Chapter 14 How Biological Diversity Evolves
Laura Coronado
Bio 10
Chapter 14
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 10
Chapter 14
MACROEVOLUTION & THE DIVERSITY OF LIFE
– Macroevolution:
• 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 10
Chapter 14
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 10
Chapter 14
PATTERNS OF EVOLUTION
Nonbranching Evolution
(no new species)
Laura Coronado
Branching Evolution
(results in speciation)
Bio 10
Chapter 14
Figure 14.1
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 10
Chapter 14
Similarity between different species
Laura Coronado
Bio 10
Diversity within one species
Chapter 14
Figure 14.2
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 10
Chapter 14
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 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
Reduced hybrid viability
Reduced hybrid fertility
Hybrid breakdown
VIABLE, FERTILE
OFFSPRING
Laura Coronado
Bio 10
Chapter 14
Figure 14.3
PREZYGOTIC BARRIERS
Habitat Isolation
Temporal Isolation
Behavioral Isolation
Mechanical Isolation
Laura Coronado
Bio 10
Gametic Isolation
Chapter 14
Figure 14.4
POSTZYGOTIC BARRIERS
Reduced Hybrid Viability Reduced Hybrid Fertility
Horse
Donkey
Mule
Laura Coronado
Bio 10
Chapter 14
Figure 14.5
Hybrid Breakdown
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 10
Chapter 14
Allopatric speciation
(occurs after
geographic isolation)
Parent
population
Sympatric speciation
(occurs without
geographic isolation)
Laura Coronado
Bio 10
Chapter 14
Figure 14.UN2
Ammospermophilus leucurus
Ammospermophilus harrisii
Laura Coronado
Bio 10
Chapter 14
Figure 14.7
Populations
become
allopatric
Populations
become
sympatric
Populations
interbreed
Gene pools merge:
No speciation
Populations
cannot
interbreed
Geographic
barrier
Reproductive
isolation:
Speciation has
occurred
Time
Laura Coronado
Bio 10
Chapter 14
Figure 14.8
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 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 10
Chapter 14
Domesticated
Triticum monococcum
(14 chromosomes)
BB
AA
Wild Triticum
(14 chromosomes)
AB
Sterile hybrid
(14 chromosomes)
T. turgidum
Emmer wheat
(28 chromosomes)
AA BB
DD
Wild
T. tauschii
(14 chromosomes)
ABD
Sterile hybrid
(21 chromosomes)
AA BB DD
Laura Coronado
Bio 10
Chapter 14
T. aestivum
Bread wheat
(42 chromosomes)
Figure 14.9-4
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 10
Chapter 14
Punctuated
model
Time
Graduated
model
Laura Coronado
Bio 10
Chapter 14
Figure 14.10
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 10
Chapter 14
Wing claw
(like reptile)
Teeth
(like reptile)
Feathers
Long tail with
many vertebrae
(like reptile)
Artist’s reconstruction
Fossil
Laura Coronado
Bio 10
Chapter 14
Figure 14.11
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 10
Chapter 14
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 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 10
Chapter 14
Chimpanzee fetus
Chimpanzee adult
Human fetus
Human adult
(paedomorphic features)
Laura Coronado
Bio 10
Chapter 14
Figure 14.13
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 10
Chapter 14
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 10
Chapter 14
Laura Coronado
Bio 10
Chapter 14
Figure 14.14
Laura Coronado
Bio 10
Chapter 14
Table 14.1
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 10
Chapter 14
Carbon-14 radioactivity
(as % of living organism’s
C-14 to C-12 ratio)
Radioactive decay
of carbon-14
100
75
50
25
0
5.6 11.2 16.8 22.4 28.0 33.6 39.2 44.8 50.4
0
Time (thousands of years)
How
carbon-14
dating is
used to
determine
the vintage
of a
fossilized
clam shell
Carbon-14 in shell
Laura Coronado
Bio 10
Chapter 14
Figure 14.15
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 10
Chapter 14
Laura Coronado
Bio 10
Chapter 14
Figure 14.16
– 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 10
Chapter 14
Cenozoic
Present
65
Eurasia
Africa
India
South
America Madagascar
Mesozoic
Laurasia
Paleozoic
251 million years ago
135
Antarctica
Laura Coronado
Bio 10
Chapter 14
Figure 14.17
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 10
Chapter 14
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 10
Chapter 14
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 10
Chapter 14
Chicxulub
crater
Laura Coronado
Bio 10
Chapter 14
Figure 14.18-3
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 10
Chapter 14
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 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 10
Chapter 14
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 10
Chapter 14
Leopard (Panthera pardus)
Tiger (Panthera
tigris)
Lion (Panthera leo)
Jaguar (Panthera onca)
Laura Coronado
Bio 10
Chapter 14
Figure 14.19
Species
Panthera
pardus
Genus
Panthera
Leopard
(Panthera pardus)
Family
Felidae
Order
Carnivora
Class
Mammalia
Phylum
Chordata
Kingdom
Animalia
Domain
Eukarya
Laura Coronado
Bio 10
Chapter 14
Figure 14.20
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 10
Chapter 14
Order
Family
Felidae
Genus
Species
Panthera
Panthera
pardus
(leopard)
Mephitis
Mephitis
mephitis
(striped skunk)
Carnivora
Mustelidae
Lutra
Lutra
lutra
(European
otter)
Canis
latrans
(coyote)
Canidae
Canis
Canis
lupus
(wolf)
Laura Coronado
Bio 10
Chapter 14
Figure 14.21
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 10
Chapter 14
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 10
Chapter 14
Laura Coronado
Bio 10
Chapter 14
Figure 14.22
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 10
Chapter 14
Iguana
Outgroup
(reptile)
Duck-billed
platypus
Kangaroo
Hair, mammary
glands
Gestation
Ingroup
(mammals)
Beaver
Long gestation
Laura Coronado
Bio 10
Chapter 14
Figure 14.23
Lizards
and snakes
Crocodilians
Pterosaurs
Common
ancestor of
crocodilians,
dinosaurs,
and birds
Ornithischian
dinosaurs
Saurischian
dinosaurs
Birds
Laura Coronado
Bio 10
Chapter 14
Figure 14.24
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 10
Chapter 14
Domain Bacteria
Earliest
organisms
Domain Archaea
The protists
(multiple
kingdoms)
Kingdom
Plantae
Domain Eukarya
Kingdom
Fungi
Kingdom
Animalia
Laura Coronado
Bio 10
Chapter 14
Figure 14.25
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 10
Chapter 14
Ancestral
mammal
Extinction of
dinosaurs
Reptilian
ancestor
Monotremes
(5 species)
Marsupials
(324 species)
Eutherians
(5,010 species)
250
65 50
Millions of years ago
200
150
100
0
Laura Coronado
American black bear
Bio 10
Chapter 14
Figure 14.26
Zygote
Gametes Prezygotic barriers
• Temporal isolation
• Habitat isolation
• Behavioral isolation
• Mechanical isolation
• Gametic isolation
Laura Coronado
Viable,
Postzygotic barriers
fertile
• Reduced hybrid viability offspring
• Reduced hybrid fertility
• Hybrid breakdown
Bio 10
Chapter 14
Figure 14.UN1