Biology · Interaction and interdependence
C4.2 — Transfers of energy and matter
Biology · SL / HL · syllabus-mapped notes
C4.2.1
Ecosystems as open systems in which both energy and matter can enter and exit
Define ecosystem, and explain why ecosystems are open systems.
C4.2.2
Sunlight as the principal source of energy that sustains most ecosystems
Explain sunlight as the principal energy source, and the chemosynthetic exception.
C4.2.3
Flow of chemical energy through food chains
Explain the one-way flow of chemical energy along a food chain.
C4.2.4
Construction of food chains and food webs to represent feeding relationships in a community
Construct food chains and food webs for a community.
C4.2.5
Supply of energy to decomposers as carbon compounds in organic matter coming from dead organisms
Explain how dead organic matter supplies energy to saprotrophs and detritus feeders.
C4.2.6
Autotrophs as organisms that use external energy sources to synthesize carbon compounds from simple inorganic substances
Define autotroph, and state what it needs to build carbon compounds.
C4.2.7
Use of light as the external energy source in photoautotrophs and oxidation reactions as the energy source in chemoautotrophs
Contrast photoautotrophs and chemoautotrophs, and explain why an external energy source is needed.
C4.2.8
Heterotrophs as organisms that use carbon compounds obtained from other organisms to synthesize the carbon compounds that they require
Define heterotroph, and distinguish saprotrophs from multicellular and unicellular consumers.
C4.2.9
Release of energy in both autotrophs and heterotrophs by oxidation of carbon compounds in cell respiration
Explain that all organisms release energy by oxidation in cell respiration.
C4.2.10
Classification of organisms into trophic levels
Classify organisms into trophic levels, and explain non-whole-number values.
C4.2.11
Construction of energy pyramids
Construct a pyramid of energy with correct units and labelling.
C4.2.12
Reductions in energy availability at each successive stage in food chains due to large energy losses between trophic levels
Explain the three reasons energy availability falls between trophic levels.
C4.2.13
Heat loss to the environment in both autotrophs and heterotrophs due to conversion of chemical energy to heat in cell respiration
Explain why heat loss is inevitable, and why energy flows while matter cycles.
C4.2.14
Restrictions on the number of trophic levels in ecosystems due to energy losses
Explain why energy losses restrict the number of trophic levels.
C4.2.15
Primary production as accumulation of carbon compounds in biomass by autotrophs
Distinguish gross from net primary production, and state the units.
C4.2.16
Secondary production as accumulation of carbon compounds in biomass by heterotrophs
Explain secondary production, and why it declines with each trophic level.
C4.2.17
Constructing carbon cycle diagrams
Construct a carbon cycle diagram using pools and fluxes.
C4.2.18
Ecosystems as carbon sinks and carbon sources
Explain when an ecosystem is a carbon sink and when a source, and how sequestration occurs.
C4.2.19
Release of carbon dioxide into the atmosphere during combustion of biomass, peat, coal, oil and natural gas
Explain how the carbon sinks formed, and what releases their carbon on combustion.
C4.2.20
Analysis of the Keeling Curve in terms of photosynthesis, respiration and combustion
Analyse the Keeling Curve in terms of photosynthesis, respiration and combustion.
C4.2.21
Dependence of aerobic respiration on atmospheric oxygen produced by photosynthesis, and of photosynthesis on atmospheric carbon dioxide produced by respiration
Explain why respiration depends on photosynthesis for oxygen, and photosynthesis on respiration for CO2.
C4.2.22
Recycling of all chemical elements required by living organisms in ecosystems
Explain how chemical elements are recycled, and the key role of decomposers.