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IB DP Biology Climate change Study Notes

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

IBDP Biology 2025 -Study Notes -All Topics

D4.3.1—Anthropogenic causes of climate change

  • Greenhouse Effect: The Earth’s atmosphere traps heat from the sun, similar to how a car parked in the sun gets hot. This is known as the greenhouse effect.
  • Greenhouse Gases: Methane and carbon dioxide are key greenhouse gases.
  • Human Activities: Burning fossil fuels (like coal, oil, and gas) and deforestation are major sources of greenhouse gas emissions.
  • Global Warming: Increased greenhouse gases trap more heat in the atmosphere, leading to a rise in global temperatures.
  • Climate Change Impacts: This warming affects weather patterns, including increased frequency and intensity of extreme weather events.

D4.3.2—Positive feedback cycles in global warming

Key Points:

  • Melting Ice and Albedo: Snow and ice have a high albedo, meaning they reflect a lot of sunlight back into space. As polar ice and sea ice melt, more of the Earth’s surface is exposed, which absorbs more heat. This leads to further warming and accelerated ice melt.

  • Permafrost Melting: Permafrost contains large amounts of organic matter. As permafrost thaws due to rising temperatures, this organic matter decomposes and releases methane, a potent greenhouse gas. This further contributes to warming and accelerates permafrost thaw.

  • Ocean Warming and Carbon Dioxide Release: As global temperatures rise, the temperature of the oceans also increases. Warmer water can hold less dissolved carbon dioxide. This leads to the release of more carbon dioxide from the oceans into the atmosphere, further amplifying warming.

These positive feedback cycles create a self-reinforcing process where warming leads to changes that accelerate further warming. They are a significant concern as they can make it more difficult to mitigate the effects of climate change.

D4.3.3—Change from net carbon accumulation to net loss in boreal forests as an example of a tipping point

  • Tipping Point in Boreal Forests: Climate change is causing warmer and drier summers in boreal forests. This increases the frequency and severity of wildfires.
  • Carbon Release: These fires release large amounts of carbon dioxide stored in the forest’s detritus (dead organic matter).
  • Reduced Carbon Storage: Wildfires also damage the forest’s ability to store carbon by killing trees and disrupting the ecosystem.
  • Shift to a Carbon Source: This combination of factors could lead to a tipping point where boreal forests transition from being a carbon sink (absorbing more carbon than they release) to being a carbon source (releasing more carbon than they absorb).

  • Ecosystem Shift: After fires, deciduous forests with trees spaced farther apart may replace the original boreal forest, further altering the ecosystem’s carbon cycle.

D4.3.4—Melting of landfast ice and sea ice as examples of polar habitat change

It explains how the melting of landfast ice and sea ice is impacting the habitats of polar animals, particularly emperor penguins and walruses.

Key Points:

  • Emperor Penguins: These penguins rely on stable landfast ice for breeding. The melting of landfast ice due to climate change is disrupting their breeding sites, leading to increased chick mortality.
  • Walruses: Walruses use sea ice as resting and feeding platforms. As sea ice melts, they are forced to spend more time on land, increasing their energy expenditure and making it harder to access food.
  • Habitat Loss: The loss of sea ice is reducing the available habitat for these animals, forcing them to adapt to changing conditions.

These examples highlight how climate change is impacting polar ecosystems and the species that depend on them. The continued loss of sea ice poses a significant threat to the survival of these iconic animals.

D4.3.5—Changes in ocean currents altering the timing and extent of nutrient upwelling

Key Points:

  • Ocean Stratification: The ocean is layered with warmer, less dense water on top of colder, denser water. Mixing between these layers is crucial for nutrient circulation.
  • Increased Stratification: Climate change increases ocean stratification. Warming water expands, making it less dense. Additionally, melting ice adds freshwater to the surface, further reducing salinity and density.
  • Reduced Upwelling: Increased stratification inhibits the mixing of ocean layers. This reduces the upwelling of nutrient-rich deep water to the surface. Upwelling is a critical process for bringing nutrients to the surface, supporting marine productivity.
  • Negative Feedback Loop: Reduced upwelling leads to decreased primary production in surface waters. This can further amplify climate change by reducing the ocean’s ability to absorb carbon dioxide from the atmosphere.

