1. Charles Darwin 1859 – “Origin of Species” published
Argued from evidence that species inhabiting Earth today descended from ancestral species *****Descent with modification explains life’s unity and diversity
Proposed a mechanism for evolution  Natural Selection
In 1844, Darwin wrote an essay on the origin of species and natural selection but did not introduce his theory publicly, anticipating an uproar
In June 1858, Darwin received a manuscript from Alfred Russell Wallace, who had developed a theory of natural selection similar to Darwin’s
Darwin quickly finished The Origin of Species and published it the next year

2. Charles Darwin had a consuming interest in nature
First studied medicine (unsuccessfully), and then theology at Cambridge University
After graduating, he took an unpaid position as naturalist and companion to Captain Robert FitzRoy for a 5-year around the world voyage on the Beagle
GREAT
BRITAIN
EUROPE
NORTH
AMERICA
ATLANTIC
OCEAN
The
Galápagos
Islands
AFRICA
Pinta
Genovesa
Marchena
Equator
SOUTH
AMERICA
Santiago
Daphne
Islands
Pinzón
AUSTRALIA
Fernandina
PACIFIC
OCEAN
Isabela
Figure 22.5 The voyage of HMS Beagle
For the Discovery Video Charles Darwin, go to Animation and Video Files.
Santa
Cruz
Andes
Cape of
Good Hope
Santa Fe
San
Cristobal
Tasmania
Florenza
Española
Cape Horn
New
Zealand
Tierra del Fuego
During his travels on the Beagle, Darwin collected specimens of South American plants and animals
He observed adaptations of plants and animals that inhabited many diverse environments

3. The most influential stop on the voyage was to the Galápagos Islands
Darwin noticed that many of the birds and reptiles were unique to specific islands in the Galápagos archipelago
These included tortoises…

5. Darwin’s theory meshed well with the hierarchy of Linnaeus
In the Darwinian view, the history of life is like a tree with branches representing life’s diversity
Darwin’s theory meshed well with the hierarchy of Linnaeus
Figure 9.9 The Linnaean classification of humans.
This classification system groups organisms into progressively smaller categories. All organisms within a category share basic characteristics, and as the groups become narrower toward the bottom of the figure, the organisms have more similarities.

6. Artificial Selection, Natural Selection, and Adaptation
Darwin noted that humans have modified other species by selecting and breeding individuals with desired traits, a process called artificial selection
Darwin then described four observations of nature and from these drew two inferences

7. Terminal bud Lateral buds Cabbage Brussels sprouts Flower clusters
Fig. 22-9
Terminal
bud
Lateral
buds
Cabbage
Brussels sprouts
Flower
clusters
Leaves
Kale
Cauliflower
Figure 22.9 Artificial selection
Stem
Wild mustard
Flowers
and stems
Broccoli
Kohlrabi

8. Observation #1: Members of a population often vary greatly in their traits

9. Observation #2: Traits are inherited from parents to offspring
Observation #3: All species are capable of producing more offspring than the environment can support
Observation #4: Owing to lack of food or other resources, many of these offspring do not survive

10. Inference #1: Individuals whose inherited traits give them a higher probability of surviving and reproducing in a given environment tend to leave more offspring than other individuals
Inference #2: This unequal ability of individuals to survive and reproduce will lead to the accumulation of favorable traits in the population over generations

11. An example of the process of evolution:
Some populations of head lice won’t be killed by the chemical permethrin, a common treatment
Studies have shown that this evolution occurred after only about 30 months (40 generations of lice)

12. The Process of Evolution
Individuals DO NOT evolve
One louse did not, all of a sudden, have the ability to stay alive when permethrin was in the environment
The resistance that developed was genetic, passed on from one generation to the next
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

13. (a) A flower mantid in Malaysia (b) A stick mantid in Africa
Fig
(a) A flower mantid
in Malaysia
(b) A stick mantid
in Africa
Figure Camouflage as an example of evolutionary adaptation

14. Direct Observations of Evolutionary Change
New discoveries continue to fill the gaps identified by Darwin in The Origin of Species
Examples provide evidence for natural selection:
Alcohol metabolizing flies
evolution of drug-resistant HIV
Antibiotic resistance in bacteria
Pesticide resistance in insects

