Here's why:
* Variation: Bacteria naturally exhibit variation in their genetic makeup. Some bacteria might have genes that make them slightly more resistant to antibiotics.
* Selection: When antibiotics are introduced, bacteria without resistance are killed off, leaving behind only those with the resistant genes.
* Inheritance: The resistant bacteria reproduce, passing on their genes for resistance to their offspring.
* Result: Over time, the population of bacteria becomes dominated by resistant strains, making antibiotics less effective.
This example clearly shows how natural selection favors traits that provide an advantage in a given environment (in this case, the presence of antibiotics), leading to changes in the population over time.
Other good examples include:
* The evolution of camouflage in animals: Predators with better camouflage are more likely to survive and reproduce, leading to an increase in camouflaged individuals in the population.
* The evolution of pesticide resistance in insects: Similar to antibiotic resistance, insects with genes that provide resistance to pesticides survive and reproduce, leading to a population dominated by resistant insects.
It's important to remember that natural selection is a constant process, always shaping populations and species over time.
