1. 2.5 Ecosystem Functions

2. Major Functions of 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 sun light 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
respiration backwards!

6. 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. Photosynthesis and Respiration
Glucose / Oxygen
CO2/ Water

8. Energy Transfers in Ecosystem
ESSENTIAL QUESTIONS How 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 QUESTIONS What 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.
Include competition, 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 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?
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.”

9. Energy Flow Diagram

10. Water Cycle

11. Nitrogen Cycle

12. Carbon Cycle

13. 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,

14. 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

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

16. 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 ?

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. 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

19. 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
SUN
PLANT
DECOMPOSERS
RESPIRATION
…………………………….
(~98% of energy is here)
HERBIVORES

20. 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

21. Respiratory loss by decomposers
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
Trophic Level
Gross Production
Respiratory Loss
Loss to decomposers
Producers
60724
36120
477
1° Consumer
21762
14700
3072
2° Consumer
714
576 42
3° Consumer 7 4 1
Respiratory loss by decomposers
---
3120
Construct an energy flow model to 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 Productivity for
NPP for Producers
NSP for 1°Consumers, 2°Consumers, 3°Consumers
NSP for Decomposers

22. ENERGY FLOW MODEL 1st. Carnivores Top Carnivores Producers Herbivores
60724
21762
1st.
Carnivores
Top
Carnivores
714 7
Producers
Herbivores
3072 42
477 1
Decomposers
R=3120

23. Productivity Calculations
NPP of Producers:
( )
=24127 kJ.m-2.yr-1
NSP of 1 Consumer
21762
-( )
=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
-( )
=4088 kJ.m-2.yr-1
NSP of Decomposers:
( )
-3120
=472 kJ.m-2.yr-1

24. How to measure 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

25. Measuring productivity continued
4.Radiosotope method-use c14 tracer in photosynthesis.
5.Chlorophyl measurement- assumes a correlation between the amount of chlorophyll and rate of photosynthesis.