Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
PowerPoint Lectures for Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Chapter 26
Chapter 26
Overview: Investigating the Tree of Life
• Phylogeny is the evolutionary history of a species
or group of related species
– Biologists draw on the fossil record, which
provides information about ancient organisms
• Systematics is an analytical approach to
understanding the diversity and relationships of organisms, both present-day and extinct
– Systematists use morphological, biochemical,
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Concept 25.2: Phylogenetic systematics connects
classification with evolutionary history
• Taxonomy is the ordered division of organisms
into categories based on characteristics used to assess similarities and differences
– In 1748, Carolus Linnaeus published a system
of taxonomy based on resemblances.
– Two key features of his system remain useful
Binomial Nomenclature
• The two-part scientific name
of a species is a binomial
• The first part of the name is
the genus
• The second part is called the
specific epithet
• The first letter of the genus
is capitalized
• Both parts together name
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Which of the following taxonomic names
includes the fewest number of species?
a) Animalia
b) Panthera
c) Felidae
d) Carnivora
Morphological and Molecular Homologies end c
mon
• Phylogenetic history can be inferred from fossils
as well as morphological and molecular similarities in living organisms
– Organisms with very similar morphologies or
similar DNA sequences are likely to be more closely related than organisms with vastly
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Sorting Homology from Analogy
• In constructing a phylogeny, systematists need to
distinguish whether a similarity is the result of homology or analogy
• Homology is similarity due to shared ancestry
• Analogy is similarity due to convergent evolution
– Analogous structures or molecular sequences that
evolved independently are also called
Linking Classification and Phylogeny
• Systematists depict evolutionary relationships in
branching phylogenetic trees
Carnivora Panthera pardus (leopard) Mephitis mephitis (striped skunk) Lutra lutra (European otter) Canis familiaris (domestic dog) Canis lupus (wolf) S p ec ie s G en u s F am ily O rd er
Felidae Mustelidae Canidae
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 26.5
Branch point:
where lineages diverge
ANCESTRAL LINEAGE
This branch point represents the
common ancestor of taxa A–G.
This branch point forms a polytomy: an unresolved pattern of divergence.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
What We Can and Cannot Learn from
Phylogenetic Trees
• Phylogenetic trees show patterns of descent, not
phenotypic similarity
• Phylogenetic trees do not indicate when species
evolved or how much change occurred in a lineage
• It should not be assumed that a taxon evolved
from the taxon next to it
Phylogenetic systematics informs the construction of phylogenetic trees based on shared characteristics
• Cladistics: common ancestry is the primary
criterion used to classify organisms
• A cladogram depicts patterns of shared
characteristics among taxa: it is a hypothesis!
• A clade is a group of species that includes an
ancestral species and all its descendants
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• A polyphyletic grouping consists of various species that lack a common ancestor
Polyphyletic
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
If new evidence were
uncovered indicating
that taxon E in the
figure is the sister taxon
of a group consisting of
taxa D and F, how
would this change the
phylogeny below?
a)
b)
Shared Primitive and Shared Derived Characteristics
• In cladistic analysis, clades are defined by their
evolutionary novelties
– A shared primitive character is a character that is shared beyond the taxon we are trying to define
– A shared derived character is an
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
For chimps and mice, fur and mammary glands are
Figure 26.11 TAXA Lancelet (outgroup) Lamprey Bass Frog Turtle Leopard Vertebral column (backbone) Four walking legs Hinged jaws Amnion Hair Vertebral column Hinged jaws
Four walking legs
Amnion
Hair
(a) Character table (b) Phylogenetic tree
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Animals that possess homologous structures probably _____.
a) evolved from the same ancestor
b) are headed for extinction
c) by chance had similar mutations in the past
d) are not related
Which of the following pairs is/are homologous, which is/are analogous, and which is/are neither?
a) struts in dragonfly wing and bones in penguin flipper
b) struts in dragonfly wing and bones in bat wing
c) bones in bat wing and bones in seal flipper
d) seal flipper and penguin flipper
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Which of the following shared characteristics is not useful for distinguishing among the terrestrial vertebrates?
a) four walking legs
b) amniotic egg
c) feathers
Which of the following would make the most
suitable outgroup species for a cladogram relative to the other species?
a) frog
b) tuna
c) snake
d) penguin
LE 25-14
Human
0
Mushroom
30%
0
Tulip
40%
40% Human
Mushroom
0 Tulip
Percentage differences between sequences
Comparison of possible trees
15% 15% 20%
5% 5%
10% 15%
25%
Phylogenetic Trees with Proportional Branch
Lengths
• In some trees, the length of a branch can reflect
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 26.12
Lancelet
Drosophila
Zebrafish Frog
• In other trees, branch length can represent
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 26.13
Mouse Human Chicken Frog Zebrafish Lancelet
Drosophila
Present CENOZOIC MESOZOIC
PALEOZOIC
Millions of years ago