Author: Admin

📌Definition Table

📌Introduction

Environmental change — whether natural or human-induced — can alter species niches by shifting the conditions and resources available. Organisms may respond by moving, adapting, or facing extinction. Some species expand their range, while others become more restricted. These dynamics have profound implications for biodiversity conservation, ecosystem services, and predicting species’ future distributions.

❤️ CAS Link: Coordinate a climate-awareness campaign that highlights local species vulnerable to niche contraction due to habitat loss or climate change.

📌 Climate Change and Niche Shifts

• Rising temperatures and altered precipitation patterns change the location of suitable habitats.
• Species may shift polewards or to higher altitudes to track their climatic niche.
• Example: Alpine plants move upslope as lower elevations become too warm.
• Marine species shift towards cooler waters, disrupting fisheries and predator-prey relationships.
• Climate change also alters phenology, causing mismatches between species (e.g., pollinators and flowering times).

🧠 Examiner Tip: Always link climate change impacts to both abiotic (temperature, rainfall) and biotic (competition, predation) niche constraints.

📌 Human Activities and Niche Contraction

• Habitat destruction from agriculture, logging, and urbanisation reduces available niche space.
• Pollution can eliminate sensitive species from parts of their range.
• Overexploitation (hunting, overfishing) can shrink populations below viable levels.
• Invasive species outcompete or prey on native species, reducing their realised niche.
• Example: Native mussels in North America displaced by invasive zebra mussels.

🌍 Real-World Connection: Orangutan niches have contracted severely due to palm oil plantation expansion, forcing conservation action in remaining forests.

📌 Niche Expansion through Disturbance or Adaptation

• Disturbances such as forest fires can create new habitat for pioneer species, expanding niches temporarily.
• Reduced competition (e.g., after predator removal) allows some species to exploit new resources.
• Phenotypic plasticity enables species to survive in broader conditions without genetic change.
• Example: Coyotes expanded their niche in North America after wolf populations declined.
• Evolutionary adaptation can permanently broaden a niche, given sufficient time and selective pressure.

📝 Paper 2: Data Response Tip: When interpreting niche adaptation graphs, discuss both the direction (expansion or contraction) and the ecological drivers behind the change.

📌Definition Table

📌Introduction

Species do not live in isolation — they interact constantly with others in their ecosystem. These interactions shape ecological niches, influencing where species live, what they eat, and how they reproduce. Competition tends to narrow realised niches, while facilitative interactions like mutualism can expand them. Understanding these dynamics is essential for conservation biology and for predicting how ecosystems respond to environmental change.

❤️ CAS Link: Lead a school garden project where native plants are selected to promote beneficial interactions with pollinators and other species.

📌 Interspecific Competition

• Occurs when two or more species require the same limited resource (e.g., food, nesting sites, light).
• Reduces population growth rates for all competitors involved.
• May result in competitive exclusion (one species outcompetes the other) or resource partitioning (niche differentiation).
• Example: Different grass species competing for light and nutrients in a meadow.
• Can drive evolutionary change, selecting traits that reduce overlap in resource use.

🧠 Examiner Tip: When describing competition, always specify the resource in question and whether the competition is exploitative (indirect) or interference (direct).

📌 Predation and Herbivory

• Predation controls prey populations, preventing overpopulation and resource depletion.
• Can drive prey adaptations such as camouflage, mimicry, and defensive behaviours.
• Herbivory is a specialised form where herbivores feed on plants; plants may evolve spines, toxins, or rapid regrowth as defences.
• Predation pressure can create “landscape of fear” effects, altering prey behaviour and habitat use.
• Example: Sea otters preying on sea urchins regulates kelp forest health.

🌍 Real-World Connection: Reintroduction of wolves to Yellowstone restored balance by reducing elk overgrazing, allowing vegetation recovery.

📌 Mutualism and Commensalism

• Mutualism benefits both partners — e.g., bees and flowering plants; coral and zooxanthellae.
• Can be obligate (partners cannot survive without each other) or facultative (beneficial but not essential).
• Commensalism benefits one partner without affecting the other — e.g., barnacles on whales gain transport to nutrient-rich waters.
• Such relationships can increase survival, reproduction, and niche breadth for one or both species.
• May shift along a spectrum over time, becoming parasitic or competitive depending on conditions.

