1. Chapter 14 How Biological Diversity Evolves
Laura Coronado Bio Chapter 14

2. Biology and Society: The Sixth Mass Extinction
Over the past 600 million years the fossil record reveals five periods of extinction when 50–90% of living species suddenly died out.
Our current rate of extinction, over the past 400 years, indicates that we may be living in, and contributing to, the sixth mass extinction period.
Mass extinctions:
Pave the way for the evolution of new and diverse forms, but
Take millions of years for Earth to recover
Laura Coronado Bio Chapter 14

3. MACROEVOLUTION & THE DIVERSITY OF LIFE
Encompasses the major biological changes evident in the fossil record
Includes the formation of new species
Speciation:
Is the focal point of macroevolution
May occur based on two contrasting patterns
Laura Coronado Bio Chapter 14

4. MACROEVOLUTION & THE DIVERSITY OF LIFE
In nonbranching evolution:
A population transforms but
Does not create a new species
In branching evolution, one or more new species branch from a parent species that may:
Continue to exist in much the same form or
Change considerably
Laura Coronado Bio Chapter 14

5. Nonbranching Evolution (results in speciation)
PATTERNS OF EVOLUTION
Nonbranching Evolution
(no new species)
Branching Evolution
(results in speciation)
Figure 14.1 Two patterns of evolution
Laura Coronado Bio Chapter 14
Figure 14.1

6. Laura Coronado Bio 10 Chapter 14
THE ORIGIN OF SPECIES
Species is a Latin word meaning:
“Kind” or
“Appearance.”
The biological species concept defines a species as
“A group of populations whose members have the potential to interbreed and produce fertile offspring”
The biological species concept cannot be applied in all situations, including:
Fossils
Asexual organisms
Laura Coronado Bio Chapter 14

7. Laura Coronado Bio 10 Chapter 14
Figure 14.2 The biological species concept is based on reproductive compatibility
Similarity between different species
Diversity within one species
Laura Coronado Bio Chapter 14
Figure 14.2

8. Reproductive Barriers between Species
Prezygotic barriers prevent mating or fertilization between species.
Prezygotic barriers include:
Temporal isolation
Habitat isolation
Behavioral isolation
Mechanical isolation
Gametic isolation
Laura Coronado Bio Chapter 14

9. Reproductive Barriers between Species
Postzygotic barriers operate if:
Interspecies mating occurs and
Hybrid zygotes form
Postzygotic barriers include:
Reduced hybrid viability
Reduced hybrid fertility
Hybrid breakdown
Laura Coronado Bio Chapter 14

10. Laura Coronado Bio 10 Chapter 14
INDIVIDUALS OF
DIFFERENT SPECIES
Prezygotic Barriers
Temporal isolation
Habitat isolation
Behavioral isolation
MATING ATTEMPT
Mechanical isolation
Gametic isolation
FERTILIZATION
(ZYGOTE FORMS)
Postzygotic Barriers
Figure 14.3 Reproductive barriers between closely related species
Reduced hybrid viability
Reduced hybrid fertility
Hybrid breakdown
VIABLE, FERTILE
OFFSPRING
Laura Coronado Bio Chapter 14
Figure 14.3

11. Laura Coronado Bio 10 Chapter 14
PREZYGOTIC BARRIERS
Temporal Isolation
Habitat Isolation
Behavioral Isolation
Mechanical Isolation
Gametic Isolation
Figure 14.4 Prezygotic barriers
Laura Coronado Bio Chapter 14
Figure 14.4

12. Laura Coronado Bio 10 Chapter 14
POSTZYGOTIC BARRIERS
Reduced Hybrid Viability
Reduced Hybrid Fertility
Hybrid Breakdown
Horse
Donkey
Figure 14.5 Postzygotic barriers
Mule
Laura Coronado Bio Chapter 14
Figure 14.5

13. Mechanisms of Speciation
A key event in the potential origin of a species occurs when a population is severed from other populations of the parent species.
Species can form by:
Allopatric speciation, due to geologic processes that can fragment a population into two or more isolated geographic populations
Sympatric speciation, without geographic isolation
Speciation occurs only with the evolution of reproductive barriers between the isolated population and its parent population.
Laura Coronado Bio Chapter 14

