D4.2  Stability and Change

Guiding Questions:  
Guiding questions help students view the content of the syllabus through the conceptual lenses of both the themes and the levels of biological organization.

• What features of ecosystems allow stability over unlimited time periods?
• What changes caused by humans threaten the stability of ecosystems?​

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​Linking Questions:  
Linking questions strengthen students’ understanding by making connections between topics.  The ideal outcome of the linking questions is networked knowledge.

• What is the distinction between artificial and natural processes? 
• Over what timescales do things change in different biological systems? 

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” in relation to ecosystem stability. 
• Discuss the impact of Amazon deforestation as an example of an ecosystem at a tipping point.

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

• Define mesocosm.
• Outline requirements of setting up a sustainable  mesocosm.
• Discuss the benefits and limitations of using mesocosms as models of ecosystems.​

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 sustainable in relation to resource harvesting. 
• Discuss the sustainable resource harvesting of a marine fish.  
• Assess the sustainability of resource harvesting by identifying the maximum sustainable yield of a resource on a population growth curve. 
• Discuss the sustainable resource harvesting of a terrestrial plant.  

 ​​​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.

• Discuss causes and effects of ecosystem eutrophication.

D4.2.9- Biomagnification of pollutants in natural ecosystems.

• Outline the process of 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 microplastic 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.  
• 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 the rewilding of the Hinewai Reserve in New Zealand.​

AHL ​​​​​​​D4.2.12- Ecological succession and its causes.

• Outline the cause and effect of ecological succession.
• Outline an example of reciprocal interactions between living organisms and the abiotic environments that cause ecological succession. 
• State an example of ecological succession triggered by an abiotic factor.
• State an example of ecological succession triggered by a biotic factor. ​

AHL ​​​​​​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.​

AHL ​​​​​​D4.2.14- Cyclical succession in ecosystems.

• Explain an example of cyclical succession in an ecosystem.​

AHL ​​​​​​D4.2.15- Climax communities and arrested succession.

• Define climax community and plagioclimax.
• Discuss the impact of grazing my farm livestock on arresting succession in a community.  
• Discuss the impact of drainage of wetlands on arresting succession in a community. ​