BIOL 112 Lecture 3

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Darwin's Voyage

HMS Beagle — chart coast of South America.

Acquired samples from all over his voyage; took 20 years to analyze and formulate hypothesis.

Galapagos Islands

Darwin obtained most of his observations here.

Islands are formed by volcanoes, so they're isolated and geographically younger compared to the landmass of South America.

• Few ways of migration
• Few founder species from mainland
  • smaller gene pool to account for variation he observed
  • Island species resembled mainland species (weren't entirely the same)
  • e.g. Finches: adapted to niches on island

Descent with Modification

Darwin developed Descent with Modification by natural selection theory

Note: know which biologists contributed what concepts to biology

• reinterpreted Linneaus' classification system: shared characteristics arise as a result of common ancestry
• reinterpreted Lamarck's inheritance theory: heritable (genetically encoded) traits—NOT acquired—are passed to progeny
• natural selection depends on genetic variation in the population (a pool of possible traits for adaptation.

Artificial Selection

Wild mustard has been cultivated into several types of vegetables: Cabbage, cauliflower, broccoli, kale, radishes, etc.

Natural Selection

A chance event (natural disasters, disease, predators) could leave some individuals vulnerable because of their traits

Vulnerable individuals are picked off (undesireable traits are lost), leaving the remaining individuals with desireable traits → Survival of the Fittest

remaining individuals reproduce, making more offspring with their own traits.

Competition

Competition for resources is the driving force behind natural selection

Every species produces more offspring than their environment can support

This combined with heritable variation defines Differential reproductive success: well-adapted individuals survive and reproduce, thus resulting in the evolution of the population.

Theory of Evolution

a scientific theory supported by evidence that describes observations

Evidence

1. Natural selection in action: viruses and bacteria become resistant to treatment
2. Fossils: Whales and dolphins evoled from a terrestrial ancestor
   • Intermediate forms of a species (progression of species evolution)
   • Vestigial characteristics (hind limbs– or lack thereof) due to misuse
3. Homology:
4. Analogy:
5. Biogeography: