1. Pre-lab Questions
Q#2 Study the individual food chains which could exist in a grassland ecosystem: Food Chain #1: plant parts  land snail  mouse  raccoon Food Chain #2: plant parts  sparrow  hawk Food Chain #3: plant parts  rabbit  fox Food Chain #4: plant parts  mouse  fox
Video Links:
Trophic Levels
Explanation of Trophic Levels

2. Answer to Questions 2-7 relates to an Ecosystem’s Trophic Structure
Organisms in a population can belong to more than one food chain
Therefore they can occupy different trophic levels. Check out the mouse.
Quaternary
Consumer
Tertiary
Consumer
raccoon CR
hawk
fox
Secondary
Consumer
mouse CR
Primary
Consumer
rabbit
sparrow
Land snail
mouse CR CR
Energy
Producers
Plant parts of all types of plants P
sunlight

3. What is Primary Production?
Primary Production (GPP): the amount of sunlight energy converted to chemical energy in the form of organic compounds like glucose and other carbs.
Net Primary Production (NPP): the gross primary production amount minus the amount of energy used by primary producers for their cellular respiration
NPP = GPP – CRautotroph
Is GPP or NPP the amount of energy that will be available for consumers?
Producers convert about 1% of the energy in the sunlight

4. Modeling Energy Transfer Oats Lab
A Mathematical Approach to Modeling Energy in the Ecosystem and the Pyramids

5. Let the transfer begin…
The sun is the source of energy for the ecosystem
Read each step of the lab carefully. Think before you begin to calculate.
Write out “knowns”, formula, substitute values and then calculate.

6. Energy In the Ecosystem Talking Points
Producers absorb energy from the sun.
Producers set the energy limit for the ecosystem.
Each level requires a certain amount of energy to sustain the organisms at that trophic level
Each level can only transfer a certain amount of energy to the next level, called available energy
Amount of available energy decreases as it moves up the trophic levels.
Biomass is the total mass of a level
Number refers to the total number of organism at a level.

7. Important Lab Information
Determine how many consumers can be supported by 1 acre of the oat grain by investigating its biomass over a year.
Calculate the number of organisms at each trophic level that would be able to support an ecosystem with 1 acre of oat grain.
Energy is measured in Calories(C) and mass is in grams (g)
Follow the lab as WRITTEN. Show all calculations and write answer on line with units.
A zip lock bag of oats represents a portion of an acre
Initial calculations (Part A) refer to 10% available.

8. Appendix Information:

9. Post Lab – Understanding the Calculations

10. Part A Primary Production Grain Calculations:
1. Mass of oats for 1/100th of the acre: 380g 2. Now calculate the total mass of the oats harvested from acre of property: 38,000g (380g)(100) = 38,000g of oats 3. Using the appendix, determine the total energy in oats. What unit will your answer be? Calories (38,000 g of oats)(8.15c/g) = 309,700 c of energy

11. Part A continued…
4. Using you answer from step 3 and other information from the appendix, determine how many primary consumers (grasshoppers) can be fed for the year. (Round to the nearest whole number) What unit will your answer be? Grasshoppers #grasshoppers = (#year/724c)(309,700c) = 428 grasshoppers 309,700c/724c/yr = 428 grasshoppers

12. Part A continued…
5. What is the amount of grasshopper tissue (biomass) in grams that can be supported at this trophic level? (428 grasshoppers)(35g/organism) = 14,980 grams
From appendix & organism is grasshopper
These types of calculations will
Be done throughout the lab. Try to find a pattern.

13. Do Now Post Lab
Describe the placement on the illustration for the words consuming, producing & absorbing. State term(s) for autotrophs and heterotrophs.

14. Photosynthesis: Makes energy available in ecosystem
Without light (ENERGY), the ecosystem will not run.
Light enters the Ecosystem through the autotrophs
Autotrophs - Source of Energy for Heterotrophs, aka the consumers.
Cellular Respiration – Provides a useable form of energy for organisms, ATP A C P

15. Think about the lab…What organisms represented the…
Producers
Primary consumer
Secondary consumer
Tertiary consumer
Quaternary consumer
Oat plants
Grasshoppers
Frogs
Trout
Humans
The order of the organisms represents a food chain
Purpose of lab is to look at the amount of energy at a given trophic level which can be transferred to next.

16. Lindeman’s Ten Percent Law
States only about 10% of the energy in trophic level will go towards creating biomass. In other words,, only about 10% will go to make stem, leave, muscle, skin, etc. tissue in the next level.
Video on the Ten Percent Rule

17. Ecological Pyramid
Is a graphical representation designed to show the biomass or bio productivity (energy) or number of organisms at each trophic level in a given ecosystem.

18. Comparing the Ecological Pyramids

19. Lab Question #6
Based on the fact that the number of calories in the oat grain is 10% of the transferred energy, how much was used by the oat plant and lost as entropy (heat)? This question wants to know the 90% that is not transferred. You were doing calculations for the 10%. It is implied in the scenario, “Using what you know about the 10% rule, you will be calculating the number of organisms that you would be able to support in an ecosystem with 1 acre of oat grain.” Total energy of the oats = 3,097,000c Energy available to grasshoppers = 309,700c Total energy of oats – energy available to grasshoppers= (3,097,000c)-(309,700c) = 2,787,300c used by oats/lost