Ch.22 History of Evolution Descent with Modification (broad definition) Change in the genetic composition of a population from generation to generation (more narrow definition) Pattern Process Change revealed by data from a range of disciplines (biology, geology, physics, chemistry) Mechanisms that produce the observed pattern of change Are the facts from observation English naturalist Modern organisms have evolved over long periods of time through descent from common ancestors English naturalist Published On the Origin of the Species (1859) Technically On the Origin of Species by Means of Natural Selection, or the Preservation of Favored Races in the Struggle for Life 1
English naturalist Independently developed similar theory to Darwin while working in Malay Archipelago Anaximander of Miletus Empedocles Animals could descend from other types of animals (even humans) Later philosophers (Plato, Aristotle) suggested all species were fixed by divine design Swedish botanist Developed classification system Grouped organisms based on shared observable characteristics (Did not group them by evolutionary ties, but Darwin noted this system often reflected those relationships anyway) Scottish geologist Geologic change takes place slowly, over very long periods of time Earth must be millions, not thousands, of years old 2
English geologist Concept of Uniformitarianism Geologic processes operating today are the same as in the past, and at the same rate (erosion, volcanism, mountain building, etc) Geologic processes occur very slowly, but the same processes occurring now have been occurring for millions of years If Earth can change over time could life change too? French naturalist Lamarck s Hypothesis Organisms change & acquire features to help live more successfully in their environment (Acquired Characteristics) Acquired traits get passed to offspring (Inheritance of Acquired Characteristics) Problems Organisms don t drive to be more perfect Species don t become better Evolution does not progress in a predetermined direction Acquired traits cannot be passed to offspring Positives Suggested species were not fixed Tried to explain evolution scientifically with natural processes Link between environment & body structures English economist Lack of food, water, shelter keeps human populations in check War, famine, disease also work against continued population growth 3
Set sail on HMS Beagle (1831-1836) Organisms were well suited to their widely diverse environments Organisms more closely resembled other living species in nearby regions Temperate S.A. organisms were more similar to tropical S.A. organisms than temperate European organisms Geologic events reinforced readings from Lyell (Uniformitarianism) Earthquakes caused shifting of coastal land masses in Chile Often found marine fossils thousands of feet up in the Andes mountains Species vary based on geographic distribution, even in relatively localized regions (Species vary locally) 4
Emu (Austrailia) Ostrich (Africa) Land Iguanas Rhea pennata Rhea americana Mainland Iguanas Marine Iguanas ~1000km off coast of Ecuador Islands are close to one another, yet have different ecological conditions Dome-back (Isabela) Galapagos tortoise shells Isabela Larger island with highlands Humid Low-growing vegetation Saddle-back (Española) Dome-back (Isabela) Galapagos tortoise shells Española Smaller island, no highlands Dry Less vegetation Saddle-back (Española) Finch beak shapes Differ based on food source available on the island 5
Finch beak shapes Differ based on food source available on the island Fossils of extinct animals were different, yet distinctly similar, to living species (still resembled S.A. organisms) Glyptodonts vs. Armadillos Glyptodonts vs. Armadillos Glyptodon / Glyptodont Megatherium vs. Tree Sloths Megatherium 6