One classic example of microevolution is the development of antibiotic resistance in bacteria.
Here's how it works:
1. Variation: Within a population of bacteria, there is natural variation. Some bacteria may possess genes that make them slightly resistant to antibiotics. This variation arises through random mutations.
2. Selection: When antibiotics are introduced, bacteria lacking resistance genes are killed, while those with resistance genes survive and reproduce. This is natural selection – the environment selects for certain traits.
3. Inheritance: The resistant bacteria pass on their resistance genes to their offspring. Over time, the population shifts to become dominated by resistant strains.
Result: The antibiotic, once effective, becomes less effective or even useless against the evolved bacterial population.
This process of microevolution can be observed in other scenarios:
* Pesticide resistance in insects: Insecticides kill susceptible insects, but those with resistance genes survive and reproduce, leading to populations dominated by resistant insects.
* Viral evolution: Viruses, such as influenza, constantly evolve, making it challenging to develop lasting immunity and vaccines.
Key points:
* Microevolution involves changes within a species, not the emergence of new ones.
* It occurs through natural selection acting on pre-existing variation.
* The process is relatively rapid and can be observed within a human lifetime.
This example demonstrates how microevolution, driven by natural selection, can have significant consequences for human health and agriculture.
