Exam 15: Parasitism and Infectious Diseases

Reduction in virulence of myxomatosis in rabbits in Australia in the second outbreak was a result of

(Figure 15.13) The figure shows population fluctuations in forest tent caterpillars over a 60-year period. The caterpillars were susceptible to a viral infection throughout this time. What causes the 10- to 15-year population fluctuation in the caterpillars?

Two populations with sample sizes of 25 and 27 are compared with a t-test. What is the value for the degrees of freedom?

In S-I-R models of infectious disease transmission, I represents _____ individuals.

Parasites generally have _____ reproductive rates than their hosts and often _____ them.

Which of the following characterizes the rate of recovery of infected individuals in an S-I-R model?

Endoparasitic roundworms and flatworms that live in the tissues of plants and animals are called

When a new disease is discovered, it is called an _____ disease.

In the disease malaria, the Anopheles mosquito is the

Describe two ways a parasite can decrease the likelihood that it will run out of potential hosts.

Why does the parasitic flatworm (Leucochloridium paradoxum) of the amber snail (Succinea putris) alter the behaviour of the snail so that it moves to the top of a plant stem?

While you are conducting a study of the optimal growing conditions for commercially grown sunflowers, all of the sunflower plants in the field you are studying die. You discover that an emerging fungal pathogen kills sunflowers by destroying their roots. The fungus uses honeybees, which pollinate your flowers, as a vector to transmit fungal spores among sunflower plants. The next year the farm reseeds, hoping that the fungus has died over the winter. Early in the growing season some plants begin dying again, but then the honeybee population develops colony collapse disorder and all of the honeybees die. To compensate for the loss in pollinators, the farmers introduce large numbers of bumblebees. The number of new sunflower plants that become infected during the remainder of the growing season drops to near zero. Using the variables in the susceptible-infected-resistant (S-I-R) model equation: R₀ = (S × I × g) ÷ (I × b), explain what has happened to alter the disease dynamics in the second year of your study and how this has occurred.

In S-I-R models, the variable g represents

In S-I-R models, which of the following represents the probability of contact between susceptible and infected individuals?

Vaccinations slow or stop the spread of diseases by

In S-I-R models, which of the following models the ratio of new infections to recoveries?

The World Health Organization estimates that _____ of human deaths are caused by infectious diseases.

Infection tolerance is the ability of a host to

Endoparasites (such as tapeworms) seem to lead an ideal life in the interior of the host, protected from natural enemies and the external environment while having a continual supply of nutrients. What are challenges that endoparasites face?

Dutch elm disease is caused by