1. Chapter 14 The Origin of Species
Chapter 14 The Origin of Species
Theories behind “Why” new species develop and “How” new species develop
Examples of supporting evidence of biological diversity

2. 14.1 The origin of species is the source of biological diversity
Microevolution = gradual change in a population overtime
Speciation = the origin of new species, is at the focal point of evolution
Macroevolution = evolutionary change on a grand scale
Replacement of one species with another
Increases biodiversity
Figure 14.1

3. 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
Scientific name = the genus and species names
Should be italicized or underlined
Homo sapiens
Homo = genus
sapien = species
Linnaeus’ system established the basis for taxonomy
The branch of biology concerned with naming and classifying the diverse forms of life

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

5. Different Views for Identifying Species
The Biological Species Concept defines a species as:
A population or group of populations whose members can interbreed and produce fertile offspring
Other Species Concepts
The morphological species concept:
Classifies organisms based on observable phenotypic traits
Primary way of classifying organisms
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
Uses physical characteristics and DNA sequencing

6. 14.3 Reproductive barriers keep species separate
Serve to isolate a species’ gene pool and prevent interbreeding  create new species
Are categorized as prezygotic or postzygotic
Table 14.3

7. Prezygotic Barriers - prevent mating or fertilization between species
Temporal isolation - two species breed at different times
Habitat isolation – live in different habitats  don’t meet
Behavioral isolation - there is little or no sexual attraction between species, due to specific behaviors
Mechanical isolation - female and male sex organs or gametes are not compatible
Gametic isolation – gametes die or fail to unite
Figure 14.3A
Figure 14.3B
Figure 14.3C

8. Postzygotic Barriers - Operate after hybrid zygotes are formed
Hybrid inviability – hybrids don’t develop
Hybrid sterility - hybrid offspring between two species are sterile and therefore cannot mate
Hybrid breakdown – first generation is viable, 2nd generation sterile or feeble
Figure 14.3D

9. MECHANISMS OF SPECIATION (the “HOW”)
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

10. 14.5 Reproductive barriers may evolve as populations diverge
Geographic isolation in Death Valley has led to the evolution of new species of pupfish
Figure 14.5B
A pupfish

11. Many plant species have evolved by polyploidy
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
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

12. 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

13. 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
Island chains provide examples of adaptive radiation (ex. Galapagos Islands)
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

14. 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
Fits Darwin’s view of the origin of species
Big changes (speciations) occur by the steady accumulation of many small changes
Time
Figure 14.10A

15. The punctuated equilibrium model draws on the fossil record
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

16. 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, Ex. Eye complexity
Other novel structures result from exaptation - the gradual adaptation of existing structures to new functions
Ex. Feathers came before flight – possibly for insulation
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

17. 14.12 Genes that control development are important in evolution
Evolutionary Biology - “Evo-devo”
A field that combines evolutionary and developmental biology
Many striking evolutionary transformations are the result of a change in the rate or timing of developmental changes
Figure 14.12A

18. Humans retain more fetus-like contours to skull
Changes in the timing and rate of growth have also been important in human evolution
Humans retain more fetus-like contours to skull
Is there a connection between our physical traits and our unusually long period of dependency (childhood)?
Stephen Jay Gould, an evolutionary biologist, contended that Mickey Mouse “evolved” juvenile traits
Figure 14.12B
Chimpanzee fetus
Chimpanzee adult
Human fetus
Human adult
Figure 14.12C
Copyright Disney
Enterprises, Inc.

19. 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
The species that endure the longest and generate the greatest number of new species determine the direction of major evolutionary trends
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