Experiment 1: Analyze Stickleback Fish from Lakes
Objective:
In this experiment, you will analyze the pelvic structures of stickleback fish collected from two lakes around Cook Inlet, Alaska, to determine whether there
are significant differences between the two populations. You will then use your data and information about the lakes to draw conclusions about the possible
environmental factors affecting the evolution of pelvis morphology.
 View a map of these lakes. |
 Watch a video about how |
Individuals that are better adapted to a particular environment live longer and reproduce more. As a result, their genetic variants are passed from one generation to the next and the associated traits increase in frequency in the population. In the ocean, a threespine stickleback with a complete pelvis is less likely to be eaten by larger fish that prey on it. Thus, the presence of predatory fish in the ocean environment is most likely selecting for the complete pelvis trait in sticklebacks. Almost all marine and sea-run threespine stickleback have a full pelvic girdle and pelvic spines.
The freshwater threespine stickleback populations in lakes in Alaska have evolved recently from sea-run stickleback populations. These freshwater lakes provide a wide range of habitats for the fish, which are different from their ancestral ocean environment.
Watch a video of the
scenery around Cook Inlet.
What features in these environments might be selecting for a complete or reduced pelvis?