History of Evolutionary Thought

1. History of Evolutionary Thought 15.1

2. Dinosaur Adaptations

3. What is Evolution? • A scientific theory • Debated still today • Enormous scientific support • Religious conflict • Keystone of biological science

4. Evolution and Some History • Evolution: is the development of new organisms from pre-existing organisms over long periods of time • Evolution: is a heritable change in the characteristics of a population from one generation to the next • In the 1700’s, many held the belief that organisms did NOT change over time and that the Earth was 6000 years old, not the 4.6 billion years old we support today • However, some scientists did not support these ideas

5. Who Thought What • The church was a strong influence regarding species remaining unchanged – biblical view • God created an infinite and continuous series of life forms, each one grading into the next, from simplest to most complex, and that all organisms, including humans, were created in their present form relatively recently and that they have remained unchanged since then • Because these beliefs were strong, no one attempted to figure out how different species came to be

6. Biological Evolution • At this time, however, there were some scientists who felt that the Earth was much older and that organisms did change over long periods of time • Charles Darwin, the famous naturalist with whom we associate biological evolution, was very much influenced by these scientists

7. Charles Darwin1809-1882 • Darwin was a naturalist (biologist) who was fortunate enough to have taken a voyage around the world over 5 years • During this time, he made many observations and collected thousands of living and dead specimens • He used this information, along with several other scientists’ to present his theory of evolution

8. Theories Influencing Darwin • Erasmus Darwin = grandfather who believed that evolution occurred in all living things and must have occurred over millions of years • The geologists***Cuvier 1769-1832 – French, observed that fossils found in deeper strata looked different than those in more shallow layers; changes were sudden, organisms became extinct and replaced by others, so Earth must have developed catastrophically - catastrophism

9. Theories Influencing Darwin, cont. • Lyell 1797-1875 - British, geologic processes that formed the Earth are still at work today and that these changes are slow and progressive – did not agree with Cuvier – uniformitarianism (developed earlier by James Hutton, a Scottish geologist); key to understanding the present is to look at the past!!! • Bottom line, both theories contribute to evolutionary theory • PS – Cuvier and Lyell strongly disagreed with one another about how the Earth changed over time, but neither accepted the Church’s view either. Cuvier did not live long enough, but Lyell in time came to support Darwin’s work on biological evolution. They remained friends up until Darwin’s death.

10. Theories Influencing Darwin, cont. • Lamarck 1744-1829 – French biologist who believed in evolution and sought to explain why • Theory of the inheritance of acquired characteristics – use and disuse • Spontaneous generation and need

11. Wait, there’s more…epigenetics!!! • http://www.teachersdomain.org/asset/biot09_vid_epigenetics/

12. Darwin’s Ideas Number one: Descent with Modification - organisms change through time - organisms are descended from pre-existing species - Galapagos island (South America) observations and finches = common ancestor!!!

13. Darwin’s Ideas, cont. Number two: Natural Selection – the mechanism for descent • Overproduction – Malthus 1766-1834 (British economist) • Genetic variation • Struggle to survive • Differential reproduction – organisms with the best adaptations survive, reproduce and pass along those characteristics to their offspring

14. Fitness and Adaptation • Fitness = hereditary success for next generation • Adaptation vs. acclimatization = is a tool which makes an organisms successful in a particular environment; acclimatization is a short term “fix” that will not be passed down through the generations • Example: a plant resists extreme drought over the course of one summer vs. cactus spines

15. Darwin’s Publication • In the 1850’s, another naturalist, Alfred Russel Wallace formed a new theory about the process of evolution • In 1858, both scientists’ ideas were presented at a conference and in 1859, Darwin published his work in a book entitled, “On the Origin of Species by Means of Natural Selection”

16. Try This! • http://www.techapps.net/interactives/pepperMoths.swf • http://www.pbs.org/wgbh/evolution/library/01/1/l_011_01.html

17. Theory of Evolution 15.2 Evidence of Evolution

18. How??? Fossils give us evidence for evolution. Problem: HOW DO LIVING ORGANISMS PROVIDE EVIDENCE FOR EVOLUTION? Solution: morphology (similarities in shape and structure), embryology (development), DNA, RNA and protein sequences.

