7.3.3 Selective Advantage

Key Steps in Selective Advantage and Evolution

1. Phenotypic Variation:

• A population contains individuals with a range of phenotypes, caused by genetic variation.

2. Environmental Change:

• A change in the environment introduces new selection pressures, such as predators, disease, or competition for resources.

3. Selective Advantage:

• Some individuals possess advantageous alleles that improve their ability to survive and reproduce under the new conditions.
• These individuals are more likely to survive, reproduce, and pass on their advantageous alleles to the next generation.

4. Reproduction:

• The offspring inherit the advantageous alleles, increasing the allele frequency of these traits within the population.

5. Evolution:

• Over generations, the population evolves as advantageous alleles become more common and less advantageous traits are selected against.

Example:

Antibiotic Resistance in Bacteria:

• Some bacteria possess a mutation that allows them to survive antibiotics.
• These bacteria have a selective advantage and reproduce, passing on the resistance allele.
• Over time, the frequency of the resistance allele increases, resulting in an evolved population resistant to the antibiotic.