The theme of OBIS revolves around ecosystems. Natural selection, food chains, species dominance and density, interactions of organisms with their environment and population structure are some of the biological topics that are woven into activities. The activities are conducted in the outdoor settings where interactions occur, and employ a variety of strategies, such as games, simulations, craft activities, role playing, experiments and data analysis. The program consists of 97 separate activities, which are grouped into 27 modules. A complete set of all 97 activities, called the Library Set, is also available.
Most activities take a little less than an hour and can be used separately or in a sequence.
Group size is flexible.