Pre-Lab
AP Lab #12
Ecosystem Studies
1. Energy
Flow
2. Chemical Cycling
AP Lab #12 we will be able to
study both cycles
AP LAB #12
 Part
a - Dissolved Oxygen in water
 Part b – Primary Productivity
 Part c – Identifying Aquatic
Organisms
Vernier Probes
DO
Probe = dissolved oxygen
Calculator will calculate %O2
Laptops to collect data.
Part a – Dissolved Oxygen
 Objectives
1.
2.
–
identify the effect of varying
temperature on amount of
dissolved oxygen in a water
sample.
set up and calibrate Dissolved
oxygen probe with calculator
Prediction
How will lower temperatures impact
dissolved oxygen in water?
1.
SLOW down gas molecules, more will remain in
water rather than escape from surface.
o
2.
How will higher temperatures impact
dissolved oxygen in water?

SPEED up the interactions of the gas molecules
with the surface  more molecules will escape.
12b - Primary Productivity
Equation NPP = GPP – Rs
Where . . .
 NPP = Net Primary
Productivity
 GPP = Gross Primary
Productivity
 Rs = Respiration
Primary Productivity
 The
rate at which light energy is captured
by autotrophs or primary producers.
Ps - photosynthesis
6 CO2 + 12 H2O + Light energy 
C6H12O6 + 6 O2 + 6 H2O
First
basic form of energy storage is
termed Primary Production.
Total Ps = gross primary
productivity
Primary Producers
Producers
need energy to
survive!
50 - 90% of GPP is lost to Rs by the
primary producers.
NPP = 10 - 50%
Animals - use only NPP, which
limits the food webs.
Rs = Respiration

C6H12O6 + 6 O2  6 CO2 + 6 H2O +
ATP
Cellular respiration is required to
release energy to do Ps
Natural Systems equilibrate
Ps : Rs

Interactions of both processes
Ps
> Rs  excess energy
Growth or Reproduction
Ps = Rs  maintenance
Ps < Rs  consumption of
stored biomass
Measuring Productivity
What
substance is present in
both Ps and Rs that can be
measured in a high school
setting?
CO2 levels
O2 levels
Ps vs. Rs
 Ps
> Rs
 Ps = Rs
 Ps < Rs
O2 levels
CO2 levels
Part C: Identifying Aquatic
Organisms
Use
Microscope
Use General Guide to Pond Life
Sketch and Identify organisms
Label sketches and note type
Producer
Consumer – specific type