Ecology unit test
A test on this unit alone, marked as a percentage and a letter grade — for the test your class is actually sitting, rather than for May. Answer everything, then submit once: seeing the answer to question 3 before attempting question 4 makes the final percentage meaningless.
Predator-prey cycles
Ten percent rule
Eutrophication
Carrying capacity (K)
Doubling time
Competitive exclusion principle
Nitrogen cycle steps
Simpson's diversity index
Lab: Fruit Fly Behavior
Limiting nutrient
Population density and dispersion
Density-dependent vs independent factors
Short answer 1. Define or explain: Age structure diagram
3 ptsShort answer 2. Define or explain: Keystone species
3 ptsShort answer 3. Define or explain: Invasive species
3 ptsShort answer 4. Define or explain: Ecosystem services
3 ptsFree response
9 ptsThis course has no free-response prompt tagged to this unit, so one from elsewhere in the course is used. It is still worth writing — the skill transfers.
A researcher studies a freshwater protist that lives in pond water far more dilute than its cytoplasm. The protist has a contractile vacuole that fills with water and periodically expels it across the plasma membrane. The researcher transfers protists into solutions of increasing solute concentration and records how often the contractile vacuole contracts.
Describe the direction of net water movement between the protist and pond water, and explain why it occurs.
Explain why the contractile vacuole requires ATP, even though the water entering the cell does not.
Predict how contraction rate changes as external solute concentration rises, and justify your prediction.
The researcher places protists in a solution isotonic to their cytoplasm. Predict the contraction rate and explain what this result shows about the vacuole's function.