14. Why do some guppies attract more mates than others?
In Why do we care about Fat? we spend quite a bit of time discussing sexual selection. We outline several hypotheses encoding the Handicap hypothesis and the Good Genes Hypothesis that are currently under investigation by ethologists (biologists who study animal behavior). We talked about fitness and natural selection in Marooned in the Galapagos. Sexual selection can be seen as another selection process. It leads to greater fitness, but not necessarily through greater survival for the individual, but instead it directly affects the number of offspring (fitness). This does not result in adaptations that contribute to survival, but adaptations that increase the likelihood that an individual will mate. Males and females must compete with other members of their sex (Intrasexual competition) to attract mates.
In this lab, you have a chance to investigate whatever characteristics that you might think that males or females might be using to select mates. In this lab, you have to rely on your ability to observe and record. You will need to start with a good idea what the fish are doing as they dart around the tank. To become familiar, do the activities in the pre-lab. Many of the movements of the males are courtship displays as they attempt to attract and mate with one or more females. You will need to be able to distinguish these from other activities. Is there a pattern to which females are courted? Do females mate with all males equally? What evidence can you supply?.
Many of the experiments you might think of are observational in nature. You can make comparisons by looking at the behavior of different fish in the same tank or different tanks. You might want to review Psychics and Scientists to refresh your memory on this type of experimental design. The readings in the first few chapters in Studying for Biology might also be a good source to review.
Hints and Suggestions
