Natural selection and genetic modification Study Guide

Charles Darwin's theory of evolution by natural selection proposes a fundamental mechanism for biological change over time. It posits that within any population, there is natural variation among individuals. Organisms produce more offspring than can survive to maturity, leading to a struggle for existence. Individuals with characteristics better suited to their environment are more likely to survive and reproduce, passing on these advantageous traits to their offspring. Over many generations, this differential survival and reproduction lead to a gradual accumulation of beneficial traits in the population, resulting in evolutionary change and the adaptation of species to their environments.

The emergence of antibiotic resistance in bacteria provides a clear, real-world example supporting Charles Darwin's theory of evolution by natural selection. Within a population of bacteria, natural genetic variations exist. Some bacteria may possess random mutations that confer resistance to certain antibiotics. When an antibiotic is used, it acts as a selective pressure, killing off the bacteria that are susceptible. The resistant bacteria, however, survive and reproduce, passing on their resistance genes to their offspring. Over successive generations, the proportion of resistant bacteria in the population increases. This change in the genetic makeup of the bacterial population over time, driven by environmental pressures (antibiotics), aligns perfectly with Darwin's principle of natural selection, demonstrating how species can evolve to better suit their environment, even if that environment includes antimicrobial agents.