You reviewed the Scientific Method in this chapter and learned that the central unifying principal of biology is the theory of Evolution. In this lesson you will read a research report by Astrid Kodric-Brown and Paul Nicoletto that describes their experiments on the courtship and reproductive behavior of the guppy fish, Poecilia reticulata, published in the journal Animal Behaviour. This research is a nice example of how the Scientific Method can be used to study the mechanisms of evolution. Click here to get and print out the article. Return to this lesson page and use it as a study guide as you read the article.

Background Information.

Males of many species of animals attempt to attract female mates with elaborate displays that can include extravagant colors or ornamentation, songs, and courtship dances. The females select the male they will mate with, presumably by evaluating the quality of the male's courtship display which in turn is a reflection of the male's genetic quality or "fitness." Charles Darwin called this process "Sexual Selection" and considered it a special form of natural selection. Male guppies have distinctive colors and enlarged fins. They engage in a courtship display that attracts females. Think of other animals that you are familiar with that may use sexual selection to determine mate selection (including humans?).

These displays vary among males and even within the same male as seasons change or with age (temporal variation). A general question then is how effectively do females respond to males as their characteristics change. As you read the abstract and introduction, be sure that you are clear on the questions that the authors are going to address in this report. Don't continue reading the rest of the report until you feel confident that you know the questions being asked.

Methods.

Read the general methods section with an eye on the controls the authors built into their procedures in an effort to produce reliable result from their experiments. Understand they are presenting females with a choice of two males to respond to. Carefully read the methods of the three specific experimental designs. They are designed to control how much communication can occur between the male and female and how consistent the male's display is from one trial to the next. Don't get to hung up over the details of the statistical analysis. Do understand that these statistical techniques are used to determine if the differences in the female's response to the males is greater than would be expected if her response was random.

Results.

The authors report their results by the various questions of intrest. Pay careful attention to the differences in the female's response when she is separated by clear glass compared to the one-way glass or the video tape situations. Keep in mind what the three conditions do the ability of the male and female to communicate with each other and the degree of consistency in the male display viewed by the female. Pay particular attention to Figures 1 and 2.

Discussion.

In this section the authors use their results to evaluate their hypotheses. Read their conclusions carefully. You will be asked to evaluate them in your assignment.

Questions: Answer these questions and send them to me as an email attachment in MS Word or RTF format.

1. What is an experimental control and why are they important? Explain how using virgin females and males that were matched for body size are necessary controls in this experiment.
2. How did the three experimental conditions (clear glass, one-way glass, and video) affect the ability of the males and females to communicate and the consistency of the male display viewed by the female?
3. Suggest a reason why the females spent more time with the bright colored males in the clear glass and the video conditions compared to the one-way glass.
4. The authors conclude that their study "demonstrates the utility of the video playback technique." Do you agree? Explain with specific examples.

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