16. Fig
100
Patient
No. 1
Patient No. 2 75
Percent of HIV resistant to 3TC 50
Patient No. 3
Figure Evolution of drug resistance in HIV 25 2 4 6 8 10 12
Weeks

18. Fig. 22-UN2

19. Natural selection does not create new traits, but edits or selects for traits already present in the population
The local environment determines which traits will be selected for or selected against in any specific population

20. There are 5 major pieces of evidence that supports the theory of evolution
1. The Fossil Record
The fossil record provides evidence of the extinction of species, the origin of new groups, and changes within groups over time
(a) Pakicetus (terrestrial)
(b) Rhodocetus (predominantly aquatic)
(c) Dorudon (fully aquatic)
(d) Balaena
(recent whale ancestor)

22. 2. Homologous structures are anatomical resemblances that represent variations on a structural theme present in a common ancestor
Fig
Humerus
Radius
Ulna
Carpals
Metacarpals
Figure Mammalian forelimbs: homologous structures
Phalanges
Human
Cat
Whale
Bat

23. Homologous Structures

24. 3. Biochemical Evidence
Molecular level  genes shared among organisms inherited from a common ancestor

25. Fig
Pharyngeal
pouches
Post-anal
tail
Figure Anatomical similarities in vertebrate embryos
Chick embryo (LM)
Human embryo
4. Comparative embryology reveals anatomical homologies not visible in adult organisms

26. 5. Vestigial structures are remnants of features that served important functions in the organism’s ancestors

28. Natural Selection Does Not Result in Perfection
Natural selection causes populations to be more fit for their environment, not necessarily “better” organisms
Increased success in one environment does not mean success in a different environment
Poisonous
bacteria

29. Natural Selection Results from Current Environmental Conditions
Changing the population:
Directional selection – the traits move in a particular direction
i.e. toward higher metabolism rates; fast metabolizers in fruit flies
Horse evolution

30. Natural Selection Results from Current Environmental Conditions
Stabilize the population:
Stabilizing selection – extremes are selected against and the traits of the population remain the same because the average condition is the most fit
i.e. birth weight of human babies (being very small or very large is not as favorable)

31. Natural Selection Results from Current Environmental Conditions
Splitting the population:
Diversifying selection – the average condition is the least fit
Increases the diversity – two or more variants are fit
i.e. HIV particles – better to evade the immune system

32. Differences in individuals arise from differences in their genes
If DNA is mutated, new alleles may occur
Natural selection and evolution will occur and the mutation will survive or die out

33. Biological Species Are Reproductively Isolated
Alleles do not spread among different species
Separate species evolve differences, such as lions and leopards
There is evidence of a common ancestor with spotted coat
Allele for spots was lost in lions but maintained in leopards

34. Biological Species Are Reproductively Isolated
Gene pool – all the alleles from all the individuals in a species
Gene flow – the spread of an allele through a species’ gene pool
A change in the frequency of an allele in a gene pool – evolution of that species
Gene flow does not occur between different species

35. The Nature of Reproductive Isolated
If two organisms of different species try to mate, no fertile offspring will be produced
This is reproductive isolation
Reproductive barriers to reproduction take two general forms…
Pre-fertilization
No attempt to mate
Or, no fertilized egg is produced – if mating is attempted
Post-fertilization
Mating does occur but offspring either do not survive or are sterile

36. The Nature of Reproductive Isolated
Pre-fertilzation barriers:
Spatial (habitat) isolation is the most obvious impediment to mating
The two species never come into contact
Behavioral isolation is one barrier to species that are close in space
Differences in mating behaviors
mating rituals, fireflies blinking, birds songs

37. The Nature of Reproductive Isolated
One example of behavioral isolation can be see in the blue-footed boobies
Male blue-footed boobies have a mating dance to attract females
Then the female engages in pointing behavior with the male
If the proper courting display is not present, mating will not occur

38. The Nature of Reproductive Isolated
A barrier to mating resulting from physical incompatibility between sexual organs of two different individuals is called mechanical isolation
A barrier resulting from the timing of reproduction is a temporal isolation
Plants produce flowers at different times of year
Cicadas
Eastern and western spotted skunks

