Question

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which statement best describes evolution by natural selection?
evolution happens within an organism’s lifetime
populations change over time as advantageous traits become common
individuals evolve new traits to survive
organisms change traits by choice

Explanation:

To determine the best description of evolution by natural selection, we analyze each option:

• "Evolution happens within an organism’s lifetime": Evolution is a change in populations over generations, not within a single organism's lifetime. Eliminate this.
• "Populations change over time as advantageous traits become common": Natural selection acts on populations. Organisms with advantageous traits (adaptations) are more likely to survive and reproduce, passing those traits on. Over time, these traits become more common in the population, leading to evolution. This matches the concept.
• "Individuals evolve new traits to survive": Individuals do not evolve new traits during their lifetime in the context of natural selection. Traits are inherited or result from genetic variation, and evolution occurs at the population level over time. Eliminate this.
• "Organisms change traits by choice": Traits are not changed by an organism's choice. Traits are determined by genetics and environmental factors, with natural selection favoring traits that enhance survival and reproduction. Eliminate this.

Answer:

B. Populations change over time as advantageous traits become common