1. How Biological Diversity Evolves
Chapter 14

2. The origin of species
What accounts for all the diversity in the millions of species (extinct and extant) on our planet?
What makes these two meadowlarks different?
A variety of barriers prevent interbreeding
Eastern and western meadowlarks are two different species and do not interbreed

3. Prezygotic barriers Temporal Isolation
Skunk species that mate at different times

4. Prezygotic barriers Habitat/Ecological Isolation
Garter snake species from different habitats

5. Prezygotic barriers Behavioral Isolation
Mating ritual of blue-footed boobies

6. Prezygotic barriers Mechanical Isolation
Snail species whose genital openings cannot align

7. Prezygotic barriers Gametic Isolation
Sea urchin species whose gametes cannot fuse

8. Postzygotic barriers Reduced Hybrid Viability
Frail hybrid salamander offspring

9. Postzygotic barriers Reduced Hybrid Fertility Horse Donkey Mule
Mule (sterile hybrid of
horse and donkey)

10. Postzygotic barriers Hybrid Breakdown
Sterile next-generation rice hybrid

11. INDIVIDUALS OF DIFFERENT SPECIES
Prezygotic Barriers
Temporal isolation
Habitat isolation
Behavioral isolation
MATING ATTEMPT
Mechanical isolation
Gametic isolation
FERTILIZATION (ZYGOTE FORMS)
Postzygotic Barriers
Reduced hybrid viability
Reduced hybrid fertility
Hybrid breakdown
VIABLE, FERTILE OFFSPRING
No Barriers

12. Mechanisms for speciation
Allopatric speciation
Sympatric speciation

13. Allopatric speciation
Ammospermophilus harrisii
Ammospermophilus leucurus

14. Sympatric speciation Chromosomes cannot pair Asexual reproduction
Species A
2n  4
Gamete
n  2
Sterile hybrid
n  5
Can reproduce
asexually
Viable, fertile
hybrid species
2n  10
Gamete
n  3
Species B
2n  6

15. The fossil record in strata

17. Plate tectonics and biogeography
North
American
Plate
Eurasian Plate
Philippine
Plate
ATLANTIC
OCEAN
Juan de
Fuca
Plate
Caribbean
Plate
Arabian
Plate
Indian
Plate
Cocos
Plate
South
American
Plate
Pacific
Plate
Nazca
Plate
Australian
Plate
African
Plate
PACIFIC
OCEAN
Scotia Plate
Antarctic
Plate
Key
Zones of violent tectonic activity
Direction of movement

18. Pangea “all land” Present Cenozoic India collides with Eurasia. 65 135
North America
Eurasia 65
Africa
South
America
India
Madagascar
Australia
Antarctica
Laurasia
135
Pangaea splits
into Laurasia
and Gondwana.
Gondwana
Mesozoic
251 million
years ago
Pangaea
Paleozoic
Pangaea is
formed.

19. Biogeography
Australia and its neighboring islands are home to more than 200 species of marsupials, most of which are found nowhere else in the world
Sugar glider, an omnivore
Tasmanian devil, a carnivore
Koala, an herbivore

20. Phylogeny for some of the members of the order Carnivora
Figure 14.22
Order
Family
Genus
Species
Panthera
pardus
(leopard)
Felidae
Panthera
Mephitis
mephitis
(striped skunk)
Mephitis
Carnivora
Mustelidae
Lutra
lutra
(European
otter)
Lutra
Canis
latrans
(coyote)
Phylogeny for some of the members of the order Carnivora
Canidae
Canis
Canis
lupus
(wolf)

21. Practical application of phylogenies
Growing food
Researchers have identified two species of wild grasses that may be maize’s closest living relatives
The genomes of these plants may harbor alleles that offer disease resistance or other useful traits that could be transferred into cultivated maize

22. Analogous structures

23. Cladistics diagram or cladogram
Iguana
Outgroup
(reptile)
Duck-billed
platypus
Hair, mammary glands
Kangaroo
Ingroup
(mammals)
Gestation
Beaver
Long gestation

24. Classification: a work in progress
Phylogenetic trees are hypotheses about evolutionary history
Linnaeus divided all known forms of life between the plant and animal kingdoms
This two-kingdom system prevailed in biology for over 200 years
In the mid-1900s, the two-kingdom system was replaced by a five-kingdom system that
placed all prokaryotes in one kingdom and
divided the eukaryotes among four other kingdoms
In the late 1900s, molecular studies and cladistics led to the development of a three-domain system, recognizing
two domains of prokaryotes (Bacteria and Archaea) and
one domain of eukaryotes (Eukarya)
The domain Eukarya is currently divided into kingdoms, but the exact number of kingdoms is still under debate