Nature of Science: Scientific Knowledge Assumes an Order and Consistency in Natural Systems

Science assumes that objects and events in natural systems occur in consistent patterns that are understandable through measurement and observation.

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.

Activity: Invertebrate Critter Cards

In this activity students explore how animals are classified. For centuries taxonomists have been classifying the diversity of animal life based on observations and measurements of animals’ body plans. And now, with DNA sequencing, scientists have for the most part confirmed the work of earlier taxonomists. Students will learn the characteristics that define five of the major invertebrate phyla by watching videos, reading and sorting animal cards. The phyla are: Cnidarians, Annelids, Arthropods, Molluscs, and Echinoderms.