1. Ch. 15.2 Evidence of Evolution Ch. 15.3
Objectives:
Describe how fossils provide evidence of evolution
Discuss morphological evidence of evolution
Explain how biochemistry provides evidence of evolution

2. 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

3. 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

4. Fossils shape ideas about evolution Fossils: direct or indirect remains of organisms preserved in media such as sedimentary rock, amber, ice, or tar
Fossilized organic matter in a leaf
Ammonite casts
Fossilized organic matter in a leaf
Ice Man”

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

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

7. What has the fossil record shown us?
The creatures alive today haven’t always been around
OBSERVATION
Different species lived in the past

8. ? ? ? ? Where are the intermediate fossils?
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 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!!

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

10. 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

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

12. 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

13. 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
How is a bird like a bug?
Solving a similar problem with a similar solution

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

15. Vestigial organs structure—a body structure in a present-day organism that no longer serves its original purpose, but was probably useful to an ancestor.
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!

16. 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

17. 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

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

19. 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

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

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

22. Insecticide resistance
Spray the field, but…
insecticide didn’t kill all individuals
variation
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.

23. Adaptations: Evidence for Evolution
an adaptation is any variation that aids an organism’s chances of survival in its environment.
According to Darwin’s theory, adaptations in species develop over many generations
Learning about adaptations in mole-rats can help you understand how natural selection has affected them.

24. Structural adaptations arise over time
camouflage, an adaptation that enables species to blend with their surroundings.
Because well-camouflaged organisms are not easily found by predators, they survive to reproduce.

25. Structural adaptations arise over time
Mimicry is a structural adaptation that enables one species to resemble another species.
Predators may learn quickly to avoid any organism with their general appearance

26. Physiological adaptations can develop rapidly
In general, most structural adaptations develop over millions of years.
However, there are some adaptations that evolve much more rapidly.
The evolution of insecticide resistance is an example of natural selection in action

27. Convergent evolution 3 groups with wings
Flight evolved 3 separate times —
evolving similar solutions to similar “problems”
3 groups with wings
Does this mean they have a recent common ancestor?
They just came up with the same answer!
NO!

28. 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

29. Natural selection acts on variations
There are three different types of natural selection that act on variation: stabilizing, directional, and disruptive.

30. Natural selection acts on variations
Stabilizing selection is a natural selection that favors average individuals in a population.
Selection for
average size
spiders
Normal variation

31. Natural selection acts on variations
Directional selection occurs when natural selection favors one of the extreme variations of a trait.
Normal
variation

32. Natural selection acts on variations
In disruptive selection, individuals with either extreme of a trait’s variation are selected for.
Selection for
light limpets
Normal variation
Selection for
dark limpets

33. The Evolution of Species
Significant changes in the gene pool could lead to the evolution of a new species over time.
The evolution of new species, a process called speciation occurs when members of similar populations no longer interbreed to produce fertile offspring within their natural environment.

34. The Evolution of Species
Geographic isolation occurs whenever a physical barrier divides a population.
A new species can evolve when a population has been geographically isolated.
Reproductive isolation can result in speciation
Reproductive isolation occurs when formerly interbreeding organisms can no longer mate and produce fertile offspring
A change in chromosome numbers- polyploidy can lead to speciation

35. Speciation rates
Gradualism is the idea that species originate through a gradual change of adaptations
Some evidence from the fossil record supports gradualism.
In 1972, Niles Eldredge and Stephen J. Gould proposed a different hypothesis known as punctuated equilibrium.
This hypothesis argues that speciation occurs relatively quickly, in rapid bursts, with long periods of genetic equilibrium in between.