Evidence of Evolutionby Natural Selection (Ch. 22) Dodo bird
Evidence supporting evolution • Fossil record • Anatomical record • Molecular record • Artificial selection
Fossil record • Layers of sedimentary rock contain fossils • new layers cover older ones, creating a record over time • Show that a succession of organisms have populated Earth throughout a long period of time
1 Rivers carry sediment to the ocean. Sedimentary rock layers containing fossils form on the ocean floor. 3 As sea levels change and the seafloor is pushed upward, sedimentary rocks are exposed. Erosion reveals strata and fossils. 2 Over time, new strata are deposited, containing fossils from each time period. Younger stratum with more recent fossils Older stratum with older fossils Formation of sedimentary strata containing fossils
(c) Leaf fossil, about 40 million years old (b) Petrified tree in Arizona, about 190 million years old (a) Dinosaur bones being excavated from sandstone (d) Casts of ammonites, about 375 million years old (f) Insects preserved whole in amber (e) Boy standing in a 150-million-year-old dinosaur track in Colorado (g) Tusks of a 23,000-year-old mammoth, frozen whole in Siberian ice A gallery of fossil types
Evolutionary change in horses 550 500 450 Equus 400 350 Body size (kg) 300 250 Merychippus 200 Mesohippus 150 Hyracotherium 100 50 Nannippus 60 55 50 45 40 35 30 25 20 15 10 5 0 Millions of years ago
Evolution of birds • Archaeopteryx • lived about 150 mya • links reptiles & birds Smithsonian Museum, Washington, DC
? ? ? ? Whales, you ask... Land Mammal Where are thetransitional fossils?
A transitional fossil linking past and present Oh. Here they Are!
2006 Fossil Discovery of Early Tetrapod • Tiktaalik • “missing link” from sea to land animals
Anatomical record • Homologous structures • similarities in characteristics resulting from common ancestry
Homologous structures • Similar structure • Similar development • Different functions • Evidence of close evolutionary relationship • recent common ancestor
Homologous structures spines leaves succulent leaves tendrils needles colored leaves
Analogous structures • Separate evolution of structures • similar functions • similar external form • different internal structure & development • different origin • no evolutionary relationship Don’t be fooledby their looks! Solving a similar problem with a similar solution
Convergent evolution • Flight evolved in 3 separate animal groups • analogous structures Does this mean they have a recent common ancestor?
Convergent evolution • Fish: aquatic vertebrates • Dolphins: aquatic mammals • similar adaptations to life in the sea • not closely related Those fins & tails & sleek bodies areanalogous structures!
Parallel Evolution • Convergent evolution in common niches • Similar ecological roles in similar environments, Similar adaptations were selected • but are not closely related marsupial mammals placental mammals
Niche Placental Mammals Australian Marsupials Burrower Marsupial mole Mole Anteater Numbat Anteater Nocturnal insectivore Marsupial mouse Mouse Climber Spotted cuscus Lemur Sugar glider Glider Flying squirrel Stalking predator Tasmanian cat Ocelot Chasing predator Wolf Tasmanian “wolf” Parallel types across continents
Vestigial organs • Structures that serve little or no function • remnants of structures that were functional in ancestral species • deleterious mutations accumulate in genes for non-critical structures without reducing fitness • snakes & whales — remains of pelvis & leg bones of walking ancestors • eyes on blind cave fish • human tail bone This is notLaMarck’s loss from “disuse”!
Vestigial organs • Hind leg bones on whale fossils Why would whaleshave pelvis & leg bonesif they were alwayssea creatures?
Comparative embryology • Similar embryological development in closely related species • all vertebrate embryos have similar structures at different stages of development • gill pouch in fish, frog, snake, birds, human, etc.
Pharyngeal pouches Post-anal tail Chick embryo Human embryo Anatomical similarities in vertebrate embryos
Human/kangaroo 100 Human/ cow Dog/ cow 75 Rabbit/ rodent Human/rodent 50 Llama/ cow Horse/ donkey Nucleotide substitutions Horse/cow Sheep/ goat Pig/ cow 25 Goat/cow 0 0 25 50 75 100 125 Millions of years ago Molecular record • Comparing DNA & protein structure • universal genetic code! • DNA & RNA • compare common genes • cytochrome C (respiration) • hemoglobin (gas exchange) Why comparethese genes? Closely related species have sequences that are more similar than distantly related species • A molecular record of evolutionary relationships
Percent of Amino Acids That Are Identical to the Amino Acids in a Human Hemoglobin Polypeptide Species 100% Human Rhesus monkey 95% Mouse 87% Chicken 69% Frog 54% 14% Lamprey Comparison of a protein found in diverse vertebrates
Comparative hemoglobin structure Dog Human Macaque Bird Frog Lamprey Why does comparingamino acid sequencemeasure evolutionaryrelationships? 8 32 45 125 67 0 10 20 30 40 50 60 70 80 90 100 110 120 Number of amino acid differences between hemoglobin (146 aa) of vertebrate species and that of humans
Building “family” trees Closely related species (branches) share same line of descent until their divergence from a common ancestor
Artificial selection • Artificial breeding can use variations in populations to create vastly different “breeds” & “varieties” “descendants” of wild mustard “descendants” of the wolf
It’s Important To Remember How Powerful And Fast Selection Can Be!!!
Natural selection in action • Insecticide & drug resistance • insecticide doesn’t kill all individuals • resistant survivors reproduce • resistance is inherited • insecticide becomes less & less effective
Patient No. 1 Patient No. 2 Percent of HIV resistant to 3TC Patient No. 3 Weeks Evolution of drug resistance in HIV
Evolution Misconceptions A Brief Discussion
“if we came from apes how come were not hairy and have a big mouth and did we end up looking like we do know and besides there isnt any serious proof of apes they showd a video saying an ape waswondering around in the forest that thing looked exactly like a costume that i had saw at a store know one ever cought an ape” -From a post on the Internet NOT THIS KIND!!! (beyond help)
Don’t Get Lazy! This Isn’t How It Happens!!!
Evolution is not goal-oriented An evolutionary trend does not mean that evolution is goal-oriented. Surviving species do not represent the peak of perfection. There is compromise & random chance involved as well Remember that for humans as well! Evolution is not the survival of the fittest. Rather it is the survival of the just good enough.
Unintelligent Design Serial circulation in the mammalian heart
"Nothing in biology makes sense except in the light of evolution." -- Theodosius DobzhanskyMarch 1973 Geneticist, Columbia University (1900-1975)
Evolution is "so overwhelmingly established that it has become irrational to call it a theory." -- Ernst MayrWhat Evolution Is2001 Professor Emeritus, Evolutionary Biology Harvard University (1904-2005)
I might be dead, but Perhaps you children would appreciate a bit of what you call the “rap” music?!?
Don’t Be Unintelligent... Ask Questions!!
Evidence of Evolutionby Natural Selection Testable Hypotheses (Ch. 22- 24)
Just Because Things Seem Obvious Doesn’t Mean They Don’t Need To Be Supported
Peppered Moths • Dark vs. light variants Year% dark% light 1848595 1895982 19951981
Peppered moth • What was the selection factor? • early 1800s = pre-industrial England • low pollution • lichen growing on trees = light colored bark • late 1800s = industrial England • factories = soot coated trees • killed lichen = dark colored bark • mid 1900s = pollution controls • clean air laws • return of lichen = light colored bark • industrial melanism
Genome sequencing • What can whole genome sequence data tell us about evolution of humans?