Natural Selection for Kids: Why Some Traits Win Out Over Time (Grade 7 and Grade 8 Science)

Hi, I'm Luna from DoodleBeez. Why do polar bears have white fur, and why do cactuses store water? Today we are learning about natural selection, the process that helps explain how living things become suited to where they live.

Step one is variation. Members of a species are not all the same. Some are darker or lighter, faster or slower. Many of these differences come from their genes, so they can be passed from parents to offspring.

Step two is competition. Living things usually have more offspring than can survive. There is not enough food, water or space for all of them. Predators and disease also take their toll.

Step three is selection. Individuals with traits that help them in their environment are more likely to survive and reproduce. They pass those helpful traits on, so more of the next generation has them.

Here is a real example. In England, peppered moths were mostly pale, matching pale tree bark. Factory soot then darkened the trees. Birds spotted pale moths more easily, so over many generations, dark moths became common.

Watch out for a common mistake. A single moth cannot change its color because it wants to. Individuals do not evolve. Populations change over many generations, as helpful traits are passed on more often.

Now it's your turn. On a snowy island, some hares have white fur and some have brown fur. Foxes hunt them. After many generations, which fur color will be more common? Pause and try. White fur, because it hides hares in snow!

Great job! Remember, natural selection needs variation, inherited traits and competition. Individuals with helpful traits survive and reproduce more, so those traits spread through the population. Practice natural selection in the Science Lab at doodlebeez.com. See you next time!