Evidence for Evolution by Natural Selection Raven Chapters 1 & 22 2006-2007
Science happens within a culture What was the doctrine of the time? TINTORETTO The Creation of the Animals 1550
Then along comes Darwin 1831-1836 22 years old!
Then along comes Darwin Descendant species & those dang finches! Ancestral species Woodpecker finch Small insectivorous tree finch Warbler finch Cactus finch Sharp-beaked finch Small ground finch Large insectivorous tree finch Vegetarian AP tree Biology finch Insect eaters Bud eater Cactus eater Seed eaters Medium ground finch Large ground finch
Darwin s finches Differences in beaks allowed some finches to successfully compete successfully feed successfully reproduce pass successful traits onto their offspring
In historical context Other people s ideas paved the path for Darwin s thinking competition: struggle for survival population growth exceeds food supply land masses change over immeasurable time
Voyage: 1831-1836 November 24, 1859, Darwin published On the Origin of Species by Means of Natural Selection
Correlation of species to food source Seed eaters Flower eaters Insect eaters Rapid speciation: new species filling niches, because they inherited successful adaptations. Adaptive radiation
Beak variation in Galapagos finches (a) Cactus eater. The long, sharp beak of the cactus ground finch (Geospiza scandens) helps it tear and eat cactus flowers and pulp. (c) Seed eater. The large ground finch (Geospiza magnirostris) has a large beak adapted for cracking seeds that fall from plants to the ground. (b) Insect eater. The green warbler finch (Certhidea olivacea) uses its narrow, pointed beak to grasp insects.
Glyptodont fossils Modern armadillos Sloth fossils Modern sloth Why should extinct species & living species be found on the same continent?
Essence of Darwin s ideas Natural selection heritable variation exists in populations over-production of offspring more offspring than the environment can support competition for food, mates, nesting sites, escape predators differential survival successful traits = adaptations differential reproduction adaptations become more common in population
Where does Variation come from? Mutation random changes to DNA errors in mitosis & meiosis environmental damage Sexual reproduction mixing of alleles genetic recombination new arrangements of alleles in every offspring new combinations = new phenotypes
LaMarckian vs. Darwinian view LaMarck in reaching higher vegetation giraffes stretch their necks & transmits the acquired longer neck to offspring Darwin giraffes born with longer necks survive better & leave more offspring who inherit their long necks
Big Idea 1 The process of evolution drives the diversity and unity of life cells DNA
What are the 4 lines of evidence that support Darwin s ideas? Human Macaque DogBird Frog Lamprey 8 32 45 67 125 0 10 20 30 40 50 60 70 80 90 100 110 120
1. What are the lines of evidence that support Darwin s ideas? Fossil record 550 500 Body size (kg) 450 400 350 300 250 200 150 100 Mesohippus Hyracotherium Merychippus Equus 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
Evolution of land animals 2006 Fossil Discovery of Early Tetrapod Tiktaalik missing link from sea to land animals from swimming (0 legs) to walking (4 legs)
Evolution of marine mammals But then, they actually found my fossil! Land Mammal???? At first, I was just a joke! Aquatic Mammal
2. What are the lines of evidence that support Darwin s ideas? Cabbage Artificial selection Terminal bud Lateral buds Brussels sprouts Flower cluster Leaves Kale Cauliflower Stem Flower and stems Broccoli Wild mustard Kohlrabi
Selective breeding the raw genetic material (variation) is hidden there
Natural selection in action Resistance NOT immunity! MRSA
3. What are the lines of evidence that support Darwin s ideas? Anatomical evidence
Homologous structures spines leaves succulent leaves Don t forget our plant friends! needles tendrils colored leaves
Analogous structures Convergent Don t be fooled by evolution their looks! Those tails Does fins this & mean & sleek they bodies have a are recent common ancestor? analogous structures! Solving a similar problem with a similar solution
Convergent evolution marsupial mammals These animals look very similar but does that mean they have a recent common ancestor? What is this evidence of? placental mammals
Parallel/convergent evolution Niche Placental Mammals Australian Marsupials Burrower Mole Convergent evolution of analogous Marsupial mole burrowing characteristics Anteater Anteater Numbat Nocturnal insectivore Mouse Marsupial mouse Climber Spotted cuscus Lemur Glider Flying squirrel Sugar glider Stalking predator Ocelot Tasmanian cat Chasing predator Wolf Tasmanian wolf
Vestigial organs These are Why would whales remnants of have pelvis & leg bones if they were always functional in sea creatures? structures that were ancestral species
4. What are the lines of evidence that support Darwin s ideas? Human Macaque Dog Bird Frog Lamprey The sequence in DNA Why & compare proteins DNA is a & molecular proteins record across of evolutionary species? relationships. Comparative hemoglobin structure 8 32 45 67 125 Why compare these genes? 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 compare common genes cytochrome C (respiration) hemoglobin (gas exchange)
Building family trees
Genome sequencing What can data from whole genome sequencing tell us about evolution of humans?
Primate Common Ancestry? Chromosome Number in the Great Apes (Hominidae) orangutan (Pogo) 48 gorilla (Gorilla) 48 chimpanzee (Pan) 48 human (Homo) 46 Hypothesis: Change in chromosome number? If these organisms share a common ancestor, then is there evidence in the genome for this change in chromosome number Could we have just lost a pair of chromosomes?
Chromosomal fusion Testable prediction: If common ancestor had 48 chromosomes (24 pairs), then humans carry a fused chromosome (23 pairs). What we should find: Ancestral Chromosomes Fusion Homo sapiens Chromosome Number in the Great Apes (Hominidae) orangutan (Pogo) 48 gorilla (Gorilla) 48 chimpanzee (Pan) Testable! 48 human (Homo) 46 This is what makes evolution science & not belief! Inactivated centromere Telomere sequences in middle of chromosome Centromere: bonding point between chromosomes Telomere: at ends of chromosomes
Guess what we found?!? Ancestral Chromosomes Fusion Chromosome 2 in Homo sapiens Inactivated centromere Telomere sequences in middle of chromosome Hillier et al (2005) Generation and Annotation of the DNA sequences of human chromosomes 2 and 4, Nature 434: 724 731. Chromosome 2 is unique to the human lineage of evolution, having emerged as a result of head-to-head fusion of two chromosomes that remained separate in other primates. The precise fusion site has been located in 2q13 2q14.1, where our analysis confirmed the presence of multiple subtelomeric duplications to chromosomes 1, 5, 8, 9, 10, 12, 19, 21 and 22. During the formation of human chromosome 2, one of the two centromeres became inactivated (2q21, which Well corresponds I ll to the centromere from chimp chromosome 13) and the be a monkey s centromeric structure quickly deterioriated. or an ape s uncle! Human Chromosome #2 shows the exact point at which this fusion took place
"Nothing in biology makes sense except in the light of evolution." -- Theodosius Dobzhansky March 1973 Geneticist, Columbia University (1900-1975) 2006-2007
Evolution is "so overwhelmingly established that it has become irrational to call it a theory." -- Ernst Mayr What Evolution Is 2001 Professor Emeritus, Evolutionary Biology Harvard University (1904-2005) 2006-2007
Don t be a Dodo Ask Questions!! 2006-2007