1. The Origin of Species Speciation in real time 11 min
Chapter 14
The Origin of Species
Speciation in real time 11 min

2. Mosquito Mystery Speciation is the emergence of new species
In England and North America
Two species of mosquitoes exist and spread West Nile virus

3. Speciation The emergence of a new species
Occurs if the members of a species are isolated from each other for so long that they evolve differently.

4. 14.1 The origin of species is the source of biological diversity
Speciation, the origin of new species
Is at the focal point of evolution
Each time speciation occurs, biological diversity increases.
Figure 14.1

5. Macroevolution
Earth’s incredible biological diversity is the result of macroevolution (dramatic changes that occur over long periods of time)
which begins with the origin of new species

6. What is the difference between microevolution and Macroevolution?

7. Appearance alone does not always define a species
14.2 What is a species?
Carolus Linnaeus, a Swedish physician and botanist
Used physical characteristics to distinguish species
Developed the binomial system of naming organisms
Linnaeus’ system established the basis for taxonomy
The branch of biology concerned with naming and classifying the diverse forms of life

8. Similarities between some species and variation within a species
Can make defining species difficult
Figure 14.2A
Figure 14.2B

9. 4 key concepts in Identifying Species
The Biological Species Concept
Morphological species concept
Ecological species concept
Phylogenic species concept

10. The Biological Species Concept
The biological species concept defines a species as
A population or group of populations whose members can interbreed and produce fertile offspring

11. What are the advantages/disadvantages of these classifications?
Other Species Concepts
The morphological species concept
Classifies organisms based on observable phenotypic traits
The ecological species concept
Defines a species by its ecological role in a community
The phylogenetic species concept
Defines a species as a set of organisms representing a specific evolutionary lineage. i.e unique set of genetic history.
Biologist trace the history of a species by comparing its physical characteristics or its DNA sequence to the corresponding data for other species.
What are the advantages/disadvantages of these classifications?

12. What prevents species that are closely related from interbreeding?

13. 14.3 Reproductive barriers keep species separate
Serve to isolate a species’ gene pool and prevent interbreeding
Are categorized as prezygotic or postzygotic
Table 14.3

14. Prezygotic Barriers Prezygotic barriers
Prevent mating or fertilization between species
There are five main typed of prezygotic barriers:
Temporal isolation
Habitat isolation
Behavioral isolation
mechanical isolation
Gametic isolation

15. In temporal isolation Two species breed at different times
Different seasons; different years, different times of the day
Figure 14.3A

16. Habitat isolation
Two species live in the same general area, but not in the same kind of places
They never meet.

17. In behavioral isolation
There is little or no sexual attraction between species, due to specific behaviors.
Courtship rituals
video
Figure 14.3B

18. In mechanical isolation
Female and male sex organs or gametes are not compatible
Many species of plants have flower structures that are adapted to specific insects or animal pollinators
Figure 14.3C

19. Gamete Isolation
The egg and sperm of different species do not unite to form a zygote.
In many organisms, the sperm cannot servive in the reproductive tract of a female of a different species

20. Postzygotic Barriers Postzygotic barriers
Operate after hybrid zygotes are formed
There are three forms of postzygotic barriers
Hybrid inviability
Hybrid sterility
Hybrid breakdown

21. One postzygotic barrier is hybrid sterility
Where hybrid offspring between two species are sterile and therefore cannot mate.
Hybrid Inviability
In other cases the hybrid does not survive
Hybrid Breakdown
1st generation is fertile,
2nd generation is either
sterile or produce feeble
offspring.
Figure 14.3D

22. Two closeley related tropical birds species live in the same forest, but one feeds and mates in the forest canopy and the other on the forest floor. This is an example of ___________________isolation , which is a_______zygotic reproductive barrier.

23. MECHANISMS OF SPECIATION
14.4 Geographic isolation can lead to speciation
In allopatric speciation
A population is geographically divided, and new species often evolve
A. harrisi
A. leucurus
Figure 14.4

24. How do geological processes fragment populations and lead to speciation?
Review:
Gene pool
Become isolated → evolutionary course
Genetic drift
Changed in allele frequency caused by natural selection
Mutations
Random changes in the alleles
All of these are unaffected by the gene flow in other populations

25. Allopatric speciation
Populations separated by geographic barriers.
Mountain ranges
A land bridge separates marine life
Allopatric speciation increases when a population is both small and isolated
Small population lead to genetic drift and natural selection
Speciation does not occur unless the genetic changes lead to reproductive barriers.

26. New species will not arise just because populations become geographically isolated. For _______________speciation to occur, changes in the gene pool must produce __________ __________.

