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Carolus Linnaeus 1707 – 1778 AD “The Father of Modern Taxonomy” Greek Philosopher

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Carolus Linnaeus 1707 – 1778 AD “The Father of Modern Taxonomy” Greek Philosopher Aristotle 384 – 322 BC Carolus Linnaeus 1707 – 1778 AD “The father of modern taxonomy” Greek philosopher Examined natural world for evidence of divine order • Classified organisms according to a Scala naturae (“Chain of Being”) binomial system, giving each a specific and • Hierarchical arrangement of forms a generic name, e.g. Homo sapiens • Species arranged linearly along a scale: God • Man Genus species Mammals Egg-laying animals • Proposed a nested system of relationships Insects Plants (as opposed to the Scala naturae) Non-living matter • Formed the basis for the western belief in a fixity of species, each of which has a typical form Carolus Linnaeus Carolus Linnaeus 1707 – 1778 AD 1707 – 1778 AD “The father of modern taxonomy” “The father of modern taxonomy” • Recognized fundamental difference between • The modernized Linnaean system • interbreeding organisms (within a species) groups organisms into: • non-interbreeding organisms (different species) Kingdom Animalia • Believed in balance of nature Chordata Phylum • Each species has its place in a divine plan Class Humans Mammalia • Species would not change or go extinct Order Primates Family Hominidae Eventually acknowledged Genus Homo limited formation of new Species sapiens species by hybridization Comte de Buffon Erasmus Darwin 1707 – 1788 AD 1731 – 1802 AD “Dégéneration” • Believed that the origin of life & species Charles Darwin’ Grandfather followed material processes • Looked for evidence in the physical & biological world • Believed Linnean hierarchy reflected common descent • British philosopher, naturalist & physician (dégéneration), with divergence over time. • Wrote Zoonomia: Or The Laws of Organic Life • Physical environment (somehow) changes organic particles • Believed organisms constantly attempted to improve • New species form when animals migrate themselves by adapting to their environment • New environment then causes change to the species • Transformism or transmutation • Change only happen within families: each family conforms to an internal mold. Species can change over • All of life consists of “one living filament” connecting all time but are limited to their original mold. living forms to a common ancestor Erasmus Darwin Jean-Baptiste Lamarck 1731 – 1802 AD 1744 – 1829 AD “Inheritance of acquired characters” Organic life beneath the shoreless waves Was born and nurs’d in ocean’s pearly caves; French professional naturalist First forms minute, unseen by spheric glass, Move on the mud, or pierce the watery mass; Theory of “transformism” These, as successive generations bloom, ! Organisms progress through a hierarchy of ever-more- New powers acquire and larger limbs assume; advanced forms (Scala naturae in reverse?) Whence countless groups of vegetation spring, And breathing realms of fin and feet and wing. "Nature, in producing in succession every species of animal, and The Temple of Nature (1802) beginning with the least perfect or simplest to end her work with the most perfect, has gradually complicated their structure." No real mechanism for this transformism ! At the base of this hierarchy, “simple” organisms constantly arise by spontaneous generation Jean-Baptiste Lamarck Thomas Malthus 1744 – 1829 AD 1766 – 1834 AD Principle of overproduction “Inheritance of acquired characters” • English clergyman • Major influence on Darwin & Wallace • An Essay on the Principle of Population (1797) Suggested a mechanism for this organic • Most organisms produce far more offspring than can possibly progression in Philosophie zoologique (1809): survive • First law: Use or disuse of a structure leads to its • Even when resources are development or diminishment plentiful, populations tend to grow geometrically until they • Second law: These acquired characters can be outstrip their food supply passed on to offspring • Poverty, disease, and famine are inevitable, leading to a “struggle for existence”. Charles Lyell Charles Lyell 1797 – 1875 AD 1797 – 1875 AD “Uniformitarianism” “Uniformitarianism” • English geologist Lyell applied his views to the living world. • His Principles of Geology was a major Initially he believed that some members of all classes of influence on Darwin & Wallace organisms existed throughout the history of the earth. • Believed earth is constantly changing What had changed was the abundance and location of • Processes that molded earth’s surface can be understood by species as well as the exact form of each species. modern-day events “[S]pecies have a real existence in nature, and that each • Uniformitarianism: earth is subject to gradual, was endowed, at the time of its creation, with the continuous change attributes and