1Two things to know first
Hiding in plain sight — and the color you're born with
You only need two ideas. Watch each one move:
Matching = hiding
An animal that matches what it sits on is hard to spot. One that doesn't match pops right out — and a hungry bird grabs the one it can see.
You're born your color
A moth is one color its whole life — it can't repaint itself. But its babies aren't all the same: some hatch pale, some hatch dark, like brown and black puppies in one litter.
2Meet the two moths
The pale one and the dark one
Both colors can live on the same tree. On clean, pale bark, watch who blends in and who sticks out:
Cream with speckles
On clean pale bark it almost disappears — the bird flies right past it.
Deep charcoal
On that same pale bark it's a black dot — easy for the bird to spot and grab.
3Your turn — smoke up the tree
Drag the soot and watch who hides now
Slide the smoke up and down. The bark changes — but look closely: no moth ever changes its own color. What changes is how easy each one is to spot. Watch the "easy to spot" meters move.
4Now let it run for real
Sooty bark — but what if there are no birds?
Start with six pale and six dark moths on sooty bark. Now remove the birds. Keep the bark, starting moths, and breeding rule the same. Predict what four generations will do when this one part of the system is missing. Afterward, bring the bird back for a comparison.
Guess before you run it
The bark stays dark, but there is no bird. Food and space are plentiful. After four generations, will dark moths become more common in this model?