2. AP Biology Lecture #39 Introduction to Evolution

3. Descent with Modification: A Darwinian View of Life

4. Evolution Evolution: the change over time of the genetic composition of populations Natural selection: populations of organisms can change over the generations if individuals having certain heritable traits leave more offspring than others (differential reproductive success) Evolutionary adaptations:a prevalence of inherited characteristics that enhance organisms’ survival and reproduction November 24, 1859

5. Life’s Natural History is a record of Successions & Extinctions Quaternary Tertiary Cretaceous Jurassic Triassic Permian Carboniferous Devonian Silurian Ordovician Cambrian Ediacaran Precambrian, Proterozoic, & Archarozoic Anaerobic Bacteria Insects Reptiles Dinosaurs Mammals Birds Land Plants Seed Plants Plants Arthropods Chordates Jawless Fish Teleost Fish Amphibians Photosynthetic Bacteria Green Algae Multicellular Animals Molluscs 1.5 4500 700 63 135 180 225 280 350 400 430 500 570 Flowering mya

6. Evolutionary history Linnaeus: taxonomy Hutton: gradualism Lamarck: evolution Malthus: populations Cuvier: paleontology Lyell: uniformitarianism Darwin: evolution Mendel: inheritance Wallace: evolution

7. Mid-Eighteenth-Century Contributions Carolus Linnaeus and Taxonomy a. Taxonomy is the science of classifying organisms;. b. Carolus Linnaeus (1707–1778) was a Swedish taxonomist. 1) Linnaeus developed a binomial system of nomenclature (two-part names for each species [e.g., Homo sapiens]).

8. 2) Like other taxonomists of his time, Linnaeus believed in the ideas of a) special creation—each species had an “ideal” structure and function; and b) fixity of species—each species had a place in the scala naturae, a sequential ladder of life.

9. 2. Georges Louis Leclerc a. Georges Louis Leclerc, known by his title, Count Buffon (1707-1788), was a French naturalist. b. He wrote on the natural history of all known plants and animals, provided evidence of descent with modification. c. His writings speculated on influences of the environment, migration, geographical isolation, and the struggle for existence. In the course of his examination of the animal world, Buffon noted that despite similar environments, different regions have distinct plants and animals, a concept later known as Buffon's Law, widely considered the first principle of biogeography.

10. 3. Erasmus Darwin a. Erasmus Darwin (1731-1802) was Charles Darwin's grandfather. b. He was a physician and a naturalist whose writings on both botany and zoology contained many comments that suggested the possibility of common descent.

11. c. He based his conclusions on 1) changes undergone by animals during development, 2) artificial selection by humans 3) the presence of vestigial organs Erasmus Darwin offered no mechanism by which evolutionary descent might occur.

12. Late Eighteenth-/Early-Nineteenth Century Contributions 1. Cuvier and Catastrophism a. George Cuvier (1769-1832), a French vertebrate zoologist, was the first to use comparative anatomy to develop a system of classifying animals. b. He founded the science of paleontology-the study of fossils- and suggested that a single fossil bone was all he needed to deduce the entire anatomy of an animal.

13. c. To explain the fossil record, Cuvier proposed that a whole series of catastrophes (extinctions) and repopulations from other regions had occurred. d. Catastrophism is the term applied to Cuvier's explanation of fossil history: the belief that catastrophic extinctions occurred, after which repopulation of surviving species occurred, giving an appearance of change through time.

14. 2. Lamarck's Acquired Characteristics a. Lamarck (1744-1829) was the first to state that descent with modification occurs and that organisms become adapted to their environments. b. Lamarck, an invertebrate zoologist, held ideas at odds with Cuvier's. c. Lamarck mistakenly saw "a desire for perfection" as inherent in all living things.

15. d. Inheritance of acquired characteristics was Lamarck's belief that organisms become adapted to their environment during their lifetime and pass these adaptations to their offspring. e. Experiments fail to uphold Lamarck's inheritance of acquired characteristics How could you test Lamarck's theory?

16. What We Know So Far 1. Taxonomy and classification emphasize similarities among species (common descent) 2. Fossils show extinct species (paleontology) 3. Isolated species are distinct (biogeography) 4. Organisms have adaptations to help them survive *At this point, no mechanism has been proposed to explain how these adaptations come to be * Special creation is still strongly held, but offers no explanation for the appearance of new species (like on an island)........................Enter Charles Darwin............................

17. Charles Darwin 1809-1882 British naturalist Proposed the idea of evolution by natural selection Collected clear evidence to support his ideas

18. Voyage of the HMS Beagle Invited to travel around the world – 1831-1836 (22 years old!) – makes many observations of nature main mission of the Beagle was to chart South American coastline Stopped in Galapagos Islands 500 miles off coast of Ecuador

19. Darwin found… birds Finch?Sparrow? Woodpecker?Warbler? Collected many different birds on the Galapagos Islands. Thought he found very different kinds…

20. Darwin was amazed to find out: All 14 species of birds were finches… Sparrow? Woodpecker? Warbler? But Darwin found… a lot of finches Large Ground Finch Small Ground Finch Warbler FinchVeg. Tree Finch But there is only one species of finch on the mainland! How did one species of finches become so many different species now?

21. Warbler finch Woodpecker finch Small insectivorous tree finch Large insectivorous tree finch Vegetarian tree finch Cactus finch Sharp-beaked finch Small ground finch Medium ground finch Large ground finch Insect eaters Bud eater Seed eaters Cactus eater Warbler finch Tree finches Ground finches Darwin’s finches Differences in beaks – associated with eating different foods – survival & reproduction of beneficial adaptations to foods available on islands

22. Darwin’s finches Darwin’s conclusions – small populations of original South American finches landed on islands variation in beaks enabled individuals to gather food successfully in the different environments – over many generations, the populations of finches changed anatomically & behaviorally accumulation of advantageous traits in population emergence of different species

23. Seeing this gradation & diversity of structure in one small, intimately related group of birds, one might really fancy that from an original paucity of birds in this archipelago, one species has been taken & modified for different ends.

24. Differences in beaks allowed some finches to… – successfully compete – successfully feed – successfully reproduce pass successful traits onto their offspring Darwin’s finches

25. Correlation of species to food source Whoa, Turtles, too! More observations…

26. Essence of Darwin’s ideas Natural selection – variation exists in populations – over-production of offspring more offspring than the environment can support – competition for food, mates, nesting sites, escape predators – differential survival successful traits = adaptations – differential reproduction adaptations become more common in population adaptations become more common in population