1. Chapter 14
The Origin of Species

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. 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
Figure 14.1

4. Earth’s incredible biological diversity is the result of macroevolution
Which begins with the origin of new species

5. CONCEPTS OF 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

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

7. Speciation

8. 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

9. Speciation in Fruit Flies

10. 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

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

12. 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

13. 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

14. 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

15. Real Examples of Possible Speciation
Rhagoletis pomonella is a fly that is native to North America. Its normal host is the hawthorn tree. Sometime during the nineteenth century it began to infest apple trees. Since then it has begun to infest cherries, roses, pears and possibly other members of the rosaceae. Quite a bit of work has been done on the differences between flies infesting hawthorn and flies infesting apple. There appear to be differences in host preferences among populations. Offspring of females collected from on of these two hosts are more likely to select that host for oviposition (Prokopy et al. 1988). Genetic differences between flies on these two hosts have been found at 6 out of 13 allozyme loci (Feder et al. 1988, see also McPheron et al. 1988). Laboratory studies have shown an asynchrony in emergence time of adults between these two host races (Smith 1988). Flies from apple trees take about 40 days to mature, whereas flies from hawthorn trees take days to mature. This makes sense when we consider that hawthorn fruit tends to mature later in the season that apples. Hybridization studies show that host preferences are inherited, but give no evidence of barriers to mating. This is a very exciting case. It may represent the early stages of a sympatric speciation event (considering the dispersal of R. pomonella to other plants it may even represent the beginning of an adaptive radiation). It is important to note that some of the leading researchers on this question are urging caution in interpreting it. Feder and Bush (1989) stated

16. 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

17. 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
The phylogenetic species concept
Defines a species as a set of organisms representing a specific evolutionary lineage

18. 14.3 Reproductive barriers keep species separate
Table 14.3
14.3 Reproductive barriers keep species separate
Reproductive barriers
Serve to isolate a species’ gene pool and prevent interbreeding
Are categorized as prezygotic or postzygotic

19. Prezygotic Barriers Prezygotic barriers
Prevent mating or fertilization between species
Figure 14.3A
In temporal isolation
Two species breed at different times

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

21. In mechanical isolation
Female and male sex organs or gametes are not compatible
Figure 14.3C

22. Postzygotic Barriers Postzygotic barriers
Operate after hybrid zygotes are formed

23. One postzygotic barrier is hybrid sterility
Where hybrid offspring between two species are sterile and therefore cannot mate
Figure 14.3D

24. 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

25. Provide examples of adaptive radiation
Island chains
Provide examples of adaptive radiation
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

26. 14.9 Peter and Rosemary Grant study the evolution of Darwin’s finches
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

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

28. 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

29. 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

30. 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

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

32. 14.12 Genes that control development are important in evolution
“Evo-devo”
Is a field that combines evolutionary and developmental biology

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

34. 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

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

36. 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
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