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 (LARGE) scale
Replacement of one species with another
Increases biodiversity
Figure 14.1

3. 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 (example: mule)
Hybrid breakdown – first generation is viable, 2nd generation sterile or feeble
Figure 14.3D
Animations of Pre Zygotic and Post Zygotic Barriers

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. 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 (genetic mutation)
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

11. CONNECTION
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

12. 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 (“Founder Effect”)
Island chains (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

13. 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

14. 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

15. Transparent protective
MACROEVOLUTION
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

16. 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

17. Tracing Evolutionary History
Chapter 15
Tracing Evolutionary History

18. MACROEVOLUTION AND EARTH’S HISTORY
15.1 The fossil record chronicles macroevolution
The fossil record documents the main events in the history of life
In the geologic record:
Major transitions in life-forms separate eras
Smaller changes divide eras into periods

19. 15.2 The actual ages of rocks and fossils mark geologic time
Relative age of fossils is determined by the rock strata in which the fossils appear
Radiometric dating (actual age) - Measures the decay of radioactive isotope; Can gauge the actual ages of fossils and the rocks in which they are found
Half-life: fixed rate of decay = the amount of time it takes for ½ of the original isotope to decay
Carbon-14 used to date younger fossils
Potassium-40 can be used for fossils hundreds of millions of years old
Half-time emitted
Uranium million yrs alpha, gamma
Plutonium ,000 yrs alpha, gamma

20. The geologic record – know the Eras and major events that occur in each
Table 15.1
p. 298

21. 15.3 Continental drift has played a major role in macroevolution
Continental drift (now Plate Tectonics) is the slow, constant movement of Earth’s crustal plates on the hot mantle
The formation of Pangaea (~250 mya) altered habitats and triggered extinctions
Breakup of Pangaea (~180 mya) created Laurasia and Gondwana
Modern continents began to take shape (~65mya)
Figure 15.3B 65
135
245
Millions of years ago
Paleozoic
Mesozoic
Cenozoic
North America
Eurasia
Africa
South
America
India
Antarctica
Australia
Laurasia
Gondwana
Pangaea
Edge of one plate being pushed over edge of neighboring plate (zones of violent geologic events)
Antarctic Plate
Australian Plate
Split developing
Indian Plate
Eurasian Plate
North American Plate
South American Plate
Nazca Plate
Pacific Plate
Arabian Plate
African Plate
Figure 15.3A

22. The separation of the continents affected the distribution and diversification of organisms
North
America
South
Europe
Asia
Africa
Australia
= Living lungfishes
= Fossilized lungfishes
Figure 15.3C
Lungfish Video
Figure 15.3D

23. 15.4 Tectonic trauma imperils local life
CONNECTION
15.4 Tectonic trauma imperils local life
Volcanoes and earthquakes result from plate tectonics
San Andreas Fault
North
American
Plate
San Francisco
Santa Cruz
Los Angeles
Pacific
California
Figure 15.4A, B

24. 15.5 Mass extinctions were followed by diversification of life-forms
Mass extinctions occurred at the end of the Permian and Cretaceous periods
The Cretaceous extinction (~ 65 mya), which included the dinosaurs, may have been caused by an asteroid which landed near the Yucatan Peninsula
A rebound in diversity follows mass extinctions
Figure 15.5
North America
Chicxulub crater
Yucatán Peninsula

25. PHYLOGENY AND SYSTEMATICS
15.6 Phylogenies are based on homologies in fossils and living organisms
Phylogeny, the evolutionary history of a group, is based on identifying homologous and molecular sequences that provide evidence of common ancestry (Phylogenetic tree)
Homologous structures – evolved from a common ancestral structure, shows shared ancestry and results from divergent evolution
Analogous structures (similarities) – structures of non-related species are similar because they evolved in similar environments, result from convergent evolution
Cladogram– a diagram depicting the pattern of shared characters
Systematics– the science of classification

26. 15.7 Systematics connects classification with evolutionary history
Taxonomists assign a binomial (scientific name) to each species
A genus may include a group of related species
Genera are grouped into progressively larger categories (know these!)
Domain, kingdom, phylum, class, order, family, genus, species
*KEY TO REMEMBER: Dear King Philip Came Over From Germany Saturday
A phylogenetic tree is a
hypothesis of evolutionary relationships
Species
Felis
catus
(domestic
cat)
Mephitis
mephitis
(striped skunk)
Lutra
lutra
(European
otter)
Canis
familiaris
(domestic dog)
lupus
(wolf)
Genus
Family
Order
Felidae
Carnivora
Mustelidae
Canidae
Figure 15.7B
Species
Genus
Family
Order
Class
Phylum
Kingdom
Domain
Felis
catus
Felidae
Carnivora
Mammalia
Chordata
Animalia
Eukarya

27. Binomial nomenclature
Ursus arctos
Genus
Species
(Grizzly Bear)

28. Classifying Species into Larger groups

29. Cladograms are diagrams based on shared characteristics among species
Iguana
Derived Characteristics
(Ingroup)
Duck-billed
platypus
Hair, mammary glands
Kangaroo
Gestation
Beaver
Long gestation
Phylogenetic Tree

30. Molecular biology is a powerful tool in systematics
Lesser
panda
Procyonidae
Phylogenetic Tree
Molecular Clocks are the predictable changes in genes caused by mutations. The changes can be used to determine the amount of time that has passed since two species diverged from a common ancestor.
Raccoon
Giant
panda
Spectacled bear
Ursidae
Sloth bear
Sun bear
American
black bear
Asian black bear
Polar bear
Brown bear 35 30 25 20 15 10
Pleistocene
Oligocene
Miocene
Pliocene
Millions of years ago

31. DOMAINS 15.10 Arranging life into kingdoms is a work in progress
Monera
Protista
Plantae
Fungi
Animalia
Earliest
organisms
Prokaryotes
Eukoryotes
Figure 15.10A
DOMAINS
Bacteria
Archaea
Eukarya
Earliest
organisms
Prokaryotes
Eukoryotes
Figure 15.10B