14. Allopatric speciation geographic isolation) geographic isolation)
(occurs after
geographic isolation)
Parent
population
Figure 14.UN2 Summary: mechanisms of speciation
Sympatric speciation
(occurs without
geographic isolation)
Laura Coronado Bio Chapter 14
Figure 14.UN2

15. Laura Coronado Bio 10 Chapter 14
Ammospermophilus harrisii
Ammospermophilus leucurus
Figure 14.7 Allopatric speciation of antelope squirrels on opposite rims of the Grand Canyon
Laura Coronado Bio Chapter 14
Figure 14.7

16. Laura Coronado Bio 10 Chapter 14
Populations
become
allopatric
Populations
become
sympatric
Populations
interbreed
Gene pools merge:
No speciation
Populations
cannot
interbreed
Geographic
barrier
Figure 14.8 Has speciation occurred during geographic isolation?
Reproductive
isolation:
Speciation has
occurred
Time
Laura Coronado Bio Chapter 14
Figure 14.8

17. Laura Coronado Bio 10 Chapter 14
Sympatric Speciation
Sympatric speciation occurs:
Occurs when part of the population becomes a new species while in the midst of its parent population
While the new & old species live in the same time and place
Due to subgroups of a population that evolve adaptations for exploiting food sources in different habitats
Due to sexual selection
Most often if a genetic change produces a reproductive barrier between the new and old species
polyploids
Laura Coronado Bio Chapter 14

18. Laura Coronado Bio 10 Chapter 14
Polyploids
Originate from accidents during cell division which may produce an extra set of chromosomes
Each cell has more than two sets of chromosomes
Occurs in a single generation
New species cannot produce fertile hybrids with its parent species
Most often result from the hybridization of two parent species, e.g. domesticated plants: oats, potatoes, bananas, peanuts, apples, coffee & wheat
Laura Coronado Bio Chapter 14

19. Laura Coronado Bio 10 Chapter 14
Domesticated
Triticum monococcum
(14 chromosomes)
Wild Triticum
(14 chromosomes) AA BB AB
Sterile hybrid
(14 chromosomes)
T. turgidum
Emmer wheat
(28 chromosomes)
AA BB DD
Wild
T. tauschii
(14 chromosomes)
Figure 14.9 The evolution of wheat (Step 4)
ABD
Sterile hybrid
(21 chromosomes)
T. aestivum
Bread wheat
(42 chromosomes)
AA BB DD
Laura Coronado Bio Chapter 14
Figure

20. What Is the Tempo of Speciation?
There are two contrasting models of the pace of evolution:
The gradual model, in which big changes (speciations) occur by the steady accumulation of many small changes
The punctuated equilibria model, in which there are
Long periods of little change, equilibrium, punctuated by
Abrupt episodes of speciation
Laura Coronado Bio Chapter 14

21. Laura Coronado Bio 10 Chapter 14
Punctuated
model
Time
Graduated
model
Figure Two models for the tempo of evolution
Laura Coronado Bio Chapter 14
Figure 14.10

22. THE EVOLUTION OF BIOLOGICAL NOVELTY
An exaptation:
Is a structure that evolves in one context, but becomes adapted for another function
Is a type of evolutionary remodeling
Account for the gradual evolution of novel structures.
Birds:
Are derived from a lineage of earthbound reptiles
Evolved flight from flightless ancestors
Laura Coronado Bio Chapter 14

23. Laura Coronado Bio 10 Chapter 14
Wing claw
(like reptile)
Teeth
(like reptile)
Figure An extinct bird: Archaeopteryx
Feathers
Long tail with
many vertebrae
(like reptile)
Fossil
Artist’s reconstruction
Laura Coronado Bio Chapter 14
Figure 14.11

24. Adaptations of Old Structures for New Functions
Birds:
Are derived from a lineage of earthbound reptiles
Evolved flight from flightless ancestors
Bird wings are modified forelimbs that were previously adapted for non-flight functions, such as:
Thermal regulation
Courtship displays
Camouflage
The first flights may have been only glides or extended hops as the animal pursued prey or fled from a predator.
Laura Coronado Bio Chapter 14

