Exam 3: Natural Selection

Based on the figure, use phylogenetic reasoning to explain whether feathers evolved for flight, and why. What other possible advantages could feathers provide? Is there a way to determine the original selective function? Explain your answer.

Imagine you are an evolutionary biologist studying reproductive trade-offs in populations of guppies that have been separated by the formation of barrier waterfalls. The upstream population faces lower predation than the downstream population, and the predators on the downstream side are larger and can eat any guppy offspring, no matter the size. Make a prediction about the reproductive strategies you might find and explain the trade-offs faced by the reproducing female guppies on each side of the barrier.

Give an example of a trait that provides a good fit to the environment but is not an adaptation. Explain why it is not an adaptation.

Organisms may not be perfectly adapted to their environments for all of the following reasons EXCEPT

The figure shows a hypothetical relationship between the growth rates of E. coli at 37 and 42 degrees Celsius. This figure illustrates what type of evolutionary constraint?

An exaptation is a trait

How can gene duplication provide an evolutionary pathway by which a protein can switch functions without loss of the original function?

The eyes of an owl are positioned in front of the head; the eyes of an ostrich are set on opposite sides of the head. What are the trade-offs in physical constraint that each of these animals face?

Fitness differences among laboratory populations of E. coli are commonly assessed using the Ara^ marker system, which allows strains to be distinguished based on color. Explain the methods and analyses you would use to determine the fitness of two E. coli strains that are labeled Ara^ and Ara^.

Spines, flowers, and a waxy stem coating are all adaptations of cacti because

Describe the three conditions that must be met in order for natural selection to occur.

What is the term for a simultaneous action of natural selection on each side of the host-pathogen interaction?

The figure illustrates a likely scenario for the molecular mechanism of treehopper helmet evolution. This process demonstrates which explanation for the evolution of complex traits?

Considering the phylogenetic evidence of feather evolution, all of the following might have been original functions of feathers EXCEPT

One constraint on what natural selection can achieve comes from the fact that it lacks foresight. This means that

The figure indicates a ________ between the number and size of offspring that a female guppy can produce.

One way that novelty can arise at the molecular level is through the process of gene sharing, where a protein that serves one function is recruited to serve a different function. In what way is gene sharing like an exaptation?

Variation is generated in a population primarily by

The formal definition of "fitness" in evolutionary biology

The figure shows the wing length of cliff swallows that died as road kill and of the population at large. What do these data indicate about natural selection acting on wing length in cliff swallows?