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A.P. Biology Mr. Tesoro. Homework Reminder: Lab Report on Population Genetics and Evolution is due Wed., April 2, 2014 Test on Evolution Thurs., Apr. 3, 3014 Do Now: What is the best evidence a scientist can use to classify a newly-found species?. Aim: What is Phylogeny?. 0.

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a p biology mr tesoro
A.P. Biology Mr. Tesoro
  • Homework Reminder:
  • Lab Report on Population Genetics and Evolution is due Wed., April 2, 2014
  • Test on Evolution Thurs., Apr. 3, 3014

Do Now: What is the best evidence a scientist can use to classify a newly-found species?

slide3
Phylogeny is the evolutionary history of a species or group of related species

Taxonomy is the ordered division and naming of organisms

binomial nomenclature
Binomial Nomenclature

In the 18th century, Carolus Linnaeus published a system of taxonomy based on resemblances

Two key features of his system remain useful today: two-part names for species and hierarchical classification

Linnaeus introduced a system for grouping species in increasingly broad categories

The taxonomic groups from narrow to broad are species, genus, family, order, class, phylum, kingdom,and domain

figure 20 3

Figure 20.3

Species: Panthera pardus

Genus: Panthera

Family: Felidae

Order: Carnivora

Class: Mammalia

Phylum: Chordata

Kingdom:

Animalia

Domain:

Bacteria

Domain:

Archaea

Domain:

Eukarya

linking classification and phylogeny
Linking Classification and Phylogeny

Systematists depict evolutionary relationships in branching phylogenetic trees

figure 20 4

Figure 20.4

1

2

Order

Family

Genus

Species

Panthera

pardus

(leopard)

Felidae

Panthera

Taxidea

taxus

(American

badger)

Taxidea

Carnivora

Mustelidae

Lutra lutra

(European

otter)

Lutra

Canis

latrans

(coyote)

Canidae

Canis

Canis

lupus

(gray wolf)

slide9
A phylogenetic tree represents a hypothesis about evolutionary relationships

Each branch point represents the divergence of two taxa from a common ancestor

Sister taxaare groups that share an immediate common ancestor

slide10
A rooted tree includes a branch to represent the most recent common ancestor of all taxa in the tree

A basal taxon diverges early in the history of a group and originates near the common ancestor of the group

A polytomyis a branch from which more than two groups emerge

figure 20 5

Figure 20.5

1

2

3

4

5

Branch point:

where lineages diverge

Taxon A

Taxon B

Sister

taxa

Taxon C

Taxon D

Taxon E

ANCESTRAL

LINEAGE

Taxon F

Basal

taxon

Taxon G

This branch point

represents the common

ancestor of taxa A−G.

This branch point forms a

polytomy: an unresolved

pattern of divergence.

sorting homology from analogy
Sorting Homology from Analogy

When 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

cladistics
Cladistics

Cladisticsclassifies organisms by common descent

A cladeis a group of species that includes an ancestral species and all its descendants

Clades can be nested in larger clades, but not all groupings of organisms qualify as clades

A valid clade is monophyletic, signifying that it consists of the ancestor species and all its descendants

figure 20 10a

Figure 20.10a

1

(a) Monophyletic group

(clade)

A

B

Group I

C

D

E

F

G

shared ancestral and shared derived characters
Shared Ancestral and Shared Derived Characters

In comparison with its ancestor, an organism has both shared and different characteristics

inferring phylogenies using derived characters
Inferring Phylogenies Using Derived Characters

When inferring evolutionary relationships, it is useful to know in which clade a shared derived character first appeared

A shared ancestral character is a character that originated in an ancestor of the taxon

A shared derived character is an evolutionary novelty unique to a particular clade

A character can be both ancestral and derived, depending on the context

figure 20 11

Figure 20.11

TAXA

Lancelet

(outgroup)

Lancelet

(outgroup)

Lamprey

Leopard

Lamprey

Turtle

Bass

Frog

Vertebral

column

(backbone)

Bass

0

1

1

1

1

1

Vertebral

column

1

1

Hinged jaws

0

1

0

1

Frog

Hinged jaws

Four

walking legs

CHARACTERS

0

1

1

0

0

1

Turtle

Four walking legs

Amnion

0

0

0

0

1

1

Amnion

Leopard

1

0

0

0

Hair

0

0

Hair

(a) Character table

(b) Phylogenetic tree

figure 20 11a

Figure 20.11a

TAXA

Lancelet

(outgroup)

Lamprey

Leopard

Turtle

Bass

Frog

Vertebral

column

(backbone)

0

1

1

1

1

1

Hinged jaws

1

1

0

1

0

1

Four

walking legs

0

0

1

0

1

1

CHARACTERS

0

1

1

0

0

0

Amnion

0

0

1

0

0

0

Hair

(a) Character table

figure 20 11b

Figure 20.11b

Lancelet

(outgroup)

Lamprey

Bass

Vertebral

column

Frog

Hinged jaws

Turtle

Four walking legs

Amnion

Leopard

Hair

(b) Phylogenetic tree

slide20
An outgroupis a species or group of species that is closely related to the ingroup, the various species being studied

The outgroup is a group that has diverged before the ingroup

Systematists compare each ingroup species with the outgroup to differentiate between shared derived and shared ancestral characteristics

phylogenetic trees with proportional branch lengths
Phylogenetic Trees with Proportional Branch Lengths

In some trees, the length of a branch can reflect the number of genetic changes that have taken place in a particular DNA sequence in that lineage

In other trees, branch length can represent chronological time, and branching points can be determined from the fossil record

figure 20 12

Figure 20.12

Drosophila

Lancelet

Zebrafish

Frog

Chicken

Human

Mouse

figure 20 13

Figure 20.13

Drosophila

Lancelet

Zebrafish

Frog

Chicken

Human

Mouse

PALEOZOIC

MESOZOIC

CENOZOIC

251

542

65.5 Present

Millions of years ago

phylogenetic trees as hypotheses
Phylogenetic Trees as Hypotheses

The best hypotheses for phylogenetic trees fit the most data: morphological, molecular, and fossil

Phylogenetic hypotheses are modified when new evidence arises

molecular clocks
Molecular Clocks

A molecular clock uses constant rates of evolution in some genes to estimate the absolute time of evolutionary change

The number of nucleotide substitutions in related genes is assumed to be proportional to the time since they last shared a common ancestor

slide26

Animation: Class Schemes

Right click slide / Select play