Charles Darwin and His Big Idea: Influences and Evidence

1. Charles Darwin and His Big Idea: Influences and Evidence

2. Tuesday February 1, 2011 Warmup: Natural selection is sometimes described as “survival of the fittest”. Lilly says that “fit” means “bigger, faster, stronger” like an Olympic athlete. • Do you agree or disagree? Why? Give an example.

3. Today we will explore: • What influenced Darwin? • What evidence did Darwin use to support his idea of evolution by natural selection?

4. Born 1809 in England Studied medicine and theology Joined HMS Beagle crew in 1831 Ship naturalist Collected specimens Made observations Recorded thoughts Darwin Movie- PBS “Evolution”

6. Patterns of Diversity Plants & animals well suited to environments Similar ecosystems had different animals present Fossils – preserved remains of ancient organisms Some resembled living organisms Some had no living counterpart

7. Small group of islands west of South America Observed many different organisms on the islands Tortoises Finches Islands had different climates and different species

8. Darwin observed that the characteristics of many animals and plants varied noticeably among the different islands of the Galapagos What would cause such variation to occur?

9. Common ideas at Darwin’s time: Earth was only a few thousand years old Neither the Earth nor its species had changed (Earth and living things are fixed) Geological features had been produced by SUDDEN catastrophic events that humans rarely witnessed

10. Ideas that shaped Darwin’s Thinking • James Hutton (1795) • Geologic forces shape Earth • Layers of rock form very slowly • Estimates Earth is millions of years old

11. Ideas That Shaped Darwin’s Thinking • Thomas Malthus (1798): • Growing human population will overwhelm resources • Darwin realized this applies even more to plants and animals that have tons of offspring!

12. Ideas That Shaped Darwin’s Thinking • Charles Lyell (1833): • Geological processes occurring now have shaped earth’s features throughout history • Scientists must explain past events using processes they can observe

13. Ideas That Shaped Darwin’s Thinking • Jean-Baptiste Lamarck (1809) • Recognized living things have changed over time • These traits can be passed on • “inheritance of acquired characteristics” • Organisms can alter the size/shape of their organs by using bodies in new ways • (slight problem with this idea)

14. Concept Map: Evidence for Natural Selection The fossil record Geographic distribution of living species Homologous body structures Similaritiesin early development Physical remains of organisms Common ancestral species Similar genes Similar genes Evidence of Evolution includes which is composed of which indicates which implies which implies

15. What is Evolution? Process by which today’s organisms have descended from ancient organisms (ancestry) + Change over time =Descent with Modification

16. Evidence for Evolution How do we know evolution happens?

17. Fossil Record • Provides a peek at the past shows how living things have changed over the past 3.5 billion years. • May have bits missing, but fossil evidence clearly shows that life is old and has changed over time.

18. Transitional Fossils Gray Whale: lives today. Early whale ancestor. Land mammal, but clearly related to whales and dolphins based on specializations of ear. The position of nostrils has changed over time. We would expect to see fossils that show intermediate forms.

19. Geographic Distribution • Some species are only found in certain parts of the world, likely because they evolved there • Alligators in United States • Marsupials on the islands of Australia and New Zealand

20. Geographic Distribution • Organisms show more similarity to species nearby than in similar climates but far apart. • Implies ancestry • Example: species on Galapagos Islands share more similarities with species on mainland South America than they do with species that live on other islands with similar climates across the world

21. Homologous Structures • Similar characteristics due to relatedness

22. Homologous Structures • The leaves look and function differently from each other, but are all derived from a common ancestral form.

23. Homologous Structures • Frogs, birds, rabbits, and lizards have different forelimbs, but they all share the same set of bones. Extinct, but shows common ancestry

24. Homologous Structures http://www.pbs.org/wgbh/evolution/library/04/2/l_042_01.html Each species has a different function for their limb. Does it seem possible that they all developed the same bone structure independent of each other? “What could be more curious…?”

25. Vestigial Organs • Traits that are not useful to an organism, but remain from a useful ancestral trait • Ear-wiggling muscles • Tail in human and all vertebrate embryos. • Appendix • Wisdom teeth • Hip bone of a whale

26. Embryology/Development • Which of these is a pig embryo? Different vertebrates show striking similarities in early stages of development. http://lhs2.lps.org/staff/sputnam/Biology/U6Evolution/embryology.jpe

27. Embryology/Development • Snakes have legged ancestors • Hind limb buds as embryos, but lose them before adulthood • Fossil evidence also shows snakes with hind limbs

28. Cellular/ Molecular Evidence • All organisms are made of cells • Produce proteins as building blocks and messengers • Membranes filled with water, proteins, lipids, carbohydrates, genetic material • Most use sugar for fuel

29. Molecular Evidence • DNA: simple four-base code that provides instructions for all living things • All life is linked to a common ancestor • Different species share some of the same genes • Worms share 25% of their genes with humans!

30. Molecular Evidence • The more similar the DNA of two living organisms, the more closely they may be to one another • Note: many other factors play a role as well • Activity: • study the amino acid sequence in the hemoglobin of humans, gorillas, and horses • use the data to show the similarities in DNA of these organisms