19. Geologic Time Scale Evidence #1 Think of the GTS as a journal that goes back 4.5 bya – developed by scientists in the 1700’s and 1800s

20. Fossils • Remains of organisms that died long ago • Can form under different conditions and in differing time periods • Very powerful evidence even today • Steno = superposition • Superposition says that undisturbed areas of the earth form in layers from bottom to top, oldest to newest • These layers contain fossils • The Geologic Time scale was developed to summarize these findings

21. Fossils, cont. • Relative age of fossils can be determined by comparing fossils found in these layers • Absolute age of fossils can be determined by radiometric dating – still an indirect method • An incomplete history – there are gaps which leave questions about evolution and how it occurred • 1.7 bya – rocks with fossils of 1st multicellular organisms

22. Fossils, cont. • Strata tell us that different organisms lived at different times, and have definitely changed over time • Organisms from the past in some cases were very much NOT like organisms today • Fossils in adjacent layers are more like one another than those farther away • Fossils provide clues as to an organism’s environment

23. Common Ancestor??? WOW • Paleontologists have discovered a fossil of a dinosaur sitting on a nest of eggs. This finding of brooding behavior, characteristic of birds, supports the hypothesis that birds share a common ancestor with dinosaurs.

24. Fossils, cont: Transitional Species • These are species that help us fill in gaps in the time scale • They allow us to make inferences between what we think existed at particular time periods and what later descendants looked like • Whales evolved from land mammals??? NO linearity!

25. Biogeography Evidence #2 • Studies where organisms live around the world • Darwin and Wallace both noticed two things: ***closely related animals living in different environments –divergence @@@unrelated animals living in similar environments -convergence ***Descent with modification at work

26. Anatomy and Embryology Evidence #3 • Structure and development • Ancestor vs. relative – descending from ape OR descending from a common ancestor • Descent from your cousin, or from your grandparent • Common structure, common ancestor, different environment, different adaptations • Homologous structures: related structures with different functions due to different adaptations - different patterns of evolution forced selective environmental pressures amongst related organisms • Analogous structures: related structures have similar functions but no common ancestor – bird, bat, moth wing – different patterns of evolution forced selective environmental pressures • Vestigial structures: left over structures which currently serve no purpose in us but do in related organisms

27. Homologous Structures

28. Analogous Structures

29. Embryology

30. “Ontogeny Recapitulates Phylogeny” • Ernst Haeckel – zoologist 1834-1919 • An organism's biological development, or ONTOGENY parallels and summarizes its species' entire evolutionary development, or PHYLOGENY • Not true – these stages of development are not representative of an adult ancestor, but are similar to the embryonic stages of the organism’s ancestor. • Patterns are repeated, not the actual form of the organism.

31. Biological Molecules • Organisms that share traits have a more recent ancestor • Still developing

32. Phylogeny, revisited

33. Tree Template

34. 15.3 Evolution in Action: Speciation • Evolution can produce new species of organisms, especially if there are new habitats to invade • When many related species evolve from a single ancestral species, this is called adaptive radiation • Divergent evolution is the process of two or more related species becoming more and more dissimilar. Adaptive radiation is a type of divergent evolution (homologous structures). • Example: Galapagos finches, Hawaiian honeycreepers, anole lizards

35. Evolution in Action, cont. • On the other hand, it is possible for unrelated species to become more and more similar in appearance as they adapt to the same kind of environment. This is called convergent evolution (analogous structures). • Examples include this cactus and spurge (euphorbia): Notice the resemblance of the cactus (upper left), which grows in the American desert, to the euphorbia, which grows in the African deserts. Both have fleshy stems armed with spines. These adaptations help the plants store water and ward off predators.

36. Artificial Selection • Where humans choose what their offspring will look like by selecting the parents for certain traits • All domesticated dogs today arose a common wolf ancestor from Eastern Asia about 15,000 years ago

37. Coevolution • When two or more species evolve together because they influence each other • Examples: bees and flowering plants, predator – prey, humans and antibiotics

38. Closure Identify each type of evidence (puzzle pieces) for evolution in the following examples: • Mammalian embryos have gill slits • Human blood proteins are very similar to chimps • Domestic chickens are descended from jungle fowl of SE Asia • All clams have two shells, right and left