Why Did Mammals Take Over? — A Cenozoic CER

Turn the story of the Age of Mammals into real reasoning with this standalone claim-evidence-reasoning worksheet for grades 5-8. No reading passages required — everything students need is built right in, so it drops into any Cenozoic Era unit.

Students answer one focus question: What allowed mammals to become the dominant land animals of the Cenozoic Era? They build a Claim, choose supporting Evidence from a six-clue Evidence Bank, and explain their Reasoning. The bank includes two plate-tectonics distractors, so students must judge which clues are actually relevant — the analysis skill that recall worksheets never ask for.

Bolded sentence starters scaffold the writing, and generous lines give room for full responses. A complete answer key identifies the correct clues, flags the distractors, and models sample Claim, Evidence, and Reasoning statements. The clean, ink-light design keeps the key easy to print.

Covers the mass extinction, adaptive radiation, and the climate shift that opened new habitats. Aligned to NGSS MS-LS4-1, CCSS RH.6-8.1, and C3 D2.His.16.6-8. Just print and teach.