“Darwin’s Finches”: the finches that Darwin found across the different Galapagos Islands which all had specific adaptations to their own island conditions.
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Adaptive Radiation: The concept of a species having different ecological niches which leads to speciation.
Giant fossils of ancient sloths which are similar to those of modern-day varieties.
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Changes through evolution: all animals evolved from previous ancestors.
Embryos look similar between vastly different species, biogeography in terms of adaptive radiation, etc.
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Common ancestry: multiple pieces of evidence Darwin gathered support that all species--in the world and in concentrated areas--descend from common ancestors.
Humans have been breeding other organisms for thousands of years. Darwin believed that humans could not be the only ones breeding.
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Natural Selection: this can be applied to nature, because nature is the breeder which decides on whether an organism survives, creating a species with higher fitness.