CHAPTER 15 – DARWIN

1. CHAPTER 15 – DARWIN "There is grandeur in this view of life, [that] from such a simple beginning, endless forms most beautiful and wonderful have been and are being evolved." Charles Darwin

2. The Puzzle of Life’s Diversity • Evolution – change over time • Process where modern organisms have descended from ancient organisms. • Scientific theory - a WELL tested explanation for a broad set of observations in nature. • It has always been seen to be true. • Has not been proven mathematically

3. Voyage of the Beagle • Charles Darwin – “Father of Biology” • Born February 12, 1809 (the same day as Abraham Lincoln). • 1831- Darwin leaves on the H.M.S. Beagle for a 5 year voyage around the world. • Suffered severe seasickness.

4. Voyage of the Beagle • Darwin made many observations and collected specimens. • Shipped many specimens home • Took a lot of very detailed notes. • Lead him to his Theory of Evolution by Natural Selection.

5. Darwin’s Observations • Saw a lot of diversity • 1 day in Brazil he collected 68 beetle species. • Saw many patterns of Diversity

6. Patterns of Diversity • Interested in why plants and animals showed such differences, but were well suited to their environment. • Impressed that organisms survived and produced offspring • Wondered if this process led to the wide variety of organisms.

7. Patterns of Diversity • Puzzled by where different species lived. • Argentina, Australia and Europe had similar grassland but different animals. • Darwin asked: Why were there no rabbits in Australia and why were there no kangaroos in England?

8. Living Organisms and Fossils • Darwin collected many fossils and compared them to other organisms. • Some resembled other organisms, but others were completely different. • Darwin asked: • Why had so many of these species disappeared? • How were they related to living species?

9. The Galapagos Islands • Group of small islands about 1000 km off the west coast of Equador(S. America). • Each island has a very different climate. • Small islands are hot, dry and nearly barren (not much life). • Higher islands have a lot of rainfall and have much more diversity of plants & animals.

10. The Galapagos Islands • Darwin was fascinated with the land tortoises and marine iguanas on Isabella Island. • He went from island to island. • Discovered that the shape of the tortoises shell could be used to identify the island where it lived.

11. The Galapagos Islands • Darwin also saw many types of small brown birds. • Collected specimens to be brought home. • Realized that they all had different shaped beaks suited for the seeds they ate. • These birds are known as Darwin’s Finches

12. The Journey Home • Darwin began to wonder if the animals living on different islands in the Galapagos had once belonged to the same species. • These species would have evolved from a single S. American ancestor after becoming isolated on the islands.

13. JAMES HUTTON • Theory of Geological Change – 1795 - detailed theory about geological forces. • Said Earth was not thousands of years old, but millions.

14. Charles Lyell – Father of Geology • Said scientists must explain past events using processes that they can observe. • These processes are the same now as in the past. • Ex. - Erosion (through water) carves out canyons. • Fossils of marine (ocean) animals were found many feet above sea level.

15. Idea’s that Shaped Darwin’s Thinking • Lyell & Hutton influenced Darwin in 2 ways: • If the Earth could change over time, might life change as well? • Realized it would have taken many years for life to change only if the Earth were extremely old. • SEE Biology & History Timeline – pgs. 374-375

16. Jean-Baptiste Lamarck • One of the 1st scientists to see that living things change over time. • One of the 1st scientists to develop a theory of Evolution. • Saw that species adapt to their environment.

17. Jean-Baptiste Lamarck • 1809 - Theory of Use & Disuse (how organisms change – “use it or lose it”). • Use or disuse of organs means organisms gained or lost certain traits during their lifetime. • Traits are passed to their offspring, leading to change in a species.

18. Lamarck’s Theory of Evolution • Theory is incorrect because for 2 reasons: • He did not know that traits were inherited • Did not know that an organism’s behavior has no effect on its inherited traits. • Lamarck’s Theory (See Fig. 15-7, pg. 376).

19. Population Growth • Thomas Malthus – 1798 noticed more babies being born that people dying. • If human population continues to grow, sooner or later there would not be enough living space and food. • Population growth is controlled by war, famine (no food) and disease.

20. Population Growth • Darwin realized that Malthus theory applied to other organisms. • Most of a species’ offspring die before they can reproduce

21. Darwin Presents His Case • Darwin’s Book: On the Orgin of Species by Natural Selection – Published in 1859 • 1858, Darwin read an essay by Alfred Russel Wallace. • Wallace’s essay had the EXACT same conclusions as Darwin (the two never met). Wallace Darwin

22. Darwin Presents His Case • Darwin’s Book: On the Orgin of Species by Natural Selection – Published in 1859 • Proposed a mechanism for evolution that he called “Natural Selection” which has been taking place for millions of years and continues in all organisms. • This notion changed the world of science FOREVER.

23. Natural Selection & Artifical Selection • Natural Variation – Differences among individuals of a species. • Ex. – some cows give more milk • Traits passed on to the next generation. • Darwin studied famers and breeders and noticed they used variation to improve crops or animals. • Termed this Artificial Selection (Selective breeding).

24. Evolution by Natural Selection • Struggle for Existence – members of each species compete to get food, living space and other necessities of life. • Predators better at getting their prey will have more food. • Prey better at avoiding predators and do not get caught. • Example: camouflauge

25. Survivial of the Fittest • Key factor in the “struggle for existence”. • How well suited is an organisms to its environment. • Fitness - the ability of an individual to survive and reproduce in its specific environment.

26. Adaptation • Any structure or behavior which allows an organism to survive in its environment. • Organisms best adapted will reproduce and pass on those traits (adaptations) that help them survive in their environment. • Examples: • Porcupines have sharp quills – structural adaptation • Animals that live and/or hunt in large groups – behavioral adaptation

27. Evidence of Evolution • Darwin argued that living things have been evolving on Earth of millions of years. • Evidence is found in: • The fossil record; • The geographical distribution of living species; • Homologous structures; and • Similarities in early development.

28. The Fossil Record • The Fossil Record: • Detailed record of evolution • Darwin pointed out that species of many different forms had appeared on Earth, lived for a time and then vanished. • The fossils that are found in the layers of rock show evidence of the slow change of organisms over time.

29. Geographic Distribution of Living Species • Darwin’s Finches – on the Galapagos • How did these birds become similar, yet different from one another. • Different from other species of finches, but also similar species in S. America. • Concluded that the Galapagos finches could have descended with adaptations from S. American ancestors. • See. Fig. 15-14., pg. 383

30. COMPARATIVE ANATOMY • Homologous Structures – Structures which are similar in structure, but different in function. • Examples – human hand & bat wing. • Analagous structures – Structures that are similar in function, but different in structure. • Example: Bat wing & bird wing.

31. COMPARATIVE ANATOMY • Vestigial Structures – Reduced in size and non functional. • Example: legs (snakes) and tails (humans – “tail” bone) and appendix. • No longer needed and become nonfunctional.