PCB 3043 Chapter 15

Would it be effective to control a parasite by vaccinating individuals in a reservoir species infected by the parasite? -Yes, because the vaccine would heal damage from the infection and leave individuals healthy and immune. -Yes, because the vaccine would attack and destroy the parasites in the tissues of the infected Individuals. -No, because the immune systems of the infected individuals are already resistant to the parasite. -No, because infected individuals of the species are vectors that do not produce an immune response.

-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? -Parasites must infect a native vector organism to reach the invasive species. -Non-native parasites become more lethal as the invasive species dies off. -Over time, the parasite may become less deadly to the invasive species. -Invasive species have naturally high resistance to all parasites.

-Over time, the parasite may become less deadly to the invasive species.

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. -A peptide collected from the skin of an Indian frog kills methicillin-resistant Staphylococcus aureus. -The bacterium that causes tuberculosis has had known mortal effects on humans throughout human history. -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.

-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.

Why are parasites often more lethal outside of their native range? -DNA mutates more quickly outside of a parasite's native range, so the parasite evolves faster. -Parasites cannot be transmitted from host to host outside of their native range. -Therapeutic treatments, like fungicides, are ineffective outside of a parasite's native range. -The host population in the new region lacks defensive adaptations against foreign parasites.

-The host population in the new region lacks defensive adaptations against foreign parasites.

Scientists collected data on two groups of organisms. The mean, x, equals 10 for the first group and 5 for the second group. In each group, the sample variance, s2, equals 4. The sample size, n, for the first group is 6 and for the second group is 8. What conclusion can be drawn about these data given a t-value of 4.63 and a t(critical)-value of 1.782 at an a of 0.05? -The means are so different that a t-test is not needed to determine statistical significance. -The variances are significantly different because the t(critical)-value is smaller than the t-value. -The means are not significantly different because the t-value is larger than the t(critical)-value. -The means are significantly different because the t-value is larger than the t(critical)-value.

-The means are significantly different because the t-value is larger than the t(critical)-value.

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 beetles that spread the disease do not survive in cities so the growth of cities has provided more disease-free habitat for American elms. -The most susceptible trees died in the initial outbreak and the more resistant survivors have passed their genes for resistance to their offspring. -Antibiotics have been developed to combat the disease, although untreated trees still quickly succumb to the disease once they are infected. -The fungus that causes the diseases began to die out as the number of new host trees dropped and the pathogen is now nearly extinct in North America.

-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 increases until everyone is infected. -The number of infected individuals fluctuates in a cyclical pattern. -The number of infected individuals stays constant regardless of new births. -The number of infected individuals decreases continuously over time.

-The number of infected individuals fluctuates in a cyclical pattern.

How does the rate of infection differ from the rate of contact? -The rate of contact is dependent on the number of susceptible people in the population, whereas the rate of infection is dependent on the number of recovered people and the number on infected people. -The rate of infection is the probability of a susceptible individual coming into contact with an infected individual, and the rate of contact is the number of susceptible individuals that the primary case infects within a given amount of time. -The rate of contact is the probability of a susceptible individual coming into contact with an Infected individual, and the rate of infection is the number of susceptible individuals that the primary case infects within a given amount of time. -The rate of contact is determined by the rate of infection, whereas the rate of infection is independent of the rate of contact.

-The rate of contact is the probability of a susceptible individual coming into contact with an Infected individual, and the rate of infection is the number of susceptible individuals that the primary case infects within a given amount of time.

What rule do researchers use to determine if two means are significantly different from each other in a t-test? -The t(critical)-value is equal to or greater than 0.05. -The t(critical)-value is larger than the t-value. -The t(critical)-value is equal to or smaller than the t-value. -The t(critical)-value is smaller than alpha, a-value.

-The t(critical)-value is equal to or smaller than the t-value.

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.

Scientists collected data on two groups of organisms. The mean, x, equals 10 for the first group and 5 for the second group. In each group, the sample variance, s2, equals 4. The sample size, n, for the first group is 6 and for the second group is 8. Determine the t(critical)-value for these data with the t-table, assuming a equals 0.05. -1.761 -2.681 -0.050 -1.782

1.782

Scientists collected data on two groups of organisms. The mean, x, equals 10 for the first group and 5 for the second group. In each group, the sample variance, s2, equals 4. The sample size, n, for the first group is 6 and for the second group is 8. Calculate the t-value for these two groups of organisms. -13.89 -4.63 -3.28 -4.27

4.63

Classify each statement as describing an endoparasite or an ectoparasite: Easily moves to and from its host.

Ectoparasite

Classify each statement as describing an endoparasite or an ectoparasite: Inaccessible to its host's immune system.

Ectoparasite

Classify each statement as describing an endoparasite or an ectoparasite: Vulnerable to variable external environments.

Ectoparasite

Classify each statement as describing an endoparasite or an ectoparasite: Easily acquires host's nutrients for feeding.

Endoparasite

Classify each statement as describing an endoparasite or an ectoparasite: Include viruses and other intracellular parasites.

Endoparasite

Classify each statement as describing an endoparasite or an ectoparasite: Protected from most competitors and predators.

Endoparasite

Classify each statement as applying to horizontal or vertical transmission of a parasite: A vector, such as a mosquito, transmits the parasite.

Horizontal transmission

Classify each statement as applying to horizontal or vertical transmission of a parasite: Transmission occurs between organisms of different species.

Horizontal transmission

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 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

Classify each statement as applying to horizontal or vertical transmission of a parasite: Transmission occurs from a parent to its offspring.

Vertical transmission

Classify each statement as applying to horizontal or vertical transmission of a parasite: Death of the host does not occur until the host has reproduced.

Vertical transmission.

What is the most effective way to prevent the spread of mad cow disease? -Give antibiotics to the entire herd of cows to kill the pathogens. -Avoid feeding other cows the ground-up bodies of infected cows. -Butcher and sell infected cows when they exhibit symptoms. -Quarantine infected cows away from the rest of the cow herd.

-Avoid feeding other cows the ground-up bodies of infected cows.

In a typical S-I-R model, why does the number of susceptible people decrease over time? -Because the number of recovered people increases. -Because the infected population dies. -Because the number of infected people increases. -Because the total number of people in the population is declining.

-Because the number of infected people increases.

Finish the following sentence. A t-test: -Defines the hypothesis for an experiment. -Describes how much variability there is in a data set. -Determines if two means are significantly different from each other. -Determines the shape of the normal distribution for a data set.

-Determines if two means are significantly different from each other.

Under which circumstance will a disease not spread beyond a few individuals in a population? -If the primary case infects a large number of people very quickly, the reproductive ration will be less than 1. -If the rate of infection is lower than the rate of recovery, the reproductive ration of the infection will be less than 1. -If the rate of recovery is lower than the rate of infection, the reproductive ration will be greater than 1. -If the reproductive ratio is greater than 1, only a few individuals in a population will be infected.

-If the rate of infection is lower than the rate of recovery, the reproductive ration of the infection will be less than 1.

Which variables are used to calculate the t-value? -Mean, variance, sample size. -Mean and variance. -Normal distribution, mean, standard deviation. -Mean, sample size, coefficient of determination.

-Mean, variance, sample size.