define localization. Describe the brain region and function. Support with one study (e.g., Maguire or HM). Briefly discuss strengths/limitations. Avoid mixing localization with neuroplasticity—focus on specific area-function relationships.

5.2 AGRICULTURE AND FOOD

📌 Definitions Table

Term	Definition (Exam-Ready, 2 Marks)
Finite Resource	A natural resource that exists in limited quantity and cannot be replenished within a human timescale (e.g., fossil fuels).
Caste	A rigid social stratification system that can affect access to land, resources, and food security in some societies.
Vertical Farms	Multi-layered indoor farming systems using controlled environments to grow crops, often in urban settings.
Pastures	Grazing lands covered with grass or similar vegetation, used primarily for feeding livestock.
Soil Erosion	The removal of topsoil by wind, water, or human activity, reducing soil fertility and structure.
Toxification	The accumulation of harmful substances, such as pesticides or heavy metals, in soil or ecosystems.
Salinisation	The build-up of salts in soil, often due to irrigation, which can reduce soil fertility and crop yield.
Desertification	The degradation of land in arid areas, turning productive land into desert due to climatic or human factors.
Infiltration	The process by which water enters the soil surface and moves downward into the ground.
Surpluses	Quantities of agricultural or resource outputs that exceed the immediate demand or consumption.
Ruminants	Herbivorous mammals (e.g., cows, sheep) that digest plant matter in a specialized stomach via fermentation.
Social Safety Nets	Public or community-based programs that provide support (e.g., food, income) during times of economic or environmental stress.
Resource Depletion	The exhaustion of natural resources due to overuse, exceeding their natural regeneration rate.

• 🧠 Exam Tips:
  
  For degradation terms (e.g., salinisation, toxification), mention impact on soil health or productivity.
  
  Link finite resource and resource depletion to sustainability for stronger evaluation.

📌 Land Use and Agricultural Systems

Land as a finite resource

• Land is limited and cannot be expanded (i.e. it is a finite resource)
• Efficient land use is crucial to meeting growing food requirements
• About 70% of ice-free land is used for agriculture and forestry
  • Agricultural land is used to grow crops (arable) and raise livestock

• As the human population grows, the demand for food increases
  • This puts pressure on available land for food production
• Urbanisation leads to the conversion of agricultural land into urban areas
  • This further reduces the availability of land for food production per capita

Agricultural land use

• Not all land is suitable for crop production
  • land must be fertile, flat, and have adequate water supply
• Unsuitable land for crops:
  • Steep slopes:
    • Risk of erosion
    • It is difficult to use machinery
  • Nutrient-poor soils:
    • Cannot support crop growth without significant fertilisation
• These lands are often used for livestock production instead
  • For example, in the UK, hilly areas like Eryri (Snowdonia, Wales) and the Scottish Highlands are used for sheep grazing due to unsuitable conditions for arable farming

Vulnerability of marginalised groups

• Marginalised groups:
  • These include:
    • Indigenous peoples
    • Low socio-economic status groups
    • Women farmers
    • People in low-income countries
  • Often have limited access to land and resources
• Impact of land-use decisions:
  • Land-use policies can increase inequalities
  • Marginalised groups are more vulnerable to changes and restrictions
  • For example, in India, many Dalits (members of a lower caste) face significant barriers to land ownership and agricultural resources
    • This is limiting their ability to improve their economic status and sustain their livelihoods
• Indigenous peoples:
  • Indigenous groups often depend on land for their livelihoods
  • Indigenous land rights are often ignored in favour of large-scale agricultural projects
  • For example, the Maasai in Kenya and Tanzania have faced land encroachment
    • This is due to expanding agriculture and tourism projects
    • This is threatening their traditional way of life

Other examples of land-use impacts on marginalised groups

• Deforestation in the Amazon:
  • Driven by agricultural expansion
  • It affects Indigenous tribes like the Yanomami
  • Leads to loss of biodiversity and traditional lands
• Land grabs in Africa:
  • Foreign investors acquire large areas of land for industrial-scale agriculture
  • Displaces local farmers and communities
  • Impacts their food security
• Urban sprawl in China:
  • Rapid urbanisation consumes agricultural land
  • Affects rural communities’ access to arable land

Variability in agricultural systems

• Global variation:
  • Agriculture systems vary globally due to differences in soil and climate
  • Soils in different biomes support different crop types and productivity levels
• Soil and climate influence:
  • Tropical soils may be nutrient-poor, affecting crop choices
    • This limits the types of crops that can be grown successfully without heavy fertilisation
    • For example, in Brazil, nutrient-poor tropical soils require heavy fertilisation for crops like soybeans
  • Temperate climates with fertile soils can support diverse crops
    • For example, in the UK, temperate climates support a variety of crops like wheat and barley

Classification of agricultural systems

• Agricultural systems can be classified in a number of ways, including:
• Outputs from the farm system:
  • Arable farming: growing crops (e.g., wheat, rice)
  • Pastoral/livestock farming: raising animals (e.g., cattle, sheep)
  • Mixed farming: combining crops and livestock
  • Monoculture: growing a single type of crop
  • Diverse farming: growing multiple types of crops
• Reasons for farming:
  • Commercial farming: producing food for sale
  • Subsistence farming: producing food for the farmer’s own use
  • Sedentary farming: farmers stay in one place
  • Nomadic farming: farmers move with their livestock
• Types of inputs required:
  • Intensive farming:
    • High inputs of labour, capital and technology
    • E.g. dairy farming in the Netherlands
  • Extensive farming:
    • Low input per unit area
    • E.g. sheep farming in Australia
  • Irrigated farming:
    • Requires artificial water supply
    • E.g. Central Valley, California: large-scale irrigation systems support the cultivation of crops such as almonds, grapes and tomatoes in this semi-arid region
  • Rain-fed farming:
    • Relies on natural rainfall
    • E.g. wheat farming in Canada
  • Soil-based farming:
    • Traditional farming in soil
    • E.g. vegetable farms in the UK
  • Hydroponic farming:
    • Growing plants without soil, using nutrient solutions
    • E.g. hydroponic lettuce farms or vertical farms in urban areas
  • Organic farming:
    • Avoids synthetic chemicals
    • E.g. organic tea plantations in India: many use natural fertilisers, compost and biological pest control methods to maintain soil fertility and produce high-quality tea without synthetic pesticides or herbicides
  • Inorganic farming:
    • Uses synthetic chemicals and fertilisers
    • E.g. large-scale corn farms in the US

Implications of agricultural systems

• Economic sustainability:
  • Varies with farming type and market access
  • Monoculture can be profitable but risky due to crop failure, e.g. due to disease
  • Diversified farming reduces risk and can be more economically sustainable
• Social sustainability:
  • Agricultural systems affect community stability and employment in different ways
  • Subsistence farming supports local communities but can limit economic growth
  • Commercial farming can create jobs but may displace small farmers
• Environmental sustainability:
  • Intensive farming can lead to soil degradation and pollution
  • Organic farming promotes biodiversity and soil health
  • Extensive farming generally has a lower environmental impact

📌 Traditional and Modern Agricultural Practices

Nomadic pastoralism

• Nomadic pastoralism is a form of agriculture where livestock is herded to different pastures in a seasonal cycle
  • For example, Bedouin tribes in the Middle East traditionally move their camels, goats and sheep across desert regions to find grazing land
• Characteristics:
  • Relies on natural pasture and water sources
  • Adapted to arid or semi-arid environments
  • Minimal permanent settlements
  • Seasonal changes control movement

Slash-and-burn agriculture (shifting cultivation)

• Slash-and-burn agriculture is a method of agriculture where forests are cut down and burned
• Crops are grown on the cleared land for a few years until the soil is depleted of nutrients
  • For example, some Indigenous peoples in the Amazon rainforest traditionally practice slash-and-burn to grow crops like cassava and maize
• Characteristics:
  • Sustainable in low-density populations
  • Allows regeneration of forest over time
  • Relies on a rotating cycle of land use

Challenges with traditional practices

• Environmental impacts:
  • Deforestation and loss of biodiversity from slash-and-burn
  • Overgrazing and soil erosion can occasionally result from nomadic pastoralism
• Modernisation and population growth:
  • Traditional agricultural methods become unsustainable as populations grow and land becomes scarce
  • Some Indigenous peoples have been observed transitioning to more sedentary lifestyles
  • This leads to overuse of land and resources

The green revolution

What was the green revolution?