In summary, climate change is altering ocean circulation patterns, leading to increased stratification and reduced upwelling. This has significant consequences for marine ecosystems, impacting nutrient availability, primary production, and the overall health of the ocean.

D4.3.6—Poleward and upslope range shifts of temperate species

Key Points:

  • Montane Species: Species that inhabit mountains are referred to as montane species. These species are adapted to specific temperature ranges at different elevations.
  • Upslope Migration: As temperatures rise due to climate change, montane species tend to migrate upslope to track their optimal temperature range. This is because they need to move to cooler areas to maintain their suitable habitat.
  • Limited Upslope Movement: Species living at the highest elevations cannot move further upslope to escape warming temperatures. This puts them at a high risk of extinction.
  • Competition and Marginal Habitats: As species move upslope, they may encounter competition from other species that have also migrated. This can force them into marginal habitats, potentially reducing their chances of survival.

 

  • Sensitivity of Tropical Montane Species: Climate change models predict that tropical montane species will be more sensitive to temperature changes than temperate montane species. This is because tropical montane regions have a narrower range of temperatures, limiting the ability of species to migrate upslope to escape warming.

In essence, climate change is causing many species to shift their ranges poleward and upslope to find suitable habitats. However, the capacity for such shifts is limited, especially for species living at high elevations or in tropical regions. This poses a significant threat to the biodiversity of mountain ecosystems.

D4.3.7—Threats to coral reefs as an example of potential ecosystem collapse

Ocean Acidification:

  • The burning of fossil fuels releases large amounts of carbon dioxide into the atmosphere.
  • A significant portion of this carbon dioxide is absorbed by the oceans.
  • This absorbed carbon dioxide reacts with seawater, forming carbonic acid.
  • This process reduces the availability of carbonate ions, which are essential for coral reefs to build their calcium carbonate skeletons.

Impact on Coral Reefs:

  • Lower carbonate ion concentrations make it difficult for corals to build and maintain their skeletons.
  • Existing coral skeletons may also dissolve in more acidic waters.
  • Ocean acidification also stresses corals by disrupting their symbiotic relationship with algae (zooxanthellae), which provide them with nutrients and color.

Consequences:

  • Coral bleaching and death are major consequences of ocean acidification.
  • The loss of coral reefs would have a significant impact on marine ecosystems, as they provide habitat for a wide variety of marine organisms and play a crucial role in coastal protection.

In summary, ocean acidification poses a serious threat to coral reefs by hindering their ability to build and maintain their skeletons and by disrupting their symbiotic relationships.

D4.3.8—Afforestation, forest regeneration and restoration of peat-forming wetlands as approaches to carbon sequestration

Carbon Sequestration:

  • Carbon sequestration involves capturing and storing carbon to mitigate climate change.
  • Natural processes like photosynthesis, biomass growth, and the formation of deep-sea sediments contribute to carbon sequestration.

Afforestation:

  • Afforestation involves planting trees in areas where they didn’t previously exist.
  • Many countries have set targets for tree planting as part of their climate change commitments.

Forest Regeneration:

  • Forest regeneration involves replanting trees in areas where forests have been depleted, often through logging.
  • This often involves planting seedlings of commercially valuable tree species.

Peatland Restoration:

  • Peatlands are waterlogged ecosystems that store large amounts of carbon.
  • Drainage of peatlands for agriculture or forestry releases this stored carbon into the atmosphere.
  • Restoring peatlands involves blocking drainage and re-establishing the natural water levels, which helps to conserve carbon and reduce the risk of fire.

In summary, afforestation, forest regeneration, and peatland restoration are important strategies for increasing carbon sequestration and mitigating climate change.

