2.3 Energy & Matter

Significant Ideas

• Ecosystems are linked together by energy and matter flows.

• The Sun’s energy drives these flows, and humans are impacting the flows of energy and matter both locally and globally.

Knowledge and Understanding

1. As solar radiation (insolation) enters the Earth’s atmosphere, some energy becomes unavailable for ecosystems as this energy is absorbed by inorganic matter or reflected back into the atmosphere.

2. Pathways of radiation through the atmosphere involve a loss of radiation through reflection and absorption as shown in figure 4.

Textbook Reading and/or Activities

• Pages 79-98

  • ToK (p.81)

  • To think about (p.85)

  • To do (p.87)

  • To do (p.90)

  • To do (p.91)

  • To do (p.93)

  • To do (p.94)

  • To do (p.95)

  • To do (p.96-97)

  • To do (p.98)

Notes

i-Biology Notes (Not available)

A detailed set of notes, created by Stephen Taylor, examining U1 - U8 and A1 - A4.

i-Biology Study Questions (Not available)

A series of questions, created by Stephen Taylor, to help check your understanding of the IB learning expectations. This is VERY GOOD practice.

Bioknowledgy Notes (Not available)

A detailed set of notes, created by Chris Paine, examining all of the IB learning expectations.

Bioknowledgy Study Questions (Not available)

A series of questions, created by Chris Paine, to help check your understanding of the IB learning expectations. This is VERY GOOD practice.

Learning Activities

Virtual Lab - DO and Aquatic Primary Productivity

This virtual lab, by Pearson, will help clarify the process by which different indicators can be used to measure primary productivity in aquatic plants.

Calculating Productivity

This activity, prepared by Newport High School, will help you improve your ability to calculate productivities from data.

The Nitrogen Cycle

This animated tutorial, produced by PBS Learning Media, will walk you through the steps of the nitrogen cycle explaining how and why each takes place.

Supplemental Reading

• • 1. Figure 4

    2. Pathways of radiation

1. Pathways of energy through an ecosystem include:

   • conversion of light energy to chemical energy

   • transfer of chemical energy from one trophic level to another with varying efficiencies

   • overall conversion of ultraviolet and visible light to heat energy by an ecosystem

   • re-radiation of heat energy to the atmosphere.

2. The conversion of energy into biomass for a given period of time is measured as productivity.Net primary productivity (NPP) is calculated by subtracting respiratory losses (R) from gross primary productivity (GPP).

   • NPP = GPP – R

3. Gross secondary productivity (GSP) is the total energy or biomass assimilated by consumers and is calculated by subtracting the mass of fecal loss from the mass of food consumed.

   • GSP = food eaten – fecal loss

4. Net secondary productivity (NSP) is calculated by subtracting respiratory losses (R) from GSP.

   • NSP = GSP – R

5. Maximum sustainable yields are equivalent to the net primary or net secondary productivity of a system.

6. Matter also flows through ecosystems linking them together. This flow of matter involves transfers and transformations.

7. The carbon and nitrogen cycles are used to illustrate this flow of matter using flow diagrams. These cycles contain storages (sometimes referred to as sinks) and flows, which move matter between storages.

8. Storages in the carbon cycle include organisms and forests (both organic), or the atmosphere, soil, fossil fuels and oceans (all inorganic).

9. Flows in the carbon cycle include consumption (feeding), death and decomposition, photosynthesis, respiration, dissolving and fossilization.

10. Storages in the nitrogen cycle include organisms (organic), soil, fossil fuels, atmosphere and water bodies (all inorganic).

11. Flows in the nitrogen cycle include nitrogen fixation by bacteria and lightning, absorption, assimilation, consumption (feeding), excretion, death and decomposition, and denitrification by bacteria in water-logged soils.

12. Human activities such as burning fossil fuels, deforestation, urbanization and agriculture impact energy flows as well as the carbon and nitrogen cycles.

Applications and Skills

1. Analyse quantitative models of flows of energy and matter.

2. Construct a quantitative model of the flows of energy or matter for given data.

3. Analyse the efficiency of energy transfers through a system.

4. Calculate the values of both GPP and NPP from given data.

5. Calculate the values of both GSP and NSP from given data.

6. Discuss human impacts on energy flows, and on the carbon and nitrogen cycles.

Guidance

1. Students should have the opportunity to measure productivity and biomass experimentally.

2. Students could design experiments to compare productivity in different systems.

3. The distinction between storages of energy illustrated by boxes in energy-flow diagrams (representing the various trophic levels), and the flows of energy or productivity often shown as arrows (sometimes of varying widths) needs to be emphasized. The former are measured as the amount of energy or biomass per unit area and the latter are given as rates, for example, J m–2 yr–1.

4. Students should understand the link between sustainable yields and productivity.

5. Values for GPP and NPP should be compared from various biomes.

6. The term “assimilation” is sometimes used instead of “secondary productivity”.

7. The roles of calcification, sedimentation, lithification, weathering and volcanoes in the carbon cycle are not required.

8. Detailed knowledge of the role of bacteria in nitrogen fixation, nitrification and ammonificaction is not required.

Key Vocabulary

• Here