This exercise introduces students to the measurement of biological diversity, the relationship between sampling effort and species diversity (optional), also known as the "species-area curve relationship", and (most importantly!) the relationship between habitat patch size and species diversity. These relationships provide a model from which we will draw conclusions about the design of nature preserves (habitat patches, if you will).
A practical question confronting conservation biologists, politicians, and the voting public is the design and management of nature preserves - national parks, wilderness areas, wildlife refuges - any chunk of habitat that has been set aside with at least one of the intentions being the preservation of biological diversity. Biological diversity, or "biodiversity" can be measured at various levels of biological organization, the two most common being: a) species diversity, that is the number of different kinds of species and their relative abundances, and b) genetic diversity (the genetic variety present within a given species, as well as among different kinds of species). Both kinds of variety are critical for the maintenance of a healthy, viable population of organisms and for the long-term health of an entire ecosystem (why?).
How big should a nature preserve be? Most of us would reply intuitively that "bigger is better" - but can we provide sound ecological reasons why bigger is better? Challenge your students to think of some of these reasons. All else being equal, a big preserve can hold more individuals than a small one, on average. Much less obvious is the prediction that a large preserve will also contain a greater variety of organisms, on average, than a small one. Why might this be so?