Aim: Evidence for Evolution Enter Date Aim: Evidence for Evolution Warm-up: DITTO: HW: Hunting for evolution clues… Elementary, my dear, Darwin! 2006-2007

Evidence supporting evolution Fossil record shows change over time Anatomical record comparing body structures homology & vestigial structures embryology & development Molecular record comparing protein & DNA sequences Artificial selection human caused evolution

1. Fossil record Layers of rock contain fossils new layers cover older ones creates a record over time fossils show a series of organisms have lived on Earth over a long period of time

Fossils tell a story… the Earth is old Life is old Life on Earth has changed

Evolution of birds Today’s organisms descended from ancestral species Fossil of Archaeopteryx lived about 150 mya links reptiles & birds The 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.

We found the fossil — no joke! Land Mammal ? Complete series of transitional fossils ? Where are the intermediate fossils? ? ? There are innumerable intermediate & transitional forms Whales as land creatures returning to the water…. Where are the intermediate forms of whale ancestors? Cartoon making fun of this idea. The cartoons disappeared 10-12 years ago when this fossil was found. Ambilocetic natans = “Walking whale who likes to swim” 4-5 intermediate forms all found in last 2 decades Indus River valley in between India & Pakistan. Someone’s idea of a joke! Ocean Mammal But the joke’s on them!!

Evolution from sea to land 2006 fossil discovery of early tetrapod 4 limbs Missing link from sea to land animals

2. Anatomical record Animals with different structures on the surface But when you look under the skin… It tells an evolutionary story of common ancestors

Compare the bones The same bones under the skin limbs that perform different functions are built from the same bones

Homologous structures Structures that come from the same origin Forelimbs of human, cats, whales, & bats same structure on the inside same development in embryo different functions on the outside evidence of common ancestor

But don’t be fooled by these… Analogous structures look different on the outside same function different structure & development on the inside different origin no evolutionary relationship

Analogous structures Dolphins: aquatic mammal Fish: aquatic vertebrate both adapted to life in the sea not closely related

Convergent evolution 3 groups with wings Flight evolved 3 separate times — evolving similar solutions to similar “problems” Convergent evolution 3 groups with wings Does this mean they have a recent common ancestor? NO!

Convergent evolution led to mimicry Why do these pairs look so similar? Monarch male poisonous Viceroy male edible Which is the moth vs. the bee? Which is the fly vs. the bee? fly bee moth bee

Because they used to walk on land! Vestigial organs No longer serve a functional purpose Why would whales have pelvis & leg bones if they were always sea creatures? Because they used to walk on land!

Comparative embryology Development of embryo tells an evolutionary story similar structures during development all vertebrate embryos have a “gill pouch” at one stage of development

Geographic Isolation Isolation caused by parts of geography For example – mountains, deserts, river Leads to speciation!!!!!!!!!!

Reproductive Isolation Leads to speciation!!!!!!!!!! Isolation due to problems with reproduction For example – courtship behavior, mating times, anatomical differences

Polyploidy An extra set of chromosomes Polyploidy causes difficulties in reproduction. Most flowering plants cannot reproduce with other species of plants due to this.

3. Molecular record Comparing DNA & protein structure everyone uses the same genetic code! DNA 10 20 30 40 50 60 70 80 90 100 110 120 Lamprey Frog Bird Dog Macaque Human 32 8 45 67 125 compare common genes compare common proteins number of amino acids different from human hemoglobin

Building “family” trees Closely related species are branches on the tree — coming from a common ancestor

Gradualism Changes in structure changes slowly over time.

Punctuated Equilibrium The development of new species is random due to random mutations.

4. Artificial selection “descendants” of wild mustard How do we know natural selection can change a population? we can recreate a similar process “evolution by human selection” “descendants” of wild mustard

Selective Breeding “descendants” of the wolf Humans create the change over time “descendants” of the wolf