Question

scientists studied a species of phytoplankton. these phytoplankton are primary producers and are an important part of marine food webs. as all organisms are regulated by their environment, so are the phytoplankton. the scientists looked at the relationship between the phytoplankton population and a virus population found in the same environment. they created three environments in a laboratory setting to collect data on the numbers of phytoplankton and viruses over a period of time and graphed the results once they were averaged, as shown below. the scientists claimed that the growth and stability of the phytoplankton populations were affected by the viruses. based on the information given, which two arguments support this claim? as the phytoplankton population reached capacity, the number of viruses began to increase because the phytoplankton were the hosts to the viruses and replicated the viruses genome. the phytoplankton population was affected by the viruses because the viruses were competitors for the food sources in the environment. the phytoplankton population was unable to absorb the light necessary for growth because the viruses covered the surface of the water. the phytoplankton population decreased as the number of viruses increased because the cells of the phytoplankton were destroyed as the viruses used them to increase the number of viruses in the environment. as the phytoplankton population increased, the number of viruses began to increase because the phytoplankton were consumed by the viruses.

Explanation:

• First Argument (Option 1):
• Viruses often rely on host cells (like phytoplankton here) to replicate. When the phytoplankton population is large (reaches capacity), there are more hosts available for viruses to infect and replicate, so virus numbers increase.
• Second Argument (Option 4):
• As viruses use phytoplankton cells (destroying them in the process of replication and increasing their own numbers), a decrease in phytoplankton population as virus numbers increase is a clear indication of the virus - phytoplankton interaction affecting phytoplankton growth and stability.
• Option 2 is incorrect because viruses are not competitors for food sources in the traditional sense (they are obligate intracellular parasites). Option 3 is incorrect as there is no indication in the problem that viruses cover the water surface. Option 5 is incorrect as viruses do not consume phytoplankton in the way described (they use them for replication, not as food).

Answer:

First Argument: As the phytoplankton population reached capacity, the number of viruses began to increase because the phytoplankton were the hosts to the viruses and replicated the viruses' genome.
Second Argument: The phytoplankton population decreased as the number of viruses increased because the cells of the phytoplankton were destroyed as the viruses used them to increase the number of viruses in the environment.