Evolution • Review Video Handout • Review Lamarck, Wallace, & Darwin • Evidence for evolution – Assignment: Finish personal part of writing assignment – Assignment: read ch 16.4/ 5.1 • • • • Fossils Anatomy Selective breeding Genetics What is Evolution? • Descent with Modification The central idea of biological evolution is that all life on Earth shares a common ancestor, just as you and your cousins share a common grandmother. Through the process of descent with modification, the common ancestor of life on Earth gave rise to the fantastic diversity that we see documented in the fossil record and around us today. Evolution .means that we're all distant cousins: humans and oak trees, hummingbirds and whales. . Evolution is NOT Evolution is NOT • “just a theory” – Theory in science is a well substantiated explanation for some aspect of the natural world – We don’t “believe” in evolution. It isn’t a religion. We accept the theory. Where did evolution come from? • Aristotle to the 1300s – Chain of being – “Lowest” to “highest” – All species were formed at the same time and had not changed since creation • Europeans began traveling and cataloging species What did they notice • Biogeography: distribution of species and communities • Comparative Morphology • Fossils • By the 1800s people wanted to reconcile these observations with the beliefs about species Biogeography Ostrich –Africa America Emu – Australia Rhea- South All live in similar habitat, are flightless, but in varied global locations – why are they so much alike? Theories of Evolution • Lamarck • Wallace • Darwin • Review the work of these scientists and makes sure you can answer the questions Theories of Evolution • Lamarck – Noticed change over times – Focused on use and disuse • Wallace & Darwin – Focus on heritable traits that aid in survival (aka adaptations) Darwin Wallace Theory of evolution by natural selection • • • • Variation Differential survival Overproduction of offspring Change in populations over time Evolution Evidence – Fossil Record – Selective Breeding – Comparative anatomy • Homologous structures • Vestigial structures • Analogous structures – Continuous variation • Speciation • Adaptive radiation – Genetics Fossil Record • Record of the past • Evidence of similarity between ancient and modern organisms • Transitional forms Fossil Record • Sequence of fossils matches our expectations • Sequence fits with ecology • Links exist Continuous variation Fossil record Evolution of Horse Feet “diagram clearly show transitional stages whereby the four-toed foot of Hyracotherium, otherwise known as Eohippus, became the single-toed foot of Equus. Fossils show that the transitional forms predicted by evolution did indeed exist.” http://evolution.berkeley.edu/evolibr ary/article/0_0_0/lines_03’ Selective breeding • A type of artificial selection – Dogs – Horses – crops - Crops Comparative Anatomy – By Darwin’s time scientists noticed similarity in animal limbs – For example, the front limbs of amphibians, reptiles, birds, and mammals contain the same basic bones. – Homologous bones, as shown by color-coding, support the differently-shaped front limbs of modern vertebrates. Homologous and Analogous Homologous structures in plants Vestigial Structures • Reduced in form or use over time • Dew claws are remains of ancestor with a greater number of claws – Why would an organism possess structures with little or no function? • One possibility is that the presence of a vestigial structure does not affect an organism’s fitness. In that case, natural selection would not eliminate it. Continuous variation Adaptive Radiation • Darwin’ Finches were distributed through out the Galapagos Islands • The wide variety deserved consideration • http://media.hhmi.org/biointeractiv e/click/finch/?_ga=2.125379913.25 4304679.1519135035909766618.1516123191 • Homologous – similar in structure but not necessarily the same use • Adaptive radiation – one ancestor showing variation in new species in a region • Similarities in organisms extend beyond bones – Similar biochemicals – Similar DNA – genes Life’s Common Genetic Code – The genetic code is nearly identical in almost all organisms, including bacteria, yeasts, plants, fungi, and animals. – This compares a small portion of the DNA for the same gene in three animals—a mouse, a whale, and a chicken. Homologous Genes – At least some homologous Hox genes are found in almost all multicellular animals, from fruit flies to humans. – For example, bacteria that live in a hot spring are very different from animals, yet many of their genes, and therefore the proteins coded by those genes, are similar to those of animals. – Such profound biochemical similarities are best explained by Darwin’s conclusion: Living organisms evolved through descent with modification from a common ancestor. Homologous Proteins – Today, we know that homology is not limited to physical structures. – Homologous proteins share extensive structural and chemical similarities. – One homologous protein is cytochrome c, which functions in cellular respiration. Remarkably similar versions of cytochrome c are found in almost all living cells, from cells in baker’s yeast to cells in humans. Natural Selection Survival of the fittest • Fitness = ability to survive and reproduce • http://evolution.berkeley.edu/evolibrary/article/ev o_25 • There is variation – Not all organisms are the same • There is differential reproduction – Not all organisms get to reproduce as much as others • There is heredity – Those that survive and reproduce pass on their traits Darwin Wallace Theory of evolution by natural selection • Populations show variation – Mutation – Meiosis – the genes passed on – Sexual reproduction – new combinations • Inherited variation matters Mutation – RANDOM changes to the DNA that may or may not change fitness – Mutations must be heritable to impact evolution • http://evolution.berkeley.edu/evolibrary/article/0_0_0/evo_20 Meiosis & Sexual Reproduction • Production cells for sexual reproduction • Copies of genes split into different cells • In reproduction new combinations are produced. Darwin Wallace Theory of evolution by natural selection • More individuals are produced than survive – Differential survival • Progressive change – Those best fit to the environment survive, reproduce, and pass down traits to offspring. – Fitness means surviving and reproducing The result of natural selection is evolution • Over time populations change Hummingbird selection – https://www.youtube.com/watch?v=KDPLig4l MFo Pepper moth simulation – http://peppermoths.weebly.com/ Natural Selection we can observe Continuous variation • England Pepper Moth • Bacteria and antibiotic • Sparrows in the US Adaptation • A trait that leads to increased fitness is an adaptation • Adaptations are successful variations Genetics and Evolution • Genetics is the part of heredity Darwin didn’t know about • We can describe al the gene in a population as a GENE POOL – Some genes in the pool will be more like to bring about breeding success – Different forms of gene are called ALLELES Evolutionary change means a change in the frequency of alleles in a gene pool • B = brown gene • b = green gene • Start at 50% each but predation could change so 75% B 25% b Sickle Cell Anemia • 280 million hemoglobin molecules in each red blood cell, each made up of 2 ά and 2 β • Sickle cell caused by a point mutation in β • RBC change shape and adhere to each other • Sickled cells get stuck in narrow blood vessels • Causes painful crisis and can lead to stroke, blindness and organ failure Alleles A and S • A = normal β S = Sickled β • Everyone get two alleles – AA = normal cells – SS = Sickled cells – AS = Make both types of cells • Usually healthy • carriers Sickle Cell and Malaria • There are 5 times more cases of sickle cell anemia in Africa then in African-American • The difference is malaria • AS do not die as frequently from malaria • The frequency of the S allele in malariainfected regions of Africa is 16% • the S allele frequency is only 4% in the United States, where malaria has been virtually eliminated
