Question 1

A researcher places purified viruses in a cell-free, nutrient-rich tube containing amino acids, nucleotides, and ATP. What is most likely to happen?

Accepted Answer

The viruses will not replicate because they require host cell machinery to make new viruses.

Question 2

A patient with an enveloped respiratory virus is treated with a drug that interferes with the virus’s outermost surface structures. After treatment, viral genomes and capsid proteins are still detected, but the virus infects far fewer host cells. Which explanation best fits this result?

Accepted Answer

The drug disrupted surface structures needed for host cell entry.

Question 3

A researcher studying lambda phage finds bacterial cells that contain viral DNA but are not producing new virus particles. After UV exposure, the same cells begin making phages and then lyse. Which explanation best fits these observations?

Accepted Answer

The phage existed as a prophage before switching to the lytic cycle.

Question 4

A public health team finds that several new flu strains have spread globally since last year’s vaccine was made. Why might last year’s immune memory provide limited protection against these strains?

Accepted Answer

Flu mutations can alter viral targets, making new strains less recognizable to existing memory cells.

Question 5

A hospital begins testing patients earlier and starts treatment sooner, shortening the average time that infected patients remain contagious. How would this change most likely affect the basic reproduction number, $$R_0$$?

Accepted Answer

$$R_0$$ would decrease because a higher recovery rate gives each patient less time to infect others.

Question 6

During a virus outbreak, many infected people recover and become immune, reducing the number of susceptible individuals in the population. Which measure should researchers use to estimate how many people each infected person will infect under these current conditions?

Accepted Answer

$$R_e$$, because it accounts for the smaller susceptible population after immunity increases.

Question 7

A wildlife biologist marks 50 turtles, releases them, and later captures 40 turtles. Only 5 of the second group are marked. What does this result suggest about the total turtle population? (Use the Lincoln-Petersen estimator: $$N = \frac{n_1$ 	imes n_2$}{m_2$})$$

Accepted Answer

The population is likely large because marked turtles made up a small fraction of the second sample.

Question 8

A marine biologist tracks 1,000 sea turtle hatchlings and finds that only 100 survive the first month, but most survivors live for many years afterward. Which survivorship curve best represents this pattern?

Accepted Answer

Type III survivorship curve

Question 9

A population of 1,000 rabbits increases by 45 individuals in one year after accounting for births, deaths, immigration, and emigration. What is the per capita change in population size for that year?

Accepted Answer

$$0.045$$ individuals per individual per year

Question 10

A few rabbits colonize an island with abundant food and few predators. Their population grows rapidly at first, but years later food becomes limited and growth slows as the population approaches $$K. $$Which interpretation best describes the population’s growth pattern?

Accepted Answer

The population begins with exponential growth, then shifts toward logistic growth as density increases.

Question 11

A drought reduces the amount of food available to a deer population, and as the population becomes more crowded, individuals compete more intensely for the remaining food. Which explanation best classifies these population limits?

Accepted Answer

The drought is density-independent, while competition within the deer population is density-dependent.

Question 12

A wildlife manager compares three populations using the logistic growth model $$R = rN\left(\frac{K-N}{K}\right). $$Which population would be expected to have the lowest growth rate?

Accepted Answer

A population where $$N = K$$ and births balance deaths.

Question 13

In a classic Paramecium experiment, two species each show logistic growth when grown separately. When grown together in the same flask with the same food source, one species survives and the other disappears. Which explanation best fits these results?

Accepted Answer

The two species have overlapping niches, causing competitive exclusion of one species.

Question 14

Two lizard species can both survive across the same range of temperatures and perch heights when tested separately. In the wild, one species mainly uses lower branches because the other dominates the upper branches. Which conclusion best explains this pattern?

Accepted Answer

Competition reduces the weaker competitor’s realized niche to part of its fundamental niche.

Question 15

A population of garter snakes becomes better at detecting toxic newts. Over several generations, newts with higher toxin levels survive more often, and later snakes with greater toxin resistance become more common. Which explanation best describes this pattern?

Accepted Answer

Snakes and newts show reciprocal adaptation driven by repeated exploitation.

Question 16

A student samples 100 insects from a prairie and finds 50 beetles, 30 ants, and 20 grasshoppers. How should these observations be used to calculate Shannon diversity?

Accepted Answer

Use the relative abundance of each species: 0.50, 0.30, and 0.20

Question 17

A rocky intertidal community contains a small number of sea stars that prey on mussels. When sea stars are removed, mussels spread across the rocks and many other species decline. Which conclusion is best supported?

Accepted Answer

Sea stars are a keystone species because they have a large effect on diversity despite low abundance.

Question 18

Refer to the life table provided. What is the value of $$a ($$the missing $$l_x m_x$$ value for age 2)?

Accepted Answer

$$0.5$$

Question 19

Based on the marine food chain diagram, what would likely happen to the otter population if kelp were eradicated by a new pathogen?

Accepted Answer

Otter population would decrease due to loss of kelp and subsequent decline in sea urchins.

Question 20

In the terrestrial food chain diagram, which process between trophic levels reduces the amount of energy transferred from rabbits to foxes?

Accepted Answer

Cellular respiration and heat loss

Population Ecology, Life Tables, and Food Webs: Step-by-Step Study Guidance

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