MS-LS4.A Evidence of Common Ancestry and Diversity

The fossil record documents the existence, diversity, extinction, and change of many life forms throughout the history of life on Earth.

Anatomical similarities and differences between various organisms living today and between them and organisms in the fossil record, enable the reconstruction of evolutionary history and the inference of lines of evolutionary descent.

Associated Shape of Life Content

The Secrets of Fossils

In this lesson students make connections between fossils and modern day organisms. Using the information about the Cambrian Explosion, they explore theories about how and why organisms diversified. Students hypothesize what evidence might be helpful to connect fossil organisms to modern organisms to show evolutionary connections. Students use three videos from

Who Was "Hunter Eve?"

The paleontological evidence of the first animal to hunt is tiny trails that have been fossilized in rocks. To start this lesson, students will consider the tracks and traces left by modern animals and what they can learn about an animal from its tracks. They then think about which animal might have been the first hunter. The class considers what it takes to be a hunter and what kind of evidence can we use to figure out what was the first hunter. Students write their ideas in their science notebooks and the teacher shares the ideas with the entire class.

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.

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.

Who Was Animal Eve?

In this lesson students make a guess as to what was the first animal. The class watches the Sponge video from the and writes down what evidence they saw that sponges were the first animals. Then the class discusses what evidence they need to figure out what might have been the first animal. They watch the scientist video “Mitchell Sogin, Evolutionary Biologist: Proof of the First Animal” and write down the evidence that is presented for the sponge being the first animal.