1. Evolution 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. Why use fossils?
Scientists have used the fossil record to construct a history of life on Earth.
Earth’s life forms appeared 3.5 billion years ago
Fossil record is not complete, but pretty good for general information

4. 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

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

6. 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.

7. ? ? ? ? Where are the intermediate fossils? But the joke’s on them!!
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!!

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

9. Fossil Evidence
Fossils are formed when organisms become buried in sediments, causing little decomposition of the organism.
Over time the calcium in their bones and other hard tissues is replaced by minerals as the sediment itself is changed to rock.
As time progresses various sedimentary layers get deposited, with the oldest on the bottom and the youngest on the top. By observing the appearance, abundance and types of fossils in each of these layers we can understand the progression of the species that lived in that location over time.
Fossils are also formed through freezing, being embedded in amber, preserved in tar, or even footprints and imprints.

10. Scientists can tell how old a fossil is by carbon or radioactive dating them.
Once the fossil has been dated it can be used as an index with other fossils from the same period of time. This allows for a comparison of evolutionary evens at different locations by comparing the fossils that are in the time periods before and after them.
It has been found that fossils of similar organisms show large or small differences with the ones that are in other time periods.
In some cases fossil evidence allows scientist to trace animals alive today to early ancestors that may now be extremely different in appearance.

11. Figure 2
This stratigraphic column shows the order in which organisms appeared. Each layer represents a particular time frame and shows an organism which was found during that time.
The oldest fossils appear in lower layers, and the most recent fossils at the top. This allows for placement of fossils to be used as an aid in dating the organism found.

12. Comparative Anatomy
Comparative Anatomy includes Homologous and Analogous structures as well as vestigial features.
Comparisons of anatomical features in different organisms often provides evidence to support the theory of evolution. As Organisms are often classed together according to similarities in their structures.
It was through comparing the anatomy of organisms that scientist discovered phylogeny, meaning the evolutionary history of a group of organisms.
“What can be more curious than that the hand of a man, formed for grasping, that of a mole for digging, the leg of a horse, the paddle of the porpoise, and the wings of the bat, should all be constructed on the same pattern, and should include the same bones, in the same relative positions.
-Darwin.

13. Homologous Structures
Homologous structure are structures that share a common origin but may serve different functions in modern species.
These structures are evidence that organisms with similar structure evolved from a common ancestor.
Examples include the forelimbs of a variety of mammals. For example, human, cat, whale and bat.
These species show the same skeletal elements. Is in the humerus, radius and ulna.
However these skeletal elements have been modified over time to suit the different functions suitable for the type of mammal.
Homologous structures result from divergent evolution meaning their ancestral lines started out fairly similar, but evolved along different paths, becoming more different over time.

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

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

16. 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

17. 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
Solving a similar problem with a similar solution

18.
Figure 3
Structures that are similar due to evolutionary origin, such as the forearm bones of humans, birds, porpoises, and elephants, are called homologous. However, structures that evolve separately to perform a similar function are called analogous. The wings of birds, bats, and insects, for example, have different embryological origins but are all designed for flight.

19. Analogous Structures
Analogous structures are a contrast to homologous structures.
They serve the same function between organisms but are different in internal anatomy.
Such as the wings of birds and butterflies or the eyes of lobsters and fish.
These structures are of no use in classifying organisms or in working out their evolutionary relationships with each other.
Figure 4

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

21. 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!

22. 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

23. 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!

24. 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

25. Evidence from genetics.
All organisms share the same basic mechanism of heredity (DNA/RNA)
E.g.: mtDNA evidence for human evolution
A branching tree radiating from a common ancestor – phylogenetic tree
We can conduct research on other species to understand our own genes. 25

26. Similarities in DNA Sequence

27. 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

28. 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

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

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

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

32. 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.

33. Parallel Evolution not closely related
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
not closely related
marsupial
mammal
placental
filling similar roles in nature, so have similar adaptations

34. 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

35. Vestigial Organs
Vestigial organs provide further evidence for evolutionary change.
These organs are usually dwarfed and useless to the organism.
Examples of these include:
The human appendix which is useless in humans, but in other mammals it is necessary for digestion of high cellulose diet.
The human external ear muscles.
The tail bone.
Wisdom teeth.
Some snakes have skeletal limbs.
Sometimes vestigial organs may be adapted for new uses e.g. penguin winds can’t be used for flight , yet they are adapted for swimming.
Even though organisms have these organs there is no significant disadvantage to the organism.

36. Examples of Vestigial Structures
Vestigial organs associated with eye structures
Vestigial remains of a pelvic girdle in a whale

37. Embryology
Embryology of organisms can be used to demonstrate the existence and even degree of relatedness of organisms.
In the early stages of development embryos of many organisms look extremely similar.
Embryos in mammals, birds, reptiles and fish have many body similarities in common e.g. Gill slits, two chambered heart, and tail.
As the embryos develop further, the similarities gradually disappear.
This embryonic resemblances indicated that organisms are related by their common ancestors.

38. Homeobox (Hox) genes that regulate the expression of hundreds of other genes appear to determine the path that embryo development follows.
Depending on the Hox genes control the expression of other genes, parts of organisms develop differently. Similarities in Hox genes give strong indications of the presence of a relatively recent common ancestor.
Also, homologous features can appear during embryonic development. These features serve no function as the organism grows
In the early weeks of development, human embryos posses a tail similar to that in chicken and fish embryos.

39. Similarities in Embryos
Figure 7

40. The study of geography provides evidence of evolution.
island species most closely resemble nearest mainland species
populations can show variation from one island to another

41. Summary
The layers of fossils in sedimentary rock shows the progression of organisms through time.
Homologous structures are structures that are similar in appearance but not In function.
Analogous structures are structures that are similar in function but not in appearance.
Vestigial Features are organs and structures that still remain in animals, however they serve no function or purpose in the organism.
Embryology shows the similarities that organisms have at a very early stage of development.