• The green revolution refers to a series of research, development and technologyinitiatives that took place between the 1950s and 1960s
  • These initiatives aimed to increase agricultural production and food security globally
• It is also known as the third agricultural revolution

Key initiatives of the green revolution

• High-yielding varieties (HYVs):
  • Breeding of crops like wheat, rice and maize to produce higher yields
  • E.g. IR8 rice, known as ‘Miracle Rice’, developed in the Philippines
• Improved irrigation systems:
  • Development and expansion of irrigation infrastructure
  • Helped transform arid and semi-arid lands into highly productive agricultural areas
  • E.g. the Indus Basin Irrigation System in Pakistan
• Synthetic fertilisers:
  • Use of chemical fertilisers to provide essential nutrients to crops
  • The production of synthetic fertilisers is dependent on nitrogen fixation
    • This means their production relies on fossil fuels
• Pesticides:
  • Application of chemical pesticides to protect crops from pests and diseases

Positive consequences of the green revolution

• Increased food production:
  • Significant increase in crop yields and food availability
  • Helped alleviate hunger and food shortages in many regions
• Economic growth:
  • Boosted agricultural economies and increased farmer incomes
  • For example, Mexico became a major wheat exporter due to green revolution practices
• Technological advancements:
  • Led to further agricultural research and innovation

Negative consequences of the green revolution

• Environmental impacts:
  • The overuse of chemical fertilisers and pesticides led to soil degradation and water pollution
  • Loss of biodiversity due to intense monoculture practices
• Economic inequality:
  • Resulted in greater economic benefits for larger, wealthier farmers compared to small-scale farmers
  • Increased debt for farmers who could not afford new technologies
• Sociocultural effects:
  • Displacement and loss of traditional farming practices
  • Increase in rural to urban migration due to changes in agricultural labour demands
• Selective implementation:
  • The green revolution was not universal
  • It did not reach all developing nations
  • Regions without access to necessary resources and infrastructure saw limited benefits

Synthetic fertilisers & sustainable methods

• Synthetic fertilisers are chemical compounds applied to soil to supply essential nutrients for plant growth
  • Their purpose is to maintain high commercial productivity in intensive farming systems
• Advantages:
  • Immediate nutrient supply to crops
  • Increased crop yields and faster growth
• Disadvantages:
  • Soil degradation over time
  • Water pollution from runoff
  • Dependency on fossil fuels for production

Sustainable methods for improving soil fertility

• In sustainable agriculture, there are many alternative methods for improving soil fertility

Sustainable Methods for Improving Soil Fertility

Method	Definition	Benefits
Fallowing	Leaving land uncultivated for a period	Allows soil to recover and regain nutrientsReduces need for synthetic fertilisers
Organic Fertiliser	Using manure from farm animals or human waste (humanure)	Improves soil structure and fertilityReduces need for synthetic fertilisers
Herbal Mixed Leys	Planting a mixture of herbs and grasses	Provides diverse nutrients to the soilImproves soil health and biodiversity
Mycorrhizae	Symbiotic fungi that enhance plant nutrient uptake	Increases plant access to nutrientsReduces need for synthetic fertilisers
Continuous Cover Forestry	Maintaining a continuous canopy of trees	Prevents soil erosion due to root systems binding soil and interception of rain by forest canopyIncreases soil organic matter and fertility
Agroforestry	Integrating trees and shrubs into agricultural landscapes	Improves soil healthReduces soil erosionProvides additional sources of income (e.g. fruit, timber)

🔍 TOK Tip: How do different knowledge systems define “sustainable agriculture”?

📌 Soil Conservation

Soil conservation techniques

• Soil conservation techniques are used to maintain the health and productivity of our soils
• As soil fertility declines, various detrimental processes can occur, such as:
  • Soil erosion
  • Toxification
  • Salinisation
  • Desertification
• These processes lead to significant environmental and agricultural challenges
• Soil conservation techniques can be used to:
  • Mitigate soil degradation
  • Preserve the important characteristics of fertile soils
• Soil conservation techniques can be classified in several ways, including:
  1. Techniques that reduce soil erosion
  2. Techniques that increase soil fertility (using soil conditioners)
  3. Cultivation techniques

❤️ CAS Tip: Set up a school composting system or a permaculture garden.

Protecting Soils from Erosion

Soil conservation technique	Type of erosion reduced	Description	Effect
Strip cultivation	Water	Planting crops in alternating strips or bands, leaving natural vegetation between the strips	Reduces soil erosion by trapping water, slowing down runoff and increasing infiltrationwhile still allowing for crop production in the cultivated stripsIncreases biodiversity
Terracing	Water	Creating levelled steps on sloped lands	Reduces soil erosion by slowing down water movement and increasing infiltrationMinimises soil loss on steep slopes
Contour ploughing	Water	Ploughing parallel to the contour lines of the land instead of up and down slopes	Minimises soil erosion by reducing length and speed of water flow downhillPrevents gully formation and increases infiltration
Bunding	Water	Building embankments or barriers along fields	Controls water flowPrevents soil erosion and waterlogging
Drainage systems	Water	Installing systems to manage excess water	Prevents waterloggingReduces erosion and nutrient loss
Cover crops	Water	Planting crops that cover the soil	Reduces water erosionImproves soil structure
Windbreaks	Wind	Planting trees or hedges to block and reduce wind speed	Provides physical barrier to windReduces wind erosionProtects topsoilProtects crops from wind damage

Conservation of Fertility with Soil Conditioners

Soil conservation technique	Description	Effect
Lime	Adding lime to soil	Improves soil pH, reducing soil acidityEnhances nutrient availabilityPromotes beneficial microbial activity
Compost	Using decomposed organic matter	Enriches soil with nutrientsImproves soil structureIncreases water-holding capacityPromotes beneficial microbial activity
Green manure	Growing plants (e.g. cover crops) specifically to be ploughed into the soil	Increases organic matterEnhances soil fertility

Cultivation Techniques

Soil conservation technique	Description	Effect
Avoid marginal land	Not farming on land that is vulnerable to erosion or poor in nutrients	Protects fragile ecosystemsPrevents soil degradationMaintains soil health
Avoid overgrazing / overcropping	Managing livestock and crop levels to prevent depletion	Maintains soil coverPrevents soil erosion and compaction
Mixed cropping	Growing different types of crops together	Improves soil healthReduces pest and disease issues
Crop rotation	Rotating different crops on the same land	Maintains soil nutrientsReduces disease and pest buildup
Reduced tillage	Minimising ploughing and soil disturbance	Preserves soil structureMaintains moisture levels
Agroforestry	Integrating trees and shrubs into farming systems	Enhances soil structureProvides shade and wind protection
Reduced use of heavy machinery	Minimising the use of heavy equipment on fields	Prevents soil compactionMaintains soil structure

🌐 EE Tip: Compare soil health under different farming systems (organic vs conventional) using physical and chemical indicators.

📌 Sustainability of Food Production Systems

Increasing sustainability of terrestrial food production

• Humans are omnivores, consuming a variety of foods, including:
  • Fungi
  • Plants
  • Meat
  • Fish
• Diets that include more food from lower trophic levels, such as plant-based diets, are generally more sustainable
  • This is due to their reduced environmental impact

Crop vs. livestock production

• Yield and cost:
  • Crops:
    • The yield of food per unit of land area is significantly higher with crops than with livestock
    • Crop production also has lower financial costs associated with it
  • Livestock:
    • Producing food through livestock requires more land and resources
    • It is usually more expensive

Plant-based diets

• Increasing the proportion of plant-based foods in diets can make agriculture more sustainable
• This is because plant-based diets decrease the demand for resource-intensive livestock farming
• Energy efficiency is greater in a plant-based diet compared to a meat-eating diet due to several factors:

1. Trophic levels:
   • Energy is lost at each trophic level as it moves up the food chain
   • When we consume plant-based foods directly, we bypass the energy loss associated with raising animals for meat
   • By consuming plants (the primary producers) directly, we utilise energy more efficiently
2. Feed conversion efficiency:
   • Animals raised for meat require significant amounts of feed to grow and develop
   • However, a large portion of the energy from the feed is used for the animals’ own bodily functions and metabolic processes, rather than being converted into edible biomass
   • This inefficiency in feed conversion results in higher energy losses when obtaining nutrition from meat
3. Land use efficiency:
   • Producing meat requires vast amounts of land for grazing or growing animal feed crops
   • This land could otherwise be used more efficiently to cultivate plant-based foods directly for human consumption
   • By consuming plant-based foods, we optimise land use and reduce the energy required for livestock farming

• By focusing on lower-trophic-level food production, such as promoting plant-based diets, it is possible to:
  • Maximise food production per unit area
  • At the same time, mitigating the pressure on land resources

Global food production and distribution

• Current production:
  • Global agriculture currently produces enough food to feed approximately eight billion people (the global population currently stands at 8.1 billion in 2024)
• Despite this, food is not distributed equitably around the world
  • Some regions experience surpluses, while others face severe shortages
• Food waste:
  • It is estimated that at least one-third of all food produced is wasted
  • This can be during:
    • Post-harvest
    • Storage
    • Transport and distribution
• SDG goal:
  • The United Nations’ Sustainable Development Goal 12 aims to:
    • “…ensure sustainable consumption and production patterns.”
  • Target 12.3 within this goal focuses on:
    • Reducing global food waste by 50% per capita at the retail and consumer levels (i.e. halving global food waste) by 2030
    • By minimising food losses throughout production and supply chains (including post-harvest losses)