27. Freshman biology skip to slide 33

28. population populations
14.5 Reproductive barriers may evolve as populations diverge
Laboratory studies of fruit flies
Have shown that changes in food sources can cause speciation
Starch medium
Maltose medium
Initial sample
of fruit flies
Results of
mating experiments
Female
Starch Maltose
Same Different
population populations
Maltose Starch
Male
Different Same
Mating frequencies
in experimental group
in control group 22 9 20 8 12 18 15
Figure 14.5A

29. Geographic isolation in Death Valley
Has led to the evolution of new species of pupfish
Figure 14.5B
A pupfish

30. 14.6 New species can also arise within the same geographic area as the parent species
In sympatric speciation
New species may arise without geographic isolation

31. Many plant species have evolved by polyploidy
Multiplication of the chromosome number due to errors in cell division
Figure 14.6B
Parent species
Meiotic
error
Self-fertilization
Offspring may be viable and self-fertile
Zygote
Unreduced
diploid gametes
2n = 6
Diploid
4n = 12
Tetraploid
O. gigas
O. lamarckiana
Figure 14.6A

32. CONNECTION 14.7 Polyploid plants clothe and feed us
Many plants, including food plants such as bread wheat
Are the result of hybridization and polyploidy AA BB AB
AA BB DD
ABD
AA BB DD 
Wild Triticum
(14 chromosomes)
Triticum monococcum
(14 chromosomes)
Sterile hybrid
(14 chromosomes)
Meiotic error and
self-fertilization 
T.tauschii
(wild)
(14 chromosomes)
T.turgidum
Emmer wheat
(28 chromosomes)
Sterile hybrid
(21 chromosomes)
Meiotic error and
self-fertilization
Figure 14.7A
T.aestivum
Bread wheat
(42 chromosomes)
Figure 14.7B

33. 14.8 Adaptive radiation may occur in new or newly vacated habitats
In adaptive radiation, the evolution of new species
Occurs when mass extinctions or colonization provide organisms with new environments

34. Island chains Provide examples of adaptive radiation
In the Galapagos, the islands were formed by underwater volcano’s. They gradually were occupied by plants and other organisms. video
Cactus-seed-eater
(cactus finch)
Seed-eater
(medium ground finch)
Tool-using insect-eater
(woodpecker finch) 1 2 3 4 5 A B C D
Figure 14.8B
Figure 14.8A

35. Why would allopatric speciation be less common on an island close to a mainland than a more isolated island of the same size?
Mainland populations promote continued gene flow for those islands closer to them. The further away a the island is to the main land, the smaller the gene pool.

36. Skip to 14.3 slide 47

37. TALKING ABOUT SCIENCE
14.9 Peter and Rosemary Grant study the evolution of Darwin’s finches
Peter and Rosemary Grant
Have documented natural selection acting on populations of Galápagos finches
Figure 14.9

38. The occasional hybridization of finch species
May also have been important in their adaptive radiation

39. 14.10 The tempo of speciation can appear steady or jumpy
According to the gradualism model
New species evolve by the gradual accumulation of changes brought about by natural selection
Time
Figure 14.10A

40. The punctuated equilibrium model draws on the fossil record
Where species change the most as they arise from an ancestral species and then change relatively little for the rest of their existence
Time
Figure 14.10B

41. Transparent protective
MACROEVOLUTION
14.11 Evolutionary novelties may arise in several ways
Many complex structures evolve in many stages
From simpler versions having the same basic function
Figure 14.11
Light-sensitive
cells
Fluid-filled cavity
Transparent protective
tissue (cornea)
Cornea
Layer of
light-sensitive
cells (retina)
Nerve
fibers
Optic
nerve
Eyecup
Retina
Lens
Patch of light-
sensitive cells
Simple pinhole
camera-type eye
Eye with
primitive lens
Complex
Limpet
Abalone
Nautilus
Marine snail
Squid

42. Other novel structures result from exaptation
The gradual adaptation of existing structures to new functions

43. 14.12 Genes that control development are important in evolution
“Evo-devo”
Is a field that combines evolutionary and developmental biology

44. Many striking evolutionary transformations
Are the result of a change in the rate or timing of developmental changes
Figure 14.12A

45. Changes in the timing and rate of growth
Have also been important in human evolution
Figure 14.12B
Chimpanzee fetus
Chimpanzee adult
Human fetus
Human adult

46. Stephen Jay Gould, an evolutionary biologist
Contended that Mickey Mouse “evolved”
Figure 14.12C
Copyright Disney
Enterprises, Inc.

47. 14.13 Evolutionary trends do not mean that evolution is goal directed
Evolutionary trends reflect species selection
The unequal speciation or unequal survival of species on a branching evolutionary tree
A general trend in evolution of mammals was toward larger brain size relative to body size. Use the species model to explain how such a trend could occur
Hippidion and other genera
Nannippus
Neohipparion
Hipparion
Sinohippus
Megahippus
Archaeohippus
Callippus
Hypohippus
Anchitherium
Miohippus
Parahippus
Paleotherium
Propalaeotherium
Pachynolophus
Orohippus
Epihippus
Equus
Pliohippus
Merychippus
Mesohippus
Hyracotherium
Grazers
Browsers
EOCENE
OLIGOCENE
MIOCENE
PLIOCENE
E RECENT
PLEISTOCEN
Figure 14.13

48. A general trend in evolution of mammals was toward larger brain size relative to body size. Use the species model to explain how such a trend could occur.