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

2. Compare the bones (anatomical structures)
The same bones under the skin
limbs that perform different functions are built from the same bones
How could these very different animals have the same bones?

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

4. But don’t be fooled by these…
Analogous structures
look similar
on the outside
same function
different structure & development
on the inside
different origin
no evolutionary relationship
Convergent evolution!!
How is a bird like a bug?
Solving a similar problem with a similar solution

5. Analogous structures Dolphins: aquatic mammal Fish: aquatic vertebrate
both adapted to life in the sea
not closely related
Watch the tail!

6. Because they used to walk on land!
Vestigial organs
Hind leg bones on whale fossils
Why would whales have pelvis & leg bones if they were always sea creatures?
Because they used to walk on land!

7. Vestigial organs Structures on modern animals that have no function
remains of structures that were functional in ancestors
evidence of change over time
some snakes & whales have pelvis bones & leg bones of walking ancestors
eyes on blind cave fish
human tail bone

8. 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

9. 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

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

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

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

13. I liked breeding pigeons!
Artificial Selection
…and the examples keep coming!
I liked breeding pigeons!

14. Artificial Selection gone bad!
Unexpected consequences of artificial selection
Pesticide resistance
Antibiotic resistance

15. Insecticide resistance
Spray the field, but…
insecticide didn’t kill all individuals
variation
resistant survivors reproduce
resistance is inherited
insecticide becomes less & less effective
Genetic Drift!
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. This is an example of genetic drift.

17. So, do individuals or populations evolve?
So…what is a species?
species
population whose members can breed & produce viable, fertile offspring
reproductively compatible
Distinct species: songs & behaviors are different enough to prevent interbreeding
So, do individuals or populations evolve?
Eastern Meadowlark
Western Meadowlark

18. Many factors can affect speciation
Many factors can affect speciation. (the formation of a new species) But first, populations must be isolated

19. There are two ways to isolate a population
geographically isolated
reproductively isolated
isolated populations
evolve independently based
on the conditions they are
living in.

20. Chemical Changes to DNA Small isolated populations
Forces of Evolutionary Change So once a population has been isolated….what mechanisms can cause evolution to occur?
Gene Flow
Genetic Drift
Mutation
Migration
Chemical Changes to DNA
Small isolated populations
Non-random mating
Selection Pressure
Natural Selection
Sexual Selection

21. Patterns of Evolution
Different patterns of evolution occur in different environments
Convergent evolution
Divergent evolution (also called adaptive radiation)
Coevolution

22. Convergent Evolution unrelated species
When unrelated species live in similar environments in different parts of the world
similar environmental pressures
similar pressures of natural selection
unrelated species

23. CONVERGENT EVOLUTION EXAMPLE
Life Sciences-HHMI Outreach. Copyright 2006 President and Fellows of Harvard College.

24. common ancestor Adaptive radiation is a type of divergent evolution
populations that were once similar change and adapt to different living conditions
common ancestor

25. Adaptive Radiation Example
When one species splits into many species to fill open habitats.
Darwin’s finches 25

26. Coevolution
Two or more species reciprocally affect each other’s evolution
predator-prey
disease & host
competitive species
mutualism
pollinators & flowers