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1. The document describes a lecture on phylogeny and the tree of life from Campbell Biology. It discusses how systematists use morphological and molecular data to infer evolutionary relationships and construct phylogenetic trees showing these relationships. 2. Key points include how homologies are used to determine shared ancestry, while analogies indicate convergent evolution. Maximum parsimony and maximum likelihood methods are used to evaluate potential phylogenetic trees. 3. Shared derived characters that appear for the first time in a particular clade provide evidence for which groups of species share a more recent common ancestor on the tree of life.

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LECTURE PRESENTATIONS For CAMPBELL BIOLOGY, NINTH EDITION Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson © 2011 Pearson Education, Inc. Lectures by Erin Barley Kathleen Fitzpatrick Phylogeny and the Tree of Life Chapter 26
Overview: Investigating the Tree of Life • Legless lizards have evolved independently in several different groups © 2011 Pearson Education, Inc.
Figure 26.1
• 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 © 2011 Pearson Education, Inc.
Figure 26.2
Figure 26.2a
Figure 26.2b
Figure 26.2c
Concept 26.1: Phylogenies show evolutionary relationships • Taxonomy is the ordered division and naming of organisms © 2011 Pearson Education, Inc.
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 © 2011 Pearson Education, Inc.
• The two-part scientific name of a species is called a binomial • The first part of the name is the genus • The second part, called the specific epithet, is unique for each species within the genus • 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) © 2011 Pearson Education, Inc.
Hierarchical Classification • Linnaeus introduced a system for grouping species in increasingly broad categories • The taxonomic groups from broad to narrow are domain, kingdom, phylum, class, order, family, genus, and species • A taxonomic unit at any level of hierarchy is called a taxon • The broader taxa are not comparable between lineages – For example, an order of snails has less genetic diversity than an order of mammals © 2011 Pearson Education, Inc.
Figure 26.3 Species: Panthera pardus Genus: Panthera Family: Felidae Order: Carnivora Class: Mammalia Phylum: Chordata Domain: Bacteria Kingdom: Animalia Domain: Archaea Domain: Eukarya
Linking Classification and Phylogeny • Systematists depict evolutionary relationships in branching phylogenetic trees © 2011 Pearson Education, Inc.
Figure 26.4 Order Family Panthera pardus (leopard) Genus Species Canis latrans (coyote) Taxidea taxus (American badger) Lutra lutra (European otter) Canis lupus (gray wolf) Felidae Carnivora PantheraTaxidea Mustelidae Lutra Canidae Canis
• Linnaean classification and phylogeny can differ from each other • Systematists have proposed the PhyloCode, which recognizes only groups that include a common ancestor and all its descendents © 2011 Pearson Education, Inc.
• 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 © 2011 Pearson Education, Inc.
• A rooted tree includes a branch to represent the last 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 polytomy is a branch from which more than two groups emerge © 2011 Pearson Education, Inc.
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. Sister taxa Basal taxon Taxon A Taxon B Taxon C Taxon D Taxon E Taxon F Taxon G
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 © 2011 Pearson Education, Inc.
Applying Phylogenies • 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 © 2011 Pearson Education, Inc.
Minke (Southern Hemisphere) Unknowns #1a, 2, 3, 4, 5, 6, 7, 8 Minke (North Atlantic) Humpback (North Atlantic) Humpback (North Pacific) Gray Blue Unknowns #10, 11, 12 Unknown #13 Unknown #1b Unknown #9 Fin (Mediterranean) Fin (Iceland) RESULTS Figure 26.6
Concept 26.2: Phylogenies are inferred from morphological and molecular data • To infer phylogenies, systematists gather information about morphologies, genes, and biochemistry of living organisms © 2011 Pearson Education, Inc.
Morphological and Molecular Homologies • Phenotypic and genetic similarities due to shared ancestry are called homologies • Organisms with similar morphologies or DNA sequences are likely to be more closely related than organisms with different structures or sequences © 2011 Pearson Education, Inc.
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 © 2011 Pearson Education, Inc.
