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Study of the life history and ecology of insectivorous bats in the United States was accelerated by the discovery m 1953 (Courter, 1954) that these ubiquitous mammals are hosts to rabies virus. There was strong suspicion that insectivorous bats of the southwestern United States might be in contact with the rabies-transmitting vampire bats of Mexico (Courter, op. cit.). Consequently four projects concerned with bat rabies and ecology were set up in this area under financial support from the U. S. Public Health Service. Early work on these projects verified three significant features of the bat problem in the Southwest: (1) rabies is common in bats of this area (Eads, 1955); (2) the most abundant kind of bat in the Southwest is Tadarida brasiliensis mexicana (Sanssure), the Mexican Free-tailed, or Mexican Guano Bat 2 (Eads, 1957; Villa, 1956) ; and (3) bats of this kind move from Mexico into the Southwestern United States each spring and back into Mexico each fall (Glass, 1958; Villa, op. cit.).

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This chapter describes the history of case study teaching, types of cases, and experimental data supporting their effectiveness. It also describes a model for comparing the efficacy of the various case study methods.

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Wood frogs breed in a variety of ponds and lakes in central Alaska. Dates of first appearance of frogs ranged from 24 April to 22 May. Egg laying began 4—6 days later. Egg laying was completed in a pond 4—8 days after the first egg mass appeared. Wood frogs tend to lay their egg masses at the same spot. The average number of eggs per mass was 778 with an egg diameter of 1.6 mm. Development of eggs was directly related to water temperature and occured at the same rate as that shown for wood frogs from New York. Temperature limits that permit at least 50% survival of eggs through hatching were 6°—24°C. Temperature tolerance of eggs and tadpoles varied with age and acclimatization. Temperature preference of tadpoles followed a normal curve and ranged from 9° to 29°C. Development in the field varied among different ponds and different years. Rapid growth occured once the larvae were free swimming. Average maximum weight ranged from 2.15 to 2.85 g; maximum length varied from 5.5 to 6.0 cm. Time to metamorephosis ranged from 53 to 78 days. Two periods of development are distinguished: In period I, fertilization to free—living stage, growth rate is determined by water temperature. This period occupies one—third of the development time but has a higher mortality rate than period II. The later period includes the free—swimming stage until climax metamorphosis, and development rate is determined by environmental factors such as food and population density, as well as temperature.

This study explores biology undergraduates’ misconceptions about genetic drift. We use qualitative and quantitative methods to describe students’ definitions, identify common misconceptions, and examine differences before and after instruction on genetic drift. We identify and describe five overarching categories that include 16 distinct misconceptions about genetic drift. The accuracy of students’ conceptions ranges considerably, from responses indicating only superficial, if any, knowledge of any aspect of evolution to responses indicating knowledge of genetic drift but confusion about the nuances of genetic drift. After instruction, a significantly greater number of responses indicate some knowledge of genetic drift (p = 0.005), but 74.6% of responses still contain at least one misconception. We conclude by presenting a framework that organizes how students’ conceptions of genetic drift change with instruction. We also articulate three hypotheses regarding undergraduates’ conceptions of evolution in general and genetic drift in particular. We propose that: 1) students begin with undeveloped conceptions of evolution that do not recognize different mechanisms of change; 2) students develop more complex, but still inaccurate, conceptual frameworks that reflect experience with vocabulary but still lack deep understanding; and 3) some new misconceptions about genetic drift emerge as students comprehend more about evolution.