IB DP Biology Climate change Study Notes
IB DP Biology Climate change Study Notes
IB DP Biology Stability and change Study Notes at IITian Academy focus on specific topic and type of questions asked in actual exam. Study Notes focus on IB Biology syllabus with guiding questions of
- What are the drivers of climate change?
- What are the impacts of climate change on ecosystems?
Standard level and higher level: 3 hours
Additional higher level: 1 hour
D4.3.1 – Anthropogenic Causes of Climate Change
🧠 What Are Anthropogenic Causes?
- Anthropogenic means caused by humans.
- Focus on human activities increasing carbon dioxide (CO₂) and methane (CH₄) in the atmosphere.
🌿 Main Greenhouse Gases from Humans
| Gas | Source | Impact |
|---|---|---|
| Carbon dioxide (CO₂) | Burning fossil fuels (coal, oil, gas), deforestation | Traps heat, contributes to global warming |
| Methane (CH₄) | Agriculture (rice paddies, livestock), landfill waste | More effective at trapping heat but shorter-lived than CO₂ |
🔍 Correlation vs Causation
- Positive correlation: Two variables increase together (e.g., CO₂ levels and global temperature).
- Correlation ≠ Causation: Correlation alone doesn’t prove one causes the other.
- Example: Antarctic ice core data shows CO₂ and temperature rise together over 100,000+ years.
- However, other evidence (e.g., lab experiments, climate models) supports CO₂ causing temperature increase.
📍 Why This Matters
- Understanding human impact helps target actions to reduce greenhouse gas emissions.
- Distinguishing correlation and causation prevents misunderstanding of climate science.
🧠 Summary Box:
Human activities increase atmospheric CO₂ and methane, driving climate change.
CO₂ mainly from burning fossil fuels; methane from agriculture and waste.
Positive correlation between greenhouse gases and temperature exists, but causation requires additional evidence.
Clear understanding of these concepts is crucial for interpreting climate data.
Human activities increase atmospheric CO₂ and methane, driving climate change.
CO₂ mainly from burning fossil fuels; methane from agriculture and waste.
Positive correlation between greenhouse gases and temperature exists, but causation requires additional evidence.
Clear understanding of these concepts is crucial for interpreting climate data.
D4.3.2 – Positive Feedback Cycles in Global Warming
🧠 What Are Positive Feedback Cycles?
- Positive feedback cycles amplify or accelerate global warming.
- A change causes effects that increase the original change further.
🌿 Key Examples of Positive Feedback in Global Warming
| Feedback Process | How It Accelerates Warming |
|---|---|
| CO₂ release from deep ocean | Warming oceans release stored CO₂, adding greenhouse gases to atmosphere. |
| Loss of reflective snow and ice (albedo effect) | Less ice means less sunlight is reflected; more absorbed heat warms Earth faster. |
| Accelerated decomposition of peat and organic matter in permafrost | Warmer temperatures speed up decay, releasing CO₂ and methane (CH₄). |
| Methane release from melting permafrost | Methane is a powerful greenhouse gas, increasing warming. |
| Increased droughts and forest fires | Fires release CO₂ and reduce forests’ ability to absorb CO₂, worsening warming. |
📍 Why Positive Feedback Is Concerning
- These cycles create a vicious circle that speeds up climate change.
- Makes it harder to slow or reverse global warming once certain thresholds are crossed.
🧠 Summary Box:
Positive feedback loops amplify global warming effects.
Examples include greenhouse gas releases from oceans and permafrost, and loss of reflective ice.
Forest fires and droughts further increase atmospheric CO₂.
Understanding feedback cycles is key to predicting and managing climate change.
Positive feedback loops amplify global warming effects.
Examples include greenhouse gas releases from oceans and permafrost, and loss of reflective ice.
Forest fires and droughts further increase atmospheric CO₂.
Understanding feedback cycles is key to predicting and managing climate change.
D4.3.3 – Change from Net Carbon Accumulation to Net Loss in Boreal Forests: An Example of a Tipping Point
🧠 What is a Tipping Point?