D4.3.9—Phenology as research into the timing of biological events

It explains phenology, which is the study of the timing of seasonal biological events in plants and animals.

Key Points:

  • Day Length as a Cue: Day length (photoperiod) is a crucial environmental cue that influences the timing of many biological events in plants and animals.
  • Plant Responses to Day Length:
    • Flowering: Some plants flower when day length is short (short-day plants), while others flower when day length is long (long-day plants).
    • Bud Set and Budburst: In deciduous trees, changes in day length trigger bud set (cessation of growth in autumn) and budburst (emergence of new leaves in spring).

  • Bird Migration: Changes in day length are a primary cue for bird migration.

Phenological data is valuable for monitoring the impacts of climate change. Changes in the timing of seasonal events, such as earlier budburst or delayed migration, can indicate shifts in environmental conditions and provide evidence of climate warming.

D4.3.10—Disruption to the synchrony of phenological events by climate change

Key Points:

  • Phenological Mismatch: Many biological events, such as plant flowering, insect emergence, and bird migration, are synchronized with the availability of food resources. Climate change can disrupt this synchrony by altering the timing of these events.

  • Example: Great Tits and Caterpillars: A study on great tits showed that the peak caterpillar biomass (their primary food source) is occurring earlier due to warmer spring temperatures. However, the timing of great tit breeding has not shifted accordingly. This mismatch results in fewer chicks and lower chick survival rates.

  • Impact on Other Species Interactions: Phenological mismatches can also disrupt other species interactions, such as plant-herbivore, predator-prey, and pollinator-plant relationships.

  • Example: Caribou and Plant Development: Caribou in Greenland are experiencing a decline due to a mismatch between their migration timing and the availability of their preferred food plants. Climate change has altered the timing of plant development, making it harder for caribou to find enough food during their spring migration.

In essence, climate change can disrupt the delicate balance of ecological interactions by altering the timing of phenological events. This can have cascading effects on ecosystems and the species that depend on them.

D4.3.11—Increases to the number of insect life cycles within a year due to climate change

Key Points:

  • Warmer Temperatures and Beetle Development: Warmer temperatures can accelerate the development of certain insect species, such as the spruce bark beetle.
  • Shorter Life Cycles: Under warmer conditions, some insect species can complete their life cycle in one year instead of the usual two years.
  • Synchronized Outbreaks: When insect development is synchronized, large numbers of beetles emerge simultaneously, increasing the severity of attacks on trees.
  • Increased Tree Vulnerability: Warmer temperatures and drought stress can weaken trees, making them more susceptible to beetle attacks.

Example: Spruce Bark Beetle

  • In areas with warmer temperatures, spruce bark beetles can complete their life cycle in one year instead of two.
  • This leads to synchronized emergence of large numbers of beetles, causing widespread tree mortality.

In summary, climate change can alter insect life cycles by increasing the rate of development. This can lead to synchronized outbreaks and increased pest pressure on trees, potentially causing significant damage to forests.

D4.3.12—Evolution as a consequence of climate change

Tawny Owls and Plumage Coloration:

  • Tawny owls exhibit variation in plumage color, ranging from pale grey to brown. This coloration is a heritable trait, likely controlled by a single gene with a simple Mendelian pattern of inheritance (brown being dominant over grey).

Climate Change and Selection Pressure:

  • In Finland, milder winters over the past 30 years have resulted in reduced snow cover.
  • This change in environment has likely created a selection pressure favoring the brown morph of the tawny owl.
  • With less snow, the grey morph might be more conspicuous against the lighter background, making them more vulnerable to predators.

Evolutionary Consequence:

  • The reduced snow cover is expected to have led to an increase in the frequency of the brown morph in the tawny owl population over time. This is an example of how climate change can act as a selective force, driving evolutionary change in a population.

In essence, the image illustrates how a changing environment (in this case, reduced snow cover due to milder winters) can exert selective pressure on a population, favoring individuals with certain traits (brown coloration) and leading to evolutionary change.

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