25. Evo-Devo: Development & Evolutionary Novelty
A subtle change in a species’ genes that control the development from a zygote to an adult can have profound effects, changing the:
Rate
Timing
Spatial pattern of development
Evo-devo, evolutionary developmental biology, is the study of the evolution of developmental processes in multicellular organisms.
Laura Coronado Bio Chapter 14

26. Laura Coronado Bio 10 Chapter 14
Paedomorphosis
Is the retention into adulthood of features that were solely juvenile in ancestral species
Has occurred in the evolution of
Axolotl salamanders
Humans
Laura Coronado Bio Chapter 14

27. Laura Coronado Bio 10 Chapter 14
Chimpanzee fetus
Chimpanzee adult
Figure Comparison of human and chimpanzee skull development
Human fetus
Human adult
(paedomorphic features)
Laura Coronado Bio Chapter 14
Figure 14.13

28. Laura Coronado Bio 10 Chapter 14
Homeotic Genes
Master control genes that regulate:
When structures develop
How structures develop
Where structures develop
Mutations in homeotic genes can profoundly affect body form.
Laura Coronado Bio Chapter 14

29. EARTH HISTORY AND MACROEVOLUTION
Macroevolution is closely tied to the history of the Earth.
The fossil record is:
The sequence in which fossils appear in rock strata
An archive of macroevolution
Geologists have established a geologic time scale reflecting a consistent sequence of geologic periods.
Laura Coronado Bio Chapter 14

30. Laura Coronado Bio 10 Chapter 14
Figure A gallery of fossils
Laura Coronado Bio Chapter 14
Figure 14.14

31. Laura Coronado Bio 10 Chapter 14
Table 14.1 The Geologic Time Scale
Laura Coronado Bio Chapter 14
Table 14.1

32. Geologic Time & Fossil Record
Fossils are reliable chronological records only if we can determine their ages, using:
The relative age of fossils, revealing the sequence in which groups of species evolved, or
The absolute age of fossils, requiring other methods such as radiometric dating
Is the most common method for dating fossils
Is based on the decay of radioactive isotopes
Helped establish the geologic time scale
Laura Coronado Bio Chapter 14

33. (as % of living organism’s Carbon-14 radioactivity
Radioactive decay
of carbon-14
100 75
(as % of living organism’s
Carbon-14 radioactivity
C-14 to C-12 ratio) 50 25
5.6
11.2
16.8
22.4
28.0
33.6
39.2
44.8
50.4
Time (thousands of years)
How
carbon-14
dating is
used to
determine
the vintage
of a
fossilized
clam shell
Carbon-14 in shell
Figure Radiometric dating
Laura Coronado Bio Chapter 14
Figure 14.15

34. Plate Tectonics and Macroevolution
The continents are not locked in place. Continents drift about the Earth’s surface on plates of crust floating on a flexible layer called the mantle.
The San Andreas fault is:
In California
At a border where two plates slide past each other
Plate tectonics explains:
Why Mesozoic reptiles in Ghana (West Africa) and Brazil look so similar
How marsupials were free to evolve in isolation in Australia
Laura Coronado Bio Chapter 14

35. Laura Coronado Bio 10 Chapter 14
Figure California's San Andreas fault
Laura Coronado Bio Chapter 14
Figure 14.16

36. Laura Coronado Bio 10 Chapter 14
About 250 million years ago:
Plate movements formed the supercontinent Pangaea
The total amount of shoreline was reduced
Sea levels dropped
The dry continental interior increased in size
Many extinctions occurred
About 180 million years ago:
Pangaea began to break up
Large continents drifted increasingly apart
Climates changed
The organisms of the different biogeographic realms diverged
Laura Coronado Bio Chapter 14

37. Laura Coronado Bio 10 Chapter 14
Present
Cenozoic
North America
Eurasia 65
Africa
South
America
India
Madagascar
Australia
Antarctica
Laurasia
135
Mesozoic
Gondwana
Figure The history of plate tectonics
251 million years ago
Pangaea
Paleozoic
Laura Coronado Bio Chapter 14
Figure 14.17

