Evolutionary History of Biological Diversity - PowerPoint PPT Presentation

Loading...

PPT – Evolutionary History of Biological Diversity PowerPoint presentation | free to download - id: 72fe55-NjRiO



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

Evolutionary History of Biological Diversity

Description:

Title: Evolutionary History of Biological Diversity Author: TECHNOLOGY Last modified by: Smith, Charlotte Created Date: 2/3/2009 9:50:57 PM Document presentation format – PowerPoint PPT presentation

Number of Views:54
Avg rating:3.0/5.0
Slides: 71
Provided by: Technology80
Learn more at: http://csmithbio.wikispaces.com
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: Evolutionary History of Biological Diversity


1
Evolutionary History of Biological Diversity
  • AP Chapter 26

2
The Tree of Life
3
Investigating the Tree of Life
  • Phylogeny is the evolutionary history of a
    species or group of related species
  • The discipline of systematics classifies
    organisms and determines their evolutionary
    relationships
  • Systematists use fossil, molecular, and genetic
    data to infer evolutionary relationships

4
  • Taxonomy is the ordered division and naming of
    organisms
  • 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

5
Binomial Nomenclature
  • The two-part scientific name of a species is
    called a binomial first genus, second species
  • The first letter of the genus is capitalized, and
    the entire species name is italicized
  • Both parts together name the species (not the
    specific epithet alone)

6
Fig. 26-3
Species Panthera pardus
Genus Panthera
Family Felidae
Order Carnivora
Class Mammalia
Phylum Chordata
Kingdom Animalia
Archaea
Domain Eukarya
Bacteria
7
Linking Classification and Phylogeny
  • Systematists depict evolutionary relationships in
    branching phylogenetic trees
  • Linnaean classification and phylogeny can differ
    from each other

8
Fig. 26-4
Species
Order
Family
Genus
Pantherapardus
Panthera
Felidae
Taxidea taxus
Taxidea
Carnivora
Mustelidae
Lutra lutra
Lutra
Canis latrans
Canidae
Canis
Canis lupus
9
  • A phylogenetic tree represents a hypothesis about
    evolutionary relationships
  • Each branch point represents the divergence of
    two species
  • Sister taxa are groups that share an immediate
    common ancestor
  • A polytomy is a branch from which more than two
    groups emerge

10
Fig. 26-5
Branch point (node)
Taxon A
Taxon B
Sister taxa
Taxon C
ANCESTRAL LINEAGE
Taxon D
Taxon E
Taxon F
Common ancestor of taxa AF
Polytomy
11
What We Can and Cannot Learn from Phylogenetic
Trees
  • Phylogenetic trees do show patterns of descent
  • Phylogenetic trees do not indicate when species
    evolved or how much genetic change occurred in a
    lineage

12
Applying Phylogenetics
  • Phylogeny provides important information about
    similar characteristics in closely related
    species
  • A phylogeny was used to identify the species of
    whale from which whale meat originated
  • Phylogenies of anthrax bacteria helped
    researchers identify the source of a particular
    strain of anthrax

13
Does hamburger meat have horse meat in it?
14
  • 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 in function due to
    convergent evolution

15
Homologies/Analogies?
Fig. 26-7
16
  • Convergent evolution occurs when similar
    environmental pressures and natural selection
    produce similar (analogous) adaptations in
    organisms from different evolutionary lineages

17
Being careful about homoplasies
  • Bird heats and mammal hearts are analogous
    because they evolved independently of each other
    (homoplasies). According to data, bird and
    mammals are in separate clades.

18
  • The same with bat and bird wings.They are
    homologous as forelimbs, but analogous as
    functional wings.
  • Homology can be distinguished from analogy by
    comparing fossil evidence and the degree of
    complexity

Ancestors of bats could not fly!
19
Evaluating Molecular Homologies
  • Systematists use computer programs and
    mathematical tools when analyzing comparable DNA
    segments from different organisms

20
  • Organisms with similar morphologies or DNA
    sequences are likely to be more closely related
    than organisms with different structures or
    sequences

21
Fig. 26-8
1
Deletion
2
Insertion
3
4
22
Determining Best Fit
ACGTGCACG AGTGAGG
ACGTGCACG A GTG AGG
23
Cladistics
  • Cladistics groups organisms by common descent
  • A clade is 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
    (need common ancestor)

24
  • A valid clade is monophyletic, signifying that it
    consists of the ancestor species and all its
    descendants
  • A paraphyletic grouping consists of an ancestral
    species and some, but not all, of the descendants
  • A polyphyletic grouping consists of various
    species that lack a common ancestor

