ACT Preparation / Unit 22 ACT 2107 short lesson, about 20 seconds
Natural Selection
Captions available
The idea
Natural selection changes a population over time: individuals whose inherited traits help them survive or have more offspring pass those alleles on, so the alleles become more common.
In practice
If darker beetles escape birds more often on dark bark, the dark allele becomes more common there.
Where people slip
Selection acts only on heritable traits; a trait an individual acquires during life is not passed on.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
Builds on
Unlocks
- Nothing yet depends on this.
Something wrong in this lesson? Flag it · Sources for ACT Preparation