38. Mass Extinctions & Explosive Diversifications of Life
The fossil record reveals that five mass extinctions have occurred over the last 600 million years.
The Permian mass extinction:
Occurred at about the time the merging continents formed Pangaea (250 million years ago)
Claimed about 96% of marine species
The Cretaceous extinction:
Occurred at the end of the Cretaceous period, about 65 million years ago
Included the extinction of all the dinosaurs except birds
Permitted the rise of mammals
Laura Coronado Bio Chapter 14

39. The Process of Science: Did a Meteor Kill the Dinosaurs?
Observation: About 65 million years ago, the fossil record shows that:
The climate cooled
Seas were receding
Many plant species died out
Dinosaurs (except birds) became extinct
A thin layer of clay rich in iridium was deposited
Question: Is the iridium layer the result of fallout from a huge cloud of dust that billowed into the atmosphere when a large meteor or asteroid hit Earth?
Laura Coronado Bio Chapter 14

40. The Process of Science: Did a Meteor Kill the Dinosaurs?
Hypothesis: The mass extinction 65 million years ago was caused by the impact of an extraterrestrial object.
Prediction: A huge impact crater of the right age should be found somewhere on Earth’s surface.
Results: Near the Yucatán Peninsula, a huge impact crater was found that:
Dated from the predicted time
Was about the right size
Was capable of creating a cloud that could have blocked enough sunlight to change the Earth’s climate for months
Laura Coronado Bio Chapter 14

41. Laura Coronado Bio 10 Chapter 14
Chicxulub
crater
Figure Trauma for planet Earth and its Cretaceous life (Step 3)
Laura Coronado Bio Chapter 14
Figure

42. CLASSIFYING THE DIVERSITY OF LIFE
Systematics focuses on:
Classifying organisms
Determining their evolutionary relationships
Taxonomy is the:
Identification of species
Naming of species
Classification of species
Laura Coronado Bio Chapter 14

43. Some Basics of Taxonomy
Scientific names ease communication by:
Unambiguously identifying organisms
Making it easier to recognize the discovery of a new species
Carolus Linnaeus (1707–1778) proposed the current taxonomic system based upon:
A two-part name for each species
A hierarchical classification of species into broader groups of organisms
Laura Coronado Bio Chapter 14

44. Laura Coronado Bio 10 Chapter 14
Naming Species
Each species is assigned a two-part name or binomial, consisting of:
The genus
A name unique for each species
The scientific name for humans is Homo sapiens, a two part name, italicized and latinized, and with the first letter of the genus capitalized.
Laura Coronado Bio Chapter 14

45. Hierarchical Classification
Species that are closely related are placed into the same genus.
The taxonomic hierarchy extends to progressively broader categories of classification, from genus to:
Family
Order
Class
Phylum
Kingdom
Domain
Laura Coronado Bio Chapter 14

46. Laura Coronado Bio 10 Chapter 14
Leopard (Panthera pardus)
Tiger (Panthera
tigris)
Lion (Panthera leo)
Figure The four species within the genus Panthera
Laura Coronado Bio Chapter 14
Jaguar (Panthera onca)
Figure 14.19

47. Laura Coronado Bio 10 Chapter 14
Species
Panthera
pardus
Genus
Panthera
Leopard
(Panthera pardus)
Family
Felidae
Order
Carnivora
Class
Mammalia
Figure Hierarchical classification
Phylum
Chordata
Kingdom
Animalia
Domain
Eukarya
Laura Coronado Bio Chapter 14
Figure 14.20

48. Classification and Phylogeny
The goal of systematics is to reflect evolutionary relationships.
Biologists use phylogenetic trees to:
Depict hypotheses about the evolutionary history of species
Reflect the hierarchical classification of groups nested within more inclusive groups
Laura Coronado Bio Chapter 14

49. Laura Coronado Bio 10 Chapter 14
Order
Family
Genus
Species
Panthera
pardus
(leopard)
Felidae
Panthera
Mephitis
mephitis
(striped skunk)
Mephitis
Carnivora
Mustelidae
Lutra
lutra
(European
otter)
Lutra
Figure The relationship of classification and phylogeny for some members of the order Carnivora
Canis
latrans
(coyote)
Canidae
Canis
Canis
lupus
(wolf)
Laura Coronado Bio Chapter 14
Figure 14.21

