Key Concepts of Evolutionary Mechanisms to Know for AP Biology

Evolutionary mechanisms shape how species adapt and change over time. Key processes like natural selection, genetic drift, and gene flow drive these changes, influencing genetic diversity and the survival of traits. Understanding these concepts is essential in biology courses.

1. Natural selection

   • The process by which individuals with advantageous traits are more likely to survive and reproduce.
   • It leads to adaptations in populations over time, enhancing fitness in a specific environment.
   • Natural selection can act on phenotypic variations, which are influenced by genetic differences.

2. Genetic drift

   • A random process that can cause allele frequencies to change in a population, especially in small populations.
   • It can lead to the loss of genetic variation and fixation of harmful alleles.
   • Genetic drift can result in significant evolutionary changes over time, independent of natural selection.

3. Gene flow

   • The transfer of genetic material between populations through migration of individuals or gametes.
   • It can introduce new alleles into a population, increasing genetic diversity.
   • Gene flow can counteract the effects of natural selection and genetic drift by homogenizing populations.

4. Mutation

   • A change in the DNA sequence that can create new alleles and contribute to genetic diversity.
   • Mutations can be beneficial, neutral, or harmful, influencing an organism's fitness.
   • They are the original source of genetic variation upon which natural selection acts.

5. Sexual selection

   • A form of natural selection where individuals with certain traits are more likely to attract mates.
   • It can lead to the development of secondary sexual characteristics, such as elaborate plumage or courtship behaviors.
   • Sexual selection can result in sexual dimorphism, where males and females of a species exhibit different traits.

6. Genetic hitchhiking

   • The phenomenon where an allele increases in frequency because it is linked to a beneficial allele undergoing positive selection.
   • It can lead to the spread of neutral or even deleterious alleles along with advantageous ones.
   • Genetic hitchhiking illustrates how selection can affect the entire genetic landscape of a population.

7. Meiotic drive

   • A form of biased inheritance where certain alleles are transmitted to offspring more frequently than expected.
   • It can disrupt Mendelian inheritance patterns and lead to rapid changes in allele frequencies.
   • Meiotic drive can have significant evolutionary implications, particularly in sexual reproduction.

8. Horizontal gene transfer

   • The transfer of genetic material between organisms in a manner other than traditional reproduction, common in prokaryotes.
   • It can facilitate rapid adaptation and evolution, especially in response to environmental changes.
   • Horizontal gene transfer plays a crucial role in the spread of antibiotic resistance among bacteria.

9. Genetic bottleneck

   • An event that drastically reduces the size of a population, leading to a loss of genetic diversity.
   • It can result from environmental events, such as natural disasters, or human activities.
   • Populations that experience a bottleneck may have reduced adaptive potential due to decreased genetic variation.

10. Founder effect

    • Occurs when a small group of individuals establishes a new population, leading to reduced genetic diversity.
    • The new population may have different allele frequencies compared to the original population, influencing its evolution.
    • The founder effect can result in unique traits or increased prevalence of certain genetic disorders in isolated populations.