Ecology - Ecosystem Ecology Questions

1. To measure primary production of algae in a stream, youplace two sealed chambers in the stream, each enclosing thesediments as well as the water above them. One chamber is coveredwith black tape (blocking all light) while the other is transparentto light.

You measure dissolved oxygen (DO) before and after a 24-hourincubation. DO in the light chamber increases by 30mg/m² while DO in the dark chamber decreased by 10mg/m^2.

What is the estimated Re for the stream? mgO₂ m^-2 day^-1

2. What is the stream's esitmated NEP? mgO₂ m^-2 day^-1

3. Based on these data, what was the stream's GPP? mgO₂ m^-2 day^-1

4. The position of Earth's continents has shifted dramaticallyover its history. Imagine that all of Earth's land mass was bunchedtogether with approximately equal areas above and below theEquator. Assume that seasonal patterns of growth and respirationare otherwise similar, with the Northern Hemisphere's summeroccurring June-August and the Southern Hemisphere's summeroccurring December-February.

How will this new configuration affect seasonal swings in averageglobal CO₂?

a. Seasonal swings would be larger, butCO₂ would still peak in late April.

b. Seasonal swings would be similar, butCO₂ would now peak in late August.

c. Seasonal swings would be larger, butCO₂ would now peak in late August.

d. Seasonal swings would be much smaller,perhaps even undetectable.

5. In the four-link food chain shown to the right, plantsare infested by caterpillars, caterpillars are parasitized bybraconid wasps, and braconid wasps are parasitized by tinyiridescent wasps. What can you say about whether each of theEltonian pyramids (energy, numbers, and biomass) describing thissystem will be inverted or not? Give reasons for your predictionsusing the concepts in this section.