Evidence for Evolution. Fossils. Evidence for evolution. Fossils. Show: Evolution Primer: How do we know evolution happens?. Evidence for evolution. DNA All life uses the same 4 DNA bases: thymine, adenine, guanine, cytosine
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The finches on the Galapagos are thought to have evolved from a single species of ancestral finch, probably the generic sort of seed-eating finch shown in the center. When a population of finches was reproductively isolated on one of the islands, it adapted over time to feed on a new food source. After time, it was sufficiently different from its ancestor to be considered a new species.
- Result of environmental change, species interactions
This graph shows extinction rates. You can see that five times in the last 600 million years, the rate has spiked up. Those are MASS EXTINCTIONS. The last one is when the dinosaurs died. Between mass extinctions, there is a more steady extinction rate, called BACKGROUND EXTINCTION.