Directions: Read the passage below and use it to answer the questions that follow.
The Effects of Biomagnification
One of the effects of human activity on food webs in ecological systems is biomagnification. Biomagnification is the increase of toxic substances that have accumulated in organisms and that increases at each trophic level. Toxins that are introduced at the producer level will be passed up the trophic levels as they are consumed, as shown in the diagram to the left.
This means that organisms at higher trophic levels have a higher rate of biomagnification. It is possible to calculate biomagnification factors by looking at normal pesticide found in fat tissues within an organism and comparing this to pesticide found in the fat tissues of the prey of that organism. If the prey has a higher biomagnification factor, the pesticides are accumulating through the food chain.
An example of biomagnification that has impacted an ecosystem was the use of DDT, a pesticide once widely used for insect control and then banned in 1972. The use of this pesticide was believed to be linked to the thinning of eggshells in many bird species, including the bald eagle, leading to a decrease in the populations. DDT was sprayed on crops and then would enter the food chain through the producers. The level of DDT increased up the food chain as organisms fed on lower organisms with DDT stored in their tissues. The organisms in the higher trophic levels such as bald eagles and peregrine falcons had higher levels of DDT due to eating contaminated fish. How do you think DDT impacted the birds' populations?
The bald eagle was placed on the endangered species list. Thanks to efforts from scientists and environmental agencies, the bald eagle was removed from the endangered list in 2007. A potential side effect of biomagnification is the decrease in population of secondary and tertiary consumers. The higher the trophic level, the higher the concentration of toxin, which could decrease the population affecting the flow of matter and energy within the ecosystem.
Scientists have to think critically about the effects of future chemical use in ecosystems and counter the negative impacts of chemicals that are already in use. Scientists and environmental agencies must consider long term damage to organism populations, ecosystems, humans, and economies. There are many technologies that are available to help monitor biomagnification. Scientists can use radiotracers that show how contaminants move through the food chain. Radiotracers can track substances such as mercury and pesticides. Scientists also track and monitor water quality over time using different technologies. This allows scientists to watch for trends in the water quality and respond to emergencies such as an oil spill.
Question 1
What can be inferred about the use of DDT in the ecosystem?(1 point)
Responses
a. DDT only affected bird species, including the bald eagle.
a. DDT only affected bird species, including the bald eagle.
b. DDT had no impact on the populations of secondary and tertiary consumers.
b. DDT had no impact on the populations of secondary and tertiary consumers.
c. DDT levels were highest in producers due to direct spraying on crops.
c. DDT levels were highest in producers due to direct spraying on crops.
d. DDT entered the food chain and increased in concentration as organisms consumed contaminated prey.
d. DDT entered the food chain and increased in concentration as organisms consumed contaminated prey.
Question 2
How did the use of DDT affect the population of bald eagles?(1 point)
Responses
a. The population of bald eagles increased due to the abundance of contaminated prey.
a. The population of bald eagles increased due to the abundance of contaminated prey.
b. The population of bald eagles remained unaffected by the use of DDT.
b. The population of bald eagles remained unaffected by the use of DDT.
c. The population of bald eagles decreased due to the thinning of eggshells.
c. The population of bald eagles decreased due to the thinning of eggshells.
d. The population of bald eagles was unaffected by biomagnification.
d. The population of bald eagles was unaffected by biomagnification.
Question 3
Which statement best summarizes the potential consequences of biomagnification?(1 point)
Responses
a. Biomagnification can lead to the increase in the population of secondary and tertiary consumers.
a. Biomagnification can lead to the increase in the population of secondary and tertiary consumers.
b. Biomagnification can disrupt the flow of matter and energy within an ecosystem.
b. Biomagnification can disrupt the flow of matter and energy within an ecosystem.
c. Biomagnification has no significant impact on organism populations.
c. Biomagnification has no significant impact on organism populations.
d. Biomagnification can be prevented by reducing the use of chemicals in ecosystems.
d. Biomagnification can be prevented by reducing the use of chemicals in ecosystems.
Question 1
c. DDT levels were highest in producers due to direct spraying on crops.
Question 2
c. The population of bald eagles decreased due to the thinning of eggshells.
Question 3
b. Biomagnification can disrupt the flow of matter and energy within an ecosystem.