📌Definition Table

📌Introduction

An ecological niche defines how a species interacts with its environment and other organisms, encompassing its habitat, resource use, and role in energy and nutrient cycles. The distinction between a fundamental niche and a realised niche highlights the gap between theoretical potential and ecological reality. Studying niches is crucial for understanding biodiversity patterns, predicting species distributions, and managing ecosystems under environmental change.

❤️ CAS Link: Organise a local biodiversity survey and map the niches of key species in a nearby park, linking species presence to specific habitat features and resources.

📌 Fundamental vs. Realised Niches

• Fundamental Niche represents the total possible conditions a species can tolerate, determined by its physiological limits and resource needs.
• Realised Niche is narrower due to interspecific competition, predation, parasitism, and human disturbance.
• Example: Barnacle species — Chthamalus occupies higher shore (fundamental niche broader but restricted by competition), while Balanus dominates lower shore.
• Abiotic factors (temperature, salinity, pH) primarily shape the fundamental niche, while biotic factors constrain the realised niche.
• Niche modelling uses environmental data to predict potential distributions, crucial for conservation planning.

🧠 Examiner Tip: In application questions, always mention both abiotic and biotic influences when explaining why a realised niche is smaller than a fundamental niche.

📌 Competitive Exclusion Principle

• States that two species with identical niches cannot coexist in the same habitat long-term.
• Leads to local extinction of one species or evolutionary divergence into different niches.
• Example: Paramecium aurelia outcompetes Paramecium caudatum in lab experiments when grown together.
• Encourages natural selection for traits that minimise direct competition.
• Forms the basis for predicting invasive species impacts on native communities.

🌍 Real-World Connection: The decline of native red squirrels in the UK is partly due to competitive exclusion by the invasive grey squirrel, which is more efficient at exploiting certain food resources.

📌 Resource Partitioning

• Occurs when species divide resources by specialising in different aspects of the niche.
• Can be spatial (different habitats), temporal (different activity times), or dietary (different prey or plant species).
• Example: Anole lizards in the Caribbean occupy distinct vertical zones of forest to avoid competition.
• Reduces direct competition, allowing coexistence of ecologically similar species.
• Often associated with morphological adaptations, such as beak size in Darwin’s finches.

🔍 TOK Perspective: The concept of a “niche” is a human framework — how might different cultures or indigenous knowledge systems describe species’ ecological roles differently?

📌Measuring and Modelling Niches

• Niche Breadth — range of resources used; broad niches indicate generalists, narrow niches indicate specialists.
• Niche Overlap — degree to which species share resources; higher overlap increases competition.
• Ecological Modelling Tools — e.g., MaxEnt software uses occurrence records to predict distributions based on environmental parameters.
• Field Experiments — manipulation of resource availability or competitor presence tests niche limits.
• Applications in Conservation — niche models guide reintroduction programs and habitat restoration efforts.

📝 Paper 2: Data Response Tip: When interpreting niche diagrams, clearly label the fundamental and realised niches, and explain limiting factors in context of the given data.

📌Definition Table

📌Introduction

Life in extreme environments requires unique physiological, structural, and behavioural adaptations. In habitats with low oxygen — such as high altitudes, deep seas, or burrows — organisms must maximise oxygen uptake, transport, and storage. Similarly, specialised environments such as deserts, polar regions, and hydrothermal vents impose multiple stresses including temperature extremes, pressure, and nutrient limitations. Adaptations often involve convergent evolution where unrelated species evolve similar solutions to environmental challenges.

❤️ CAS Link: Partner with a mountaineering club to create a training workshop on physiological preparation for high-altitude treks, including oxygen acclimatisation strategies.

