Stability & Change (IB Topic D4.2)

Essential Idea(s): Ecosystem stability arises from complex interactions among species, resources, and environmental conditions, allowing ecosystems to resist or recover from change, but this stability can be disrupted by human activities and natural disturbances that push systems toward tipping points.

Unit Length: 4 Lessons (+2 AHL)

  Guiding Questions

◊ What features of ecosystems allow stability over unlimited time periods?

◊ What changes caused by humans threaten the stability of ecosystems?

Materials:

Self-Teaching Slides (SL) / Self-Teaching Slides (AHL) Quizlet Vocab Set
Notes Template (SL) / Notes Template (AHL)

 

IB Statement(s) and Objective(s)

 

D4.2.1: Stability as a property of natural ecosystems

  • Define stability as a property of an ecosystem
  • Describe an example of a stable ecosystem

 

D4.2.2: Requirements for stability in ecosystems

  • Outline requirements for stability in an ecosystem
  • Outline types of environmental change that can interfere with ecosystem stability

 

D4.2.3: Deforestation of Amazon rainforest as an example of a possible tipping point in ecosystem stability

  • Define tipping point
  • Discuss the impact of Amazon deforestation as an example of an ecosystem at a tipping point
  • SKILL: Calculate percentage change 

 

D4.2.4: Use of a model to investigate the effect of variables on ecosystem stability

  • Define mesocosm
  • List types of mesocosms
  • Outline the purpose of mesocosms
  • Outline requirements of setting up a mesocosm

 

D4.2.5: Role of keystone species in the stability of ecosystems

  • State the role of a keystone species in an ecosystem
  • Outline an example of a keystone species in an ecosystem

 

D4.2.6: Assessing sustainability of resource harvesting from natural ecosystems

  • Describe requirements for sustainability in ecosystems
  • Define resource harvesting
  • Define sustainability (in relation to resource harvesting)
  • Assess the sustainability of resource harvesting by identifying the maximum sustainable yield of a resource on a population growth curve
  • Describe an example of sustainable resource harvesting of a fish species
  • Describe an example of sustainable resource harvesting of a terrestrial species

 

D4.2.7: Factors affecting the sustainability of agriculture

  • Discuss factors that negatively impact the sustainability of agriculture

 

D4.2.8: Eutrophication of aquatic and marine ecosystems due to leaching

  • Define eutrophication
  • Explain the process of eutrophication, in terms of: increased availability of nitrate and other ions, increased growth of producers, increased decomposition after death of producers. increased aerobic respiration by decomposers. reduction in dissolved oxygen, death of organisms requiring dissolved oxygen in water

 

D4.2.9: Biomagnification of pollutants in natural ecosystems

  • Outline the process of biomagnification
  • Outline common properties of toxins that lead to biomagnification 
  • Discuss the cause and effect of mercury biomagnification in an ecosystem
  • Discuss the cause and effect of DDT biomagnification in an ecosystem

 

D4.2.10: Effects of microplastic and macroplastic pollution of the oceans

  • Define biodegradable
  • State that plastics are not biodegradable
  • Define microplastic and macroplastic
  • Discuss the cause and effect of microplastic pollution on an ocean ecosystem

 

D4.2.11: Restoration of natural processes in ecosystems by rewilding

  • Define rewilding
  • Discuss the methods of restoration of an ecosystem by rewilding
  • Outline an example of rewilding (Hinewai Reserve, New Zealand)

Additional Higher Level Topics

D4.2.12: Ecological succession and its causes

  • Define ecological succession
  • State an example of ecological succession triggered by an abiotic factor
  • State an example of ecological succession triggered by a biotic factor

 

D4.2.13: Changes occurring during primary succession

  • Describe changes occurring during primary succession in a community, including: increases in size of plants, amount of primary production, species diversity, complexity of food webs and amount of nutrient cycling

 

D4.2.14: Cyclical succession in ecosystems

  • Define cyclical succession
  • Explain an example of cyclical succession in an ecosystem

 

D4.2.15: Climax communities and arrested succession

  • Define climax community and plagioclimax
  • Give an example of a plagioclimax community
Activities: ⓟ = podcast / ⍰ = inquiry 5 / ⓦ = Write it /  Ӕ = The academy  / Ⓡ = Read it

ⓟ/ⓦ: How We Could Colonize Space: Jayne Poynter’s Story of Biosphere 2 (👫 max 3)

Imagine living for two years inside a sealed “mini-Earth,” where every breath of air, drop of water, and bite of food depends on a carefully balanced ecosystem — with no outside help. In this NPR clip on a project called Biosphere 2, one of the participants reflects on what the experiment revealed about sustainability, ecosystem stability, and unexpected feedback loops in closed systems. Watch the TED Talk and create a short podcast to discuss what Biosphere 2 can teach us about maintaining stable ecosystems on Earth. Here are a few guiding questions, if you need some:

  • Can Biosphere 2 be considered a large-scale mesocosm? Why is it useful as a model for studying ecosystem stability (D4.2.4)?
  • Did Biosphere 2 experience any tipping points where small changes led to major ecosystem shifts?
  • Were there organisms in Biosphere 2 that functioned like keystone species? How did their presence or absence affect stability?
  • What challenges in Biosphere 2 mirror sustainability issues in agriculture or natural ecosystems today (D4.2.7)?
  • How might ecological succession have unfolded inside Biosphere 2 if the experiment continued longer (D4.2.12–D4.2.15)?

…more forthcoming!