Transfers of energy and matter Flashcards
What is the difference between an open and closed system, and which is an ecosystems?
Open systems: both energy and matter can enter and exit (ecosystem)
Closed systems: only energy is able to pass in and out.
What is the principal source of energy that sustains most ecosystems? Are there exceptions?
Sunlight
Yes, e.g ecosystems in caves, deep ocean water
Exist in total darkness.
What is the flow of chemical energy through food chains
The process of passing energy from one organism to another through feeding
What is a food chain?
What is a food web?
What do they both represent?
A sequence showing the feeding relationships and energy flow between species.
Multiple food chains and how they are connected
Feeding relationships in a community
What are the two types of decomposers?
How do they acquire energy? Include examples
Saprotrops and detritivores.
Decomposers break down non-living food sources e.g faeces, dead parts of organisms, dead whole organisms
Saprotrophs secrete enzymes onto dead matter and absorb the nutrients
Detritivores ingest dead matter and digest it inside their bodies
What are autotrophs/producers?
Organisms that use external energy sources to synthesize carbon compounds from simple inorganic substances
What are the two different types of autotrophs and how do they differ? Include examples.
Photoautotrophs take light energy from the sun, combine it with inorganic substances, and obtain chemical energy in the form of a carbon compound. E.g cynobacteria, pine trees
Chemoautotrophs use oxidation reactions as an energy source to convert carbon dioxide into complex food molecules. E.g iron-oxidising bacteria
What are heterotrophs?
Organisms that use carbon compounds obtained from other organisms (autotrophs or other heterotrophs) to synthesize the carbon compounds that they require
How do autotrophs and heterotrophs release energy?
Oxidation of carbon compounds (e.g glucose) in cell
respiration
What are trophic levels used for and how are organisms classified into them?
To indicate how many organisms the energy in the system has flowed through
1st trophic level: producers
2nd trophic level: primary consumers
3rd trophic level: secondary consumers
4th trophic level tertiary consumers
What are energy pyramids used for?
To show how much and how fast energy flows from one trophic level to the next in a community
Reductions in energy availability at each successive stage in food chains due to large energy
losses between trophic levels
Decomposers and detritus feeders are not usually considered to be part of food chains. However, students
should understand the role of these organisms in energy transformations in food chains. Consider the
causes of energy loss.
Heat loss to the environment in both autotrophs and heterotrophs due to conversion of
chemical energy to heat in cell respiration
Include the idea that energy transfers are not 100% efficient so heat is produced both when ATP is
produced in cell respiration and when it is used in cells.
Restrictions on the number of trophic levels in ecosystems due to energy losses
At each successive stage in food chains there are fewer organisms or smaller organisms. There is therefore
less biomass, but the energy content per unit mass is not reduced.
Primary production as accumulation of carbon compounds in biomass by autotrophs
The units should be mass (of carbon) per unit area per unit time and are usually g m−2 yr−1. Students should
understand that biomes vary in their capacity to accumulate biomass. Biomass accumulates when
autotrophs and heterotrophs grow or reproduce.
Secondary production as accumulation of carbon compounds in biomass by heterotrophs
Students should understand that, due to loss of biomass when carbon compounds are converted to
carbon dioxide and water in cell respiration, secondary production is lower than primary production in an
ecosystem.
Constructing carbon cycle diagrams
Students should illustrate with a diagram how carbon is recycled in ecosystems by photosynthesis,
feeding and respiration.
Ecosystems as carbon sinks and carbon sources
If photosynthesis exceeds respiration there is a net uptake of carbon dioxide and if respiration exceeds
photosynthesis there is a net release of carbon dioxide.
Release of carbon dioxide into the atmosphere during combustion of biomass, peat, coal, oil and
natural gas
Students should appreciate that these carbon sinks vary in date of formation and that combustion
following lightning strikes sometimes happens naturally but that human activities have greatly increased
combustion rates.
Analysis of the Keeling Curve in terms of photosynthesis, respiration and combustion
Include analysis of both the annual fluctuations and the long-term trend.
Dependence of aerobic respiration on atmospheric oxygen produced by photosynthesis, and of
photosynthesis on atmospheric carbon dioxide produced by respiration
The fluxes involved per year are huge, so this is a major interaction between autotrophs and heterotrophs.
Recycling of all chemical elements required by living organisms in ecosystems
Students should appreciate that all elements used by living organisms, not just carbon, are recycled and
that decomposers play a key role. Students are not required to know details of the nitrogen cycle and
other nutrient cycles.
