Through a sequence of “explore-before-explain” laboratory investigations, coupled with segments from the Shape of Life videos, students study molluscs in the present and their long evolutionary history. The module includes those listed below, which can also stand alone.
Nature of Science: Science, Models, Laws, Mechanisms, and Theories Explain Natural Phenomena
Associated Shape of Life Content
In this hands-on activity, students study the beautiful shells not as objects of beauty but as artifacts born of an evolutionary arms race.
Lab dissection of a representative of Class Bivalvia. Supported by several Shape of Life segments, students interpret bivalve adaptations as a radical case of divergent evolution: A simple ancestral snail with a mobile lifestyle, single dome-shaped shell, bilateral symmetry, and a head (“cephalization”) transformed into a headless, double-shelled, sedentary filter-feeder whose bilateral form is obscure.
Students explore the diversity and adaptations of marine arthropods.
Lab dissection of a squid, a member of Class Cephalopoda (along with the octopus and nautilus). Supported by several Shape of Life segments, students interpret squid adaptations as a radical case of divergent evolution: A line of ancestral snails abandoned the life of sluggish grazing and foraging in favor of a new niche as speedy open water predators. Students will understand that the shelled, but squid-like nautilus, is a “transitional form” en route to the swimming, shell- less cephalopods. Finally, they use the squid to explore another macroevolutionary pattern: convergent evolution.
A brief hands-on investigation of Class Gastropoda (snails and slugs), followed by a critical thinking exercise centered on segments of the Shape of Life. Students first examine the bodies and behavior of live slugs or snails, then use water balloons to model their unique style of locomotion, and finally tackle a series of analytical questions designed to cultivate a grasp of divergent evolution: the branching of a single ancestral form into multiple new forms for diverse new functions, niches, and habitats.
In this lesson students engage in the practice of science by observing behaviors using Shape of Life videos with the audio and closed captioning turned off.