Strategies for sustainable food supply

1. Reducing demand and food waste:
   • Encouraging plant-based diets: shifting towards plant-based diets can reduce the demand for resource-intensive animal products
   • Improving food distribution systems: increasing the efficiency of food distribution can help ensure that food reaches those in need and reduce waste. For example:
     • Using refrigerated transport to keep food fresh longer
     • Optimising delivery routes to reduce transport time
     • Collecting and redistributing surplus food to those in need
   • Educating consumers: raising awareness about the importance of reducing food waste at the consumer level can have a significant impact
2. Reducing greenhouse gas emissions:
   • Plant-based meat substitutes: developing and promoting plant-based alternatives to meat can reduce greenhouse gas emissions associated with livestock
     • These products mimic the taste and texture of meat but are made from plants
   • Low methane rice cultivation: using rice cultivation practices that produce less methane can help reduce agricultural emissions. For example:
     • Periodically draining and re-flooding rice fields
     • Applying additives that reduce methane emissions
   • Reducing methane release by ruminants: adjusting livestock diets and using dietary additives like seaweed can lower methane emissions from ruminants
3. Increasing productivity without expanding agricultural land use:
   • Extending shelf life: improving preservation methods to extend the shelf life of food can help reduce waste. For example:
     • Improved packaging
     • Improved refrigeration
   • Genetic modification: using genetic modification to create crops with increased productivity. For example:
     • Crops that produce higher yields with the same inputs
     • Crops that are more resistant to pests and diseases
   • In-field solar-powered fertiliser production: using solar energy to produce fertilisers on-site
     • Reduces the need for synthetic fertilisers
     • Reduces reliance on fossil fuels (required for production of synthetic fertilisers)
     • Reduces production and transport costs

📌 Food Security

• Food security can be defined as:

Key components of food security

1. Availability: ensuring that enough food is produced and supplied to meet the population’s needs
2. Access: ensuring that individuals have the resources (economic means) to obtain the food they need (i.e. food is affordable)
3. Use: ensuring food is used properly alongside a healthy diet, clean water, sanitation and healthcare to achieve good nutritional health
4. Stability: ensuring consistent and reliable access to food at all times, without disruptions from economic or climate-related issues

🔍 TOK Tip: Is food security a scientific or ethical problem?

Regional food security

• Developed regions:
  • Generally high levels of food security
  • Good infrastructure, economic stability and social safety nets ensure food availability and access
  • Examples: North America, Western Europe
• Developing regions:
  • Varying levels of food security, often lower than in developed regions
  • Issues include poverty, poor infrastructure and political instability
  • Examples: Sub-Saharan Africa, parts of South Asia, Latin America

Factors affecting food security

• Economic factors:
  • Income levels, food prices and employment opportunities impact individuals’ ability to purchase food
• Environmental factors:
  • Climate change, natural disasters and resource depletion impact food production and availability
• Social and political factors:
  • Government policies, conflict and social inequality impact food distribution and access

5.1 SOIL

📌 Definitions Table

Term	Definition
Parental Rock	The original rock material that breaks down through weathering to form soil.
Natural Soil Mineralisation	The process by which organic matter decomposes, releasing nutrients into the soil in mineral form.
Parent Material	The base geological material from which soil develops, including rock or transported sediments.
Natural Seed Bank	A reserve of viable seeds present in the soil that can germinate under suitable conditions.
Sink	A part of the system where matter or energy is absorbed and stored for a significant period.
Stores	Components of a system that hold energy or matter temporarily, such as soil, biomass, or atmosphere.
Sources	Components of a system that release matter or energy into other parts of the system.
Primary Productivity	The rate at which producers convert solar energy into biomass through photosynthesis.

• 🧠 Exam Tips:
  
  When discussing sources and sinks, link them to nutrient cycles (e.g., carbon or nitrogen).
  
  For productivity terms, distinguish between GPP and NPP if specified.

📌 Components and Structure of Soil

Soil components

• Soil is made up of a complex mixture of interacting components, including inorganic and organic components, water and air

Inorganic components

• Mineral matter:
  • Rock fragments
  • Sand
  • Silt
  • Clay
• These components come from the weathering of parental rock

Organic components

• Living organisms:
  • Bacteria
  • Fungi
  • Earthworms
• Dead organic matter:
  • Decaying plants
  • Animal remains
  • Animal waste (faeces)

Other components

• Water:
  • Essential for chemical reactions and life
• Air:
  • Oxygen and other gases necessary for organism survival

Soils as systems

• Soils are dynamic systems within larger ecosystems 
• As with any system, soil systems can be simplified by breaking them down into the following components:
  • Storages
  • Flows (inputs and outputs)
  • Transfers (change in location) and transformations (change in chemical nature, state or energy)

Image source: savemyexams.com

Soil System Storages

Storage	Description
Organic matter	Accumulation of plant and animal matter in various stages of decompositionProvides nutrients, improves soil structure and enhances water-holding capacity
Organisms	Includes microorganisms, fungi, bacteria, insects and other living organisms present in the soilThey play essential roles in nutrient cycling, organic matter decomposition and soil structure formation
Nutrients	Elements necessary for plant growth, such as nitrogen, phosphorus and potassiumNutrients are stored in the soil and are made available to plants through various biological and chemical processes
Minerals	Inorganic components of the soil derived from weathering of rocks and mineralsContribute to the physical properties and fertility of the soil
Air	Pore spaces within the soil are filled with air, allowing oxygen to be available for root respiration and microbial activities
Water	Soil acts as a reservoir for water, holding it for plant uptake and providing a suitably moist habitat for soil organisms

Soil System Inputs

Input	Description
Dead organic matter	Inputs of plant material (e.g. leaf litter) and other organic materials (e.g. dead animal biomass or animal faeces) that contribute to the organic matter content in the soil
Inorganic matter from rock material	Contributes to the mineral composition of soil, derived from parent materials (e.g. bedrock) and the weathering of exposed rock at the soil surface
Precipitation	Rainfall or snowfall that provides water (containing dissolved minerals) to the soil system
Energy	Solar radiation and heat influence soil temperature and biological activities
Anthropogenic inputs	E.g. compost, fertilisers, agrochemicals, water from irrigation

Soil System Outputs

Output	Description
Leaching	Loss of dissolved minerals and nutrients from the soil into streams, rivers, lakes and oceans through water movement
Uptake by plants	Absorption of minerals and water by plant roots for growth and development
Soil erosion	Removal of soil particles by water or wind, leading to the loss of topsoil and degradation of soil quality
Diffusion and evaporation	Diffusion of gases and evaporation of water from soil

Soil System Transfers

Transfer	Description
Infiltration	Process by which water enters the soil from the surface
Percolation	Movement of water through the soil and its layers, typically downward through the soil profile
Groundwater flow	Movement of water through the subsurface soil layers, often feeding into aquifers and other groundwater reserves
Biological mixing	Movement of soil particles and materials by soil organisms, including burrowing animals, earthworms and root growthContributes to the mixing of organic matter and minerals, enhancing soil structure and nutrient distribution
Aeration	Process by which air is circulated through and mixed with soil
Erosion	Process by which soil particles are detached and transported by wind or water
Leaching	Process in which minerals dissolved in water are moved downwards or horizontallythrough the soil profileResults in the loss of nutrients from the root zone, particularly in areas with high rainfall or excessive irrigation

Soil System Transformations

Transformation	Description
Decomposition	The process of organic matter breakdown by microorganisms, results in the release of carbon dioxide, water and nutrientsInvolves the conversion of complex organic compounds into simpler forms
Weathering	Physical and chemical processes that break down rocks and minerals into smaller particles, contribute to soil formationIncludes physical weathering (mechanical breakdown) and chemical weathering (alteration of minerals through chemical reactions)
Nutrient cycling	The cycling of nutrients within the soil-plant system involves uptake, assimilation, release and recycling of elements like nitrogen, phosphorus and potassiumEnsures the availability and redistribution of essential nutrients for plant growth
Salinisation	Accumulation of soluble salts in the soil, which can be detrimental to plant growth and soil structureIt often results from improper irrigation practices, high evaporation rates, or natural soil mineralisation
Humification	Process of organic matter transformation into stable humusIt involves the accumulation of complex organic compounds, leading to the dark colouration and improved water-holding capacity of soilContributes to soil fertility and structure

Soil profiles

• Soil profiles develop as a result of long-term interactions within the soil system
• These interactions and processes form distinct layers known as horizons
• These layers vary in composition and characteristics from the surface downward
  • This reflects the processes of soil formation over time
• Profiles usually transition from organic-rich layers near the surface to more mineral-rich layers deeper down
  • These lower layers generally contain more inorganic material

Image source: savemyexams.com

• The development of soil profiles is influenced by factors such as:
  • Climate
  • Vegetation
  • Parent material
  • Time

Real-world examples

• Tropical rainforests:
  • Often have thick, organic-rich top soils due to rapid decomposition and high biological activity
• Desert regions:
  • Characterised by shallow, mineral-dominated soils with distinct horizons due to low organic matter input and minimal leaching
• Peat soils in boreal forests (e.g. Scandinavia):
  • Soils characterised by thick layers of partially decomposed organic matter (peat)
  • This is due to the cold, wet conditions that slow down decomposition rates, resulting in highly acidic and nutrient-poor soils
• Prairie soils in the Great Plains, USA:
  • Soils known for their deep, dark topsoil have developed over millennia
  • This is due to the accumulation of organic matter from grassland vegetation and the semi-arid climate

📌 Functions and Properties of Soil

Soil functions

• Soils carry out important functions in terrestrial ecosystems
• Soils support plant growth, biodiversity and biogeochemical cycles

