Which term denotes the process by which species change over time?

• A. Evolution
• B. Messenger RNA
• C. Sex chromosome
• D. Mutation

Answer: (A)

Evolution is the process by which species change over time. It describes how populations accumulate heritable differences across generations, leading to new traits, adaptations, and sometimes new species. The changes arise as allele frequencies shift due to forces like natural selection, genetic drift, gene flow, and mutation. Mutation provides new genetic variation—the raw material for evolution—while the other forces act to sort and spread those variants. Messenger RNA is involved in protein synthesis, not long-term species change; sex chromosomes are parts of the genome that influence sex determination, not the process of evolution.