📌 High-Altitude Adaptations

• Increased Hemoglobin Affinity — Ensures oxygen loading in thin air (e.g., llamas, yaks).
• Higher Red Blood Cell Count — Increases oxygen-carrying capacity of blood.
• Expanded Lung Volume — Improves oxygen uptake per breath.
• Increased Capillary Density — Enhances oxygen delivery to tissues.
• Behavioural Acclimatisation — Gradual ascent reduces risk of altitude sickness in humans.

🧠 Examiner Tip: In application questions, always distinguish between short-term acclimatisation and long-term genetic adaptations.

📌 Aquatic Low-Oxygen Environments

• Large Gills or Respiratory Surfaces — Maximise oxygen extraction from water.
• Cutaneous Respiration — Amphibians and some fish absorb oxygen directly through skin.
• Air Breathing in Fish — Lungfish use lungs in stagnant, oxygen-poor waters.
• High Myoglobin Concentration — In diving mammals, stores oxygen in muscles for extended dives.
• Bradycardia — Slowed heart rate during dives conserves oxygen.

🌍 Real-World Connection: Free-divers study marine mammal adaptations to extend breath-holding limits safely.

📌 Deep-Sea Adaptations

• Pressure-Resistant Enzymes — Function normally under high hydrostatic pressure.
• Slow Metabolism — Reduces oxygen demand.
• Bioluminescence — Used for prey attraction, camouflage, and communication in dark waters.
• Large Eyes — Optimised for detecting minimal light.
• Flexible Skeletons — Prevent structural damage under pressure.

🔍 TOK Perspective: Studying deep-sea species challenges our assumptions about the limits of life and “habitability” of environments.

📌 Adaptations in Burrowing and Nocturnal Animals

• Low Metabolic Rates — Reduce oxygen needs in poorly ventilated burrows.
• Tolerance to High CO₂ Levels — Special hemoglobin variants prevent acid–base imbalance.
• Efficient Ventilation Movements — Rapid breathing when emerging above ground to replenish oxygen stores.
• Use of Anaerobic Pathways — Temporarily sustain energy production without oxygen.
• Water Conservation — Linked to burrow life in arid climates.

📌 Hydrothermal Vent and Extremophile Adaptations

• Chemosynthesis — Bacteria use hydrogen sulfide instead of sunlight for energy production.
• Symbiotic Relationships — Tube worms rely on internal bacteria for nutrients.
• Heat-Stable Enzymes — Allow survival at temperatures near boiling.
• Pressure-Resistant Membranes — Maintain fluidity and function under extreme pressure.
• Toxin Resistance — Proteins resistant to heavy metals and toxins in vent water.

📝 Paper 2: Data Response Tip: For environmental adaptation questions, always link the adaptation to both the specific environmental stress and the physiological outcome.

📌Definition Table

📌Introduction

Water and salt balance is crucial for maintaining osmotic pressure, enzyme function, and metabolic processes. Different environments — freshwater, marine, and terrestrial — present unique challenges to organisms. Adaptations can be structural, physiological, or behavioural, enabling organisms to survive and reproduce while conserving or excreting water appropriately.

❤️CAS Link: Design an awareness campaign on sustainable freshwater use, linking it to how animals adapt to water scarcity and salinity challenges.

📌 Osmoregulation in Freshwater Animals

• Hyperosmotic to Environment — Body fluids contain more salts than surrounding water, causing water influx and ion loss.
• Active Ion Uptake — Gills absorb salts through specialised chloride cells.
• Large Volume Dilute Urine — Kidneys excrete excess water while retaining salts.
• Low Permeability to Water — Mucus-covered skin reduces water influx.
• Behavioural Strategies — Freshwater fish avoid areas with strong currents that increase water influx.

🧠 Examiner Tip: When comparing osmotic strategies, always specify the direction of water and ion movement for full marks.

📌 Osmoregulation in Marine Animals

• Hypoosmotic to Environment — Body fluids contain less salt than seawater, causing water loss and ion gain.
• Drinking Seawater — Compensates for water loss; excess salts actively excreted.
• Salt Glands — Found in seabirds and reptiles for excreting concentrated salt solutions.
• Small Volume Concentrated Urine — Conserves water while removing salts.
• Countercurrent Exchange in Gills — In fish, aids in salt excretion and oxygen uptake simultaneously.

