answer

pelvic spines a threespine stickleback with long pelvic spines Threespine sticklebacks are small fish found in oceans or lakes. They may have sharp spikes called pelvic spines on their bellies. Same sticklebacks have long spines that stick out from their bodies. Others have short spines that are hardly visible. Long spines can protect sticklebacks from larger fish. Larger fish cannot swallow sticklebacks with long spines as easily as they can swallow sticklebacks with short spines. However, some insects catch sticklebacks by grabbing their spines. These insects can catch sticklebacks with long spines more easily than they can catch sticklebacks with short spines. The graphs below describe pelvic spine length in an isolated population of threespine sticklebacks at the start and end of a time period long enough for natural selection to occur. At the start of this time period, the threespine sticklebacks' environment changed. Population at start Population at end |. Fish with long pelvic spines mf Fish with short pelvic spines: Describe how the threespine stickleback population changed over this time period. Use the theory of natural selection to construct a possible explanation for this change. The percentage of sticklebacks with long pelvic spines * in the population. This suggests that sticklebacks with short spines were * likely to survive and reproduce than sticklebacks with long spines. This may have occurred because there were significantly * large fish after the population's environment changed. So sticklebacks with long spines were * likely to be caught by predators than sticklebacks with short spines