Topic 2.3: Flows of energy of matter Starter: The sun releases 63 million joules of energy per second per metre (Js-1m-1) . Only about 700 Joules per second per metre (Js-1m-1) reaches our Earth’s surface. What’s happened to the rest of it? Topic 2.3: Flows of energy of matter

Solar radiation entering our earth has two fates, it is either absorbed or reflected. Reflection Absorption Scatter 3% Molecules and Dust 17% Clouds 19% Clouds 3% Ground 9% Ground 49% Total: 31% Total: 69% In your books: Using the data above: Draw a diagram to show the fate of the solar radiation reach the Earth. How do we draw energy flow diagrams?

We are going to practice some exam questions on the mini-white boards. Some simpler multiple choice question, followed by a more complicated multi-stage question involving some calculations.

1. The diagram below shows energy transfer in a cow. Secondary Productivity (SP) is A. C + R. B. C – (R + U + F). C. C – (U + F). D. C + R + U + F.

2. If C = 4000 kJ day–1 and SP = 200 kJ day–1, the efficiency of conversion is B. 10 %. C. 5 %. D. 2 %.

3. Net Primary Production is the amount of energy A. produced from ‘alternative’ sources in developing countries. B. fixed in an ecosystem by photosynthesis. C. fixed in an ecosystem by photosynthesis, minus the losses due to respiration by producer organisms. D. fixed by the herbivores in an ecosystem.

4. Most food chains seldom have more than four trophic levels because A. in most ecosystems, competition for food is very great. B. the total biodiversity in any ecosystem is limited. C. energy is lost as it moves along a food chain and little remains at the level of the top carnivore. D. in many parts of the world, many species have become extinct and complex ecosystems are rare.

Gross Productivity (kg day–1) Net Productivity (kg day–1) 5. An animal population is given 50 kg of feed per day, of which 40 kg is consumed. 20 kg of feed per day is used in respiration and 15 kg of faeces per day is released. Which of the following are the correct values for gross and net productivity?   Gross Productivity (kg day–1) Net Productivity (kg day–1) A. 40 25 B. 5 C. 50 35 D.

Mass of vegetation / g dry weight 6. A group of students investigating primary productivity selected a relatively uniform field of grass to study. Three 0.25 m2 plots were labelled A, B and C. All the vegetation (including roots) was removed from plot A. Plot B was covered in black opaque plastic. Plot C was left untouched. One week later the students returned to the site and removed all vegetation (including roots) from plots B and C. All samples were cleaned to remove soil and rocks. The following data were obtained from the investigation. Plot Mass of vegetation / g dry weight A 35.2 B 33.1 C 39.0

Show that net primary productivity (NPP) and respiration (R) for this site for the duration of the study period are 15.2 g m–2 and 8.4 g m–2 respectively. Assuming that NPP and respiration stay constant throughout the year, calculate annual NPP and annual respiration. Using the data from part (ii), calculate annual gross primary productivity (GPP) for this site, giving your answer to the nearest hundred grams. Assuming that 10 % of NPP in any given trophic level is available to the next level, calculate the energy available to consumers from the study site in g m–2 yr–1. Give your answer to two significant figures.

Flows and cycles Energy flows through ecosystems in one direction. Entering as solar radiation and finally leaving as heat released through respiration. Most chemical nutrients are however cycled. These elements never escape a cycle. We call these biogeochemical cycles. We will be looking at two major cycles: Carbon Nitrogen

The Carbon Cycle

What have you found out about… Photosynthesis The process of turning carbon dioxide (CO2) and water (H2O) into glucose (C6H12O6) Word equation: carbon dioxide + water (+ light energy)  glucose + oxygen Chemical equation: 6CO2 + 6H2O  C6H12O6 + 6O2 Where does photosynthesis take place in the plant?

glucose + oxygen  carbon dioxide + water + energy What have you found out about… Respiration The breaking down of glucose (and other food) into carbon dioxide and water Word equation: glucose + oxygen  carbon dioxide + water + energy Chemical equation: C6H12O6 + 6O2  6CO2 + 6H2O + energy Where does respiration take place in the cell?

Fuel + oxygen  carbon dioxide + water What have you found out about… Combustion The process of burning something. Word equation: Fuel + oxygen  carbon dioxide + water Example chemical equation: CH4 + 2O2  CO2 + 2H2O Why might it be a good idea to plant forests near power plants?

What have you found out about… Decomposition The breaking down of dead material by bacteria, animals or fungi (decomposers) Where will decomposition happen quickest, in a hot or cold place? Why?

CO2 O2 Respiration OUT IN Photosynthesis

CO2 in the atmosphere In your books: Hidden around the room are 8 clues, use this to fill in your sheet. CO2 in the atmosphere 1 2 3 4 5 6 7 8 9

A large amount of carbon is also stored in the oceans. CO2 is dissolved in the actual water. More complex carbon compounds in sea life. Huge amounts is stored in the deep ocean as inorganic compounds. (More than any other storage)

Storage (sinks) and flows Photosynthesis Death and decomposition Respiration Fossilisation Fossil fuels Combustion Organisms Dissolving Feeding Soil Atmosphere Sea life Rocks Oceans In your books: Sort the above into two columns, storage and flows In your books: How have humans effected the rate of various flows?

The Nitrogen Cycle All living organism need nitrogen as it is an essential element in proteins and DNA. It is the most abundant gas in our atmosphere, but nitrogen is an inert gas, so atmospheric nitrogen is unavailable to plants and animals Some specialized micro-organisms can fix atmospheric nitrogen. For plants to absorb nitrogen it must be in more reactive forms (nitrates NO3- and ammoniums ions NH4+). Animals gain nitrogen by feeding

How do humans affect the nitrogen cycle? Use the iPads to research how humans can affect the nitrogen cycle.