Medium for plant growth

• Soils act as a natural seed bank, providing a substrate for germination and root development
• They store water crucial for plant hydration, nutrient uptake and photosynthesis
• They store essential nutrients for plants such as nitrogen, phosphorus and potassium
• These essential nutrients support healthy plant growth
  • For example, in the Amazon rainforest, the fertile soils contain high levels of nutrients
  • This allows these soils to support diverse plant life
  • This has led to the Amazon’s status as the world’s largest tropical rainforest

Contribution to biodiversity

• Soils provide habitats and niches for a wide range of species
• Soil communities support high biodiversity, including microorganisms, animals and fungi
  • For example, in the UK, ancient woodlands are rich in soil biodiversity
  • Their soils support rare fungal species that play important roles in nutrient cycling

Role in biogeochemical cycles

• Soils allow the recycling of elements essential for life, such as carbon, nitrogen and phosphorus
• Dead organic matter from plants is a major input into soils, where it decomposes and releases nutrients

Carbon storage dynamics

• Soils can function as carbon sinks, stores, or sources, depending on environmental conditions
• For example, tropical forest soils generally have low carbon storage due to rapid decomposition rates
  • This is because the warm and moist conditions accelerate the decomposition of organic matter by microorganisms
  • This causes carbon to be released back into the atmosphere quickly
• Tundra, wetlands and temperate grasslands can accumulate large amounts of carbon in their soils
  • This is because colder temperatures and waterlogged conditions slow down the decomposition process
  • This allows organic matter to build up in the soil over time without being fully decomposed and released as CO₂

Soil texture

• Soil texture describes the physical make-up of soils
• It depends on the proportions of sand, silt, clay and humus within the soil
• Soil texture influences various soil properties and plant growth

Components of soil texture

• Sand: larger particles that feel gritty
• Silt: medium-sized particles that feel smooth
• Clay: very fine particles that feel sticky when wet
• Humus: organic matter, dark brown or black, crumbly texture from partially decayed plant material

Determining soil texture

• Soil texture can be determined using several methods
• Each method provides insight into:
  • The soil’s properties
  • How suitable the soil is for different plants and crops

1. Using a soil key:
   • A soil key is a more systematic and detailed method
   • It uses a step-by-step guide to classify soil texture based on specific criteria
   • The key helps identify the proportions of sand, silt, and clay by guiding the soil tester (the user) through a series of questions or observations
   • It often includes descriptions of soil behaviour when moistened and manipulated
   • Soil keys are often used in more formal or scientific settings where precise classification is needed
2. Feel test:
   • The feel test is a simpler method
   • It involves rubbing moistened soil between the fingers to assess its texture
   • Sand feels gritty, silt feels smooth and clay feels sticky
   • It is a quick, informal assessment that can be done in the field without additional tools
   • The feel test is commonly used by farmers, gardeners, and others needing a quick assessment
3. Laboratory test:
   • The laboratory test involves mixing soil with water and allowing it to settle into distinct layers
   • This method provides a clear visual representation of the proportions of sand, silt and clay
   • Any large debris like rocks, roots, or organic matter, are first removed from the sample
   • The sample is added to a transparent container
   • Water is added and the container is shaken vigorously
   • The container is left on a flat surface and left undisturbed (e.g. for 24 hours)
   • Silt settles first, then clay, and finally sand
   • The thickness of these layers can be measured to determine their proportions

Image source: savemyexams.com

• In the example above:
  • The sand layer is 2.5 cm
  • The silt layer is 2 cm
  • The clay layer is 2.5 cm
  • The total thickness is 7 cm
• These measurements can be used to calculate the percentage of each soil component:
  • The percentage of sand is (2.5 ÷ 7) × 100 = 35.7%
  • The percentage of silt is (2 ÷ 7) × 100 = 28.6%
  • The percentage of clay is (2.5 ÷ 7) × 100 = 35.7%

Influence of soil texture on primary productivity

• Soil texture affects primary productivity by influencing:
  • Nutrient availability
  • Water retention
  • Soil aeration
• Nutrient retention vs. leaching:
  • Humus contributes significantly to the nutrient content of soils
  • It lies beneath leaf litter and has a loose, crumbly texture
  • It is formed by the partial decay of dead plant material
  • Soils with more humus retain nutrients better
  • Less humus means nutrients are more likely to be washed away
    • For example, forest floors, like those in the New Forest in Hampshire, UK, have rich humus layers that support diverse plant life
• Water retention vs. drainage:
  • Clay and humus-rich soils retain water well
  • Sandy soils drain quickly but may not retain enough moisture for some plants
    • For example, sandy soils in East Anglia, UK, require more frequent irrigation for crops
• Aeration vs. compaction or waterlogging:
  • Well-aerated soils support root growth and beneficial microbial activity
  • Clay soils can become compacted, limiting aeration
  • Humus helps improve aeration in clay soils
    • For example, compacted clay soils in urban areas often need organic matter added to improve their structure and aeration

3.3 CONSERVATION AND REGENERATION

📌 Definitions Table

Term	Definition
Flagship Species	Charismatic species used to raise public awareness and support for biodiversity conservation.
Keystone Species	A species with a disproportionately large effect on ecosystem structure and function relative to its abundance.
Sluices	Water-control structures that regulate flow, often used in wetland or floodplain management.
Target Species	Species specifically monitored or managed in conservation programs or ecological studies.
Viable Populations	Populations that are sufficiently large and genetically diverse to survive and reproduce in the long term.
Microclimates	Localized climate conditions that differ from the surrounding area, often influenced by vegetation, topography, or structures.
Gene Flow	The transfer of genetic material between populations, promoting genetic diversity and adaptability.
Apex Predators	Top-level predators with no natural enemies, regulating populations of other species and maintaining ecosystem balance.
Communities	All interacting populations of different species living in the same habitat at the same time.
Succession	The gradual process of change in species composition and ecosystem structure over time.
Earth System	The interacting physical, chemical, and biological components of Earth, including the atmosphere, hydrosphere, lithosphere, and biosphere.
Holocene Epoch	The current geological epoch, beginning around 11,700 years ago, characterized by relative climatic stability.
Biosphere Integrity	The maintenance of biodiversity and ecosystem functions critical to Earth system stability.
Environmental Justice	The fair treatment and meaningful involvement of all people in environmental decision-making, regardless of race, income, or nationality.

• 🧠 Exam Tips:
  
  Use examples (e.g., wolves as keystone species, tigers as flagship species) when asked to justify or evaluate.
  
  For biosphere integrity and environmental justice, link to sustainability and systems interconnections.

📌 Preserving Biodiversity

• There are many reasons for maintaining and preserving biodiversity, including:
  • Aesthetic reasons
  • Ecological reasons
  • Economic reasons
  • Ethical reasons
  • Social reasons

Aesthetic reasons

• Humans find great joy and pleasure in the beauty of nature
  • It provides inspiration for human creativity, including photography, poetry, music and art
  • There is a strong argument for preserving biodiversity because of its aesthetic benefits

Ecological reasons

• Species and habitats contribute to vital ecological processes and services
  • E.g. pollination, water purification, climate regulation and maintaining soil fertility
• Biodiversity has a major effect on the stability and resilience of an ecosystem
  • A more diverse ecosystem is better able to recover from disturbances and adapt to environmental changes or threats
• For example, if the temperature of a species-rich lake rises due to global warming:
  • Some species of fish in the ecosystem are unable to cope with the change while others can or may be able to adapt
  • The fish that are able to cope or adapt will survive, reproduce and keep contributing to the ecosystem, allowing the ecosystem to continue to function
• Within communities, there are keystone species that have a larger impact on the ecosystem than others
  • When these species are lost there are knock-on effects
  • Bush elephants in the African savannah are a keystone species
    • They graze in a very extreme way, knocking over and eating several species of tree
    • This destruction of vegetation actually helps to maintain the ecosystem by preventing any one plant species from dominating, creating habitats for other species and increasing biodiversity
    • Elephant dung also provides a habitat for many important fungi and insect species
    • In cases where elephants have been illegally poached for their ivory and their numbers greatly reduced, ecologist have observed major negative impacts on the savannah ecosystem

Economic reasons

• Ecotourism is a major source of income for many countries
  • Natural areas attract tourists, generating revenue for local economies and providing jobs
    • E.g. many tourists travel to and spend money in National parks so they can see wildlife
• Natural capital:
  • Natural ecosystems provide resources like timber, fish and clean water
  • Maintaining these resources supports long-term economic prosperity
• Genetic resources:
  • Wild species are sources of genes for crop improvement, medicine, and biotechnology
  • Preserving this genetic diversity could be essential for future innovations and food security
• Many of the medicines used today have originated from plants, fungi and bacteria
  • For example, the cancer-fighting drug paclitaxel is sourced from Pacific and Himalayan Yew Trees
    • The Himalayan Yew has declined in numbers due to over-harvesting for fuel and medicine
  • Due to the large number of drugs that have already been sourced from nature it is reasonable to assume that there are many other drug still to be found in nature that could be used in the future

Ethical reasons

• Many people believe that species and habitats have intrinsic value (i.e. they have inherent worth, independent of their usefulness to humans)
• Many believe that humans have a moral obligation to prevent the loss of biodiversity that results from human activities
  • Humans share the planet with millions of other species and many people hold the view that they have no right to cause the extinction of other species
  • As humans are the most intelligent, dominant and powerful species on the planet, many believe that it is our responsibility to protect and value all organisms on Earth
  • Many believe that is also our ethical obligation to preserve nature for future generations

Social reasons

• Many people enjoy spending time in the natural environment
  • There are many activities that people can do together in nature, e.g. birdwatching, walking, climbing
  • Access to natural spaces improves mental and physical health
  • Such environments may be lost if their biodiversity is not conserved, resulting in the loss of the social benefits that they can bring

🔍 TOK Tip: Should species be conserved based on ecological value or emotional appeal (e.g. flagship species)?

