Evidence of Evolution by Natural Selection

AP Biology Evidence supporting evolution
Fossil record  Evidence of Evolution by Natural Selection transition species
Anatomical record   homologous & vestigial structures embryology & development
Molecular record  protein & DNA sequence
Artificial selection  AP Biology 2007-2008 Dodo bird Fossil record human-caused evolution AP Biology Fossil Record
Layers of sedimentary rock contain fossils new layers cover older ones, creating a record over time  fossils within layers show that a succession of organisms have populated Earth throughout a long period of time  AP Biology Fossil record AP Biology Evolutionary change in horses
A record showing us that today’s organisms 550 descended from ancestral species 500 Body size (kg) 450 Equus 400 350 300 250 Merychippus 200 150 Mesohippus Hyracotherium 100 50 AP Biology AP Biology Nannippus 60 55 50 45 40 35 30 25 20 15 10 5 0 Millions of years ago 1 AP Biology Evolution of birds
Archaeopteryx Land Mammal ? lived about 150 mya links reptiles & birds   ? ? ? Smithsonian Museum, AP Biology Washington, DC 2006 Fossil Discovery of Early Tetrapod
Tiktaalik  “missing link” from sea to land animals AP Biology Anatomical record
Homologous structures  similarities in characteristics resulting from common ancestry AP Biology Homologous structures
Similar structure
Similar development
Different functions
Evidence of close evolutionary relationship  AP Biology recent common ancestor Homologous structures leaves succulent leaves needles AP Biology spines tendrils AP Biology colored leaves 2 AP Biology Analogous structures Convergent evolution
Flight evolved in 3 separate animal groups
Separate evolution of structures similar functions similar external form  different internal structure & development  different origin  no evolutionary relationship     evolved similar “solution” to similar “problems” analogous structures Does this mean they have a recent common ancestor? Don’t be fooled by their looks! Solving a similar problem with a similar solution AP Biology Convergent evolution
Fish: aquatic vertebrates
Dolphins: aquatic mammals AP Biology Parallel Evolution
Convergent evolution in common niches  similar adaptations to life in the sea  not closely related   filling similar ecological roles in similar environments, so similar adaptations were selected but are not closely related marsupial mammals placental mammals Those fins & tails & sleek bodies are analogous structures! AP Biology AP Biology Parallel types across continents Niche Burrower Placental Mammals Mole Vestigial organs
Modern animals may have structures that Australian Marsupials Marsupial mole serve little or no function  Anteater Anteater Nocturnal insectivore Numbat  Mouse Climber Marsupial mouse
snakes & whales — remains of pelvis & leg bones of walking ancestors Spotted cuscus Lemur Glider Stalking predator AP Biology Chasing predator Flying squirrel Ocelot Wolf remnants of structures that were functional in ancestral species deleterious mutations accumulate in genes for non-critical structures without reducing fitness
eyes on blind cave fish Sugar glider
human tail bone Tasmanian cat Tasmanian “wolf” AP Biology This is not LaMarck’s loss from “disuse”! 3 AP Biology Vestigial organs
Hind leg bones on whale fossils Comparative embryology
Similar embryological development in closely related species  Why would whales have pelvis & leg bones if they were always sea creatures?
gill pouch in fish, frog, snake, birds, human, etc. AP Biology AP Biology Comparative hemoglobin structure Molecular record
Comparing DNA & protein structure  universal genetic code! Human Macaque Why compare these genes?
DNA & RNA  all vertebrate embryos have similar structures at different stages of development compare common genes
cytochrome C (respiration)
hemoglobin (gas exchange) Human/kangaroo
DNA & proteins are a molecular record of evolutionary relationships Nucleotide substitutions 100 Closely related species have sequences that are more similar than distantly related species Dog/ cow 75 Human/ cow 8 0 25 32 45 67 125 Human/rodent Pig/ cow 0 10 20 30 40 50 60 70 80 90 100 110 120 Goat/cow 0 Lamprey Horse/cow Sheep/ goat 25 AP Biology Llama/ cow Frog Why does comparing amino acid sequence measure evolutionary relationships? Rabbit/ rodent 50 Horse/ donkey Dog Bird 50 75 100 Millions of years ago 125 Building “family” trees Closely related species (branches) share same line of descent until their divergence from a common ancestor AP Biology Number of amino acid differences between hemoglobin (146 aa) of vertebrate species and that of humans Artificial selection
Artificial breeding can use variations in populations to create vastly different “breeds” & “varieties” “descendants” of wild mustard AP Biology AP Biology “descendants” of the wolf 4 AP Biology Natural selection in action
Insecticide & drug resistance insecticide didn’t kill all individuals  resistant survivors reproduce  resistance is inherited  insecticide becomes less & less effective  "Nothing in biology makes sense except in the light of evolution." -- Theodosius Dobzhansky March 1973 Geneticist, Columbia University (1900-1975) AP Biology AP Biology 2007-2008 Don’t be a Dodo… Evolution is "so overwhelmingly established that it has become irrational to call it a theory." Ask Questions!! -- Ernst Mayr What Evolution Is 2001 Professor Emeritus, Evolutionary Biology Harvard University (1904-2005) AP Biology AP Biology 2007-2008 5