C4.2  Transfers of Energy and Matter

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 is the reason matter can be recycled in ecosystems but energy cannot?
• How is the energy that is lost by each group of organisms in an ecosystem replaced?

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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.

• How does the transformation of energy from one form to another make biological processes possible?
• What are the direct and indirect consequences of rising carbon dioxide levels in the atmosphere?

​​Resources:

• At SHS, Topic C4.2 is taught in the Anerobic Respiration, Energy Flow, Carbon Cycle and Climate Change units. 
• Quizlet study set for this topic.  Coming soon!
• View the general sequence of the SHS course
• View the SHS units mapped to the IB Biology curriculum roadmap

C4.2.1-- Ecosystems as open systems in which both energy and matter can enter and exit.

• Define ecosystem.
• Compare open and closed systems. 
• State the ecosystems are open systems. ​

​C4.1.2— Sunlight as the principal source of energy that sustains most ecosystems.

• State that sunlight is the primary energy source for most ecosystems. 
• Outline an example of an exception of sunlight as the principal energy source in most ecosystems.

C4.2.3— ​Flow of chemical energy through food chains.

• Define food chain.
• Identify producers and consumers in a food chain. 
• Identify the apex predator in a food chain.
  
• State what is indicated by the arrow in a food chain.

C4.2.4— Construction of food chains and food webs to represent feeding relationships in a community.

• Draw a food chain, labeling the producer, primary consumer, secondary consumer and tertiary consumer.
• State the reason why food webs are better representations of trophic relationships in an ecological community than a food chain.​

​C4.2.5— Supply of energy to decomposers as carbon compounds in organic matter coming from dead organisms.

• Outline the role of decomposers in a food web. 
• List examples of decomposers, including both detritivores and saprotrophs. ​​

​C4.2.6- Autotrophs as organisms that use external energy sources to synthesize carbon compounds from simple inorganic substances.

• Define autotroph.
• Define carbon fixation.
• State the reason why autotrophs must “fix” carbon.
• List the two primary uses of energy in autotrophs.

C4.2.7- Use of light as the external energy source in photoautotrophs and oxidation reactions as the energy source in chemoautotrophs.

• ​Compare the energy sources used by photoautotrophs and chemoautotrophs.
• List examples of photoautotrophs.
• List examples of chemoautotrophs.
• Outline how oxidation reactions serve as a source of energy in iron-oxidizing bacteria.

​C4.2.8- Heterotrophs as organisms that use carbon compounds obtained from other organisms to synthesize the carbon compounds that they require.

• Define heterotroph.
• Outline the functions of digestion, assimilation and synthesis of carbon compounds in heterotrophs.

C4.2.9- Release of energy in both autotrophs and heterotrophs by oxidation of carbon compounds in cell respiration.

• State that both autotrophs and heterotrophs perform cellular respiration to produce ATP.
• Describe cellular respiration as an oxidation reaction.

​C4.2.10- Classification of organisms into trophic levels.

• Define trophic level. 
• Identify the trophic level of an organism in a food chain.
• State that many organisms have a varied diet and occupy different trophic levels in different food chains.

C4.2.11- Construction of energy pyramids.

• State the unit used for communicating the energy in each trophic level of a food chain.
• Describe the shape of a pyramid of energy.
• Draw a pyramid of energy given data for an ecosystem.

​​​C4.2.12- Reductions in energy availability at each successive stage in food chains due to large energy losses between trophic levels.

• Outline three reasons why the amount of energy decreases at higher trophic levels.
• State the average amount of energy passed through each trophic level in a food chain.

C4.2.13- Heat loss to the environment in both autotrophs and heterotrophs due to conversion of chemical energy to heat in cell respiration.

• Describe the reasons why heat created by living organisms is eventually lost from the ecosystem.

C4.2.14- Restrictions on the number of trophic levels in ecosystems due to energy losses.

• State that at each successive trophic level there are few organisms and less biomass. 
• Explain why there is a limited number of  trophic levels in an ecosystem.

C4.2.15- Primary production as accumulation of carbon compounds in biomass by autotrophs.

• Define biomass.
• Define gross and net primary production. 
• State the unit of primary production. 
• Outline why different biomes will vary in their capacity to accumulate biomass. ​

C4.2.16- Secondary production as accumulation of carbon compounds in biomass by heterotrophs.

• Define secondary production. 
• Explain why secondary production is lower than primary production in an ecosystem. ​

C4.2.17- Constructing carbon cycle diagrams.

• Define sink, pool and flux as related to the carbon cycle. 
• Draw a diagram of the carbon cycle through a terrestrial ecosystem; include processes of diffusion, photosynthesis, feeding and respiration.​

​​​​C4.2.18- Ecosystems as carbon sinks and carbon sources.

• State the conditions under which an ecosystem is a carbon sink. 
• State the conditions under which an ecosystem is a carbon source. 
• Define sequestration in relation to a carbon sink.​

​​​​C4.2.19- Release of carbon dioxide into the atmosphere during combustion of biomass, peat, coal, oil and natural gas.

• Define combustion. 
• State the reactants and products of a combustion reaction. 
• State sources of fuel for a combustion reaction. 
• Outline formation of peat, coal, oil, natural gas and biomass.​

​​​​C4.2.20- Analysis of the Keeling Curve in terms of photosynthesis, respiration and combustion.

• Sketch a graph of the annual fluctuation in atmospheric carbon dioxide concentration.
• Explain the annual fluctuation in atmospheric carbon dioxide concentration in terms of photosynthesis and respiration.
  
• State the long-term trend depicted in the Keeling curve.
• Explain the reason for the long term trend depicted in the Keeling curve.

​​​​C4.2.21- Dependence of aerobic respiration on atmospheric oxygen produced by photosynthesis, and of photosynthesis on atmospheric carbon dioxide produced by respiration.

• State the source of atmospheric oxygen. 
• Explain the interdependence of aerobic respiration and photosynthesis. 
• Outline how the annual flux of CO2 is estimated, including the unit.​

​​​​C4.2.22- Recycling of all chemical elements required by living organisms in ecosystems.  

• State that chemical elements can be recycled but energy can not.
• List elements required by living organisms that must be cycled through ecosystems. 
• Outline the generalized flow of nutrients between the abiotic, autotrophic and heterotrophic components of an ecosystem.
• State the role of decomposers in nutrient cycles. ​