Human Impacts on Ecosystems

Multiple Choice Questions

1. Which of the following is the best indicator of water quality? (A) High levels of nitrates (B) Low levels of dissolved oxygen (C) High levels of dissolved oxygen (D) High levels of turbidity

2. A lake with high biological oxygen demand (BOD) is most likely to have: (A) High levels of dissolved oxygen (B) Low levels of dissolved oxygen (C) Low levels of nutrients (D) High levels of biodiversity

Free Response Question

A local community is concerned about the health of a nearby river. They have noticed a decrease in fish populations and an increase in algae growth. Scientists have measured the following parameters in the river: dissolved oxygen (DO), biological oxygen demand (BOD), and nutrient levels.

(a) Describe how each of the following parameters can be used to assess the health of the river: (i) Dissolved oxygen (DO) (ii) Biological oxygen demand (BOD) (iii) Nutrient levels

(b) Explain how an increase in nutrient levels can lead to a decrease in dissolved oxygen in the river.

(c) Identify ONE anthropogenic (human-caused) source of increased nutrient levels in a river.

(d) Describe ONE method that can be used to reduce the impact of increased nutrient levels on the river.

Answer Key

Multiple Choice:

1. (C)
2. (B)

Free Response:

(a) (i) Dissolved oxygen (DO): High DO levels indicate good water quality, as aquatic organisms need oxygen to survive. Low DO levels can indicate pollution or stress on the ecosystem. (ii) Biological oxygen demand (BOD): High BOD levels indicate that there is a high demand for oxygen by microorganisms, which can lead to low DO levels. Low BOD levels indicate that there is less organic matter in the water, and thus less demand for oxygen. (iii) Nutrient levels: High nutrient levels, such as nitrates and phosphates, can lead to eutrophication, which can cause excessive algae growth and decrease DO levels. Low nutrient levels are generally better for water quality.

(b) An increase in nutrient levels can lead to excessive algae growth. When these algae die, they are decomposed by microorganisms, which use up large amounts of dissolved oxygen in the process. This can lead to a decrease in DO levels, which can harm fish and other aquatic life.

(c) One anthropogenic source of increased nutrient levels is runoff from agricultural fields that contain fertilizers.

(d) One method to reduce the impact of increased nutrient levels is to implement best management practices on farms to reduce fertilizer runoff. This can include using cover crops, buffer strips, and reduced tillage.

Multiple Choice Question

1. Which of the following is a consequence of oil spills in marine environments? (A) Increased biodiversity (B) Decreased water turbidity (C) Harm to wildlife and ecosystems (D) Improved water quality

Free Response Question

The Deepwater Horizon oil spill was a major environmental disaster. The spill had significant impacts on the ecosystem and the local economy. Use your understanding of environmental science to answer the following questions.

(a) Describe TWO environmental impacts of the Deepwater Horizon oil spill.

(b) Explain ONE method used to clean up the Deepwater Horizon oil spill.

(c) Discuss ONE economic impact of the Deepwater Horizon oil spill on the local community.

(d) Identify ONE way that future oil spills could be prevented.

Answer Key

Multiple Choice:

1. (C)

Free Response:

(a) Two environmental impacts of the Deepwater Horizon oil spill include: (i) Death of marine wildlife such as fish, birds, and marine mammals due to oil toxicity and suffocation. (ii) Damage to coastal habitats such as marshes and beaches due to oil contamination.

(b) One method used to clean up the Deepwater Horizon oil spill was the use of chemical dispersants. These chemicals break down the oil into smaller droplets that are more easily dispersed in the water column.

(c) One economic impact of the Deepwater Horizon oil spill on the local community was a decrease in tourism revenue due to the negative impact of the oil spill on beaches and coastal areas.

(d) One way that future oil spills could be prevented is by implementing stricter regulations on offshore drilling and improving safety measures on drilling rigs.