- A tipping point is when a small change causes a big, often irreversible shift in an ecosystem or system.
- For boreal forests, it’s the shift from absorbing carbon to releasing more carbon than they store.
🌿 Boreal Forests and Carbon
- Boreal forests (taiga) typically accumulate carbon by absorbing CO₂ during photosynthesis.
- They act as carbon sinks, helping reduce atmospheric CO₂.
🔍 Causes of the Shift to Net Carbon Loss
| Cause | Effect on Boreal Forests |
|---|---|
| Warmer temperatures | Increase drought stress and reduce plant growth (primary production). |
| Decreased winter snowfall | Less snow means less insulation for soil and plants, worsening drought. |
| Increased drought incidence | Weakens trees, reducing growth and carbon uptake. |
| Forest browning | Visible decline in forest health and productivity. |
| More frequent and intense forest fires | Fires release stored carbon (legacy carbon combustion) back into atmosphere. |
📍 Why This Tipping Point Matters
- Boreal forests switching to carbon sources accelerates global warming.
- Increased fires and drought reduce forest ability to act as carbon sinks.
- Highlights vulnerability of ecosystems to climate change.
🧠 Summary Box:
Boreal forests are shifting from carbon sinks to sources due to warming and drought.
Less snowfall and more fires cause forest stress and carbon release.
This tipping point worsens climate change feedback loops.
Protecting boreal forests is vital for climate stability.
Boreal forests are shifting from carbon sinks to sources due to warming and drought.
Less snowfall and more fires cause forest stress and carbon release.
This tipping point worsens climate change feedback loops.
Protecting boreal forests is vital for climate stability.
D4.3.4 – Melting of Landfast Ice and Sea Ice as Examples of Polar Habitat Change
🧠 What is Landfast Ice and Sea Ice?
- Landfast ice: Sea ice attached to the coastline, stable and important for some animal breeding.
- Sea ice: Floating ice covering polar oceans, essential habitat for many species.
🌿 Effects of Melting Ice on Polar Habitats
| Polar Region | Species Affected | Impact of Melting Ice |
|---|---|---|
| Antarctic | Emperor penguin (Aptenodytes forsteri) | Early breakup of landfast ice disrupts penguin breeding grounds. |
| Arctic | Walrus | Loss of sea ice reduces resting, breeding, and feeding areas. |
🔍 Why These Changes Matter
- Loss of breeding grounds threatens survival and reproduction of key species.
- Habitat loss affects food availability and safety from predators.
- Melting ice contributes to global sea level rise and alters ocean ecosystems.
🧠 Summary Box:
Melting of landfast and sea ice is a major consequence of polar warming.
Emperor penguins lose breeding sites due to early ice breakup in Antarctica.
Walruses suffer from shrinking sea ice in the Arctic.
Protecting ice habitats is critical for polar wildlife survival.
Melting of landfast and sea ice is a major consequence of polar warming.
Emperor penguins lose breeding sites due to early ice breakup in Antarctica.
Walruses suffer from shrinking sea ice in the Arctic.
Protecting ice habitats is critical for polar wildlife survival.
D4.3.5 – Changes in Ocean Currents Altering Nutrient Upwelling
🧠 What is Nutrient Upwelling?
- Upwelling is the rising of cold, nutrient-rich water from deep oceans to the surface.
- Nutrients support growth of phytoplankton, the base of marine food chains.
🌿 How Ocean Currents Affect Upwelling
Ocean currents drive the movement of water that brings nutrients up.
Warmer surface waters can create a stronger barrier (thermocline), blocking upwelling.
🔍 Effects of Reduced Upwelling
| Effect | Consequence |
|---|---|
| Less nutrient availability | Reduced phytoplankton growth (primary production) |
| Lower primary production | Less food for zooplankton and higher trophic levels |
| Decreased energy flow | Marine food chains weaken, affecting fish and predators |
| Impact on fisheries | Reduced fish populations affect human fishing industries |
📍 Why This Matters
- Nutrient upwelling supports some of the most productive ocean ecosystems.
