Purdue University

STAT 503

STAT 503 – Statistical Methods for Biology Homework 3 24 Points (26 available). Due at 11:59 PM on Monday, Sept 28, 2020 Please use complete sentences unless the question is marked with an asterisk (*). 1. 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) as a result of changing ecological conditions. Squirrels eat acorns (the seeds of oak trees), but they do not eat all of the acorns as soon as they are collected. Instead, they bury most of the acorns in the ground and store them for later. The majority 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 the acorn and eats it), then the buried acorn will be protected from cold, desiccation (water-loss), and fire. As a result, it will have a much better chance of surviving and establishing a new seedling than it would have if it had never been collected in the first place. If squirrels bury and then abandon enough acorns, then oak trees tree will produce more seedlings in systems that have squirrels than in systems without squirrels. This would mean that the squirrels act as mutualists. On the other hand, if fewer acorns are buried and then abandoned, the production of seedlings will be higher in the absence of squirrels. In that case, the squirrels function as seed predators instead of mutualists. Suppose that squirrels collect 80% of the acorns produced by a particular population of oak trees. They bury 70% of the acorns that they collect, and the remaining acorns that were collected are eaten immediately. In addition, only 1% of the collected-and-buried acorns are abandoned. The squirrels eventually d