Exam 16: Competition

Researchers studying sex ratios among field mice expect to find a 50:50 ratio of males to females. Instead they find 1120 females and 975 males at their site. Use a chi-square analysis to determine whether the field mouse population at their site significantly differs from a 50:50 sex ratio. Assume a critical chi-square value of 3.841 for α = 0.05 and 1 degree of freedom.

Imagine a population of 600 mice and 350 chipmunks. The chipmunks and mice eat some of the same food, but the food to support 1000 mice would support only 300 chipmunks. What would α and β be for this population in which mice are species 1 and chipmunks are species 2?

Researchers perform an experiment on a long-lived perennial shrub in a semiarid site where the soil is low in nitrogen. They fertilize the plants with nitrogen, but the treated plants do not increase their growth compared with control plants. What is a reasonable hypothesis for this result?

In an experiment involving seed-eating ants and rodents in Arizona deserts, the exclusion of rodents caused an increase in the number of ant colonies over the first few years. However, over many decades the number of ant colonies actually declined. Plant diversity also declined. Why did this occur?

In David Tilman's experiments with the diatoms Cyclotella and Asterionella, when the diatoms were grown at silicon/phosphorus ratios between 6 and 90, why did the two species coexist?

Closely related species

In Connell's experiment with upper and lower intertidal barnacles, the rock barnacle excluded the Poli's stellate barnacle from deeper water because

Connell's research on competition between the rock barnacle and Poli's stellate barnacle in upper and lower intertidal zones is an example of

Tansley's experiments with bedstraw (Galium) showed that closely related species reduce competition by

In Lotka-Volterra competition models, the variable K represents

Researchers studying the effects of hay-scented fern on the recruitment of red maple and sugar maple expected to find that the fern employed interference competition on the tree seedlings by casting shade. What did researchers actually discover when they employed fences to exclude rodents?

In the experiment in which goldenrod fields were either sprayed with insecticide or left as untreated controls, the treated goldenrod increased growth and shaded out all of the other species. The result was near monocultures of goldenrod in the treated fields compared with the control fields, where the density and height of goldenrod was reduced. What did researchers conclude from this result?

Interspecific competition occurs

Which of the following is NOT a renewable resource?

Which of the following is NOT a renewable resource for a species of predatory bird?

Leibig's law of the minimum

Which of the following is NOT an example of a resource?

Hemlocks cast much deeper shade than birch trees. The tree that competes more successfully for light is

In experiments with competitive barnacle species distributed along upper and lower intertidal zones, researchers found a trade-off between ability to _____ and ability to _____.

You are studying the competitive interactions between two desert plant species, the prickly pear cactus and the ocotillo. During your research, you discover that the ocotillo produces a flower that is preferentially consumed by mule deer, a major desert herbivore. When the deer population is large and has consumed most of the available ocotillo flowers, it eats the flowers of the prickly pear cactus, which reduces the prickly pear's fecundity. Further, you know that the ocotillo and prickly pear compete for water, nutrients, and light. You also discover that the prickly pear secretes a chemical into the soil that inhibits the growth and survival of the ocotillo. For each of these examples of competition between the prickly pear cactus and the ocotillo, name and describe what type of competitive interaction is taking place.