Evolution, Fossil Dating, and Biogeography: Key Concepts for Biology

Darwin's Finches

31 finch specimens collected by Darwin from 3 Galápagos Islands. Beak shapes vary depending on the type of food they eat, suggesting adaptation to environment.

Artificial Selection

Change initiated by humans by choosing certain phenotypes over others, e.g., breeding pugs or agricultural crops.

Fossilization

Process where an organism is buried in sediment; calcium in bones mineralizes and surrounding sediment hardens into rock. Rare event.

Relative Dating

Estimating the age of fossils by their position in layers of rock; older layers usually below newer layers.

Isotopic Dating

Determining fossil age by measuring radioactive isotopes.

Potassium-40

Half-life 1.25 billion years (used for old fossils).

Carbon-14

Half-life 5,700 years (used for recent fossils).

Evolutionary Transitions

Intermediate fossils showing how major transitions occurred, Archaeopteryx, which has both dinosaur and bird traits.

Homologous Structures

Body structures that have different functions but share a common ancestor origin.

Embryonic Development

Study of early development in organisms early stages of organisms showing ancestral traits

Imperfect Adaptations

Traits that are not perfectly suited to their function due to evolutionary constraints or compromises.Evolution modifies existing structures; it does not design perfectly.

Vestigial Structures

Structures with no apparent function but inherited from ancestors. Examples: Manatee nails, Whale pelvic bones, Pseudogenes (non-functional genes).

Pseudogenes

Genes that were once functional in ancestors but no longer work in modern organisms.

Biogeography

Study of the geographic distribution of species

Convergent Evolution

Different species develop similar traits due to similar environmental pressures (not shared ancestry).

Colonization & Divergence

Species reach islands via dispersal; once there, they often evolve into new species adapted to local conditions.

Phylogeny reflects Ontogeny

Early developmental stages of an organism (ontogeny) can show patterns similar to the evolutionary history (phylogeny) of that species.

Traits that are not perfectly suited to their function due to evolutionary constraints or compromises.

Biogeography trend

Islands are separated from continents, so not all species from the mainland can get there naturally

Potassium-40 (K-40)

Half-life 1.25 billion years; used for dating ancient fossils.

Carbon-14 (C-14)

Half-life 5,700 years; used for dating recent fossils.

Anatomical Evidence for Evolution

Traits in the bodies of different species show that they share a common ancestor.

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