25
Fig. 26-10
A paraphyletic grouping consists of an ancestral
species and some, but not all, of descendants
A
A
A
Group I
B
B
B
C
C
C
D
D
D
Group III
Group II
E
E
E
F
F
F
G
G
G
(b) Paraphyletic group
(a) Monophyletic group (clade)
(c) Polyphyletic group
A polyphyletic grouping consists of various
species that lack a common ancestor
A valid clade is monophyletic, signifying that it
consists of the ancestor species and all its
descendants
26
The yellow group (sauropsids) is monophyletic,
the blue group (traditional reptiles) is
paraphyletic, and the red group (warm-blooded
animals) is polyphyletic
27
  • Cladograms are constructed by grouping organisms
    together based on their shared derived
    characteristics.

http//highered.mcgraw-hill.com/sites/9834092339/s
tudent_view0/chapter23/animation_-_phylogenetic_tr
ees.html
28
  • A shared ancestral (or primitive) 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

29
A cladogram showing derived characters
30
(No Transcript)
31
Plesiomorphies and apomorphies another fancy way
of talking about primitve and derived characters
  • A plesiomorphy is an "ancestral", "less
    specialized", or "primitive" character.
  • An apomorphy is a "derived", "specialized", or
    "advanced" character. Every taxon possesses a
  • mixture of plesiomorphies and apomorphies.

32
  • An outgroup is a species or group of species that
    is closely related to the ingroup, the various
    species being studied but does not claim
    immediate common ancestry.
  • Used to differentiate between shared derived and
    shared ancestral characteristics

33
Fig. 26-11
TAXA
Lancelet (outgroup)
Lancelet (outgroup)
Salamander
Lamprey
Lamprey
Leopard
Turtle
Tuna
Tuna
Vertebral column (backbone)
0
1
1
1
1
1
Vertebral column
Hinged jaws
0
0
1
1
1
1
Salamander
Hinged jaws
CHARACTERS
1
0
0
0
1
1
Four walking legs
Turtle
Four walking legs
0
0
0
0
1
1
Amniotic (shelled) egg
Amniotic egg
Leopard
Hair
0
0
0
0
0
1
Hair
(a) Character table
(b) Phylogenetic tree
34
Venn diagrams can be constructed to make a
cladogram.
35
Our example
http//www.bu.edu/gk12/eric/cladogram.pdf
36
(No Transcript)
37
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
  • But no actual numbers are given

38
Fig. 26-12
Drosophila
Lancelet
Zebrafish
Frog
Chicken
Human
Mouse
The branch lengths are proportional to the
amount of genetic change.
39
  • In some trees, branch length can represent
    chronological time, and branching points can be
    determined from the fossil record
  • The shorter branches are between taxa, the more
    related they are, particularly in molecular data.

40
Fig. 26-13
Drosophila
Lancelet
Zebrafish
Frog
Chicken
Human
Mouse
CENOZOIC
MESOZOIC
PALEOZOIC
Present
65.5
251
542
Millions of years ago
41
How do systemists deal with a lot of data to make
a tree?
  • They narrow possibilities by applying the
    principles of maximum parsimony and maximum
    likelihood
  • - Fewest evolutionary events
  • - fewer derived characters overall
  • - Most likely sequence of events
    based on DNA analysis more similar DNA
    sequences more likely related

42
Fig. 26-15-1
Species III
Species I
Species II
Three phylogenetic hypotheses
I
I
III
II
II
III
I
III
II
43
Fig. 26-15-4
Site
4
3
2
1
1/C
Species I
T
C
T
A
I
I
III
1/C
Species II
C
C
T
T
III
II
II
1/C
Species III
C
A
A
G
II
III
I
1/C
1/C
T
T
A
G
Ancestral sequence
3/A
3/A
2/T
I
I
III
3/A
2/T
4/C
III
II
II
2/T
4/C
4/C
The best one is the first one due to less
changes.
II
I
III
3/A
3/A
2/T
2/T
4/C
4/C
I
III
I
II
III
II
I
II
III
7 events
7 events
6 events
44
Computer programs are used to search for trees
that are parsimonious and likely.
45
Occam's razor (also written as Ockham's razor
from William of Ockham (c. 1287 1347), is a
principle of parsimony, economy, or succinctness
used in problem-solving. It states that among
competing hypotheses, the hypothesis with the
fewest assumptions should be selected.
46
Fig. 26-UN5
47
Fig. 26-UN10
Answer to question In book.
48
Phylogenetic Trees are Hypotheses
  • The best hypotheses for phylogenetic trees fit
    the most data morphological, molecular, and
    fossil
  • Time is implied, not explicitly stated unless
    coordinated with a time line.

