Students should evaluate different local habitats in order to make comparisons. Optimal means the best, but organisms often solve multiple problems so any one problem is not solved best. An optimal function is produced for sugar ingestion rates versus sucrose concentration through butterfly proboscides and pipets by humans. A choice experiment is performed using probing by a butterfly proboscis toward one of two concentrations of sucrose. Cost variation for sugar intake rates is then measured from the function shape and related to nectar concentration variation.
Soil contains a wider variety of microorganisms than in other types of environments.
Many kinds of bacteria, algae, protozoans, yeasts, molds, and microscopic worms are present in soil. Bacteria are the dominant species found in soil and many of the biological changes that occur in soil are due to bacteria. These biological changes include fixation of nitrogen for photosynthetic plants, and the recycling of other important biological elements from the decomposition of plants and animals. This laboratory exercise involves isolating an unknown bacterium from soil, maintaining a pure culture of the microbe, determining the staining, cultural, and physiological characteristics of the organism, and narrowing the identification of the bacterium to a specific microbial group. Student research teams then design an experiment using the acquired techniques to determine the degree of dissociation of different electrolytes, or the effect of molecular weight, lipid solubility, age of cell membrane, species variability, or physiological state of the cell on diffusion rate.