Natural selection

你需要知道的

• Individuals in a species vary, and they pass their DNA to their offspring.
• In a habitat where dark frogs are harder to see, those frogs survive and leave more offspring.
• Over many generations the helpful trait becomes more common in the population.
• A difference only spreads if it changes survival or the number of offspring.

这个短片讲了

从 youtube-nocookie.com 播放。按下播放之前，YouTube 不会写入任何 cookie。