David A. Klingbiel 12/7/00
Introduction.
In this experiment, we studied how photosynthesis and respiration affected carbon dioxide levels in a closed forest ecosystem. We also looked at other ways humans affect carbon dioxide levels. A model forest ecosystem was constructed by planting tree seedlings and other plants in an aquarium. This aquarium could then be sealed off from the outside atmosphere with a lid. The lid to our aquarium was then connected to a carbon dioxide gas analyzer by two hoses that circulated air through the model ecosystem.
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The carbon dioxide analyzer told us how much carbon dioxide was in the atmosphere of our ecosystem model in parts per million (PPM) at any given time. We then examined how the carbon dioxide levels changed in response to different environmental situations and discussed why they changed.
Photosynthesis vs. Respiration
Let's look at the chemical equations for Photosynthesis and
Respiration.
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Photosynthesis: Sun light CO2 + H20 -----------> C6H12O6 + O2 Or Carbon Dioxide and Water react with Light and produce Glucose and Oxygen |
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Respiration: C6H12O6 + O2 --------->CO2 + H2O + ATP Or Glucose and Oxygen react to produce Carbon Dioxide, Water, and ATP
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Alright, these equations might look confusing but let me explain
what they mean. First of all, the compounds on the left of the arrows are needed
for these reactions to take place. The compounds on the right side of the arrows
are produced by the reactions. They are called products. Knowing that, what
do you notice about these two equations? Do they look like one is the reverse
of the other? They basically are! When photosynthesis takes place, carbon dioxide
and water are absorbed (remember left side of the arrow) and with the presence
of light, without which this equation could not take place, glucose(sugar) and
oxygen are produced (right side of the arrow). You can learn more about photosynthesis
in the "A Tree from
The Air" section. Respiration doesn't need light to take place (notice the
word "light" is not written over the reaction arrow) but it does require the
products (right side of the arrow) from photosynthesis, glucose and oxygen.
Respiration then produces carbon dioxide, water, and something called ATP. ATP
is the energy form cells produce to permit cellular function. What other organisms
respire? PEOPLE DO! Think about this scenario: You eat an apple for lunch (sugars)
and breath oxygen into your lungs. Your body then uses that sugar and oxygen
to create ATP (energy) and releases carbon dioxide and water. RELEASE WATER!?
Have you ever breathed out on a cold mirror? What forms on it? That's right,
small water droplets. People exhale water vapor into the air.
Photosynthesis and Respiration Experiment
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