Final answer:
The theory of evolution by natural selection explains how species change over time and refers to Charles Darwin and Alfred Russel Wallace proposing this theory.
Step-by-step explanation:
The theory of evolution by natural selection explains how species change over time. Charles Darwin and Alfred Russel Wallace proposed this theory, which states that individuals with traits that make them more fit for their environment are more likely to survive and pass on their genes to the next generation. Over time, this can lead to major changes in the characteristics of living things. The theory of evolution by natural selection is a fundamental concept in biology that explains both the unity and diversity of life on Earth.