- Changes can disrupt marine biodiversity and food security.
- Understanding these changes helps predict impacts of climate change on oceans.
🧠 Summary Box:
Warmer surface water can stop nutrient-rich deep water from rising.
This decreases ocean primary production and weakens marine food chains.
Upwelling changes threaten marine ecosystems and fisheries worldwide.
Warmer surface water can stop nutrient-rich deep water from rising.
This decreases ocean primary production and weakens marine food chains.
Upwelling changes threaten marine ecosystems and fisheries worldwide.
D4.3.6 – Poleward and Upslope Range Shifts of Temperate Species
🧠 What Are Range Shifts?
- Range shifts occur when species move their habitats towards the poles or higher altitudes (upslope) in response to climate change.
- Species seek cooler conditions as temperatures rise.
🌿 Evidence-Based Examples
| Region | Species | Range Shift | Cause |
|---|---|---|---|
| New Guinea (tropical montane birds) | Various bird species | Moved upslope to higher elevations | Warming temperatures pushing them to cooler habitats |
| North America (tree species) | Various temperate trees | Northward spread and range contraction in southern areas | Climate warming causes habitat suitability to shift north |
🔍 Why Range Shifts Occur
- Rising temperatures make original habitats too warm or unsuitable.
- Cooler habitats at higher altitudes or latitudes become accessible.
- Species follow these shifting climate zones to survive and reproduce.
📍 Implications of Range Shifts
- Can cause changes in community composition and ecosystem dynamics.
- May lead to competition between native and migrating species.
- Species unable to move or adapt risk local extinction.
🧠 Summary Box:
Species are moving poleward and upslope to escape warming climates.
Examples: Montane birds in New Guinea move upslope; North American trees shift north.
Range shifts alter ecosystems and may threaten species unable to adapt or migrate.
Species are moving poleward and upslope to escape warming climates.
Examples: Montane birds in New Guinea move upslope; North American trees shift north.
Range shifts alter ecosystems and may threaten species unable to adapt or migrate.
D4.3.7 – Threats to Coral Reefs as an Example of Potential Ecosystem Collapse
🧠 Why Are Coral Reefs Important?
- Coral reefs are diverse ecosystems supporting many marine species.
- Corals build reefs by calcification – depositing calcium carbonate to form their skeletons.
🌿 Main Threats to Coral Reefs
| Threat | Cause | Effect on Corals |
|---|---|---|
| Ocean acidification | Increased atmospheric CO₂ dissolves in ocean, lowering pH. | Suppresses coral calcification, weakening skeletons. |
| Rising water temperatures | Global warming raises sea temperatures. | Causes coral bleaching – loss of symbiotic algae, leading to coral stress and death. |
🔍 Consequences of Coral Loss
- Reef ecosystems collapse without healthy corals.
- Loss of habitat affects fish and marine biodiversity.
- Impacts human communities relying on reefs for food, tourism, and coastal protection.
📍 Why This Example Matters
- Coral reefs show how climate change can cause ecosystem collapse.
- Highlights urgent need for reducing greenhouse gas emissions.
🧠 Summary Box:
Increased CO₂ causes ocean acidification, harming coral skeleton formation.
Higher temperatures cause coral bleaching and death.
Loss of corals leads to collapse of diverse reef ecosystems.
Coral reefs are a clear example of climate change’s ecological risks.
Increased CO₂ causes ocean acidification, harming coral skeleton formation.
Higher temperatures cause coral bleaching and death.
Loss of corals leads to collapse of diverse reef ecosystems.
Coral reefs are a clear example of climate change’s ecological risks.
D4.3.8 – Afforestation, Forest Regeneration, and Restoration of Peat-Forming Wetlands as Approaches to Carbon Sequestration
🧠 What is Carbon Sequestration?
- Carbon sequestration is the process of capturing and storing atmospheric CO₂ to reduce global warming.
