Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Lectures by Chris C. Romero
PowerPoint® Lectures for
Essential Biology, Third Edition
– Neil Campbell, Jane Reece, and Eric Simon
Essential Biology with Physiology, Second Edition
– Neil Campbell, Jane Reece, and Eric Simon
CHAPTER 14
How Biological Diversity
Evolves
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
MACROEVOLUTION AND THE DIVERSITY OF LIFE
• Macroevolution
• Evolutionary Theory
• Generates biological diversity (Origin of new
species)
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WHAT IS A SPECIES?
•The biological species concept defines a species
as a population or group of populations whose
members have the potential to interbreed with
one another in nature to produce fertile offspring.
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•Speciation
Is the formation of new species; occurs when one or
more new species branch from a parent species,
which may continue to exist.
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• Nonbranching
evolution
• Evolution that can
transform a population
significantly but does
not create a new
species.
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Branching evolution splits a lineage into
two or more species, thereby increasing
the total number of species. New
formations are called speciation.
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REPRODUCTIVE BARRIERS BETWEEN SPECIES
•Prezygotic barriers prevent mating between species.
•Postzygotic barriers are mechanisms that operate
should interspecies occur and form hybrid zygotes.
•Geographic ranges overlap yet they maintain a
species boundary
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin CummingsFigure 14.4
Reproductive Barriers
Gene pools:
• Prezygotic
• Postzygotic
(Depends when they
block interbreeding -
before or after
formation of zygotes)
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Prezygotic barriers include:
• Temporal isolation - species breed in different seasons
• Habitat isolation - species live in same region, different habitats
• Behavioral isolation - recognizable traits for reproduction
Albatross, Giraffe, and Blue-Footed Boobies
Courtship Ritual
• Mechanical isolation - male/female sex organs anatomically
incompatible
• Gametic isolation - copulation but incompatible gametes; no
reproduction
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Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Behavioral isolation
• Traits that enable individuals to
recognize potential mates, such as
odor, coloration, or courtship ritual,
can also function as reproductive
barriers.
• In many bird species, for example,
courtship behavior is so elaborate that
individuals are unlikely to mistake a
bird of a different species as one of
their kind.
Ex: Courtship ritual - These blue-footed boobies, inhabitants of
the Galápagos Islands, will mate only after a specific ritual of
courtship displays. Part of the “script” calls for the male to high-
step, a dance that advertises the bright blue feet characteristic of
the species.
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin CummingsFigure 14.5
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Postzygotic barriers
• Mechanisms that operates should interspecies mating actually
occur and form hybrid zygotes.
• Hybrid Inviability - offspring die before reaching reproductive
maturity
• Hybrid Sterility - offspring fail to develop normally because of
genetic incompatibilities between the two species or infertile
• Hybrid Breakdown - first generation hybrids are viable and
fertile, when these hybrids mate with one another or with either
parent species, the offspring is sterile and less likely to survive
Ex: Hybrid sterility - Horses and donkeys remain separate species because their hybrid
offspring, mules, are sterile.
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin CummingsFigure 14.6
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
MECHANISMS OF SPECIATION
•A key event in the potential origin of a species occurs
when a population is somehow severed from other
populations of the parent species.
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• The two modes of speciation are
• Sympatric speciation
• Process where new species evolve from a
single ancestral species while in the same
region.
• Allopatric speciation (geographic speciation)
• Occurs when biological population of the
same species get isolated from each other
preventing interchange.
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin CummingsFigure 14.7
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
ALLOPATRIC SPECIATION
Geologic processes
Continuous action, series in a definite manner
affecting a specific region. Can be physical or human
caused
Examples include:
Grand Canyon
Galápagos Islands Overview
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin CummingsFigure 14.8
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
• (example in next slide)
• In the both example there is an allopatric scenario
but then the top becomes different because it
doesn‟t go though speciation but creates
interbreed species.
• In the bottom example there is speciation which in
time would not create interbreed species
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin CummingsFigure 14.9
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
SYMPATRIC SPECIATION
When a species is developed or created
without any natural/physical barriers, but still
within the same population and area
Examples include most shrubs, trees and
fungi, and some insects
E.G. -A fruit fly may lay eggs on a mango, but
another variation of fruit fly may lay eggs in
oranges causing behavioral differences down
the line
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Classifying the Diversity of Life
• Systematics
The study of the diversity and relationships of
organisms, both past and present
Taxonomy
The identification, naming and classification of
species
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SOME BASICS OF TAXONOMY
•Carolus Linnaeus
A Swedish Physician and Botanist. Her system has
two main characteristics, a two-part name for each
species and a hierarchical classification of species
into broader and broader groups of organisms.