📌 Conservation Strategies

• Conservation strategies are methods used to protect and preserve biodiversity
  • These strategies can be divided into:
    • Species-based conservation
    • Habitat-based conservation
    • Mixed approaches

Species-based conservation

• Species-based conservation focuses on protecting individual species, especially those that are endangered
• This often involves ex situ strategies
  • This means conservation actions are taken outside the natural habitat of the species

Ex situ strategies

• Botanic gardens:
  • Botanic gardens are specially designed areas where a wide variety of plants are grown for scientific, educational and ornamental purposes
  • Botanic gardens cultivate and maintain plant species outside their natural habitats
  • They provide a safe environment for endangered plants and facilitate research and education.
    • For example, Kew Gardens in London holds over 30 000 different plant species.
• Zoos:
  • Zoos keep and breed animals in captivity, often focusing on endangered species
  • They play a role in education, research and breeding programmes to reintroduce species into the wild
    • Captive breeding is the process of breeding animals in controlled environments, such as zoos, aquariums, or wildlife sanctuaries
    • These programmes are often used to help restore populations of endangered species that have declined in the wild
    • For example, the San Diego Zoo in the United States runs breeding programmes for species like the California Condor
  • Zoos also play a role in conservation by raising public awareness and funding other conservation efforts
• Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES):
  • CITES is an international agreement that aims to ensure that international trade in wild animals and plants does not threaten their survival
  • It regulates and monitors the trade of endangered species through a licensing system
    • For example, CITES has helped to protect many species, including elephants, rhinos and tigers
• Seed banks:
  • Seed banks are places where seeds of different plant species are stored to preserve genetic diversity
  • They act as a backup against the loss of plants in their natural habitats
    • For example, the Svalbard Global Seed Vault in Norway holds seeds from all around the world

Habitat-based conservation

• Habitat-based conservation focuses on protecting and restoring habitats to support the species that live there
• This often involves in situ strategies
  • This means conservation actions are taken within the natural habitat of the species

In situ measures

• National parks:
  • National parks protect large areas of natural habitat, preserving the ecosystems and species within them
  • They also provide opportunities for research, tourism and education
    • For example, Yellowstone National Park in the USA protects a variety of ecosystems and species, including grizzly bears and wolves
• Reserves and sanctuaries:
  • Wildlife reserves and sanctuaries are areas set aside for the protection of particular species and their habitats
  • They often involve community participation and sustainable use of resources
    • For example, the Maasai Mara National Reserve in Kenya protects a range of species including lions, elephants and wildebeest

Mixed conservation approach

• A mixed conservation approach combines species-based and habitat-based strategies
  • This approach often focuses on flagship or keystone species to justify the conservation of entire ecosystems

Flagship species

• Flagship species are charismatic species that are well-known and popular with the public, such as elephants, pandas or tigers
• They can be used as symbols for conservation efforts and can help to raise awareness and supportfor conservation efforts
• By protecting charismatic species, their habitats and other species in the same ecosystem may also be protected
  • An example of a flagship species is the mountain gorilla (Gorilla beringei beringei)
  • These primates are found in the Virunga Mountains, which span Rwanda, Uganda, and the Democratic Republic of Congo
  • The mountain gorilla population has faced threats from habitat destruction, poaching, and human conflict
  • By focusing on the conservation of mountain gorillas and their habitat, conservation organisations have been able to protect not only this species but also the many other plants and animals that share their ecosystem

Keystone species

• Keystone species are species that have a disproportionate effect on the structure and function of their ecosystem.
• Their removal can cause significant changes in the ecosystem, including the loss of other species
• By protecting keystone species, the integrity of the ecosystem can be maintained, which can in turn benefit other species in the ecosystem
  • For example, the sea otter is a keystone species in the kelp forest ecosystem in the Pacific Northwest of the United States
  • It feeds on sea urchins
  • This helps to control the population of sea urchins, which are herbivores that can significantly damage the kelp forests

Case Study

Chengdu Research Base of Giant Panda Breeding

• The Chengdu Research Base of Giant Panda Breeding in China is a good example of a mixed conservation approach, combining species-based and habitat-based strategies to protect the giant panda

Objectives and strategies:

• Captive breeding: running a breeding program to increase the giant panda population.
• Habitat restoration: restoring and expanding bamboo forests, the natural habitat of giant pandas
• Public education and awareness: educating the public through tours, programs and exhibits to generate support for conservation
• Research and collaboration: conducting research on panda biology and collaborating with international organisations

Facilities:

• Breeding centres: areas for breeding and raising panda cubs
• Veterinary hospital: provides medical care for pandas
• Enclosures and habitats: naturalistic spaces for pandas to live and play
• Research laboratories: equipped for scientific research on panda conservation

Achievements:

• Increased panda population: successful breeding programs have raised the number of giant pandas
• Genetic diversity: genetic diversity have been maintained through careful breeding
• Habitat protection: has played a key role in restoring and protecting panda habitats
• Wider ecosystem and species conservation: by focusing on this flagship species, the base has also helped to protect the broader ecosystem and other species within it

🧠 Examiner Tips:

Make sure you know the definitions of the terms ex situ and in situ in the context of conservation strategies. 

Be prepared to give examples of both the types of strategies.

Convention on Biological Diversity

• The Convention on Biological Diversity (CBD) is a United Nations treaty aimed at promoting sustainable development and conserving biodiversity
  • It was signed at the Earth Summit in Rio de Janeiro in Brazil in 1992

• Objectives:
  • The conservation of biodiversity by use of a variety of different conservation methods
  • The sustainable use of biological resources
  • Identify and protect marine areas beyond national jurisdictions
• Nagoya Protocol:
  • The CBD also includes the Nagoya Protocol, which is the part that ensures fair sharing of benefits arising from the use of genetic resources
• The countries that signed the convention agreed to:
  • Design and implement national strategies for the conservation and sustainable use of biodiversity
  • Organise international cooperation and further international meetings

📌 Habitat Management and Designing Protected Areas

Habitat management

• Habitat conservation strategies aim to protect species by preserving and managing their natural environments
  • This may involve the protection of wild areas or active management
• These strategies are crucial for maintaining biodiversity and ensuring the survival of various species

Protection of wild areas

• Protecting wild areas involves:
  • Setting aside land that is left in its natural state
  • Ensuring this land remains free from significant human interference
• This helps to maintain the habitat necessary for the survival of many species, allowing ecosystems to function naturally
  • For example, large areas of the Amazon Rainforest are protected to preserve the rich biodiversity found there

Active management

• Active management refers to human intervention to maintain or restore habitats to a desired condition
• Methods include:
  • Controlled burning: this can be used to manage grasslands and forests, promoting the growth of desired plant species
  • Reforestation: planting trees to restore deforested areas
  • Invasive species control: removing non-native species that threaten local biodiversity

Case Study

Ecosanctuary with pest-exclusion fencing: Zealandia, New Zealand

• Location: Wellington, New Zealand
• Habitat type: forest and scrubland
• Conservation strategies:
  • Pest-exclusion fencing: a predator-proof fence encircles the sanctuary to keep out invasive species like rats, stoats and possums
    • These are major threats to New Zealand’s native species
  • Reintroduction of native species: species such as the little spotted kiwi and tuatara have been reintroduced to the area
    • These reintroduction efforts have helped boost populations of species that had declined drastically due to predation by invasive species
• Surrounding land use: the sanctuary is located near urban areas but is isolated by the fence, creating a safe habitat for native wildlife

Factors in conservation area design

• Effective conservation of biodiversity in conservation areas depends on:
  • A detailed understanding of the biology of the target species
  • The size and shape of the conservation area
• These factors help ensure that the ecosystem or habitat:
  • Meets the needs of the species
  • Maintains ecological processes

Biology of target species

• Habitat requirements: understanding what specific conditions the species needs to thrive, such as food, water, shelter and breeding sites
• Home range: knowing the area size that individual animals or groups need to roam and find resources
• Life cycle: understanding the different life stages of the species and their varying habitat requirements
• Threats: identifying natural and human threats to the species, such as predation, disease, habitat destruction and climate change

Size and shape of conservation areas

• Factors that need to be considered when designing protected areas include:
  • Size
  • Shape
  • Edge effects
  • Corridors
  • Proximity to potential human influence

