GED Science Practice Test: Darwin’s Theory of Natural Selection

Natural selection is the process, or mechanism that causes evolution to occur over time. Darwin developed his theory of natural selection through his observations and analysis of three facts about populations of a given species:

  1. more offspring are produced than can possibly survive,
  2. traits vary among individuals in a population, leading to different rates of survival and reproduction, and
  3. differences in traits are often heritable, meaning that they can be passed down from parents to offspring.

Thus, when members of a population die, they are replaced by the offspring of parents who have traits that help them be better adapted to survive and reproduce in the environment in which natural selection takes place. This process creates and preserves traits that are seemingly fitted for the functional roles they perform.

The phrase “survival of the fittest” is often used to describe the process of evolution by natural selection.  In some ways, this phrase contributes to understanding:  those organisms most fit to survive a situation will live and reproduce.  Concurrently, those organisms least fit to survive a situation will not live to reproduce.  However, this phrase is also misleading in that it leads you to believe that organisms get perfected over time until only the fittest are left.  Natural selection simply talks about organisms that are most fit to reproduce surviving to the next generation.  It does not say that those organisms are most fit in a health, behavioral, or social sense.  Furthermore, populations can chance randomly through processes you will learn about later in this lesson.


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