- Natural ecosystems like forests and peatlands act as carbon sinks by storing carbon in plants and soils.
🌿 Approaches to Carbon Sequestration
| Method | Description | Key Points |
|---|---|---|
| Afforestation | Planting trees on land that was not previously forested | Can increase carbon storage but choice of species (native vs. non-native) matters. |
| Forest regeneration | Allowing natural regrowth of forests after disturbance | Often supports native biodiversity and long-term carbon storage. |
| Restoration of peat-forming wetlands | Re-establishing waterlogged conditions to enable peat formation | Peatlands store large amounts of carbon in waterlogged soils; formation is slow but very effective. |
🔍 Scientific Debate
- Whether to plant non-native tree plantations or encourage rewilding with native species is debated.
- Native species often better support ecosystems but may sequester carbon more slowly.
- Non-native plantations might sequester carbon faster but risk ecological imbalance.
📍 Peat Formation
- Peat forms naturally in waterlogged soils where decomposition is slow.
- Occurs mainly in temperate and boreal zones, but also rapidly in some tropical ecosystems.
- Peatlands are critical carbon stores but can release carbon if drained or disturbed.
🧠 Summary Box:
Afforestation, forest regeneration, and peatland restoration help capture CO₂.
Choice between native species rewilding and non-native plantations is actively debated.
Peatlands are important long-term carbon sinks due to slow organic matter decay.
Protecting and restoring these ecosystems is vital for climate mitigation.
Afforestation, forest regeneration, and peatland restoration help capture CO₂.
Choice between native species rewilding and non-native plantations is actively debated.
Peatlands are important long-term carbon sinks due to slow organic matter decay.
Protecting and restoring these ecosystems is vital for climate mitigation.
D4.3.9 – Phenology as Research into the Timing of Biological Events
🧠 What is Phenology?
- Phenology studies the timing of natural biological events in plants and animals.
- Focuses on when events like flowering, migration, and breeding happen.
🌿 Key Variables Influencing Phenology
| Variable | Example Effect on Biological Events |
|---|---|
| Photoperiod (day length) | Triggers flowering, budburst, and bud set in deciduous trees. |
| Temperature patterns | Affects timing of bird migration and nesting behaviors. |
🔍 Examples of Phenological Events
- Flowering and budburst in trees respond to increasing daylight and temperature.
- Bird migration and nesting times shift based on seasonal temperature changes.
- Changes in these timings can indicate climate change impacts on ecosystems.
📍 Why Phenology Matters
- Helps scientists track how climate and environment affect living organisms.
- Provides early warnings of ecological changes.
- Important for agriculture, conservation, and understanding ecosystem health.
🧠 Summary Box:
Phenology studies the timing of natural events like flowering and migration.
Photoperiod and temperature are major influences.
Shifts in phenology can signal environmental and climate changes.
Phenology research is vital for monitoring ecosystem responses.
Phenology studies the timing of natural events like flowering and migration.
Photoperiod and temperature are major influences.
Shifts in phenology can signal environmental and climate changes.
Phenology research is vital for monitoring ecosystem responses.
D4.3.10 – Disruption to the Synchrony of Phenological Events by Climate Change
🧠 What is Synchrony in Phenology?
- Synchrony means different species or populations time their biological events to match each other.
- This timing is crucial for survival, such as food availability matching breeding.
🌿 How Climate Change Disrupts Synchrony
- Different species may use different cues for timing, such as temperature or photoperiod.
- Climate change alters temperature patterns, but photoperiod stays the same.
- This causes mismatches where one species’ event no longer aligns with another’s.
🔍 Examples of Disrupted Synchrony
| Ecosystem | Species & Event | Cue | Disruption |
|---|---|---|---|
| Arctic | Arctic mouse-ear chickweed (Cerastium arcticum) spring growth | Temperature | Growth shifts earlier due to warming. |
| Arctic | Migrating reindeer (Rangifer tarandus) arrival | Photoperiod | Arrival timing remains the same, leading to mismatch with food availability. |
| North European forests | Great tit (Parus major) breeding | Temperature | Breeding shifts earlier due to warmer springs. |
| North European forests | Peak caterpillar biomass | Photoperiod | Peak timing stays constant, causing food mismatch for chicks. |
📍 Why This Matters
- Mismatches reduce survival chances of offspring dependent on food availability.