Protected Area Design Factors

Criteria for designing protected area	Explanation
Size	Larger areas can support more species, have larger populations and provide a greater range of habitatsThe size should be large enough to maintain viable populations of target species
Shape	The shape of a protected area can affect its biodiversity by influencing the distribution of habitats and the movement of organismsA complex shape can increase edge effects, while a simple shape may not provide enough habitat varietyIrregular shapes that follow natural features like rivers and ridges can provide better connectivity and help ecological processes
Edge effects	Edge effects refer to the changes that occur at the boundary between two different habitats or land-use types, e.g. at the boundary of a protected areaProtected areas with high edge-to-area ratios can have negative effects on biodiversity due to increased exposure to human disturbances, invasive species and variable microclimatesMinimising edge effects can be achieved by creating protected areas with simple shapes or using buffer zones around the edges
Corridors	Corridors are narrow strips of land that connect otherwise isolated areas of habitatThey can facilitate the movement of organisms and allow for gene flow between populationsCorridors can also provide additional habitat and increase the effective size of a protected areaThe effectiveness of corridors depends on their width, length and the surrounding land use
Proximity to potential human influence	Human activities can have negative impacts on biodiversityProtected areas that are close to human settlements or infrastructure may be subject to habitat destruction, pollution and huntingIt is important to balance the need for accessibility and the potential for human impact when designing protected areas

Surrounding land use

• Agricultural land: risk of pollution (e.g. via nutrient runoff), habitat fragmentation and human-wildlife conflicts
• Urban areas: higher risk of human disturbance and spread of invasive species, but can provide education and recreational opportunities
• Industrial areas: potential pollution and habitat destruction

Distance from urban centres

• Close proximity: easier access for management and public education, but higher human pressure and disturbance
• Remote locations: less human disturbance, better preservation of natural states, but harder for conservation workers to access and manage

📌 Rewilding

• Human activities such as deforestation and overharvesting of resources can disrupt, damage and destabilise ecosystems
• Conservation efforts at the ecosystem level aim to restore ecosystem stability by restoring natural ecosystem processes
  • These processes may include:
    • Predator-prey relationships
    • Seed dispersal
    • Nutrient cycling 
• This type of ecosystem restoration project is also known as rewilding
• Restoration strategies may involve:
  1. Species reintroduction
     • Reintroduction of apex predators will reduce herbivore populations and allow the restoration of habitat vegetation
     • This may boost the diversity of plant species
     • This, in turn, enhances total biodiversity
       • For example, wolves were reintroduced to Yellowstone National Park, USA
       • The wolves help to control deer populations
       • This has allowed certain types of vegetation to recover
     • Reintroducing keystone species can improve the structure of an ecosystem
       • For example, beavers have been reintroduced to parts of the UK
       • Beavers build dams
       • These dams create large wetland areas that support diverse wildlife
  2. Improving habitat connectivity
     • This involves connecting fragmented habitats to allow free movement of species
     • Creating wildlife corridors, such as hedgerows on farmland, connects small pockets of habitat
     • This allows wildlife to roam over larger areas, increasing the resources available
     • This allows larger population sizes to establish
  3. Stopping agriculture
     • Allowing land previously used for farming to return to its natural state
       • For example, the Knepp Estate in England has been rewilded
       • This former farmland now supports wild ponies, pigs and longhorn cattle
       • These species promote biodiversity by disturbing soils, dispersing seeds and grazing on vegetation, so no single plant species dominates
  4. Limiting human influence
     • This may involve preventing the harvesting of resources, e.g. by logging or fishing
     • Ecological management techniques, e.g. controlled grazing or burning, may be used to restore a habitat
     • The aim is to minimise direct human management and let ecosystems self-regulate as much as possible

📌 Biodiversity Planetary Boundary

• The planetary boundaries model outlines nine critical processes and systems that have regulated the stability and resilience of the Earth system during the Holocene epoch
  • The model identifies the level of human disturbance on certain fundamental ecological processes and systems
  • It aims to highlight where action is needed in order to avoid abrupt and irreversible changes

• The biodiversity planetary boundary refers to the limits within which humanity can safely operate to maintain the Earth’s biodiversity
  • The boundary is often referred to as biosphere integrity
  • Protecting biosphere integrity means preventing the loss of species (and therefore genetic diversity) and the loss of ecosystem functioning
  • This is important as biodiversity loss can have significant negative impacts on human life and the planet’s health

Current state of the biodiversity planetary boundary

• Biodiversity loss is occurring at an alarming rate due to human activities such as deforestation, pollution and overfishing, as well as human-induced climate change
  • Scientists estimate that we have already crossed the biodiversity planetary boundary
  • This means the current rate of species extinction is higher than the safe limit
• Conservation and ecosystemregeneration measures can be used to reverse this decline in biodiversity
  • The aim is to move back towards a safe operating space for humanity within the biodiversity planetary boundary
• In order for this to be achieved, these measures will need to be implemented at all levels, including:
  1. Individual behaviours, e.g.
     • Reduce, reuse, recycle
     • Sustainable consumption
  2. Collective actions, e.g.
     • Local conservation projects, such as tree planting or habitat restoration,
     • Increase understanding of biodiversity issues within communities through workshops and educational programmes
  3. National measures, e.g.
     • Establish national parks and wildlife reserves
     • Enforce laws that prevent illegal logging, poaching and trade in endangered species
     • Providing financial incentives for businesses and farmers to adopt environmentally friendly practices
  4. International efforts, e.g.
     • Participate in international treaties and agreements, such as the Convention on Biological Diversity (CBD)
     • Contribute to international funds that support biodiversity projects in developing countries
     • Sharing scientific knowledge and technologies across borders to enhance conservation efforts

📌 Conservation Perspectives

Impact of environmental perspectives and value systems

• Environmental perspectives and value systemsinfluence the choice of conservation strategies
  • Ecocentric perspectives:
    • Focus on the intrinsic value of biodiversity
    • Prioritise low-intervention in situ strategies
    • This refers to conservation strategies that involve minimal human interference and are implemented within the natural habitats or ecosystems where species live
    • Example: setting aside large areas of land as wilderness reserves or national parks, such as the Cairngorms National Park in Scotland (UK)
  • Anthropocentric/technocentric perspectives:
    • Focus on the economic and societal value of biodiversity
    • Encourage scientific interventions, zoos, gene banks and ecotourism
    • Example: conservation breeding programme for European bison at the Highland Wildlife Park in Scotland (UK)

Factors influencing conservation success

• The success of conservation and regeneration measures depends on:
  • Community support:
    • Engaging local communities in conservation efforts
    • Getting volunteers to help complete projects
    • Example: Snowdonia National Park Authority has a successful partnership with local farmers in Wales (UK) to manage and conserve the upland landscapes of Snowdonia National Park (known as Eryri)
  • Adequate funding:
    • Securing financial resources for conservation projects
    • Example: the National Lottery Heritage Fund supports biodiversity conservation projects across the UK
  • Education and awareness:
    • Raising public awareness about conservation issues
    • Example: millions of people watched the BBC’s Blue Planet II documentary series, which highlighted the effects of plastic pollution on marine ecosystems
  • Appropriate legislation:
    • Implementing laws and regulations to protect biodiversity
    • Example: the Wildlife and Countryside Act 1981 in the UK provides legal protection to endangered species and habitats
  • Scientific research:
    • Informing conservation decisions through scientific knowledge.
    • Example: the British Trust for Ornithology (BTO) conducts extensive research on bird populations to guide conservation efforts

Environmental justice considerations

• It is also important to consider issues of environmental justice in conservation efforts
• Conservation efforts should try to ensure that different social groups receive a fair share of conservation benefits and burdens
  • For example, the Marine Conservation Zones (MCZs) in the UK are established to protect marine habitats and species while also considering the livelihoods of local communities
  • Stakeholders, including fishermen, conservationists and local residents, are involved in the decision-making process to balance ecological protection with economic and social needs
  • This collaborative approach helps ensure that the benefits of conservation, such as improved fish stocks and healthier ecosystems, are shared among different social groups
  • At the same time, the potential burdens to certain groups, like restrictions on fishing, are fairly managed

🔍 TOK Tip: How does language shape how we value nature?

3.2 HUMAN IMPACT ON BIODIVERSITY

📌 Definitions Table

Term	Definition
Invasive Species	Non-native species that spread rapidly in a new environment, outcompeting native species and disrupting ecosystem balance.
Arboreal	Organisms that live in or primarily use trees as their habitat.
IUCN (International Union for Conservation of Nature)	A global organization that assesses the conservation status of species and publishes the Red List of Threatened Species.
Tragedy of the Commons	The overexploitation of shared, open-access resources due to individual self-interest, leading to resource depletion.

• 🧠 Exam Tips:
  
  For invasive species, always mention their impact on native biodiversity.
  
  For tragedy of the commons, include key terms like “shared resource” and “depletion” for full marks.

