Limits on Evolution: video worksheets, differentiated.

Have you ever been asked why evolution hasn’t let people fly? This engaging PBS film clearly explains the limits and constraints on evolution. Several classic “forbidden phenotypes” are described: animals with wheels, super-sized organisms, flying humans. An engaging analogy with chariots in the ancient world. The fitness landscape and local optima. The human eye inferior to the octopus eye; Hox gene mutations. No evolution without pressure – analogy with the Trabant. Physical constraints: gravity and the square-cube law. Atmospheric oxygen and Meganeuropsis. Some apparent forbidden phenotypes do arise: herbivorous spiders today (Bagheera kiplingi); all terrestrial life would have seemed impossible from the point of view of the Cambrian era.

Fnd the film by searching YouTube’s Be Smart channel for “What is Impossible in Evolution?"

16 questions for the 20-min film. Differentiated! Both versions look very similar, but “B” version has subtle clues. Excellent subtitles: scripted, not auto-generated. Answer sheet. Very easy to mark. .doc & .pdf for all files. Link to film on all sheets.