Understanding Biological Evolution

Misconceptions and Terminology

• Common misconceptions about evolution:
  • Individuals do not evolve; populations do.
  • Fitness refers to reproductive success, not physical strength.
  • Evolution does not necessarily lead to complexity.
• Terminology in biology vs. casual use:
  • Theory: In science, a well-substantiated explanation.
  • Fitness: Related to the number of offspring produced.

Definition of Biological Evolution

• Change in a population's inherited traits over generations.
• Population: A group of organisms of the same species.
• Gene pool: The variety of genes in a population.

Mechanisms of Evolution

1. Gene Flow

   • Movement of genes between populations through migration.

2. Mutations

   • Can be harmful, beneficial, or neutral.
   • Source of genetic variation.

3. Genetic Drift

   • Change in genetic makeup due to random events.
   • Example: Grasshoppers affected by a lawn mower.

4. Natural Selection

   • Traits that enhance survival and reproduction become more common.
   • Example: Green grasshoppers are better camouflaged, thus surviving and reproducing more.

Evidence of Evolution

1. Homologies

   • Molecular Homologies
     • DNA, amino acids, and protein characteristics.
     • Example: Turkeys and emus have a more recent common ancestor than turkeys and termites.
   • Anatomical Homologies
     • Homologous structures: Similar arrangement and components but not necessarily the same function.
     • Analogous structures: Same function but not common ancestry (e.g., bird and insect wings).
   • Vestigial Structures
     • Structures that have lost most or all of their function (e.g., claw on a chicken's wing).
   • Developmental Homologies
     • Similar embryonic development stages indicating shared ancestry.
     • Example: Vertebrates have pharyngeal slits and a postanal tail during development.

2. Fossil Record

   • Provides insights into how traits have changed over time.
   • Uses radiometric dating to estimate the age of fossils.

3. Biogeography

   • Studies the geographic distribution of organisms.
   • Example: Marsupials in Australia and South America share common ancestry due to continental drift.

Conclusion

• Evolution is an ongoing process.
• Observable in organisms with short generation times, like bacteria.
• Continues to provide insights into the diversity and adaptation of life on Earth.

Amoeba Sisters reminder: Stay curious!