Darwin's theory of evolution suggests the reason for the differences between species is due to

• A. Mutation
• B. Genetic drift
• C. Natural selection
• D. Acquired characteristics

Answer: (C)

The main idea is that inherited variation in a population leads to differential survival and reproduction, so those traits that help organisms thrive become more common over generations. Natural selection acts on the existing variation, sorting which traits are favored by the environment and accumulating those advantageous traits in the lineage. Over long timescales this process can produce the differences we see between species as they adapt to different habitats or ways of life.

Mutation provides the raw material of variation, but it is natural selection that decides which variations increase in frequency. Genetic drift can cause changes as well, especially in small populations, but it is random and not the primary mechanism that explains widespread differences between species. Acquired characteristics aren’t inherited through genetic information, so traits learned or developed during an organism’s lifetime don’t directly produce heritable changes in a population.