🌍 Real-World Connection: Desalination technology mimics ion transport mechanisms found in marine animals to remove salt from seawater.

📌 Adaptations in Terrestrial Animals

• Water Conservation — Thick cuticles in insects, keratinised skin in reptiles and mammals.
• Efficient Kidneys — Long loops of Henle in desert mammals maximise water reabsorption.
• Nocturnal Behaviour — Reduces water loss through evaporation during cooler nights.
• Metabolic Water — Produced during oxidation of food molecules, important for desert animals like kangaroo rats.
• Excretion of Concentrated Waste — Uric acid in birds and reptiles minimises water loss compared to urea excretion.

📌 Kidney Function in Osmoregulation

• Filtration — Glomerulus filters blood under high pressure.
• Selective Reabsorption — Proximal tubule reabsorbs glucose, amino acids, and most water.
• Loop of Henle — Generates concentration gradient in medulla; longer in desert species for maximal water reabsorption.
• Distal Tubule and Collecting Duct — Adjust salt and water balance under hormonal control (ADH, aldosterone).
• Urine Concentration — Final osmolarity reflects both water needs and environmental demands.

📝 Paper 2: Data Response Tip: For questions with urine concentration graphs, explain patterns using both kidney structure and environmental water availability.

📌Definition Table

📌Introduction

Temperature regulation is essential for maintaining optimal enzyme activity, metabolic rate, and cellular processes. Endotherms use metabolic heat production combined with behavioural and physiological adaptations to stabilise body temperature, while ectotherms rely largely on environmental heat sources. Survival in extreme hot or cold environments requires a range of structural, behavioural, and physiological traits that reduce thermal stress and energy expenditure.

❤️ CAS Link: Create an educational campaign showing how different animals adapt to extreme temperatures, including interactive models and infographics for local schools.

📌 Adaptations in Cold Environments

• Insulation — Thick fur or feather layers trap air for insulation; blubber in marine mammals reduces heat loss.
• Small Surface Area-to-Volume Ratio — Compact body shapes (Allen’s Rule) minimise heat loss.
• Behavioural Strategies — Huddling, burrowing, or seasonal migration to warmer regions.
• Countercurrent Heat Exchange — Found in penguins and Arctic foxes to retain core heat in cold limbs.
• Increased Metabolic Heat Production — Shivering thermogenesis and brown adipose tissue metabolism in mammals.

🧠 Examiner Tip: In application questions, link each structural feature (e.g., fur length) directly to the thermoregulatory advantage it provides.

📌 Adaptations in Hot Environments

• Large Surface Area-to-Volume Ratio — Long limbs and ears (e.g., fennec fox) facilitate heat dissipation.
• Reduced Insulation — Short fur or seasonal shedding to prevent overheating.
• Behavioural Cooling — Seeking shade, burrowing during the day, being nocturnal to avoid peak heat.
• Evaporative Cooling — Sweating in humans; panting in dogs; gular flutter in birds.
• Tolerance of Higher Body Temperatures — Camels can allow their body temperature to rise to reduce water loss from sweating.

🌍 Real-World Connection: Desert survival training often applies knowledge of evaporative cooling and hydration strategies based on animal adaptations.

📌 Endothermy vs. Ectothermy

• Endotherms — Stable internal temperatures allow activity in varied conditions but require high energy intake.
• Ectotherms — Lower metabolic demands but activity restricted to suitable environmental temperatures.
• Behavioural Regulation — Ectotherms bask to warm up and retreat to shade to cool down; endotherms may migrate seasonally.
• Ecological Niches — Endothermy allows colonisation of colder regions; ectothermy often limits species to warmer climates.
• Thermal Acclimatisation — Both groups can adjust tolerance ranges seasonally to match environmental conditions.

🔍 TOK Perspective: The classification of animals into endotherms and ectotherms is a simplification — many species exhibit traits of both under certain conditions.

