#1: 2/2 = 1 pt. #2: + + + 3/3 = 1 pt. 26 Points Total
#3. (1 pt.) Where zebra mussels are present, the carrying capacities of native mussel population in lake ecosystems are most likely… a)Decreased b)Eliminated c)Increased d)Unchanged #4: (1 pt.) +
#5. (1 pt.) Zebra mussels filter plankton and other matter from lake and river water. What are 2 likely results of this filtration? a)Decreased plankton populations and decreased water clarity. b)Increased plankton populations and increased water clarity. c)Decreased plankton populations and increased water clarity. d)Increased plankton populations and decreased water clarity. #6. (2 pts.) Describe the long-term impact that an invasive species such as zebra mussels may likely have on lake ecosystems. “Zebra mussels could out-compete native species in the ecosystem and lead to extinctions. This could upset the natural balance in lakes.” 2/2: The student correctly describes the long-term impact invasive species such as zebra mussels will have on lake ecosystems. Two examples include out- competing native species and filtering too much food out of the water. 1/2: Student gives an incomplete description of the long-term impact invasive species such as zebra mussels will have on lake ecosystems
#7. (2 pts.) Questions about zebra mussels… a)Type a question about zebra mussels that is better approached through a controlled laboratory experiment than through a field investigation. “One question that may be answered through a controlled experiment is, “How much salt can zebra mussels tolerate?” b)Explain why your question is better approached through a controlled experiment. “This question is best answered in a laboratory experiment because salinity conditions can be controlled better in a laboratory than in a natural environment.” 2/2: The student correctly identifies a question that would best be answered by a controlled laboratory experiment and explains why that question is best approached through controlled experimentation. Explanations should recognize that controlled experimentation is superior to field observation. 1/2: The student correctly identifies a question that would best be answered by a controlled laboratory experiment but fails to explain why that question is best approached through controlled experimentation.
#8. (1 pt.) Which of these questions can be answered by performing tests on the water samples collected by the students? a)How deep is the lake? b)What is the fish population in the lake? c)What pollutants are present in the lake? d)In what direction does water flow through the lake? #9. Write the name of the 3 objects into the diagram to show how carbon flows through an ecosystem. 3/3 = 1 pt.
#10. (1 pt.) What is the ultimate energy source for the organisms in this lake ecosystem? + #11. (2 pts.) For each trophic level, write the name of 1 organism from the food web into the appropriate box. ProducerPrimary Cons.Sec. Cons.Tertiary Cons. AlgaeZooplanktonAquatic InvertsDuck Aquatic PlantsAquatic InvertsSmall FishBig Fish Duck Heron InsectsBird Producers & Consumers = +2 Producer Only = +1 Consumers Only = +1
#12. (1 pt.) Mr. Lang’s students made 4 statements as they conducted research at the lake. Which statement is quantitative? a)“The phosphorus level in the lake is high.” b)“The algae population is growing rapidly.” c)“The lake water looks much greener today than last time.” d)“The phosphorus level in the lake has risen 3 micrograms per liter (ug/L).” #13. (1 pt.) Which calculation best describes the changes in lake-water phosphorus levels? a)Total micrograms per liter on August 1 b)Percent increase from May 1 to August 1 c)Average micrograms per liter of all 4 dates d)Difference between phosphorus and chlorophyll levels on August 1
#14. (1 pt.) Assuming that phosphorus levels influence chlorophyll levels, how would chlorophyll levels change over time if the people in surrounding areas gradually stopped fertilizing their fields and lawns with phosphorus? Plot 3 points (“+”) to show the trend in chlorophyll levels. + + + Downward trend = 1 pt.
#15. (3 pts.) The students observe that as the phosphorus level increases, the amount of algae in the lake also increases. However, they are not sure that the increase in phosphorus is the cause of the increased amount of algae. Describe a simple experiment to demonstrate that an increase in phosphorus causes an increase in algae growth. “In a lab, take 5 – 50 ml beakers and place them under the same strength lights and fill each beaker with 30 ml of water taken from the same lake. Then add 1 ml of algae to each beaker and let it sit for a day. Then the next day add ½ a ml of phosphorus to the first beaker, 1 ml to the second beaker, and 1 ½ ml to the third beaker, 2 ml to the forth beaker, and 2 ½ ml to the fifth beaker. Then let the beakers sit for a week. Take the beakers and filter out the water to measure the amount of algae grown. If the 5 th beaker has the most, then we know that phosphorus is a reason for algae growth.” 3/3: A simple experiment is described that demonstrates that an increase in phosphorus causes an increase in algae growth. The experiment must include… 2 or more samples Only 1 manipulated variable At least 1 controlled variable (Example – Initial algae, Light, Time, Temp., or amount of water At least 1 responding variable that would show an increase in algae. 2/3: 3 of 4 Criteria 1/3: 2 of 4 Criteria
#16. (3 pts.) You will be listing 3 organisms in this ecosystem that would be affected if a local extinction of the zooplankton occurred. a)List 1 organism in the ecosystem that would be affected if a local extinction of the zooplankton occurred. Explain what would likely happen to the population and why this change would occur. “Small fish would be affected if the zooplankton became extinct. The probable effect on the population would be a dramatic decrease because the small fish no longer have a food source, thus many would starve and competition between the fish would greatly increase” b)List a second organism in the ecosystem that would be affected if a local extinction of the zooplankton occurred. Explain what would likely happen to the population and why this change would occur. “Algae would also be affected by the extinction of zooplankton, and the population of it would most likely greatly increase because the zooplankton is responsible for eating the algae”
3/3: Student lists 3 organisms and accurately explains what would happen to each organism and why this change to the organism would occur. 2/3: 2 organisms explained 1/3: 1 organism explained c) List a third organism in the ecosystem that would be affected if a local extinction of the zooplankton occurred. Explain what would likely happen to the population and why this change would occur. “The heron population in this region would be likely to decrease because the herons depend on small fish for food, which depend on the zooplankton. After the decrease in small fish because of their lack of food the heron would also suffer a loss of food supply.”
#17. Decomposers in an ecosystem… a)Explain why decomposers are important in maintaining the flow of nutrients through an ecosystem. “Decomposers break down nutrients and put them back in the soil so plants can continue to get the nutrients they need to grow and survive. Animals and other organisms get the nutrients they need from the plants they eat. Without decomposers, plants would not be able to get their needed nutrients, and neither would anything higher up on the food chain.” a)Predict what would happen if decomposers were removed from an ecosystem. “If decomposers were removed, dead organisms could not be broken down into nutrients. Waste would not be broken down and the ecosystem would become overfilled with waste. Plants would not be able to get their needed nutrients from the soil which would also cause the animals higher up on the food chain to not get their needed nutrients. Eventually the ecosystem would fail, and everything in it would die.”
3/3: Student clearly and completely explains that decomposers are important in returning nutrients to an ecosystem and making them available to other organisms by explaining that… Decomposers break down dead organisms and waste Decomposers return important nutrients to the soil and make them available for other organisms AND The student clearly makes a reasonable prediction of what would happen if decomposers were removed from the ecosystem. 2/3: 2 of key points 1/3: 1 of key points 26 Total Points