Darwin’s Theory of Evolution (Chapter 15) Please set up your notebook for Cornell Notes

Evolution  change over time Theory  a well supported, testable explanation of events that occurs in the natural world

Darwin’s Journey Traveled on the HMS Beagle starting in 1831 His detailed drawings and observations helped him piece together his ideas on why life is so diverse Observations Plants and animals were well suited for the environment that they lived in Some animals are widely distributed while others are only found in certain areas Some living animals resembled fossils of animals from long ago Some fossils did not resemble any living organism

Galapagos Islands Each island has a different climate Giant Tortoises found on each island were different Several types of small birds were found on each island but they all had different sized beaks On Darwin’s journey home he began to wonder if all the different animals on the islands were once the same species

Ideas before Darwin James Hutton  proposed that the geological forces that shape Earth’s surface occur very slowly Rocks are moved by forces under Earth’s surface Charles Lyell  the same geological forces that occurred long ago are continuing today Jean-Baptiste Lamarck  the use or disuse of certain features are passed on to offspring Giraffes have long necks because their parents stretched their necks Thomas Malthus  if human population continues to grow unchecked, we will run out of room and food

On the Origin of Species by Means of Natural Selection The variation found in populations are important Artificial selection  humans select the traits in animals or plants they want the next generation to have Hairless Chihuahua Evolution by natural selection Struggle for existence  members of each species compete with each other for food, water, mates and shelter The ability of an organism to survive and reproduce in it’s environment is called fitness Adaptations are inherited characteristics that increase an organism’s fitness Natural selection  organisms that are best suited for survival in an environment will reproduce more and pass their advantageous traits on to their offspring All living species have descended from other species over time  descent with modification All living things descended from a common ancestor

Evidence for evolution Fossil record  shows that life on earth has changed over time Animals living in different areas with similar climate have similar features Homologous body structures Structures that come from a common ancestor but are different in the adult form Vestigial structures  the remains of structures that are no longer used Pelvic bone in whales Similarities in embryological development