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NAMING SPECIES
This system assigns each species a two part
latinized name, or binomial. The first part of the
binomial is the genus (plural, general) to which
species belong. The second part of a binomial refers
to one particular species within the genus.
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HIERARCHICAL CLASSIFICATION
1st step of hierarchical classification is built into the
binomial. We group the species that are closely
related into the same genus. Hierarchical
Classification also puts species into broader
categories of classification; family into orders, orders
into classes, classes into phyla, and phyla into
kingdoms and kingdoms into domains.
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Hierarchical Classification
Kingdom:
Animalia
Plantae
Fungi
Protista
Archaea
Bacteria
Domain Highest/ largest
classification
Eukarya
Kingdom Kingdom is put into
Domain
Animalia
Phylum Phylum is put into
kingdom
Chordata
Class Class is put into phylum Mammalia
Order Order is put into class Carnivora
Family Family is put into order Felidae
Genus Genus is put into family Felis
Species Name of species Felis catus
Domain:
Bacteria
Archaea
Eukarya
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin CummingsFigure 14.21
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
CLASSIFICATION AND PHYLOGENY
Phylogeny: the evolutionary history of a species.
How an organism is named and classified should
reflect its place within the evolutionary trees of life
The final product takes place on the branching
pattern of a phytogenetic tree.
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin CummingsFigure 14.22
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
SORTING HOMOLOGY FROM ANALOGY
•Homologous structures
• Homologous structures is a source of information about
phylogenetic relationships. Homologous structures may
look different and function very differently in different
species, but they exhibit fundamental similarities
because they evolved from the same structure that
existed in a common ancestor. The greater the number
of homologous structures between two species, the more
closely the species are related.
• An example is, the whale limb is adapted for steering in
the water; the bat wing is adapted for flight. There are
many basic similarities in the bones supporting these
two structures.
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• Convergent evolution: Species from different
evolutionary branches may have certain
structures that are superficially similar if natural
selection has shaped analogous adaptations
• Analogy: similarity due to convergence
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MOLECULAR BIOLOGY AS A TOOL IN SYSTEMATICS
•Molecular systematics
• Comparing the genes and proteins of organisms to
find their evolutionary relationships. The more
recently two species have branched from a similar
ancestor, the more similar their DNA and amino
acid sequences will be.
• Molecular systematics provides a new way to test
hypotheses about the phylogeny of species
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin CummingsFigure 14.23
This slide shows an example of molecular systematics. The strongest support for
any such hypothesis is agreement between molecular data and other means of
tracing phylogeny, such as evaluating anatomical homology and analyzing the
fossil record. Some fossils are preserved in a way that it is possible to extract DNA
fragments for comparison with modern organisms
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•Scientific search for „Clades‟
–Consists of ancestral
species and all of its
descendants; a distinctive
branch in the tree of life.
•Derived from Greek word
“Branch”
•Focuses on evolutionary
relationships between
organisms rather than
Taxonomic
Cladistics
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The Cladistic Revolution
• Cladistics: A scientific search for clades or specific
branches on the tree of life, with ancestrial species
and all their descendants. This search involves
finding homologies, which connect species into
smaller groups.
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin CummingsFigure 14.24
-This is an example of
cladistics. -In the picture the 3
mammals are compared to
the turtle.
-The primitive and derived
characters are separated,
with the primitive characters
being those contained by all
animals because of common
ancestry and derived
characters being those
developed through evolution.
-The chart shows each point
which changes along the way
to evolution, creating new
species.
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
• Cladistics is the process of hypothesizing
relationships (branches) between species
• Members share common ancestors
• Can classify species into a specific genus
• All organisms can be connected to one tree, but
they are separated into
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin CummingsFigure 14.25
All forms of genus share one common ancestor from eons ago, but many species
have developed new traits that can put them in these different genera ranging from
fish or mammals
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin CummingsFigure 14.26
Genera can be classified by specific traits that they have, like jaws or thumbs. For example,
a shark and a dolphin may look similar in shape (pectoral and dorsal fins, tails) but they also
have defining characteristics, like a sharks cartilage and a dolphin’s blowhole.