1. A brief history of biology

2. A brief history of biology

3. A brief history of biology
Not to mention development, immunology, neuroscience, microbiology, ecology, …

4. A brief history of biology
Not to mention development, immunology, neuroscience, microbiology, ecology, …
Biology is recent …

5. European exploration stimulated interest in biological diversity
e.g. Joseph Banks, naturalist on Cook’s voyage ( )

6. European exploration stimulated interest in biological diversity
e.g. Joseph Banks, naturalist on Cook’s voyage ( )
Geology revealed an ancient and changing Earth

7. European exploration stimulated interest in biological diversity
e.g. Joseph Banks, naturalist on Cook’s voyage ( )
Geology revealed an ancient and changing Earth
Diverse ideas of evolution emerged in the early 19th C
- Lamarck’s Philosophie Zoologique (1809)
- Erasmus Darwin speculated in poetry and prose (~1790)
- Chambers’ Vestiges of the Natural History of Creation (1844)

8. Charles Darwin ( )

9. Charles Darwin ( )
A keen naturalist

10. Charles Darwin (1809-1882) A keen naturalist Voyage of the Beagle
( )

11. Charles Darwin (1809-1882) A keen naturalist Voyage of the Beagle
( )
Lyell’s Principles of Geology

12. Charles Darwin (1809-1882) A keen naturalist Voyage of the Beagle
( )
Lyell’s Principles of Geology
Darwin explained coral atolls

13. Charles Darwin (1809-1882) A keen naturalist Voyage of the Beagle
( )
Lyell’s Principles of Geology
Darwin explained coral atolls
Sought to explain the “mystery of mysteries”
by current mechanisms:
- fossils, geography ….

14. Thought of natural selection in September, 1838
If variation be admitted to occur occasionally in some wild animals, and how can we doubt it, when we see thousands of organisms, for whatever use taken by man, do vary. If we admit such variations tend to be hereditary, and how can we doubt it when we remember resemblances of feature and character… . If we admit selection is steadily at work, and who will doubt it, when he considers amount of food on average fixed and reproductive powers act in geometric ratio If we admit that external conditions vary, as all geology proclaims, they have done and are now doing—then, if no law of nature be opposed, there must occasionally be formed races, slightly differing from the parent races.
(from an 1842 sketch of the theory)

15. Thought of natural selection in September, 1838
If variation be admitted to occur occasionally in some wild animals, and how can we doubt it, when we see thousands of organisms, for whatever use taken by man, do vary. If we admit such variations tend to be hereditary, and how can we doubt it when we remember resemblances of feature and character… . If we admit selection is steadily at work, and who will doubt it, when he considers amount of food on average fixed and reproductive powers act in geometric ratio If we admit that external conditions vary, as all geology proclaims, they have done and are now doing—then, if no law of nature be opposed, there must occasionally be formed races, slightly differing from the parent races.
(from an 1842 sketch of the theory)
Spurred to publish by a letter from Wallace (1858)

16. The Origin of Species (1859) led to wide acceptance of evolution
Brought many phenomena together in one framework
Natural selection was not widely accepted as the key mechanism of evolution until a century later.
Huxley, Galton emphasised the importance of 'sports’
Spencer, Haeckel … invoked some directed tendency or force
Only two empirical studies of natural selection in the 19th century
Bumpus (sparrows), Weldon (crabs)

17. Natural selection faced real difficulties:
origin of complex adaptations
age of the Earth - William Thomson (Lord Kelvin)
blending inheritance
Fleeming Jenkin, "The Origin of Species". North British Review 46:

18. Natural selection faced real difficulties:
origin of complex adaptations
age of the Earth - William Thomson (Lord Kelvin)
blending inheritance
Fleeming Jenkin, "The Origin of Species". North British Review 46:

19. Rediscovery of Mendel's work in 1900 strengthened the dispute
15 years of experiments: 22 true-breeding lines of pea, 30,000 plants
Results read at the Brunn Natural History Society in 1865, published 1866

20. Rediscovered in 1900 by Correns, de Vries and von Tschermak
Classical genetics developed by Bateson, Morgan, .....

21. Rediscovered in 1900 by Correns, de Vries and von Tschermak
Classical genetics developed by Bateson, Morgan, .....
applies to all sexual organisms
linkage, multiple alleles ....
genes are on chromosomes

22. Mendelian inheritance was seen as incompatible with Darwinian selection:
Mendelian variation distinct from continuous variation :
Wilhelm Johannsen:
selection cannot have any effect on pure lines
selection on a mixed population can only sift amongst existing variation

23. Alleles of small effect + random variation -> continuous variation
Understood by Mendel, Bateson, Pearson, Yule (1902)

24. Alleles of small effect + random variation -> continuous variation
Understood by Mendel, Bateson, Pearson, Yule (1902)
Nilsson-Ehle (oats & wheat)

25. Selection builds up favourable
combinations of genes, step-by-step

26. Artificial selection (maize, hooded rats)

27. Artificial selection (maize, hooded rats)
Fisher, R. A The correlation between relatives on the supposition of Mendelian inheritance. Proceedings of the Royal Society of Edinburgh 52:

28. Population genetics established in 1920s
Fisher, Haldane, Wright

29. Population genetics established in 1920s Fisher, Haldane, Wright
Evolutionary Synthesis ~
Theodosius Dobzhansky,
E.B. Ford

30. Population genetics established in 1920s Fisher, Haldane, Wright
Evolutionary Synthesis ~
Theodosius Dobzhansky,
E.B. Ford
Simpson (paleontology),
Mayr (taxonomy), Stebbins (botany)

31. “Evolutionary Synthesis”
Mendelian genetics is conducive to natural selection
Heritable variation is preserved
Variation is not influenced directly by environment
Mutation is random with respect to adaptation

32. “Evolutionary Synthesis”
Mendelian genetics is conducive to natural selection
Heritable variation is preserved
Variation is not influenced directly by environment
Mutation is random with respect to adaptation
Adaptation is solely due to natural selection
Many processes contribute, but only NS tends to produce organisms with better survival and reproduction
Minor differences are influenced by selection, and weak selection is effective