HMS Beagle Voyage and Galapagos Islands

HMS Beagle Voyage (1831-1836)

• The voyage aimed to survey the coast of South America.
• Charles Darwin participated as a naturalist on the voyage.
• During the voyage, Darwin read Charles Lyell's "Principle of Geology".
• Key observations made in the Galapagos Islands led Darwin to consider the variation of species.

Galapagos Islands (1835)

• The Galapagos Islands are volcanic islands visited by the Beagle.
• Darwin discovered that species from the Galapagos were new to the South American mainland.
• This led to his idea that organisms vary with their environment.

Darwin's Studies and Theories

• Darwin developed the concept of artificial selection from pigeon breeders.
• He wrote "On the Origin of Species".
• Darwin derived the idea of natural selection after reading Thomas Malthus.
• Natural selection is based on four key principles:
  • Variation: Differences within a population.
  • Heritability: Traits passed to offspring.
  • Overproduction: More offspring than the environment can support.
  • Reproductive Advantage: Dominant traits lead to survival and reproduction.

Fossil Record and Comparative Anatomy

• Derived traits are not recorded in fossils, but ancestral traits are.
• There are three types of structures:
  • Homologous: Similar structures from a common ancestor (e.g., bird wings, reptile limbs).
  • Analogous: Similar function but no common ancestor (e.g., bird wings, bee wings).
  • Vestigial: Less functional or nonfunctional (e.g., kiwi wings, wisdom teeth).

Embryology and Biochemistry

• Vertebrate embryos share homologous structures during development.
• Common ancestors share similar amino acid sequences.

Geographic Distribution and Biogeography

• Species in similar environments resemble those with common ancestors.
• Plant diversity on islands is higher due to easier dispersal.
• Biogeography studies the distribution of species globally.

Adaptations

• Adaptations increase reproductive success (fitness).
• Types of adaptations include:
  • Camouflage (e.g., chameleons).
  • Mimicry.
  • Antimicrobial resistance.
• Observations in Galapagos led to identifying different beak shapes among birds.

Consequences of Adaptation

• Some features are byproducts of evolution (e.g., human baby helplessness).

Population Genetics

• The Hardy-Weinberg Principle states that allele frequencies remain constant without evolutionary forces.
• Assumptions include:
  • No selection.
  • No mutation.
  • No migration.
  • Large populations.
  • Random mating.
• Equations include:
  • Allele frequencies: p + q = 1.
  • Genotype frequencies: p² + 2pq + q² = 1.
• Genetic Drift: Random changes in allele frequencies, significant in small populations.
• Types of genetic drift include:
  • Founder Effect: Small group separates, forming a new population.
  • Bottleneck Effect: Population drastically reduces, then rebounds.

Vocabularies

• Key terms include:
  • Gene flow.
  • Nonrandom mating.
  • Mutation.
  • Natural selection (acts on phenotype).
• Types of selection include:
  • Stabilizing.
  • Directional.
  • Disruptive.
  • Sexual.

Reproductive Isolation and Speciation

• Reproductive isolation prevents gene flow.
• Types of reproductive isolation include:
  • Prezygotic: Prevents fertilization (e.g., different mating calls).
  • Postzygotic: Offspring can't reproduce (e.g., liger).
• Speciation occurs in two ways:
  • Allopatric: Physical barrier separates populations.
  • Sympatric: No physical barrier, species diverge while coexisting.

Evolutionary Patterns

• Adaptive Radiation: Rapid diversification in different environments.
• Coevolution: Species evolve in response to each other.
• Convergent Evolution: Different species evolve similarly in similar environments.
• Speciation rates include:
  • Gradualism (slow steps).
  • Punctuated equilibrium (abrupt changes).