Chapter 13: Evolution - Summary of Campbell Biology Concepts and Connections

Introduction to Fossils

• Fossils: Imprints or remains of organisms that lived in the past.
  • Examples include footprints, burrows, and fossilized feces.
  • These provide evidence of ancient organisms' behavior.
• Strata: Layers of rock formed by sediment covering old layers and compressing them.
  • Fossils in a stratum suggest which organisms existed at the time of its formation.
  • Younger strata are on top of older ones, allowing determination of fossils' relative ages.

Homology and Evolution

• Homology: Similarity from common ancestry.
  • Homologous Structures: Structurally similar features with different functions due to common ancestry.
  • Sequence distance between species indicates the distance of their last common ancestor.
• Vestigial Structures: Remnants of features that served important functions in ancestors.
• Pseudogenes: Genes that have lost function and are inactive.
• Evolutionary Trees: Show patterns of descent.

Artificial Selection

• Composed of Variation and Heritability.
  • Variation allows selection of organisms with desirable traits for breeding.
  • Heritability is the transmission of traits from parent to offspring.
• Evolution occurs at the population level, not individual.

Genetic Variation

• Mutation: Changes in DNA sequence that introduce new alleles.
  • Only mutations in gamete-producing cells affect genetic variability.
• Population: Individuals of the same species in the same area, capable of interbreeding.
• Gene Pool: All alleles at every locus in a population.
• Microevolution: Small changes in a gene pool.

Hardy-Weinberg Equilibrium

• Formula: p + q = 1
  • p and q represent allele frequencies.
  • p² + 2pq + q² = 1 (similar to a Punnett square).

Causes of Evolutionary Change

• Natural Selection
• Genetic Drift: Random events causing allele frequencies to fluctuate.
  • Affects small populations more.
• Bottleneck Effect: Population size reduction leads to certain alleles becoming prevalent.
• Founder Effect: Small new population may not represent the larger original gene pool.
• Gene Flow: Transfer of alleles due to movement of fertile individuals or gametes.

Types of Natural Selection

• Relative Fitness: An individual's contribution to the gene pool relative to others.
• Directional Selection: Shifts population makeup by acting against one phenotypic extreme.
• Stabilizing Selection: Favors intermediate phenotypes; maintains status quo.
• Disruptive Selection: Favors extreme phenotypes, leading to multiple contrasting phenotypes.
• Balancing Selection: Maintains stable frequencies of multiple phenotypic forms.
  • Heterozygote Advantage: Heterozygous individuals have greater reproductive success.

Conclusion

• More offspring produced than can survive and reproduce.

These notes summarize the key points from the chapter on evolution, covering fossils, genetic variation, and the mechanisms of evolutionary change, as explored in "Campbell Biology Concepts and Connections".