Purdue University

STAT 503

STAT 503 – Statistical Methods for Biology Homework 3 30 Points (32 available). Due at 11:59 PM on Tuesday, February 18, 2020 Optional practice: Whitlock and Schluter: Chapter 5, questions 1-17 (pp. 139-143). The answers to practice questions are in the back of the book. Please use complete sentences unless the question is marked with an asterisk (*). 1. Squirrels eat acorns (the seeds of oak trees), but they do not eat all of the acorns as they collect them. Most of the acorns are buried in the ground and stored for later, and most of these buried acorns are eventually eaten. However, if a squirrel buries an acorn and then never returns to eat it (and if nothing else discovers it and eats it), the buried acorn will be protected from cold and desiccation (water-loss). As a result, it will have a much better chance of surviving and establishing a new seedling than it would have been if it had never been collected in the first place. The relationship between squirrels and oak trees is referred to as a conditional mutualism because it can shift from mutualistic (both parties benefit) to predatory (the squirrels benefit at the trees' expense) depending on ecological conditions. If squirrels bury and then abandon enough acorns, the tree will produce more seedlings with squirrels than without squirrels. On the other hand, if fewer acorns are buried and abandoned, then the production of seedlings will be higher without squirrels; in this case, the squirrels function as seed predators instead of mutualists. Suppose that squirrels collect 95% of the acorns produced by a particular population of oak trees. They immediately eat 20% of the acorns that they collect. The remaining collected acorns are buried, but only 2% of the buried acorns are abandoned. The squirrels eventually dig up and eat the rest of the buried acorns. In one year, 0.3% of acorns that are not collected by squirrels survive