- Can cause population declines and disrupt ecosystem balance.
🧠 Summary Box:
Climate change disrupts timing coordination (synchrony) between species.
Species using temperature cues shift timing; those using photoperiod do not.
Examples: Arctic chickweed and reindeer; great tit breeding and caterpillar peak.
Understanding these disruptions is key to predicting ecological impacts.
Climate change disrupts timing coordination (synchrony) between species.
Species using temperature cues shift timing; those using photoperiod do not.
Examples: Arctic chickweed and reindeer; great tit breeding and caterpillar peak.
Understanding these disruptions is key to predicting ecological impacts.
D4.3.11 – Increases to the Number of Insect Life Cycles Within a Year Due to Climate Change
🧠 What Happens to Insect Life Cycles with Warming?
- Warmer temperatures can speed up insect development.
- This may cause some insects to have more generations (life cycles) per year.
🌿 Example: Spruce Bark Beetle
| Species | Effect of Climate Change |
|---|---|
| Spruce bark beetle (Ips typographus / Dendroctonus micans) | Warmer climates allow it to complete more life cycles yearly, increasing population size. |
🔍 Consequences
- More generations lead to faster population growth.
- Increased beetle numbers cause more damage to spruce forests.
- Can lead to forest decline and economic loss in forestry.
📍 Why This Matters
- Shows how climate change affects ecosystem dynamics beyond just temperature.
- Highlights risks to forest health and biodiversity.
- Important for managing pest outbreaks in changing climates.
🧠 Summary Box:
Climate warming can increase the number of insect life cycles per year.
Spruce bark beetle populations grow faster due to this effect.
This leads to greater damage in forests, impacting ecosystems and industries.
Understanding insect responses helps in forest management strategies.
Climate warming can increase the number of insect life cycles per year.
Spruce bark beetle populations grow faster due to this effect.
This leads to greater damage in forests, impacting ecosystems and industries.
Understanding insect responses helps in forest management strategies.
D4.3.12 – Evolution as a Consequence of Climate Change
🧠 What is Evolution in Response to Climate Change?
- Evolution is the change in genetic traits in a population over generations due to natural selection.
- Climate change can alter environmental conditions, changing which traits are advantageous.
- This affects the fitness (survival and reproduction success) of different variants within a species.
🌿 Example: Tawny Owl (Strix aluco) Colour Variants
- Tawny owls have two main colour morphs: brown and grey.
- Fitness depends on camouflage with the environment, especially snow cover.
- Brown morphs are better camouflaged in areas with less snow.
- Grey morphs blend better in snowy environments.
🔍 Effect of Climate Change on Tawny Owl Colour Fitness
- Warmer winters mean less snow cover in some regions.
- Brown morphs have increased fitness in these areas, leading to higher survival and reproduction rates.
- Grey morphs have reduced fitness due to poor camouflage, lowering survival.
- This shift changes allele frequencies, demonstrating natural selection driven by climate change.
📍 Why This Matters
- Shows real-time evolutionary responses to environmental changes.
- Illustrates how climate change can drive adaptation in species.
- Helps predict how populations may evolve under ongoing climate shifts.
🧠 Summary Box:
Evolution can occur due to climate change altering fitness of traits.
Tawny owl colour morphs show differing fitness based on snow cover.
Reduced snow favors brown morphs; grey morphs decline.
This example demonstrates natural selection driven by changing environments.
Evolution can occur due to climate change altering fitness of traits.
Tawny owl colour morphs show differing fitness based on snow cover.
Reduced snow favors brown morphs; grey morphs decline.
This example demonstrates natural selection driven by changing environments.