2.5 Ecosystem Functions

1. 2.5 Ecosystem Functions

2. Major roles in an ecosystem • Producers-Convert sunlight energy into organic matter • Consumers- Use living organic matter as energy to grow and develop • Decomposers- Break down the dead organic matter / return nutrients to the soil

4. ENERGY ENTERS THE ECOSYSTEM AS SUNLIGHT • Only 2% of the light energy falling on plant is used to create energy • The rest is reflected, or just warms up the plant as it is absorbed

5. Photosynthesis • Process where plants use sunlight energy to create chemical energy • Photosynthesis: equation • 6CO2 + 6H2O --> C6H12O6 + 6O2 • Inputs: light energy, water, carbon dioxide • Outputs: oxygen gas, sugar • Energy transformations: Light to Chemical

6. Cellular Respiration • Process by which animals create energy through consumption of organic molecules (sugars) • Respiration: • C6H12O6 + 6O2 --> 6CO2 + 6H2O • Inputs: oxygen gas, organic molecules (sugars) • Outputs: carbon dioxide, energy in ATP, waste heat • Energy transformations: chemical to heat • Photosynthesis backwards!

7. Energy Transfers in EcosystemWhere does all the energy go? ESSENTIAL QUESTIONSHow can a species occupy two different trophic levels simultaneously in the same food web? Decomposers and consumers seem to be doing essentially the same thing. Why do environmental scientists bother to make a distinction between them? Energy transfers are always inefficient. In food chains roughly 90% of energy is lost as heat. Where does this heat go? Is this consistent with viewing the biosphere as a closed system? FLIPCAST— Food chains and the carbon cycle ESSENTIAL QUESTIONSWhat does the unit J.m-2.y-1 measure? Show that you understand the unit by breaking it down and explaining the significance of each component. Explain why the pyramid of biomass in aquatic ecosystems is often inverted? Why are harmful, non-biodegradable chemicals often found in higher concentrations in the bodies of creatures at the very top of food chains? 2.1.6 Define the terms species, population, habitat, niche, community and ecosystem with reference to local examples. FLIPCAST— Species concept CASE STUDY—California salamanders 2.1.7 Describe and explain population interactions using examples of named species. Includecompetition, parasitism, mutualism, predation and herbivory. Mutualism is an interaction in which both species derive benefit. Interactions should be understood in terms of the influences each species has on the population dynamics of others, and upon the carrying capacity of the others’ environment. Graphical representations of these influences should be interpreted. ESSENTIAL QUESTIONS Why do biologists say that no two species may occupy the same niche? What is the difference between interspecific and intraspecific competition? Parasites are harmful; but not too harmful. Why do most parasites not kill their hosts? ENDGAME—IB EXAMINATION REVIEW There is a menu containing the entire collection of “Essential Questions” from the various syllabus sections. Understanding these big picture ideas and being able to apply them in novel situations is the key to examination success in Environmental Sysytems and Societies. The is also a menu of “Facts and Skills” and a convenient review strategy called “Differentiations of Mastery.” ENDGAME QUESTIONS:1. WHAT BIG PICTURE IDEAS DO YOU NEED TO UNDERSTAND? 2. WHAT MUST YOU BE ABLE TO DO? 3. WHAT FACTS DO YOU NEED TO LEARN?

8. Energy Flow Diagram

9. Water Cycle

10. Nitrogen Cycle

11. Carbon Cycle

12. Gross productivity • Total energy captured or “assimilated” by an organism. • Measured in joules (J) • Plant (Gross Primary Productivity) • GPP = sunlight energy used during photosynthesis • Animals (Gross Secondary Productivity) • GSP = food eaten - energy in faeces Energy is stored in leaf as sugars and starches, which later are used to form flowers, fruits, seeds,

13. Net productivity • The energy left over after organisms have used what they need to survive. • All organisms have waste energy and respiratory loss given off as heat, metabolism (R) • Plants and animals have to use some of the energy they capture to keep themselves growing: • They both move water and stored chemicals around • Plants make flowers, fruits, new leaves, cells and stems • Animals create cells and need to move muscles. Net productivity = Gross productivity - Respiration Energy or using symbols: NP = GP - R

14. Net Primary vs. Net Secondary (NPP) vs. (NSP) • Calculate Net productivity for plants and animals • NPP = GPP – R PLANTS • NSP = GSP – R ANIMALS NSP NPP

15. Productivity in Food Web • In a food web diagram, you can assume that: • Energy input into an organism represents the GP • Energy output from that organism to the next trophic level represents the NP • GP-NP = R (respiration energy ) and/or loss to decomposers ?

16. Measuring Primary Productivity • Harvest method – measure biomass and express as biomass per unit area per unit time. • CO2 assimilation- measure CO2 uptake in photosynthesis and releases by respiration • 02 production-Measure O2 production and consumption

17. Therefore… • The least productive ecosystems are those with limited heat and light energy, limited water and limited nutrients. • Example biome:_______________ • The most productive ecosystems are those with high temperature, lots of water light and nutrients. • Example biome:__________________

18. Constructing an Energy Flow Diagram

19. Now check you have understood! • Draw a complete food web for an ecosystem of your choice, which should include: • the sun and its energy • named primary producers (at least 2) • named primary consumers (at least 3) • named secondary consumers (at least 2) • named decomposers (at least 2) • respiration energy loss (use red marker for this arrow) • On your diagram use arrows to show direction of energy flow

20. HERBIVORES PLANT SUN RESPIRATION ……………………………. (~98% of energy is here) DECOMPOSERS • Complete this energy flow diagram: • Label GPP, NPP and R for the primary producer • Add arrows to show missing energy pathways • (5 in total) • Fill in the blank box to explain why some sunlight is not fixed by plant

21. Draw your own energy flow diagram, rather like the one on the previous slide to show energy flows through the trophic levels in your food web. Include the following labels: • Start with sunlight energy • Include all trophic levels from your food web • Include arrows showing energy moving from each trophic level to another and to decomposers • Show energy lost in faeces • Show Respiration loss (heat energy) USE RED MARKER! • Label each individual arrow with a letter (A,B,C,D,E…) • Use the lettered arrows to write an equation for GPP, NPP • Write an equation for GSP, NSP for primary consumers

22. The data in the table below relate to the transfer of energy in a small clearly defined habitat. The units in each case are in kJ m-2 yr-1 Construct an energy flow modelto represent all these data – Label each arrow with the appropriate amount from the data table above. • Use boxes to represent each trophic level and arrows to show the flow of energy • Calculate the Net Productivityfor • NPP for Producers • NSP for 1°Consumers, 2°Consumers, 3°Consumers • NSP for Decomposers

23. ENERGY FLOW MODEL R=576 R=36120 R=14700 R=4 1st. Carnivores Top Carnivores 60724 21762 714 7 Producers Herbivores 3072 42 477 1 Decomposers R=3120

24. Productivity Calculations NPP of Producers: 60724 - (36120+477) =24127 kJ.m-2.yr-1 NSP of 1 Consumer 21762 -(14700+3072) =3990 kJ.m-2.yr-1 NSP of 2 Consumer 714 -(576+42) =96 kJ.m-2.yr-1 NSP of 3 Consumer 7 -(4+1) =2 kJ.m-2.yr-1 NSP of Consumers: 22483 -(15280+3115) =4088 kJ.m-2.yr-1 NSP of Decomposers: (477+3072+42+1) -3120 =472 kJ.m-2.yr-1