Boxi Learn › Biology › Stage 4 · Systems and Argument
Who leaves more offspring?
BIO-5 Evolution by variation and selectionX-1 Guess, then checkX-3 Look from another side
What many people think
Animals change because they need to: giraffes stretched their necks.
The idea
No individual changes; the mix of a population shifts because some variants leave more offspring than others.
Explain it
A friend says giraffes got long necks by stretching to reach leaves, and passed the stretch on. Use the tagged moth to explain what is wrong with that, and what happens instead.
Try at home
Punch 20 dots from white paper and 20 from newspaper and scatter them on a sheet of newspaper. A "bird" picks up as many as possible in 10 s; each dot left gets one copy of its own kind added. Repeat three rounds: which kind takes over?