2A BRIEF HISTORY... Charles Darwin The person who was most influential to our understanding of evolution.In 1831, at age 22, he joined the crew of the HMS Beagle as a naturalist for a 5 year voyage around the world.
3Darwin’s FindingsAfter Darwin returned to England in 1836 he filled notebooks with his ideas about species diversity and the process that he would later call evolution.He did not rush to publish his ideas because they disagreed with the fundamental scientific beliefs of his day.He asked his wife to publish his ideas when he died.
4Wallace’s EssayIn 1858, another naturalist, Alfred Russell Wallace wrote an essay describing his work in Malaysia that summarized the same ideas Darwin had been thinking about for 25 years.
5Origin of SpeciesSuddenly Darwin had incentive to publish the results of his work.In 1859, his book On the Origin of Species presented evidence and proposed a mechanism for evolution that he called natural selection.
7Evolution is NOT goal-oriented An evolutionary trend does not mean that evolution is goal-oriented.Surviving species do not represent perfection.There is random chance involved as wellTraits happen—Well suited to anenvironment, OR NOT!Evolution is the survival of the fittest, but sometimes it is survival of the just good enough.
8Evidence supporting evolution Fossil recordshows change over timeAnatomical recordcomparing body structureshomology & vestigial structuresembryology & developmentMolecular recordcomparing protein & DNA sequencesArtificial selectionHuman-caused evolution
91. Fossil record Layers of rock contain fossils new layers cover older onescreates a record over timefossils show a series of organisms have lived on Earth (over a long period of time)
10Life on Earth has changed Fossils tell a story…the Earth is oldLife is oldLife on Earth has changed
11Evolution of birds Today’s birds descended from ancestral species Fossil of Archaeopteryxlived about 150 myalinks reptiles & birdsThe avian nature of the brain and inner ear of Archaeopteryx (Alonso et al. 2004) - Archaeopteryx, the earliest known flying bird from the Late Jurassic period, exhibits many shared primitive characters with more basal coelurosaurian dinosaurs (the clade including all theropods more bird-like than Allosaurus), such as teeth, a long bony tail and pinnate feathers. However, Archaeopteryx possessed asymmetrical flight feathers on its wings and tail, together with a wing feather arrangement shared with modern birds. This suggests some degree of powered flight capability but, until now, little was understood about the extent to which its brain and special senses were adapted for flight. Alonso et al. (2004) investigated this problem by computed tomography scanning and three-dimensional reconstruction of the braincase of the London specimen of Archaeopteryx. A reconstruction of the braincase and endocasts of the brain and inner ear suggest that Archaeopteryx closely resembled modern birds in the dominance of the sense of vision and in the possession of expanded auditory and spatial sensory perception in the ear. Alonso et al. (2004) concluded that Archaeopteryx had acquired the derived neurological and structural adaptations necessary for flight. An enlarged forebrain suggests that it had also developed enhanced somatosensory integration with these special senses demanded by a lifestyle involving flying ability.11
12Transition from sea to land 2006 fossil discovery of early tetrapod4 limbsMissing link from sea to land animals
13We found the fossil — no joke! Land Mammal?Complete series of transitional fossils?Where are the intermediate fossils???There are innumerable intermediate & transitional formsWhales as land creatures returning to the water….Where are the intermediate forms of whale ancestors?Cartoon making fun of this idea.The cartoons disappeared years ago when this fossil was found.Ambilocetic natans = “Walking whale who likes to swim”4-5 intermediate forms all found in last 2 decadesIndus River valley in between India & Pakistan.Ocean Mammal13
142. Anatomical record Animals with different structures on the surface But when you look under the skin…It tells an evolutionary story of common ancestors
15How could these very different animals have the same bones? Compare the bonesThe same bones under the skinlimbs that perform different functions are built from the same bonesHow could these very different animals have the same bones?
16Homologous structures Structures that come from the same originhomo- = same-logous = informationForelimbs of human, cats, whales, & batssame structure on the insidesame development in embryodifferent functionson the outsideevidence of common ancestor
17But don’t be fooled by these… Analogous structureslook similar on the outsidesame functiondifferent structure & development on the insidedifferent originno evolutionary relationshipHow is a bird like a bug?Solving a similar problem with a similar solution
18Analogous structures Dolphins: aquatic mammal Fish: aquatic vertebrate both adapted to life in the seanot closely relatedWatch the tail!
19Vestigial organs Structures on modern animals that have no function remains of structures that were functional in ancestorsevidence of change over timeeyes on blind cave fishhuman tail bone
20Because they used to walk on land! Vestigial organsHind leg bones on whale fossilspelvis onsnakeWhy would whales have pelvis & leg bones if they were always sea creatures?Because they used to walk on land!
21They just came up with the same answer! Convergent evolutionFlight evolved 3 separate times —evolving similar solutions to similar “problems”3 groups with wingsDoes this mean they have a recent common ancestor?They just came up with the same answer!NO!
22Convergent evolution led to mimicry Why do these pairs look so similar?Monarch malepoisonousViceroy maleedibleWhich is the fly vs. the bee?Which is the moth vs. the bee?flybeemothbumblebee
25Comparative embryology Development of embryo tells an evolutionary storysimilar structures during developmentall vertebrate embryos have a “gill pouch” at one stage of development
263. Molecular record Comparing DNA & protein structure everyone uses the same genetic code!DNA102030405060708090100110120LampreyFrogBirdDogMacaqueHuman3284567125compare common genescompare common proteinsnumber of amino acids different from human hemoglobin
27Building “family” trees Closely related species are branches on the tree — coming from a common ancestor
28“descendants” of wild mustard 4. Artificial selectionHow do we know natural selection can change a population?we can recreate a similar process“evolution by human selection”“descendants” of wild mustard
29Humans create the change over time “descendants” of the wolf Selective BreedingHumans create the change over time“descendants” of the wolf
31Unexpected consequences of artificial selection Pesticide resistanceAntibiotic resistance
32Insecticide resistance Spray the field, but…insecticide didn’t kill all individualsvariationresistant survivors reproduceresistance is inheritedinsecticide becomes less & less effectiveThe evolution of resistance to insecticides in hundreds of insect species is a classic example of natural selection in action.The results of application of new insecticide are typically encouraging, killing 99% of the insects.However, the effectiveness of the insecticide becomes less effective in subsequent applications. The few survivors from the early applications of the insecticide are those insects with genes that enable them to resist the chemical attack. Only these resistant individuals reproduce, passing on their resistance to their offspring. In each generation the % of insecticide-resistant individuals increases.32