15.1Darwin’sTheoryofEvolutionbyNaturalSelection

Darwin on the HMS Beagle•  Darwin’s job on the Beagle was to be

a naturalist, and to collect biological and geological specimens during the travels.!•  When Darwin began his journey in

1831, most people thought the world was ~6000 years old, and that animals and plants were unchanging. !

The Galápagos IslandsThe different islands all had their own, slightly different varieties of animals. !

artificial selection breeding to produce offspring with desired traits!

Darwin thought if humans could change species by artificial selection, then the same could happen in nature.!New species could appear through small changes in ancestral species.!

Darwin described a process where some competitors would be better equipped for survival than others, those less equipped would die. !

natural selection: organisms with favorable variations survive, reproduce, and pass their variations to the next generation !

Darwin’s 4 Principles of natural selection:

• Individuals show variation!• Variations are inheritable!• More offspring are born than can survive!• Variations that increase reproductive success will be more common in the next generation!

The Origin of SpeciesDarwin published On the Origin of Species by Means of Natural Selection in 1859. !

Evolution- change in a group of organisms over time!Natural selection ≠ evolution!it is one way evolution can occur !