1. Chapter 2 – Darwin and Natural Selection

2. Charles Darwin (1809-1882) –An avid hunter, with strong interests in collecting, geology and botany. –At age of 16 began to study medicine, later switched to study theology at Cambridge University He did not finish. –In 1831, became the naturalist onboard the ship H.M.S Beagle, during a five-year voyage of geographical exploration. Fig 2.1 pg 21

3. Voyage of the Beagle –Darwin read Lyell's Principles of Geology, and used it to study geological features during the voyage. –Discovered fossil bones in Argentina, such as the 6m-high giant sloth, Megatherium. Fig 2.3 pg 24

4. Why are Giant sloths found in the same continent as armadillo? Tree sloth

5. Glyptodon Armadillo

6. Galapagos Islands –Small volcanic islands off western coast of South America. –Darwin collected many specimens of finch. He later noted that each island had finches with a unique beak shape. Fig 2.4 pg 25

7. Darwin's Finches –Each island has unique beak shape. –Darwin noted that the variation in beak shape provided advantages for the food source available on each island. –Beak shape modified, but how? Natural Selection Fig 2.5 pg 26

8. Lamarckian Inheritance Lamarckism – adaptations driven by an inner vital force. Principle of Use and Disuse Variation –When a feature is used, it becomes elaborated, and when it is not used it regresses. –Proposed as means for variation among species, and development of adaptations. Inheritance of Acquired Characters –Adults pass on traits by somehow passing on somatic cells.

9. Natural Selection Thomas Malthus (1766-1834) –Wrote a short paper about population growth and food sources. Populations grow geometrically (2, 4, 8,…) Food Sources grow arithmetically (1, 2, 3,…) Leads to food shortage Darwin realized food shortage acted as selection force, driving variation among species.

10. Artificial Selection Before publishing the Origin of Species, Darwin amassed considerable evidence for how adaptations occur. –Studied chicken breeds, to show how over a short period of time (generations), adaptations can be selected for (artificially). Fig 3.22 pg 59

11. Blending Inheritance Heredity was believed to be a blend of both parents – Red + White = Pink –How can adaptive variation be passed on if blended?

12. Pangenesis vs. Germ Plasm Theory Darwin's solution to problem of blended inheritance. –small particles (pangenes) derived from parent were incorporated in tissue of offspring. Was later shown to be false Germ Plasm Theory: only gonads contribute to offspring. Fig 2.9 pg 34

13. Pangenesis Theory Fig 2.9 pg 34

14. Discussion What is a better evidence supporting natural selection? 1. a useful organ 2. a useless organ (vestigial structures)

15. Discussion What are the prerequisites for natural selection to occur? Darwin : Reproductive ability Environmental restrictions Struggle for existence Heritable variations

16. Homework Due next Tuesday Describe your study using Hypothesis- testing style approach. Phenomena 現象 : 真相 or 假相 Question 問題 : Proximate 近因 or ultimate 遠因 Hypothesis: Falsifiable? 可能被否定 ? Testing: Denying or supporting 實驗結果能否 定什麼 ?

17. 打一針 KCN, 人就死了, 是  是 支持 KCN 有毒的好証據 ? 打一針 X, 人就死了, 是  是支持 X 有毒的好証據 ? 很多人 打一針 X, 就死了, 是  是 支持 X 有毒的好証據 ? 邏輯分析

19. 打一針 KCN, 人就死了, 是  是 支持 KCN 有毒的好証據 ? 未必. 打一針 X, 人就死了, 是  是支持 X 有毒的好証據 ? 很多人打一針 X, 就死了, 是  是 支持 X 有毒的好証據 ? 很多人打一針 X, 就死了, 但是打生理食鹽水的都沒事, 是  是 支持 X 有毒的好証據 ?