📌 Threats to Biodiversity

• Biodiversity is crucial for ecosystem stability, resilience and functioning
  • However, biodiversity is being negatively affected by both direct and indirect human influences

Direct threats

• Overharvesting:
  • Harvesting of species at a rate faster than their natural reproduction, leading to population decline
    • For example, overfishing of Atlantic cod in the North Sea, leading to population collapse
    • Many tropical rainforests are also under threat from overexploitation
    • They have major ecological and economic value
    • The trees are being cut down and harvested at a rate much faster than reforestation takes place
  • Continued overexploitation of a species can drive it to become extinct
• Poaching:
  • Illegal hunting or capturing of wildlife, often for trade or consumption
    • For example, poaching of African elephants for their tusks, leading to a decline in elephant populations
  • If too many individuals within a species are killed then the population will become so small that it is no longer able to survive and the species may go extinct
• Illegal pet trade:
  • Trafficking of live animals for the exotic pet market

🌐 EE Tip: Investigate human impact on a local endangered species or protected area, comparing primary and secondary data sources.

Indirect threats

• Habitat loss:
  • Destruction or fragmentation of natural habitats due to human activities such as deforestation, urbanisation, or agriculturalexpansion
    • For example, clearing of rainforests in the Amazon for cattle ranching
  • Causes of aquatic habitat loss include: destructive fishing techniques, dredging of wetlands, damage from ships, tourism and pollution
  • Causes of terrestrial habitat loss include: inland dams, deforestation, desertification, agriculture and pollution
  • When a species’ habitat is destroyed or degraded, they no longer have the support systems and resources they need to survive
• Climate change:
  • The change in global climate patterns due to greenhouse gas emissions, leading to habitat disruption, shifts in species distributions and increased frequency of extreme weather events
    • For example, melting of polar ice caps, threatening species like polar bears
• Pollution:
  • Introduction of harmful substances or contaminants into the environment, including air, water and soil pollution
    • For example, plastic pollution in oceans, endangering marine species
• Invasive alien species:
  • Non-native species introduced into an ecosystem that disrupt native species and ecosystems
    • For example, Japanese knotweed in the UK, which outcompetes native plants and causes damage to buildings
  • When humans travel between countries and continents, they often exchange (either intentionally or unintentionally) animal and plant species between their home country and the foreign country
    • These non-native species can be highly problematic as they often have no natural competitors, predators or pathogens that help limit population growth
    • Without these natural population checks, non-native species can massively increase in number
    • The large numbers of non-native species can negatively affect the native species through factors such as competition and disease

Grey Squirrel Invasion in the UK

• Alien species:
  • Grey squirrels (Sciurus carolinensis) were introduced to the UK from North America in the 19th century
  • Originally brought over as ornamental additions to estates, they have since become a major invasive species
• Impact:
  • Grey squirrels outcompete native red squirrels (Sciurus vulgaris) for resources such as food and habitat
  • They also carry the squirrelpox virus, which is fatal to red squirrels but does not affect grey squirrels
• Management strategies:
  • Culling programs: some areas have introduced culling programs to reduce grey squirrel populations, aiming to protect red squirrels and restore native biodiversity
  • Forest management: habitat management practices such as selective tree planting and creating corridors for red squirrels help to create more favourable conditions for the native species, as they are more arboreal than grey squirrels
  • Research and monitoring: continual research and monitoring of squirrel populations and their impacts can help to develop effective management strategies over time

Combined impacts

• Most ecosystems face multiple human impacts simultaneously
  • This leads to cumulative effects
  • This is when negative effects are amplified when different threats act together, reducing ecosystem resilience
    • For example, in a coral reef ecosystem, overfishing by human populations weakens the resilience of the coral reef to coral bleaching caused by climate change, making ecosystem collapse more likely

📌 Assessing Conservation Status

• International cooperation is essential if conservation is to be successful
  • There are several agreements and authorities that exist within and between countries with the aim of protecting and conserving species worldwide

IUCN

• The International Union for the Conservation of Nature (IUCN) is the global authority on the status of the natural world and the measures needed to safeguard it
• One of the duties that the IUCN carries out is assessing the conservation status of animal and plant species around the world:
  • Scientists use data and modelling to estimate the category each species should be in
• Factors used to determine the conservation status of a population include:
  • Population size (smaller populations are usually at a greater risk of extinction)
  • Rate of increase or decrease of the population
  • Degree of specialisation
  • Distribution (geographic range)
  • Reproductive potential and behaviour (breeding potential)
  • Geographic range
  • Degree of endemicity (i.e. if the species is only found in a single specific area)
  • Degree of habitat fragmentation
  • Quality of habitat
  • Trophic level (animals in higher trophic levels are usually at a greater risk of extinction)
  • Known threats

• The IUCN has their own classification system:
  • There are several different categories and levels that a species can fall into depending on its population numbers and the threats and risks to those populations
  • Species that have been assessed are categorised by the IUCN as:
    • LC = least concern
    • NT = near threatened
    • VU = vulnerable
    • EN = endangered
    • CR = critically endangered
    • EW = extinct in the wild
    • EX = extinct
  • Species can also be classed as DD (data deficient) when there is not enough data on which to base a category choice, or as NE (not evaluated)
• Animals that are on the IUCN Red List of Threatened Species™ can be seen online as this list is made public
• Giving a global conservation status highlights how vulnerable certain species are
  • This helps governments, NGOs and individuals to select appropriate conservation priorities and management strategies

🔍 TOK Tip: Should species be conserved based on ecological value or emotional appeal (e.g. flagship species)?

📌 Conservation Case Studies

Extinct species

• Passenger Pigeon (Ectopistes migratorius):
  • The Passenger pigeon was once one of the most abundant bird species in North America, numbering in the billions of individuals
  • However, due to overhunting and habitat destruction, the passenger pigeon went extinct in the early 20th century
  • The hunting of these birds for meat, as well as the destruction of their forest habitats, led to a sharp decline in their numbers
  • By the late 1800s, the species was in serious decline, and despite some attempts at conservation, it went extinct in 1914

• Tasmanian Tiger (Thylacinus cynocephalus):
  • The Thylacine, also known as the Tasmanian Tiger or Tasmanian Wolf, was a carnivorous marsupial that once inhabited the Australian island of Tasmania
  • Human activity such as hunting, habitat loss and disease transmission by introduced species caused their population to decline
  • The last known Tasmanian tiger died in captivity in 1936, marking the extinction of the species

Critically endangered species

Sumatran Orangutan (Pongo abelii):

• The Sumatran orangutan is one of three species of orangutan and is found only on the Indonesian island of Sumatra
• Habitat destruction and fragmentation due to logging, conversion of forests to agriculture, and infrastructure development have been the primary causes of its decline
• In addition, illegal hunting and capture of orangutans for the pet trade have also contributed to their decline
• The Sumatran orangutan is now critically endangered, with only around 14 000 individuals remaining in the wild

• Black rhinoceros (Diceros bicornis):
  • The black rhinoceros is a large mammal native to Africa and is critically endangered due to poaching for their horns, habitat loss, and civil unrest in the countries of their range
  • Their population has declined by over 90% since the 1960s, and there are currently only around 3 000 mature individuals remaining in the wild
  • Conservation efforts such as anti-poaching patrols, habitat restoration and captive breeding programs are underway to try to save this species from extinction

Improving species

Southern white rhinoceros (Ceratotherium simum):

• The Southern white rhinoceros was once on the brink of extinction due to poaching for their horns, with only a handful of individuals surviving in the wild in South Africa in the early 20th century
• However, conservation efforts including increased law enforcement, habitat protection, and captive breeding programs have helped their population recover to over 18 000 individuals today
• While they are still threatened by poaching and habitat loss, the Southern white rhinoceros’ conservation status has greatly improved thanks to human intervention

• Bald eagle (Haliaeetus leucocephalus):
  • The bald eagle is a bird of prey native to North America and was once on the brink of extinction due to habitat destruction, hunting, and pesticide use, which caused eggshell thinning and reproductive failure
  • Conservation efforts such as habitat protection, captive breeding programs, and the banning of harmful pesticides like DDT have helped their population recover from less than 500 pairs in the 1960s to over 10 000 pairs today
  • The bald eagle’s conservation status has greatly improved thanks to human intervention

📌 Tragedy of the Commons

Tragedy of the commons

• The tragedy of the commons describes the overuse and depletion of a shared resource
  • It occurs when individuals act in their own self-interest rather than considering the common good
  • It leads to the degradation of the resource, making it unavailable for future use

Implications for sustainability

• Overexploitation:
  • Many natural resources are used faster than they can be replenished
  • This is resulting in resource depletion and could eventually lead to the collapse of certain ecosystems
• Impact on biodiversity:
  • Result in the loss of habitats and species
  • It can also lead to reduced genetic diversity
    • These factors can weaken ecosystem resilience, threatening biodiversity

3.1 BIODIVERSITY AND EVOLUTION

📌 Definitions Table

Term	Definition
Resilience	The ability of an ecosystem to recover from disturbance and return to its original state while maintaining function and structure.
Heritable Characteristics	Traits encoded in DNA that can be passed from parents to offspring, influencing evolution through natural selection.
Adaptive Features	Traits that enhance an organism’s survival or reproduction in a specific environment.
Natural Selection	The process where organisms with favorable heritable traits survive and reproduce more successfully, leading to evolution.
Selection Pressure	Environmental factors that affect survival and reproduction, driving natural selection and adaptation.
Species Diversity	A measure of biodiversity that includes both the number of species (richness) and their relative abundance (evenness) in an area.
Species Richness	The number of different species present in a given area, regardless of their population sizes.
Biodiversity	The variety of life in all its forms, including genetic, species, and ecosystem diversity, within a given area.
Habitat Diversity	The range of different habitats or ecosystems in a given area, contributing to overall biodiversity.
Genetic Diversity	The variation of genes within a species population, contributing to adaptability and resilience.

