1. Evidence of Evolution by Natural Selection
Dodo bird

2. Evidence supporting evolution
Fossil record
transition species
Anatomical record
homologous & vestigial structures
embryology & development
Molecular record
protein & DNA sequence
Artificial selection
human-caused evolution

3. 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

4. Fossil Record

5. Fossil record
A record showing us that today’s organisms descended from ancestral species

6. Evolutionary change in horses
550
500
450
Equus
400
350
Body size (kg)
300
250
Merychippus
increase in size, loss of toes, increase in size of molars
20-25 mya grasslands became widespread in Norh America
molars = easer to eat grass
hoof = faster locomotion on grassland
200
Mesohippus
150
Hyracotherium
100 50
Nannippus 60 55 50 45 40 35 30 25 20 15 10 5
Millions of years ago

7. Evolution of birds 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.
Smithsonian Museum, Washington, DC

8. Where are the transitional fossils?
Land Mammal ?
Where are the transitional 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 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.

9. 2006 Fossil Discovery of Early Tetrapod
Tiktaalik
“missing link” from sea to land animals

10. Anatomical record Homologous structures
similarities in characteristics resulting from common ancestry

11. Homologous structures
Similar structure
Similar development
Different functions
Evidence of close evolutionary relationship
recent common ancestor

12. Homologous structures
spines
leaves
succulent leaves
tendrils
needles
colored leaves

13. Don’t be fooled by their looks!
Analogous structures
Separate evolution of structures
similar functions
similar external form
different internal structure & development
different origin
no evolutionary relationship
Don’t be fooled by their looks!
Solving a similar problem with a similar solution

14. Does this mean they have a recent common ancestor?
Convergent evolution
Flight evolved in 3 separate animal groups
evolved similar “solution” to similar “problems”
analogous structures
Does this mean they have a recent common ancestor?

15. & sleek bodies are analogous structures!
Convergent evolution
Fish: aquatic vertebrates
Dolphins: aquatic mammals
similar adaptations to life in the sea
not closely related
Those fins & tails
& sleek bodies are analogous structures!

16. Parallel Evolution Convergent evolution in common niches marsupial
filling similar ecological roles in similar environments, so similar adaptations were selected
but are not closely related
marsupial
mammals
placental
mammals

17. Parallel types across continents
Niche
Placental Mammals
Australian Marsupials
Burrower
Mole
Anteater
Mouse
Lemur
Flying
squirrel
Ocelot
Wolf
Tasmanian “wolf”
Tasmanian cat
Sugar glider
Spotted cuscus
Numbat
Marsupial mole
Marsupial mouse
Nocturnal
insectivore
Climber
Glider
Stalking
predator
Chasing

18. This is not LaMarck’s loss from “disuse”!
Vestigial organs
Modern animals may have 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 not LaMarck’s loss from “disuse”!

19. Vestigial organs Hind leg bones on whale fossils
Why would whales have pelvis & leg bones if they were always sea creatures?

20. 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.

21. Why compare these genes?
Molecular record
Comparing DNA & protein structure
universal genetic code!
DNA & RNA
compare common genes
cytochrome C (respiration)
hemoglobin (gas exchange)
Why compare these genes? 25 50 75
100
125
Millions of years ago
Horse/
donkey
Sheep/
goat
Goat/cow
Llama/
cow
Pig/
Rabbit/
rodent
Horse/cow
Human/rodent
Dog/
Human/
Human/kangaroo
Nucleotide substitutions
Closely related species have sequences that are more similar than distantly related species
DNA & proteins are a molecular record of evolutionary relationships

22. Comparative hemoglobin structure
Human
Macaque
Dog
Bird
Frog
Lamprey
Why does comparing amino acid sequence measure evolutionary relationships? 8 32 45 67
125 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

23. Building “family” trees
Closely related species (branches) share same line of descent until their divergence from a common ancestor

24. “descendants” of wild mustard “descendants” of the wolf
Artificial selection
Artificial breeding can use variations in populations to create vastly different “breeds” & “varieties”
“descendants” of wild mustard
“descendants” of the wolf

25. Natural selection in action
Insecticide & drug resistance
insecticide didn’t kill all individuals
resistant survivors reproduce
resistance is inherited
insecticide becomes less & less effective
The 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.