1. Evidence for Evolution

2. Types of Evidence for Evolution
Fossil Record (ex: horses and whales)
Biogeography
Comparative Anatomy
Homologous Structures
Vestigial Structures
Comparative Embryology
Molecular Biology / Biochemical evidence
Protein (aa sequence) comparisons
DNA sequence comparisons

3. Fossil Record Evidence: Horse evolution
one toe on ground (#3), long teeth good for eating tough blades of grass
four toes on ground (#2-5), short teeth good for eating soft leaves on shrubs & trees

4. Look at how the bones in horse feet have changed over time.
They became longer and more streamlined, enabling horses to run faster to avoid predators.
mya = million years ago

5. Whale Evolution

6. Fossil Record of Whale Evolution
Pakicetus (terrestrial)
Rhodocetus (predominantly aquatic)
Pelvis and
hind limb
Dorudon (fully aquatic)
Pelvis and
hind limb
Balaena (recent whale ancestor)

8. A lesson in Biogeography

9. The Wallace Line
Read this interesting article by Jared Diamond (author of Guns, Germs, and Steel) about “Mr. Wallace’s Line”:

10. An Example of Biogeographical Evidence: Galapagos Finches and Adaptive Radiation

11. Comparative Anatomy Evidence: Homologous Structures
Humerus
Radius
Ulna
Carpals
Metacarpals
Phalanges
Human
Cat
Whale
Bat

12. Comparative Anatomy Evidence: Vestigial Structures
Boa pelvic region
Human Coccyx (tailbone)

13. Comparative Embryology Evidence

14. Comparative Embryology Evidence
Pharyngeal
pouches
Post-anal
tail
Chick embryo
Human embryo

15. and snakes Lungfishes Amphibians Tetrapods Mammals Amniotes
Fig. 13-6
Lungfishes 1
Amphibians
Tetrapods 2
Mammals
Tetrapod limbs
Amniotes 3
Lizards
and snakes
Amnion 4
Crocodiles 5
Ostriches 6
Birds
Feathers
Hawks and
other birds

16. Biochemical Evidence: amino acid sequence of hemoglobin

17. Biochemical Evidence: amino acid sequence of cytochrome c
Note: These sequences use 1-letter amino acid codes. The “alignment” lines show where the amino acids are the same or different (+ or a blank). The + indicates a different amino acid but with the SAME R-group properties (nonpolar, polar or charged).

18. Amino Acids by R-group Properties with 3-letter and 1-letter abbreviations
(pos. charged)
(neg. charged)

19. Biochemical Evidence: DNA sequence

20. Microevolution: a change in a population’s alleles over time
How do we detect this change? Need to look at a population’s collection of alleles, or its gene pool.
Darwin’s Finches video:
Rock Pocket Mouse video:

21. Hardy-Weinberg Theorem
H-W allows you to predict allele frequencies for a non-evolving population.
For a population to be in H-W equilibrium, the following must be true:
Population must be very large in size
Population must be isolated from other pops (no gene flow: no immigration or emigration)
No mutations
Mating must be random
No natural selection (equal chance of survival & reproductive success)

22. Hardy-Weinberg Theorem
Allele frequencies
p q = 1
Genotype frequencies
p2 +
2pq q2 = 1
Dominant
homozygotes
Heterozygotes
Recessive
homozygotes
Any changes to expected allele frequencies over time may indicate that micro-evolution is occurring in the population.

23. Phenotypes (fur color) Original population Evolved population
Fig
Original
population
Frequency of
individuals
Phenotypes (fur color)
Original
population
Evolved
population
Stabilizing selection
Directional selection
Disruptive selection

24. Causes of Microevolution
Genetic Drift
Produces random changes to the gene pool of small breeding populations
An allele may be eliminated from pop by chance
Bottleneck Effect: dramatic decr in pop size due to environmental fluctuation (depletion of food supply, disease outbreak)
Examples: Cheetahs, Florida Panthers
Founder Effect: when one or a few individuals from a large pop establish a colony (new pop), and bring with them only a small fraction of genetic variation from orig pop
Example: Marine Iguanas in Galapagos

25. Original population Bottlenecking event Surviving population
Fig a-3
Original
population
Bottlenecking
event
Surviving
population

26. “By 1990s, the endangered Florida panther – a flagship species and one of the last remaining symbols of wilderness in Florida - was in serious trouble. There were fewer than 30 panthers remaining in the wild. The population suffered from several biomedical and morphological abnormalities, including low genetic diversity, heart defects, reproductive dysfunctions and kinked tails. Many of these problems were thought to be indicative of inbreeding, and conservation biologists recommended genetic restoration. This recommendation was controversial but was ultimately implemented after careful planning…”

27. Causes of Microevolution
2. Gene Flow
movement of alleles by migration of individuals to a new population
Generally increases variation within a population
3. Mutation
Unpredictable change in DNA, a source of new alleles
Introduces variation in pop
Only inheritable if occurs in gametes
Can be harmful, beneficial, or neutral
4. Natural Selection
Leads to adaptive evol change, as “fittest” indiv survive to reproduce

28. Chromosome with allele conferring resistance to pesticide
Fig. 13-3b
Chromosome with allele
conferring resistance
to pesticide
Pesticide application
Survivors
Additional
applications will
be less effective, and
the frequency of
resistant insects in
the population
will grow

29. Causes of Microevolution
5. Non-random Mating
Inbreeding: Individuals mate more freq with closely related individuals
Common in plants in the form of self-fertilization
Not always harmful but sometimes leads to inbreeding depression (lower fitness: sterility, higher juvenile mortality)
Examples: Cheetahs, Florida Panthers
Sexual selection (mate selection): individuals select mates by their phenotype
• Can change genotype frequencies
Examples: Peacocks, Mallards, Humans, etc.

30. Fig a

31. Microevolution change in allele frequencies in a population (a) (b)
Fig. 13-UN4
Microevolution
is the
may result from
change in allele
frequencies in a
population
(a)
(b)
(c)
random fluctuations
more likely in a
due to
movement of
due to
leads to
individuals
or gametes
adaptive
evolution
(d)
(g)
may be result of
of individuals
best adapted
to environment
(e)
(f)