Evolution has resulted in changes in the sizes and forms of organisms. Everything about the biology of an animal, including its physiology, anatomy, and ecology, is influenced by its body size. Frequently there seem to be limits on the sizes that different organisms can attain, even when larger size might be thought to be evolutionarily advantageous. Often an increase or decrease in size is correlated with a change in proportions. Understanding the significance of a particular morphology or interpreting the factors that underlie a particular evolutionary trend involve studying the relationships that exist among size, shape, and function. This lab introduces allometry, the study of size and its consequences, using celery and woodlice as subjects.
This is a laboratory exercise appropriate for sophomore level students. No prior math is required, and lab exercise can be adapted if computer facilities are available.
In this computer-assisted exercise first-year students explore the fundamental concept of allometry: the study of size and its consequences. Students examine the relationship between size and shape and learn how to quantify changes in proportions. They investigate how North American mammals of various sizes change proportions to compensate for changes of surface area and volume. Interactive computer programs aid each student in calculating standard dimensions from an Audubon illustration, process class data, identify lines of best-fit (using linear regression), and statistically test whether relationships between selected morphological variables exhibit isometric or allometric change.
The transport and transformation of substances in the environment are known collectively as biogeochemical cycles. These global cycles involve the circulation of elements and nutrients that sustain both the biological and physical aspects of the environment.
Both metabolic rates and brain masses are approximately 10 times as great in modern terrestrial warm-blooded animals (birds and mammals) as in cold-blooded terrestrial animals (reptiles) of the same body mass. This is one of several lines of evidence scientists have used to infer the mode of thermal regulation of dinosaurs and other extinct amniotes. In this exercise each student is assigned one of a number of dinosaurs. Students estimate brain mass from a drawing of a cranial endocast and body mass from a plastic model. They determine relative brain size and compare this to relative brain sizes of modern vertebrates. Students combine this application of allometry with information about Mesozoic environments and thermal physiology to infer the mode of thermal regulation of their assigned species.
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