49
A cladogram with time attached
50
An organisms evolutionary history is documented
in its genome
  • Comparing nucleic acids or other molecules to
    infer relatedness is a valuable tool for tracing
    organisms evolutionary history

51
Gene Duplications and Gene Families
  • Gene duplication provides more opportunities for
    evolutionary changes
  • Orthologous genes are found in a single copy in
    the genome and can diverge only after speciation
    occurs
  • Paralogous genes result from gene duplication, so
    are found in more than one copy in the genome and
    can diverge within the clade that carries them
    and often evolve new functions

52
Fig. 26-18
Ancestral gene
Ancestral species
Speciation with divergence of gene
Orthologous genes
Species A
Species B
(a) Orthologous genes
Species A
Gene duplication and divergence
Paralogous genes
Species A after many generations
(b) Paralogous genes
53
Molecular clocks help track evolutionary time
  • A molecular clock uses constant rates of mutation
    in some genes to estimate the absolute time of
    evolutionary change.
  • They are calibrated against branches whose dates
    are known from the fossil record.

54
What genes are used?
  • DNA that codes for rRNA changes relatively slowly
    and is useful for investigating branching points
    hundreds of millions of years ago
  • mtDNA evolves rapidly and can be used to explore
    recent evolutionary events

55
Neutral Theory
  • Neutral theory states that much evolutionary
    change in genes and proteins has no effect on
    fitness and therefore is not influenced by
    Darwinian selection
  • It states that the rate of molecular change in
    these genes and proteins should be regular like a
    clock

56
A molecular clock for mammals based on protein
mutations.
Fig. 26-19
90
Estimate the divergence time for a Mammal with a
total of 30 mutations?
60
Number of mutations
30
0
120
90
60
30
0
Divergence time (millions of years)
The green dots are primates species whose
proteins appear to have evolved more slowly than
those of other mammals.
57
Difficulties with Molecular Clocks
  • The molecular clock does not run as smoothly as
    neutral theory predicts
  • Irregularities result from natural selection in
    which some DNA changes are favored over others
  • Estimates of evolutionary divergences older than
    the fossil record have a high degree of
    uncertainty
  • The use of multiple genes may improve estimates

58
New information continues to revise our
understanding of the tree of life
  • Recently, we have gained insight into the very
    deepest branches of the tree of life through
    molecular systematics

59
From Two Kingdoms to Three Domains
  • Early taxonomists (Linnaeus) classified all
    species as either plants or animals
  • Later, five kingdoms were recognized Monera
    (prokaryotes), Protista, Plantae, Fungi, and
    Animalia
  • In the late 70s, the kingdom Monera was split
    into the eubacteria and the archaebacteria.

60
(No Transcript)
61
  • More recently, the the three-domain system has
    been adopted Bacteria, Archaea, and Eukarya

62
Fig. 26-21
Red lines are multicellular.
EUKARYA
Dinoflagellates
Land plants
Forams
Green algae
Ciliates
Diatoms
Red algae
Amoebas
Cellular slime molds
Euglena
Trypanosomes
Animals
Leishmania
Fungi
First to emerge.
Sulfolobus
Green nonsulfur bacteria
Thermophiles
(Mitochondrion)
Spirochetes
Chlamydia
Halophiles
COMMON ANCESTOR OF ALL LIFE
Green sulfur bacteria
BACTERIA
Methanobacterium
Cyanobacteria
(Plastids, including chloroplasts)
ARCHAEA
63
The origins of life and the three domains are
difficult to classify due to horizontal gene
transfer.
64
Classification is a work in progress?
65
A Simple Tree of All Life
  • The tree of life suggests that eukaryotes and
    archaea are more closely related to each other
    than to bacteria
  • The tree of life is based largely on rRNA genes,
    as these have evolved slowly

66
  • There have been substantial interchanges of genes
    between organisms in different domains
  • Horizontal gene transfer is the movement of genes
    from one genome to another
  • Horizontal gene transfer complicates efforts to
    build a tree of life

67
Fig. 26-23
Eukarya
Bacteria
Archaea
A ring of life. The domains emerged from the
ring.
68
  • If endosymbiosis occurred, eukaryotes are
    simultaneously most closely related to bacteria
    AND archae.

69
(No Transcript)
70
(No Transcript)
About PowerShow.com