Body Clues to Shared Ancestors
Aligned to MS-LS4-2 — Next Generation Science Standards.
What this lesson teaches
Comparing the anatomy of living and fossil organisms reveals similarities and differences that suggest how closely species are related. Similar body structures, even when used differently, are evidence of a shared ancestor.
Worked example
A human arm, a whale flipper, and a bat wing all contain the same set of bones arranged the same way, even though they do different jobs — a similarity best explained by a common ancestor whose descendants adapted.
Practice questions
- Compare your hand to a picture of a cat's paw and list bones that match.
- Sketch three animal limbs and label the matching bones to build an evidence chart.
- Construct an explanation for how matching bone patterns in different animals point to a shared ancestor.
Watch the lesson
Every lesson comes with a video taught in English and Spanish — the same video the QR code in the printed workbook opens.
▶ Watch this lessonEn español
Pistas del cuerpo sobre ancestros comunes
Comparar la anatomía de organismos vivos y fósiles revela semejanzas y diferencias que sugieren qué tan emparentadas están las especies. Las estructuras corporales parecidas, aunque se usen de forma distinta, son evidencia de un ancestro común.
Ejemplo: Un brazo humano, una aleta de ballena y un ala de murciélago contienen todos el mismo conjunto de huesos dispuestos de la misma manera, aunque cumplen funciones distintas — una semejanza que se explica mejor por un ancestro común cuyos descendientes se adaptaron.
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