Biology STAAR (State of Texas Assessments of Academic Readiness) Practice Test

Which of the following best defines natural selection?

1. A process where organisms with unfavorable traits are more likely to survive

2. A scientific theory that explains how organisms evolve over time

3. A method of gene splicing

4. A classification system for organisms

The correct answer is: A scientific theory that explains how organisms evolve over time

Natural selection is best defined as a scientific theory that explains how organisms evolve over time. This concept highlights the process through which certain traits become more common within a population due to the reproductive advantages they confer on individuals possessing those traits. Over generations, these advantageous traits can lead to adaptations that enhance the survival and reproduction of species in their environments. While the concept involves individuals with unfavorable traits being less likely to survive, that aspect alone does not encompass the full definition of natural selection. It is essential to view it within the broader framework of evolution, which illustrates how species adapt and change over time through processes like variation, competition, and environmental pressures. The idea of natural selection also contrasts sharply with methods like gene splicing, which is a direct manipulation of genetic material, and classification systems, which categorize organisms based on shared characteristics rather than explaining evolutionary mechanisms.