• 🧠 Exam Tips:
  
  For diversity terms, use “variety” and specify what is being measured (genes, species, habitats).
  
  
  Always distinguish between species richness vs. species diversity — a common exam point.

📌 Biodiversity and Resilience

Why is biodiversity important?

• Biodiversity can be thought of as a study of all the variation that exists within and between all forms of life
• Biodiversity looks at the range and variety of  habitats, species and genes within a particular region
• It can be assessed at three different levels:
  • The number and range of different ecosystems and habitats
  • The number of species and their relative abundance
  • The genetic variation within each species
• Biodiversity is very important for the resilience of ecosystems
  • This is because biodiversity allows them to resist changes in the environment and avoid ecological tipping points

Habitat diversity

• This is the range of different habitats within a particular ecosystem or biome
• If there is a large number of different habitats within an area, then that area has high biodiversity
  • A good example of this is a coral reef
  • They are very complex with lots of microhabitats and niches to be exploited
• If there is only one or two different habitats then an area has low biodiversity
  • Large sandy deserts typically have very low biodiversity
  • The conditions are basically the same throughout the whole area

Species diversity

• An ecosystem such as a tropical rainforest that has a very high number of different species would be described as species-rich
  • Species richness is the number of species within an ecosystem
• Species diversity looks at the number of different species in an ecosystem, and also the evenness of abundance across the different species present
  • The greater the number of species in an ecosystem and the more evenly distributed the number of organisms are among each species, then the greater the species diversity
• Ecosystems with high species diversity are usually more stable than those with lower species diversity as they are more resilient to environmental changes
  • For example in the pine forests of Florida, the ecosystem is dominated by one or two tree species
  • If a pathogen comes along that targets one of the two dominant species of trees, then the whole population could be wiped out and the ecosystem it is a part of could collapse

Genetic diversity

• Genetic diversity is the diversity of genes found within different individuals of a species
• Although individuals of the same species will have the same set of genes, these genes can take a variety of different forms
• This makes it possible for genetic diversity to occur between populations of the same species
• Genetic diversity within a single population also occurs
  • This diversity is important as it can help the population adapt to, and survive, changes in the environment
  • This could include changes in biotic factors such as new predators, pathogens and competition with other species
  • Or the changes could be abiotic factors like temperature, humidity and rainfall

📌 Evolutionary Processes

• Biodiversity arises from evolutionary processes
  • Evolution is the cumulative change (i.e. the overall change over time) in the heritable characteristics of a population or species
  • Natural selection is the name of the mechanism that drives this evolutionary change
    • Natural selection occurs continuously and can take place over billions of years
    • The result of this process of natural selection is the biodiversity of life on Earth we see today

Natural selection

• In any environment, the individuals that have the best adaptive features are the ones most likely to survive and reproduce
• This results in natural selection:
  • Individuals in a species show a range of variation caused by differences in genes (genetic diversity)
  • When organisms reproduce, they produce more offspring than the environment is able to support
  • This leads to competition for food and other resources, which results in a “struggle for survival“
  • Individuals with characteristics most suited to the environment have a higher chance of survival and more chances to reproduce
  • Therefore, the genes resulting in these characteristics are passed on to offspring at a higher rate than those with characteristics less suited to survival
  • This means that in the next generation, there will be a greater number of individuals with the better adapted variations in characteristics
• This theory of natural selection was put forward by Charles Darwin and became known as “survival of the fittest”

Example of natural selection

• Imagine a population of rabbits shows variation in fur colour
• The rabbits have natural predators like foxes
  • This acts as a selection pressure
• Rabbits with a white coat do not camouflage as well as rabbits with brown fur
  • This means predators are more likely to see white rabbits when hunting
• As a result, rabbits with white fur are less likely to survive than rabbits with brown fur
• The rabbits with brown fur therefore have a selection advantage
  • This means they are more likely to survive to reproductive age and be able to pass on their genes to their offspring
• Over many generations, the frequency of the gene for brown fur will increase and the frequency of the gene for white fur will decrease

• Remember that organisms better suited to their environments are more likely to survive
  • However, this does not mean their survival is guaranteed
• Organisms that are less suited to an environment are still able to survive and potentially reproduce within it
  • However, their chance of survival and reproduction is lower than the individuals that are better-adapted
• Also, it is important to be aware that an environment, and the selection pressures it exerts on an organism, can change over time
  • When a change occurs then a different characteristic may become more advantageous
• Finally, remember that all organisms (not just animals) experience selection pressures as a result of the environment they are in

Speciation

• Speciation is the generation of new species through evolution
• It occurs when populations of a species become isolated and adapt to their environments in different ways
• Over time, these populations become so different that they can no longer interbreed with each other to produce fertile offspring
• When they cannot interbreed in this way, they are considered separate species

📌 Assessing Biodiversity

Species diversity

• Species richness is the number of species in a community or defined area
  • In some cases, it can be a useful measure to compare the biodiversity of different areas
• However, in other cases, species richness can be a misleadingindicator of diversity
  • This is because it does not take into account the number of individuals of each species
• Once the abundance of each species in an area has been recorded, the results can be used to calculate the species diversity for that area
  • Species diversity looks at the number of different species in an area but also the species evenness
    • Species evenness is the evenness of abundance across the different species (i.e. their relative abundances)

Species richness vs species diversity

• Species diversity is a much more informative measurement than species richness and conservationists often favour the use of species diversity as it takes into account both species richness and evenness
• For example:
  • Area 1 and Area 2 both contain four tree species
  • However, Area 2 is actually dominated by one species and in fact, one of the species is very rare (only one individual)
  • Although the two areas have exactly the same species richness, Area 1 has a higher species evenness (and therefore a higher overall species diversity) than Area 2
  • This example illustrates the limitations of using just species richness on its own

Simpson’s diversity index

• Biological communities can be described and compared through the use of diversity indices
  • These are mathematical tools used to quantify the diversity of species within a community
• These indices provide a measure of the variety of species present, as well as their relative abundances
  • They can be used to compare different communities or to track changes in diversity over time
• A commonly used diversity index is Simpson’s index

📌 Biodiversity Management

Importance of biodiversity management

• Biodiversity refers to the variety of life on Earth, including ecosystems, habitats, species and genetic diversity
• Managing biodiversity is crucial for many reasons, including:
  • Ecosystem stability—biodiversity maintains ecosystem resilience to environmental changes
  • Medicine and pharmaceuticals—many medicines are derived from biodiversity, offering potential treatments for various diseases
  • Cultural and spiritual significance—biodiversity holds cultural and spiritual importance, preserving traditional knowledge
  • Economic benefits—biodiversity contributes to tourism and livelihoods, supporting local economies
  • Climate regulation—ecosystems help mitigate climate change by sequestering carbon dioxide
  • Pollination and food security—biodiversity, especially pollinators, is essential for crop pollination and food production.

Gathering knowledge of biodiversity

• Effective biodiversity management requires comprehensive knowledge at both global and regional levels

❤️ CAS Tip: Design a biodiversity awareness campaign or species ID workshop in your community.

Global biodiversity data collection

• International organisations:
  • Organisations like the IUCN (International Union for Conservation of Nature) and WWF (World Wildlife Fund) gather data globally
    • For example, the IUCN Red List categorises species based on their extinction risk

Regional biodiversity data collection

• National and local agencies:
  • Government-funded agencies, such as Natural England in the UK, collect data on local species and habitats
    • For example, Natural England conducts surveys on bird populations to monitor their status
• Citizen science:
  • Involves public participation in scientific research
  • Volunteers collect data on local wildlife, which is then used by scientists
    • For example, the Big Butterfly Count in the UK engages the public in counting butterfly species
• Voluntary organisations:
  • NGOs like The Wildlife Trusts (UK) work on local biodiversity projects
    • For example, the Wildlife Trusts have a long-term hedgehog monitoring programme

Training for data collection

• Indigenous people:
  • Indigenous communities often possess detailed traditional knowledge of local ecosystems
  • Training helps integrate their knowledge with scientific methods
    • For example, indigenous rangers in Australia are trained to monitor and protect native species
• Parabiologists:
  • These are local people trained to assist in biological research
  • They bridge the gap between local communities and scientific researchers
  • They may be used to gather information for use in conservation management

Biodiversity management strategies

• There are many different biodiversity management strategies but the main categories are:
  • The creation of protected areas
  • The restoration of existing but damaged habitat
  • The implementation of sustainable management strategies
• Protected areas:
  • Creating parks, reserves and conservation areas
    • For example, the establishment of marine protected areas to safeguard coral reefs
• Habitat restoration:
  • Restoring degraded ecosystems to their natural state
    • For example, rewilding projects involve the restoration of ecosystems by reintroducing native species to their original habitats
• Sustainable practices:
  • Encouraging sustainable agriculture, forestry and fishing
    • For example, certification schemes like Fair Trade promote sustainable farming practices