Nature of Science: Scientific Knowledge is Based on Empirical Evidence

Science knowledge is based upon logical and conceptual connections between evidence and explanations. 

Associated Shape of Life Content

The Eastern Oyster: A Not-So-Typical Mollusc

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.

Squid: Instructor Guide

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.

Molluscs: Gastropod - Instructor Guide

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.