Unit 3 — Variation of Traits in Living Organisms

Science — Third Preparatory

2.6 Natural versus artificial selection

Point	Natural selection	Artificial selection
Who selects	The environment	Humans
Purpose	Survival and adaptation	Human needs and benefit
Rate of change	Usually slow, over long periods	Can be relatively fast
Traits selected	Those that help survival in that environment	Traits desired by humans (yield, milk, size)
Examples	Dark moths after pollution thick fur in cold regions	Selecting high-milk cows; larger fruits

Stability and change.
Organisms keep some inherited traits for long periods, while others change with the environment or because of selection.

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