50. Sorting Homology from Analogy
Homologous structures:
Reflect variations of a common ancestral plan
Are the best sources of information used to
Develop phylogenetic trees
Classify organisms according to their evolutionary history
Convergent evolution:
Involves superficially similar structures in unrelated organisms and is based on natural selection
Similarity due to convergence:
Is called analogy, not homology and can obscure homologies
Laura Coronado Bio Chapter 14

51. Molecular Biology as a Tool in Systematics
Molecular systematics:
Compares DNA and amino acid sequences between organisms
Can reveal evolutionary relationships
Some fossils are preserved in such a way that DNA fragments can be extracted for comparison with living organisms.
Laura Coronado Bio Chapter 14

52. Laura Coronado Bio 10 Chapter 14
Figure Studying ancient DNA
Laura Coronado Bio Chapter 14
Figure 14.22

53. The Cladistic Revolution
Cladistics is the scientific search for clades.
A clade:
Consists of an ancestral species and all its descendants
Forms a distinct branch in the tree of life
Cladistics has changed the traditional classification of some organisms, including the relationships between:
Dinosaurs , Birds, Crocodiles, Lizards, & Snakes
Laura Coronado Bio Chapter 14

54. Laura Coronado Bio 10 Chapter 14
Iguana
Outgroup
(reptile)
Duck-billed
platypus
Kangaroo
Ingroup
(mammals)
Hair, mammary
glands
Figure A simplified example of cladistics
Gestation
Beaver
Long gestation
Laura Coronado Bio Chapter 14
Figure 14.23

55. Laura Coronado Bio 10 Chapter 14
Lizards
and snakes
Crocodilians
Pterosaurs
Common
ancestor of
crocodilians,
dinosaurs,
and birds
Ornithischian
dinosaurs
Figure How cladistics is shaking phylogenetic trees
Saurischian
dinosaurs
Birds
Laura Coronado Bio Chapter 14
Figure 14.24

56. Classification: A Work in Progress
Linnaeus:
Divided all known forms of life between the plant & animal kingdoms
Prevailed with his two-kingdom system 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
Divided the eukaryotes among four other kingdoms
In the late 20th century, molecular studies and cladistics led to the development of a three-domain system, recognizing:
Two domains of prokaryotes (Bacteria and Archaea)
One domain of eukaryotes (Eukarya)
Laura Coronado Bio Chapter 14

57. Laura Coronado Bio 10 Chapter 14
Domain Bacteria
Earliest
organisms
Domain Archaea
The protists
(multiple
kingdoms)
Kingdom
Plantae
Domain Eukarya
Figure The three-domain classification system
Kingdom
Fungi
Kingdom
Animalia
Laura Coronado Bio Chapter 14
Figure 14.25

58. Evolution Connection: Rise of the Mammals
Mass extinctions:
Have repeatedly occurred throughout Earth’s history
Were followed by a period of great evolutionary change
Fossil evidence indicates that:
Mammals first appeared about 180 million years ago
The number of mammalian species
Remained steady and low in number until about 65 million years ago and then
Greatly increased after most of the dinosaurs became extinct
Laura Coronado Bio Chapter 14

59. Laura Coronado Bio 10 Chapter 14
Ancestral
mammal
Monotremes
(5 species)
Extinction of
dinosaurs
Reptilian
ancestor
Marsupials
(324 species)
Eutherians
(5,010 species)
Figure The increase in mammalian diversity after the extinction of dinosaurs
250
200
150
100 65 50
American black bear
Millions of years ago
Laura Coronado Bio Chapter 14
Figure 14.26

60. Laura Coronado Bio 10 Chapter 14
Zygote
Viable,
fertile
offspring
Gametes
Prezygotic barriers
Postzygotic barriers
• Temporal isolation
• Habitat isolation
• Behavioral isolation
• Mechanical isolation
• Gametic isolation
• Reduced hybrid viability
• Reduced hybrid fertility
• Hybrid breakdown
Figure 14.UN1 Summary: reproductive barriers
Laura Coronado Bio Chapter 14
Figure 14.UN1