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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

(2)

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,

(3)

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

(4)

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

(5)

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

(6)

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

(7)

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

(8)

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

(9)

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.

(10)
(11)

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

(12)

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

(13)

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

(14)

• A polyphyletic grouping consists of various species that lack a common ancestor

Polyphyletic

(15)

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)

(16)

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

(17)

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

For chimps and mice, fur and mammary glands are

(18)

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

(19)

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

(20)

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

(21)

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

(22)

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

(23)

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%

(24)

Phylogenetic Trees with Proportional Branch

Lengths

• In some trees, the length of a branch can reflect

(25)

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Figure 26.12

Lancelet

Drosophila

Zebrafish Frog

(26)

• In other trees, branch length can represent

(27)

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

Figure

figure is the sister taxon  of a group consisting of  taxa D and F, how
Figure 26.11 TAXA Lancelet (outgroup) Lamprey Bass Frog Turtle LeopardVertebralcolumn(backbone)Four walkinglegsHinged jawsAmnion Hair Vertebral column Hinged jaws Four walking legs

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