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Unlocking the Mystery: Evolution Evolution provides a unifying theory for the diversity of life and similarities between the species. Table of Contents What is evolution? • Definition How does evolution occur? • Mechanisms • Evidence • Patterns – – – – Fossils Anatomy Embryology Biochemical • Phylogeny What is evolution? Descent with Modification From a Common Ancestor So, what exactly is modified? A CHANGE OVER TIME? Is this evolution? What must change? A CHANGE IN INHERITED TRAITS So Evolution is… A change in genetics NOT physical appearance! For Example… Is this evolution? • Oh, no 2 generation drought Is this evolution? • Food source diminishing • Several generations later… • New generation beetles weigh less • Why? • 90% green beetles • 70% brown • Why? To Elaborate… • 1st scenario – Next generation not genetically different – Weight depends on amount of food • 2nd scenario – Next generation genetically different – Color depends on genetics Which is the best definition of evolution? A. A change in a species over time B. A change in physical appearance of a species C. A change in an organism’s genetics D. A change in a population’s genetics Remember Evolution is… A change in genetics How do we know it happens? So where’s the evidence • Life has existed for billions of years • Life has changed • Where is all the evidence? Evidence from: • Fossils • Embryology • Anatomy • Biochemical Fossil Evidence • Shows transitional forms Anatomy: Homologous Structures Similar structures show common ancestry View more examples or Fish out of Water Anatomy: Analogous Structures Different ancestry but similar structure and function View more examples Anatomy: Vestigial structures Remnants of ancestral structures that are no longer used Here are some more examples We are modified versions of our ancestors We inherited their characteristics Which structure(s) is best represented in the image? A. Analogous B. Embryonic C. Homologous D. Vestigial Which structure(s) provides the weakest evidence for common ancestry? A. Analogous C. Homologous B. Embryonic D. Vestigial The human appendix is best identified as which of these structures? A. Analogous C. Homologous B. Embryonic D. Vestigial Embryology • Similarities in development • Same genes produce different structures Biochemical • DNA links all life to a common ancestor • Compare DNA (or protein) sequences to find relatedness – More similar = more related – More differences = less related Mapping Ancestry: Phylogenies How do we read this? New Species 2 species from 1 Last common ancestor Keeps Going and Going… 1.Evolution produces a pattern of relationships A B C D among lineages that is tree-like, not ladder-like. Keep in mind… • Evolution produces a pattern of relationships A B C D among lineages that is tree-like, not ladder-like. Keep in mind… • Just because we tend to read phylogenies from left to right, there is no correlation with level of “ advancement.” Keep in mind… Keep in mind… • Humans experienced same history • Humans did not evolve from chimpanzees – We have a common ancestor – We are related to not evolved from!!! Birds are Dinosaurs Phylogenies are visuals of the relatedness of species How does it happen? Could this work? How about this? Descent with Modification • Inherit traits from parents • Provides genetic variation in a population • Some variations survive and reproduce • Change in gene frequency within a population over time!! Giraffe Necks • General increase in long neck gene over time! One idea: Inheritance of Acquired Characteristics Inheritance of Acquired Characteristics • Giraffe keeps stretching neck • It gets longer • Passed on to new generation • What if we cut off a mouse tail? Comparing Ideas Genetic Variation is a MUST! Sources of variation Mutation – A change in DNA sequence Sources of Variation Gene Flow – Genes move from one population to another – Aka migration Sources of Variation 1. Sexual reproduction – Creates new gene combinations – Genetic shuffling Recap: Sources • Mutation – DNA is altered • Gene Flow or migration – Introduction of new source of genes • Sexual Reproduction – New combinations Genetic Drift • “Lucky” individuals survive and reproduce • No selection- just random events Natural Selection • Genetic variation in population • Variation is inherited • More fit variations survive • Reproduce What is ? Survival of the fittest • Fit = ability for genotype to survive and reproduce • Depends on environment!!! Adaptations • Common feature that provides improved function • Anatomical • Behavioral • Biochemical or physiological – Better protein Coevolution • Two species affect each other’s evolution • Why does this moth have such a long tongue? Coevolution • It gets its food from here! Patterns of Evolution How fast does it occur? Gradualism Gradualism • Transitional forms in fossil record • Evidence of gradual change Punctuated Equilibrium • Big changes, short time • Few to no transitions Punctuated Equilibrium Little evolution occurring Punctuated Equilibrium Oh no, the water is gong down!!! Reproductive isolation Punctuated Equilibrium Strong selection & rapid change Punctuated Equilibrium Long time, no see… Punctuated Equilibrium I win! Punctuated Equilibrium No record of change is preserved! Does No Transitions Mean Fast Evolution? 3 Explanations for same data! Diversity • Why do some lineages lead to millions when others only lead to a few? Opportunity Knocks • Environment presents opportunities • Lineage takes advantage Adaptive Radiation • One species gives rise to many? • But how? Adaptive Radiation • Organisms exploit a new niche or resource • Specialization 1. Species A migrates from the mainland to the first island. 2. Isolated from the mainland, species A evolves to species B. Species B migrates to the second island. 3. 4. 5. 6. Species B evolves in species C. Species C recolonizes the first islands, but is now unable to reproduce with species B. Species C migrates to the third island. 7. 8. Species C evolves into species D. Species D migrates to the first and second island. 9. Species D evolves to species E. 1. Species A migrates from the mainland to the first island. 2. Isolated from the mainland, species A evolves to species B. Species B migrates to the second island. 3. 4. 5. 6. Species B evolves in species C. Species C recolonizes the first islands, but is now unable to reproduce with species B. Species C migrates to the third island. 7. 8. Species C evolves into species D. Species D migrates to the first and second island. 9. Species D evolves to species E. 1. Species A migrates from the mainland to the first island. 2. Isolated from the mainland, species A evolves to species B. Species B migrates to the second island. 3. 4. 5. 6. Species B evolves in species C. Species C recolonizes the first islands, but is now unable to reproduce with species B. Species C migrates to the third island. 7. 8. Species C evolves into species D. Species D migrates to the first and second island. 9. Species D evolves to species E. 1. Species A migrates from the mainland to the first island. 2. Isolated from the mainland, species A evolves to species B. Species B migrates to the second island. 3. 4. 5. 6. Species B evolves in species C. Species C recolonizes the first islands, but is now unable to reproduce with species B. Species C migrates to the third island. 7. 8. Species C evolves into species D. Species D migrates to the first and second island. 9. Species D evolves to species E. 1. Species A migrates from the mainland to the first island. 2. Isolated from the mainland, species A evolves to species B. Species B migrates to the second island. 3. 4. 5. 6. Species B evolves in species C. Species C recolonizes the first islands, but is now unable to reproduce with species B. Species C migrates to the third island. 7. 8. Species C evolves into species D. Species D migrates to the first and second island. 9. Species D evolves to species E. The Galapagos Islands The Finches Specialization Types of Selection Directional • One extreme is selected for – SURVIVE AND REPRODUCE • Produces a change in genetics Stabilizing • Average is selected for – SURVIVE AND REPRODUCE • Produces a change in genetics Disruptive • Both extremes selected for – SURVIVE AND REPRODUCE • Produces a change in genetics There is no end product!