14.11.1 The Effects of Human Population Growth: Lake Eutrophication

Question 1

The Effects of Human Population Growth: Lake Eutrophication

Answer 1

• Human populations may affect ecosystem level processes, such as chemical cycling.
• The human population is currently undergoing an exponential growth phase with a population exceeding 6 billion.
• One effect of human population growth is lake eutrophication.
• By studying ecology, humans can learn to lessen their impact on ecosystems.

Question 2

carrying capacity

Answer 2

• Question: How do humans affect the Earth’s ecosystems?
• Human population growth limits the resources available to other organisms and affects ecosystem level processes such as chemical cycling.
• Review: Exponential growth is the geometric increase of a population that has access to unlimited resources.
• The graph on the far left charts human population growth over time. Currently in many countries, the human population growth approaches an exponential curve. Eventually, human population change will be affected by limited resources and approach carrying capacity (graph on immediate left).

Question 3

eutrophication

Answer 3

• Review: eutrophicationis the nutrient enrichment of a lake or a stream that causes a change in the lake’s community. It sometimes occurs during the process of ecological succession.
• Eutrophication can also result from the runoff of fertilizer or the addition of sewage. An increased residential use of phosphate enriched detergents resulted in the eutrophication of Lake Erie. The nutrients upset the existing community balance, causing algae blooms. Algae use large quantities of oxygen vital to other organisms.
• When the algae die, the action of detritivores depletes the oxygen supply further. Eventually, Lake Erie was declared dead. When phosphate-free detergent was used instead, the lake began to improve. Certain native fish and invertebrates still have not repopulated the lake.

Question 4

The phosphate in detergents was a limiting resource (nutrient) to _____________ in Lake Erie.

Answer 4

• algae

Question 5

True or false?

Human population growth has finally reached the carrying capacity of the planet.

Answer 5

• false

Question 6

True or false?

Eutrophication is entirely a product of human activity.

Answer 6

• false

Question 7

Which factor was the major cause of the serious eutrophication of Lake Erie?

Answer 7

• Detergents

Question 8

Exponential growth is found in situations with

Answer 8

• unlimited resources

Question 9

Which of the following is not a consequence of lake eutrophication?

Answer 9

• decreased nutrient levels

Question 10

Lake Erie was called a “dead” lake because of:

Answer 10

• lack of oxygen

Question 11

True or false?

Lake eutrophication involves the enrichment of lake waters, allowing algae to thrive.

Answer 11

• true

Question 12

The maximum size of a population under logistic growth is:

Answer 12

• the carrying capacity