In historical context. Other people’s ideas paved the path for Darwin’s thinking. competition: struggle for survival population growth exceeds food supply. land masses change over immeasurable time. The History Behind THE Theory. Aristotle
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struggle for survivalpopulation growth exceeds food supply
land masses change over immeasurable time
Determined some past organisms differ greatly from living species by looking at fossils in various strata
Some organisms became extinct
Published his idea of gradualism: the Earth had been molded by several events over time
Armadillos are native to the Americas, with most species found in South America.
Why should extinct armadillo-like species& living armadillos be found on the samecontinent?
Mylodon (left) Giant ground sloth (extinct)
“This wonderful relationship in the same continent between the dead and the living will…throw more light on the appearance of organic beings on our earth, and their disappearance from it, than any other class of facts.”
Collected many different birds on the Galapagos Islands.
Thought he found very different kinds…
Darwin was amazed to find out:
All 14 species of birds were finches…
But there is only one species of finch on the mainland!
Large Ground Finch
Small Ground Finch
How didone species of finches becomeso many differentspecies now?
Veg. Tree Finch
Veg. Tree Finch
Rapid speciation:new species filling new niches,because they inheritedsuccessful adaptations.
Large ground finch
…perhaps these are the first steps in the splitting of one speciesinto several?