In Mr. Harkin’s fifth grade class, the students have been given the weighty charge of keeping a (simulated) endangered species alive. The endangered animals are living in a specially designed environment, sharing the space with other flora and fauna that collectively comprise a carefully balanced ecosystem. The environment consists of several discrete but connected habitats occupying the four walls of the classroom, among which the creatures may migrate freely, with each habitat managed by a student work team. The individual habitats have distinctive environmental characteristics, resulting in a spatially heterogeneous distribution of species that depends on their morphologies, availability of food sources, and presence of predators. Controls for ambient temperature and lighting allow students to manage the environmental characteristics of the habitats.

Over the course of several weeks, the endangered species faces two serious threats. First, the lighting unit in one of the habitats fails, causing a rapid migration of some of the creatures into the remaining habitats. Later, an invasive species enters the environment through a breach in one of the habitats, disrupting the ecosystem’s food web. In each case, the students are challenged to manipulate the environmental controls to try to stabilize the population of the endangered species.

Critical to the success of the students’ work is the periodic monitoring of the populations of the various species inhabiting the environment; without a method for characterizing the relative population sizes over time, students have no way of knowing which species are thriving and which are dwindling. However, the populations are fairly large (numbering in the hundreds of creatures), and to make matters worse, students have access to the habitats only through small visual portals on each wall that allow them to see only a fraction of the animals and vegetation within each habitat.

Understanding the state of the overall environment (and the endangered species) requires them to build on each other’s work as a whole class. Consequently, the students’ work, in science, becomes a matter of "counting" the creatures that they see in their portals, recording these data in personal “field guides,” and using those counts to estimate species’ populations in the local habitats and across the environment. Through whole-class discussions guided by the teacher, students develop "standard" methods for counting and using sample counts to estimate population sizes. Students graph the population sizes over time on large paper posters on the wall, allowing them to recognize fluctuations, plan interventions, and to observe the impact of their manipulations.