Evolution: Evidence of Change & How Change Occurs Evolution - Change over time - Process where modern organisms have descended from ancestors with modifications Early Evolutionary Ideas 1.Lamarck - among the first to explain how organisms change over time - later disproved Lamarck - relied on 2 assumptions: 1.Use and disuse 2.Inheritance of acquired traits - both later disproved 2. Charles Darwin (1809-1882) - developed the theory of evolution by natural selection - traveled around the world as a naturalist (1831-1836) Galapagos wildlife Darwin’s Finches & their food Large seeds Small seeds Insects Leaves Evolution by Natural Selection - Natural Selection is the result of 3 natural processes: 1. Natural Variation: - all organisms produced sexually are genetically different due to gene recombination and mutations Variation in Human Height 2. Adaptation This natural variation or mutation may be an adaptation that helps them outcompete others to survive and reproduce. 2. Competition - resources (food, space, water) mates constant struggle for existence winners reproduce Gazelles struggling to reach food. Male caribou competing for mates. .Natural Selection or survival of the fittest - Those best suited will survive longer and reproduce. - Those not suited will not survive or reproduce as often. 3. Heredity - Those that survive will pass on the very traits that helped it survive. Woodpecker Artificial Selection - similar to natural selection - domestic crops and animals vary a lot Artificial Selection Artificial Selection - only the best animals or plants are allowed to produce offspring Artificial Selection Recent Examples of Evolution 1. Peppered Moths a.Before industrial revolution, most moths were grayish and well camouflaged. b. During the industrial revolution, soot stained the bark black. - Rarer dark moths were then better camouflaged. - The more common light moths were easily seen and eaten. c.Dark moths had greater fitness and became more common. 2.Resistant Diseases & Pests a. Increased resistance to antibiotic by bacteria b. Insects have become more resistant to pesticides Resistant Pests C. Speciation - development of one species from another species C. Speciation Kaibab Squirrel Abert Squirrel 1. Process of Speciation a. Separation of original population by a geographic barrier b. Changed environment c. Gene pool changes d. Reproductive isolation - two populations can no longer interbreed e. New species arises (a) Single species; Same habitat (b) Speciation Geographical barrier; isolated populations (c) Genetic drift; tan vs white mice Barrier removed; mix but don’t interbreed (d) 2. Divergent Evolution (Adaptive Radiation) - ancestral population evolves into several different species 2. Adaptive Radiation Hawaiian Honeycreepers 2. Adaptive Radiation 3. Convergent Evolution - different organisms evolve similar adaptations to survive in similar niches - develop analogous structures (similar function with different underlying anatomy) 3. Convergent Evolution 3. Convergent Evolution European Hare (lagamorph)) Patagonian “Hare” (rodent) Banded Wallaby (marsupial) 3. Convergent Evolution Tasmanian “Wolf” Coyote Placentals Marsupials Tasmanian “Wolf” Wolf Ocelot Anteater Flying Squirrel Quoll Numbat Flying Phalanger Marmot Wombat 3. Convergent Evolution American Cactus African Euphorb D.Evolutionary Theory Evolves 1. Genetic Drift - random changes in allele frequency produce new traits D.Evolutionary Theory Evolves 1. Genetic Drift Masai Giraffe Rothschild Giraffe Reticulated Giraffe D.Evolutionary Theory Evolves 2. Unchanged Gene Pools - "living fossils": sharks, horseshoe crabs, coelacanth Chambered Nautilus Coelacanth Horseshoe Crab 3. Gradualism: - slow change over time 4.Punctuated Equilibrium - periods of little change, followed by abrupt change Gradualism Punctuated Equilibrium