Natural and Artificial Selection
Populations change over time as some traits become more common and others fade. Sometimes nature does the choosing, and sometimes humans do. Comparing natural selection with artificial selection is a clean way to understand how living things change, and it is a reliable source of test questions.
This lesson explains both processes and what they share.
Natural selection is the process where organisms with traits better suited to their environment survive and reproduce more, so those traits become more common over generations. Artificial selection is when humans choose which organisms reproduce to promote desired traits. Both change a population over time by selecting which individuals pass on their genes.
How does natural selection work?
Natural selection rests on a few simple facts. Individuals in a population vary. More offspring are produced than can survive, so there is competition. Individuals with traits that fit the environment are more likely to survive and reproduce, passing those traits on. Over many generations, helpful traits spread and the population adapts. The classic example is the peppered moth: darker moths survived better on soot-darkened trees, so dark coloring became common.
How is artificial selection different?
Artificial selection follows the same logic, but a human, not the environment, decides who reproduces. Farmers breed cows that give more milk, and dog breeders pair animals with desired looks or temperaments. Every breed of dog and nearly every crop you eat is the result of humans selecting traits over generations. The mechanism is the same as natural selection; only the selector changes.
| Feature | Natural selection | Artificial selection |
|---|---|---|
| Who selects | The environment | Humans |
| Basis | Survival and reproduction | Traits humans want |
| Example | Peppered moths | Dog breeds, crops |
What do they have in common?
Both processes need variation to work: there must be differences to select among. Both act over many generations, and both change which genes are common in a population. The key insight is that selection does not create new traits; it favors traits that already exist because of variation and mutation. Understanding that keeps the two ideas from blurring together.
Watch: A Short Video Lesson
PoseKnows Biology walks through this skill clearly in a few minutes. It is a helpful companion to the reading above:
A routine for selection questions
- Ask who is doing the selecting: the environment or humans.
- Environment selecting for survival means natural selection.
- Humans choosing traits means artificial selection.
- Confirm variation exists to select among.
- Remember selection favors existing traits; it does not invent them.
Practice questions
- In natural selection, what decides which organisms survive and reproduce?
- Give an example of artificial selection.
- What must a population have for selection of any kind to work?
- Why did dark peppered moths become common on sooty trees?
- Does selection create brand-new traits? Explain.
- True or false: artificial selection is guided by human choice.
Answers:
- The environment, through survival and reproduction.
- Any of: breeding dogs, breeding cows for milk, or developing crops.
- Variation among individuals.
- They were better camouflaged, so they survived and reproduced more.
- No. It favors traits that already exist from variation and mutation.
- True.
Where this fits
Selection acts on the variation from reproduction and variation and is the engine described in evolution and natural selection. The results show up as evidence for evolution. Explore all topics on the ASVAB General Science Learning Hub.
Recommended Prep Books
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