📌 Physiological Mechanisms of Thermoregulation in Humans

• Hypothalamic Control — Detects changes in blood temperature and initiates corrective responses.
• Vasodilation and Vasoconstriction — Control blood flow to skin to regulate heat exchange.
• Sweating and Shivering — Increase or decrease heat production and loss.
• Metabolic Adjustments — Thyroid hormone levels influence long-term metabolic heat production.
• Acclimatisation — Gradual physiological adjustments to temperature extremes improve survival and performance.

📌 Extremophile Thermoregulation

• Thermophilic Bacteria — Enzymes adapted to function at high temperatures; heat-stable membranes.
• Polar Fish — Antifreeze proteins prevent ice crystal formation in body fluids.
• Alpine Plants — Grow in rosettes to trap heat and reduce wind exposure.
• Insects in Deserts — Use stilting behaviour to keep their bodies above hot sand.
• Reptiles in Cold Climates — Hibernate to survive long periods of low temperatures.

📝 Paper 2: Data Response Tip: In data interpretation questions on temperature regulation, link observed patterns to both structural and physiological adaptations — not just one type.

📌Definition Table

📌Introduction

Locomotion is essential for many animals to survive, reproduce, and interact with their environment. It involves a combination of skeletal, muscular, and nervous systems working together to generate coordinated movement. The efficiency of locomotion depends on joint flexibility, muscle strength, lever mechanics, and adaptations suited to an organism’s ecological niche. Range of motion and locomotor patterns are determined by both anatomy and lifestyle.

❤️ CAS Link: Collaborate with the sports department to conduct a school-wide flexibility and movement workshop using goniometers, teaching participants how joint mobility impacts performance.

📌 Reasons for Locomotion

• Foraging — Movement to obtain food resources, such as predators hunting prey or herbivores searching for plants.
• Escape from Predators — Rapid movement, camouflage relocation, or shelter seeking to avoid predation.
• Mating and Reproduction — Travel to breeding grounds or displaying courtship movements to attract mates.
• Migration — Seasonal long-distance movements to exploit changing environmental resources.
• Territorial Defence — Patrolling and marking territory boundaries to deter competitors.

🧠 Examiner Tip: When asked about migration, always mention triggering cues such as temperature, photoperiod, and food availability.

📌 Joint Movement and Range of Motion

• Joint movement depends on joint type, ligament elasticity, muscle length, and tendon flexibility.
• Synovial joints allow various motions: hinge (flexion/extension), ball-and-socket (rotation, abduction/adduction), pivot (rotation), saddle, and gliding movements.
• ROM can be measured with a goniometer for clinical or sports performance purposes.
• Flexibility training can increase ROM, while injury or arthritis can reduce it.
• Different sports place varying demands on ROM (e.g., gymnasts require extreme flexibility, sprinters prioritise explosive force).

🌍 Real-World Connection: Physiotherapists use ROM measurements to track recovery after injuries such as ACL tears or shoulder dislocations.

📌 Locomotor Adaptations

• Aquatic Animals — Streamlined bodies reduce drag; fins/flippers act as paddles or hydrofoils (e.g., dolphins, seals).
• Flying Animals — Lightweight skeletons, wing adaptations, and strong flight muscles (e.g., birds, bats, insects).
• Terrestrial Runners — Long limbs for stride efficiency; springy tendons store and release energy (e.g., cheetahs, horses).
• Burrowers — Strong forelimbs with claws for digging (e.g., moles, armadillos).
• Climbers — Prehensile tails, opposable digits, and flexible joints for grip (e.g., monkeys, geckos).

📌 Link Between Locomotion and Joint Structure

• Joint structure is optimised for specific movement types (e.g., shoulder joint sacrifices stability for flexibility; hip joint prioritises stability).
• Ligament and tendon arrangement influences both mobility and injury risk.
• Muscle fibre type distribution (fast-twitch vs. slow-twitch) affects endurance vs. speed performance.
• Lever mechanics determine whether movement prioritises force or speed.
• Evolution shapes locomotor features based on environmental pressures and lifestyle needs.

📝 Paper 2: Data Response Tip: When interpreting movement data, always link observed ROM or locomotor ability to both anatomical structure and ecological function for maximum marks.