Quiz 14 (Chapter 15)
What is the most effective way to prevent the spread of mad cow disease?
Avoid feeding other cows the ground‑up bodies of infected cows.
Classify each statement as describing an endoparasite or an ectoparasite.
Endoparasite: - protected from most competitors and predators - easily acquires host's nutrients for feeding - includes viruses and other intracellular parasites Ectoparasite: - inaccessible to its host's immune system - vulnerable to variable external environment - easily moves to and from its host
Classify each statement as applying to horizontal or vertical transmission of a parasite.
Horizontal transmission: - Transmission occurs between organisms of different species - A vector, such as a mosquito, transmits the parasite Vertical transmission: - Transmission occurs from a parent to its offspring - Death of the host does not occur until the host has reproduced
Would it be effective to control a parasite by vaccinating individuals in a reservoir species infected by the parasite?
No, because the immune systems of the infected individuals are already resistant to the parasite.
What is one reason that using a parasite in an attempt to control an invasive host species might be problematic?
Over time, the parasite may become less deadly to the invasive species.
Why are parasites often more lethal outside of their native range?
The host population in the new region lacks defensive adaptations against foreign parasites.
Why are American elm trees less likely to die of Dutch elm disease now than when the disease was first brought to North America from Asia?
The most susceptible trees died in the initial outbreak and the more resistant survivors have passed their genes for resistance to their offspring.
According to the S-I-R model of parasite and host dynamics, how does the number of infections change over time if new susceptible individuals are born into the population at regular intervals?
The number of infected individuals fluctuates in a cyclical pattern.
Place the steps of the Lyme disease cycle in the correct order, beginning in spring when ticks hatch from eggs.
Uninfected ticks hatch from eggs as larvae -> Larval ticks feed on bacteria-infected rodents -> Infected larvae molt into the next developmental stage -> Nymphs engorge themselves on new host, then molt -> Adult ticks feed on deer blood and find mates -> -> Female ticks lay eggs
Using the S-I-R model, identify each statement as describing the outcome over time of susceptible individuals, infected individuals, or recovered individuals. These individuals host the pathogen and and transmit the infection.
infected individuals
Using the S-I-R model, identify each statement as describing the outcome over time of susceptible individuals, infected individuals, or recovered individuals. These individuals acquire immunity through resistance and remain immune to any future infections.
recovered individuals
Using the S-I-R model, identify each statement as describing the outcome over time of susceptible individuals, infected individuals, or recovered individuals. These individuals can be infected depending on rate of transmission and probability of infection on contact.
susceptible individuals
Identify scenarios that describe an emerging infectious disease.
- Reported cases of Lyme disease in humans have increased steadily since its relatively recent recognition in 1976. - An infectious fungus observed in the black poplar tree recently appeared in the Eastern cottonwood tree. - Malaria cases have increased exponentially due to malaria's resistance to drugs and mosquitoes' resistance to pesticides.