organization by which it is now • But without progress or development distinguished.” • Earth remains at a steady state Charles Darwin Charles Darwin 1809 – 1882 AD 1809 – 1882 AD The Voyage of the Beagle (1831–1836) The Man • An English “gentleman of private means” • Was able to focus on his life’s work: the development of the theory of evolution by natural selection • Read Lyell’s Principles of Geology while on board (and correctly applied the principle of uniformitarianism to the formation of coral reefs) • Developed an appreciation of biogeographical patterns Charles Darwin Charles Darwin 1809 – 1882 AD 1809 – 1882 AD Biogeography on the Beagle Biogeography on the Beagle • Noticed that two similar species often coexisted • Why do different groups of organisms live in in a “boundary zone” – neither one better areas separated by barriers (like the ocean)? adapted than the other • These species must compete with each other Why are the rhea and the ostrich so different, even though they have Rheas - a flightless South American bird similar lifestyles under Rhea americana (common rhea) similar circumstances? Pterocnemia pennata (Darwin’s rhea) Would a creator be limited by boundaries to migration? Charles Darwin Charles Darwin 1809 – 1882 AD 1809 – 1882 AD Biogeography on the Beagle Biogeography on the Beagle • Why do different groups of organisms live in • Why do different groups of organisms live in areas separated by barriers (like the ocean)? areas separated by barriers (like the ocean)? On the Galapagos Islands, Darwin was told that even islands that were very close together had giant tortoises that were distinct from one another Charles Darwin 1809 – 1882 AD "When I see these Islands in sight of each other, and possessed of but a scanty stock on animals, tenanted by these birds, but slightly differing in structure and filling the same place in Nature, I must suspect they are only varieties....If there is the slightest foundation for these remarks the zoology of Archipelagoes - will be well worth examining; for such facts would undermine the stability of Species." (1836) Dr. Robert Rothman Charles Darwin Charles Darwin 1809 – 1882 AD 1809 – 1882 AD Back in Britain: The origin of species The theory of natural selection • As natural selection acts on geographically • Darwin recognized several critical facts: isolated populations, they become • Variability exists within species increasingly different from each other • Variant traits may be inherited (Darwin didn’t know how) • Malthus’s Principle of Overproduction implies that many • This leads to the individuals must die or fail to reproduce formation of first • Individuals slightly better suited to their environment varieties within a must be more likely to survive species, then separate • Therefore, some variants will be preserved over time species, then genera, more than others. The composition of populations etc., in an ever- branching process. must change over time !Evolution by natural selection. Alfred R. Wallace 1823 – 1913 AD Evolution made public Natural selection co-discovered • English professional naturalist Charles Lyell and Joseph Hooker quickly arranged for • In 1858, sent a letter to Darwin Darwin's and Wallace's views to be co-presented at the describing his independent discovery of meetings of the Linnean Society in London in 1858. natural selection • Like Darwin, travelled around the world observing The next year, Darwin published The Origin of biodiversity and biogeography Species by Means of Natural Selection. The depth and breadth of Darwin's book, developed over twenty • Like Darwin, he’d read Lyell and Malthus, and years of thought and research, revolutionized science. eventually realized that “[the] self-acting process [of natural selection] would necessarily improve the race, because in every generation the inferior would inevitably be killed off and the superior would remain – that is, the fittest would survive.” Gregor Mendel Gregor Mendel 1822 – 1884 AD 1822 – 1884 AD Mendelian genetics Mendelian genetics • The greatest weakness of the theory of • The greatest weakness of the theory of natural selection was lack of knowledge natural selection was lack of knowledge of how inheritance worked of how inheritance worked • Mendel’s work (re-discovered in 1900 by Carl Correns & Hugo de Vries) clarified the • Mendel’s rules explain why laws of inheritance (at least for discrete offspring tend to resemble their traits like pea color) parents. • Show that variation is not lost over time due to reproduction alone • Still unclear whether these rules apply to continuously varying traits (height, weight, etc.) R. A. Fisher 1890 – 1962 AD Image credits Uniting Mendelian and quantitative Aristotle: www.columbia.edu/cu/philosophy/ admissions/text/process.html genetics Linnaeus: www.nhm.ac.uk/library/linn/ Buffon: www.ucmp.berkeley.edu/history/buffon2.html • In
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