Solved by a verified expert:Viruses and Evolution
As you learned in the content for this week, bacteria and viruses evolve in
response to changes in their environment, just as other organisms do. You may
not have realized, but the disease causing agents aren’t the only things that can
evolve. The organism that contracts a disease can also evolve in response to
the virus.
1.
Explain, in your own words, how viruses evolve to
become resistant to treatment.
Real World Example: Evolution Of Virus and Host
In 1859, European rabbits were introduced into Australia for hunting
purposes. Since there were no natural predators for rabbits in Australia, the
rabbits soon multiplied in an uncontrolled fashion and became a major problem.
The rabbits attacked and ate crops intended for human consumption. Australians
needed a way to get rid of the rabbits.
In 1950, two virologists introduced a virus into the rabbit population of
Australia. This virus, called a myxomavirus, had been shown effective
in killing rabbits found in America. Though the actual viral effects on the
European rabbit were not known at the time, it was hoped that it could be used
to control the rabbits of Australia. Mosquitoes were to spread the disease
throughout the rabbit population.
Results of the Program
Year 1 — 90% of the rabbit population died
Year 2 — 90% of the remaining rabbit population died
Year 3 — 50% of the remaining rabbit population died
Years 4 to 6 – the rabbit population begins to increase
Year 7 — An experiment is conducted. The same strain of the virus that
was initially released in 1950 was injected into a sample of rabbits caught
from the wild. Only 25% of the rabbits died.
Use this information to answer the questions on the following page.
2.
The data above can be explained by evolution. Which
organism evolved? Briefly explain how you came to that conclusion.
3.
Three conditions must be met for evolution by natural
selection to occur (see your textbook). Explain how these conditions were met
in this scenario (i.e. list each condition, and clearly explain how that
condition was met in the case of these rabbits).
Apply
4.
The Ebola
virus kills approximately 70% of the people who become infected. The death rate
among untreated patients has changed little despite many years of Ebola outbreaks in Africa. Give two possible
reasons why we do not see the same rapid decline in death rates for a human
population infected with Ebola as we
saw for the rabbits infected with myxoma
(i.e what are some possible reasons that evolution is not proceeding at the
same rate in both cases).
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