HMS Beagle Voyage and Galapagos Islands

Study Notes

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.

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 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.

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).

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.

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.

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

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.

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).