39. The Nature of Reproductive Isolated
Gamete incompatibility is the most common pre-fertilization barrier
Mating does occur, but the egg and sperm are not compatible
Fertilization does not occur

40. The Nature of Reproductive Isolated
Post-fertilization barriers:
Most interspecies hybrids – offspring of parents from two different species – do not survive long after fertilization
Incompatibility between genes in different species is the primary cause
In the case of some species, such as horses and donkeys, the difference in genes is not so large, which is why mules survive and exist  sterile

41. The Process of Speciation
Speciation is the evolution of one or more species from an ancestral form
Three steps are necessary for one species to give rise to another:
Isolation of gene pools of populations
Evolutionary change in gene pools
Evolution of reproductive isolation preventing gene flow

42. Isolation & Divergence of Gene Pools
Gene pools may become isolated if a small population migrates to a location far from the main population
Figure 11.5 Migration leads to speciation.
The ancestor of Hawaiian silverswords was the much smaller and less dramatic California tarweed. Tarweed seeds were blown or carried by birds to the Hawaiian Islands, creating an isolated population. With no gene flow between the two populations, Hawaiian silverswords evolved into a very different group of species.

43. Isolation & Divergence of Gene Pools
The intrusion of a geologic barrier may also isolate gene pools from each other
Figure 11.7 Physical separation leads to speciation.
Species of snapping shrimp on either side of the Isthmus of Panama can be paired according to similarities in appearance and habit. Pairs are numbered for simplicity—the letter C before the number indicates the species is found on the Caribbean side of the Isthmus, while a P indicates a Pacific species. This pattern indicates that recent speciation in this group occurred during the period that the isthmus was emerging and therefore was dividing formerly continuous populations of ancestral species.

44. Isolation and Divergence of Gene Pools
Allopatric species: isolated populations due to barriers or distance
Sympatric species: isolated by other means – populations are near one another

45. The Evolution of Reproductive Isolation
The exact mechanism of the development of reproductive isolation is still unknown
When it occurs, the two species follow different evolutionary paths
The rapidity and course of different forms evolving from a common ancestor is a source of debate between two hypotheses

46. The Evolution of Reproductive Isolation
Gradualism – an accumulation of tiny changes over millions of years
Punctuated equilibrium – no change for millions of years and then drastic changes that are fairly quick (thousands of years)
The fossil record seems to support the punctuated equilibrium hypothesis

47. What is a species?
The biological species concept defines species as a group of individuals that can reproduce with each other, but not other species
Most commonly used by biologists interested in the process of species formation

48. Genealogical species concept allows easier identification
The genealogical species concept defines a species as the smallest group of reproductively compatible organisms containing all of the known descendants of a single common ancestor
This definition emphasizes evolutionary lineages
Can be used with asexual organisms
Genealogical species concept allows easier identification
If a population is consistently different from other populations, it is a different species, even if it can reproduce with other populations

49. The Morphological Species Concept
Paleontologists use the morphological species concept to define a species – a group of individuals that have some reliable physical characteristics distinguishing them from all other species
They have a similar morphology; look alike in some key feature
Easy to use in practice on both living and fossil organisms
Only a few key features needed for identification
Fossils could represent different ages and genders rather than different species

50. Convergent Evolution
Sugar
glider
Convergent evolution is the evolution of similar, or analogous, features in distantly related groups
Analogous traits arise when groups independently adapt to similar environments in similar ways
Convergent evolution does not provide information about ancestry
Flying
squirrel

51. Changes in allele frequencies due to chance is called genetic drift
Founder Effect
Occurs when a small sample of a larger population establishes a new population
The sample’s gene pool differs from the larger population’s

52. Population Bottleneck
A dramatic but short-lived population size reduction followed by a rapid increase is called a population bottleneck
Like the founder effect, it results in the new population differing from the original

53. Genetic Drift in Small Populations
Small populations are highly susceptible to changes in allele frequency even by chance
Humans have a long history of small populations, and thus have been quite vulnerable to genetic drift

54. Sexual Selection Mate preferences exist in many populations
When a trait influences the likelihood of mating the trait is under the influence of sexual selection, a form of natural selection
Male peacocks have large showy tails
Male lions have dramatic manes
Traits sometimes appear to have not relation to fitness