Topic 4: Ecology (12hs)

4.1 Species, communities and Ecosystems

Nature of Science

Looking for patterns, trends and discrepancies—plants and algae are mostly autotrophic but some are not. (3.1)


Why bees are disappearing? by Marla Spivak for Ted

International Mindedness

• The need for sustainability in human activities could be discussed and the methods needed to promote this.


• Species are groups of organisms that can potentially interbreed to produce fertile offspring.
• Members of a species may be reproductively isolated in separate populations.
• Species have either an autotrophic or heterotrophic method of nutrition (a few species have both methods).
• Consumers are heterotrophs that feed on living organisms by ingestion.
• Detritivores are heterotrophs that obtain organic nutrients from detritus by internal digestion.
• Saprotrophs are heterotrophs that obtain organic nutrients from dead organisms by external digestion.
• A community is formed by populations of different species living together and interacting with each other.
• A community forms an ecosystem by its interactions with the abiotic environment.
• Autotrophs obtain inorganic nutrients from the abiotic environment.
• The supply of inorganic nutrients is maintained by nutrient cycling.
• Ecosystems have the potential to be sustainable over long periods of time.

Applications and Skills

• Skill: Classifying species as autotrophs, consumers, detritivores or saprotrophs from a knowledge of their mode of nutrition.
• Skill: Setting up sealed mesocosms to try to establish sustainability. (Practical 5)

The Winogradky Column Link

Try these activities – Virtual ecosphere link

• Skill: Testing for association between two species using the chi-squared test with data obtained by quadrat sampling.

Quadrat sample spreadsheet link

EarthRef database Link 

• Skill: Recognizing and interpreting statistical significance.

Topic 4.2 Energy flow

Use theories to explain natural phenomena—the concept of energy flow explains the limited length of food chains. (2.2)

International Mindedness

The energetics of food chains is a factor in the efficiency of food production for the alleviation of world hunger.


• Most ecosystems rely on a supply of energy from sunlight.
• Light energy is converted to chemical energy in carbon compounds by photosynthesis.
• Chemical energy in carbon compounds flows through food chains by means of feeding.
• Energy released from carbon compounds by respiration is used in living organisms and converted to heat.
• Living organisms cannot convert heat to other forms of energy.
• Heat is lost from ecosystems.
• Energy losses between trophic levels restrict the length of food chains and the biomass of higher trophic levels.

The produccers simulation Link

Food web simulation Link

Applications and Skills

• Skill: Quantitative representations of energy flow using pyramids of energy.

Trophic cascades by HHMI

Energy flow virtual lab by Glencoe

Rabbit.Grass.Weed Model by NetLogo

Topic 4.3 Carbon cycling

Making accurate, quantitative measurements—it is important to obtain reliable data on the concentration of carbon dioxide and methane in the atmosphere. (3.1)


• Autotrophs convert carbon dioxide into carbohydrates and other carbon compounds.
• In aquatic ecosystems carbon is present as dissolved carbon dioxide and hydrogen carbonate ions.
• Carbon dioxide diffuses from the atmosphere or water into autotrophs.
• Carbon dioxide is produced by respiration and diffuses out of organisms into water or the atmosphere.
• Methane is produced from organic matter in anaerobic conditions by methanogenic archaeans and some diffuses into the atmosphere or accumulates in the ground.
• Methane is oxidized to carbon dioxide and water in the atmosphere.
• Peat forms when organic matter is not fully decomposed because of acidic and/or anaerobic conditions in waterlogged soils.
• Partially decomposed organic matter from past geological eras was converted either into coal or into oil and gas that accumulate in porous rocks.
• Carbon dioxide is produced by the combustion of biomass and fossilized organic matter.
• Animals such as reef-building corals and mollusca have hard parts that are composed of calcium carbonate and can become fossilized in limestone.

Dead stuff: The secret ingredient in our food chain – John C. Moore TedEd

Carbon cycle game by BiomanBio 

Applications and Skills

• Application: Estimation of carbon fluxes due to processes in the carbon cycle.
• Application: Analysis of data from air monitoring stations to explain annual fluctuations.
• Skill: Construct a diagram of the carbon cycle.

CO2 concentrations by EarthCO2 Link

Our World data Link

Topic 4.4 Climate change

Assessing claims—assessment of the claims that human activities are producing climate change. (5.2)


Try these Climate change games Link

Theory of Knowledge

The precautionary principle is meant to guide decision-making in conditions where a lack of certainty exists. Is certainty ever possible in the natural sciences?

Science Direct Link

International Mindedness

Release of greenhouse gases occurs locally but has a global impact, so international cooperation to reduce emissions is essential.

International Energy Agency IEA Link

Our world data Link

United Nations Climate Change Link



• Carbon dioxide and water vapour are the most significant greenhouse gases.
• Other gases including methane and nitrogen oxides have less impact.
• The impact of a gas depends on its ability to absorb long wave radiation as well as on its concentration in the atmosphere.
• The warmed Earth emits longer wavelength radiation (heat).
• Longer wave radiation is absorbed by greenhouse gases that retain the heat in the atmosphere.
• Global temperatures and climate patterns are influenced by concentrations of greenhouse gases.
• There is a correlation between rising atmospheric concentrations of carbon dioxide since the start of the industrial revolution 200 years ago and average global temperatures.
• Recent increases in atmospheric carbon dioxide are largely due to increases in the combustion of fossilized organic matter.

Greenhouse animation link

300 years of fossil fuels in 20sec video by Post carbon Institute

How Do Greenhouse Gases Actually Work? Video

Applications and Skills

• Application: Threats to coral reefs from increasing concentrations of dissolved carbon dioxide.

Australia’s Great Barrier Reef disappearing due to climate change Link

• Application: Correlations between global temperatures and carbon dioxide concentrations on Earth.
• Application: Evaluating claims that human activities are not causing climate change.

Climate Change Debate: Last Week Tonight with John Oliver (HBO) Video

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