• Convergent evolution occurs when similar environmental pressures and natural selection produce similar (analogous) adaptations in organisms from different evolutionary lineages © 2011 Pearson Education, Inc.
Figure 26.7
• Bat and bird wings are homologous as forelimbs, but analogous as functional wings • Analogous structures or molecular sequences that evolved independently are also called homoplasies • Homology can be distinguished from analogy by comparing fossil evidence and the degree of complexity • The more complex two similar structures are, the more likely it is that they are homologous © 2011 Pearson Education, Inc.
Evaluating Molecular Homologies • Systematists use computer programs and mathematical tools when analyzing comparable DNA segments from different organisms © 2011 Pearson Education, Inc.
Figure 26.8-1 1 2 1
Figure 26.8-2 Deletion Insertion 1 1 2 2 2 1
Figure 26.8-3 Deletion Insertion 1 1 1 2 2 2 2 1 3
Figure 26.8-4 Deletion Insertion 1 1 1 1 2 2 2 2 2 1 3 4
• It is also important to distinguish homology from analogy in molecular similarities • Mathematical tools help to identify molecular homoplasies, or coincidences • Molecular systematics uses DNA and other molecular data to determine evolutionary relationships © 2011 Pearson Education, Inc.
Figure 26.9
Concept 26.3: Shared characters are used to construct phylogenetic trees • Once homologous characters have been identified, they can be used to infer a phylogeny © 2011 Pearson Education, Inc.
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 © 2011 Pearson Education, Inc.
• A valid clade is monophyletic, signifying that it consists of the ancestor species and all its descendants © 2011 Pearson Education, Inc.
Figure 26.10 (a) Monophyletic group (clade) (b) Paraphyletic group (c) Polyphyletic group Group Ι Group ΙΙ Group ΙΙΙ A B C D E F G A B C D E F G A B C D E F G
Figure 26.10a (a) Monophyletic group (clade) Group Ι A B C D E F G
• A paraphyletic grouping consists of an ancestral species and some, but not all, of the descendants © 2011 Pearson Education, Inc.
Figure 26.10b (b) Paraphyletic group Group ΙΙ A B C D E F G
• A polyphyletic grouping consists of various species with different ancestors © 2011 Pearson Education, Inc.
Figure 26.10c (c) Polyphyletic group Group ΙΙΙ A B C D E F G
Shared Ancestral and Shared Derived Characters • In comparison with its ancestor, an organism has both shared and different characteristics © 2011 Pearson Education, Inc.
• 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 © 2011 Pearson Education, Inc.
Inferring Phylogenies Using Derived Characters • When inferring evolutionary relationships, it is useful to know in which clade a shared derived character first appeared © 2011 Pearson Education, Inc.
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 CHARACTERS Lancelet (outgroup) Lamprey Bass Frog Turtle Leopard 0 0 0 0 0 1 0 0 0 0 1 1 0 0 0 1 1 1 0 0 1 1 1 1 0 1 1 1 1 1
Figure 26.11a TAXA Vertebral column (backbone) Four walking legs Hinged jaws Amnion Hair (a) Character table CHARACTERS Lancelet (outgroup) Lamprey Bass Frog Turtle Leopard 0 0 0 0 0 1 0 0 0 0 1 1 0 0 0 1 1 1 0 0 1 1 1 1 0 1 1 1 1 1
Figure 26.11b Lancelet (outgroup) Lamprey Bass Frog Turtle Leopard Vertebral column Hinged jaws Four walking legs Amnion Hair (b) Phylogenetic tree
• An outgroup is 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 © 2011 Pearson Education, Inc.
• Characters shared by the outgroup and ingroup are ancestral characters that predate the divergence of both groups from a common ancestor © 2011 Pearson Education, Inc.
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 © 2011 Pearson Education, Inc.
Figure 26.12 Lancelet Drosophila Zebrafish Frog Chicken Human Mouse
• In other trees, branch length can represent chronological time, and branching points can be determined from the fossil record © 2011 Pearson Education, Inc.
Figure 26.13 Mouse Human Chicken Frog Zebrafish Lancelet Drosophila Present CENOZOICMESOZOICPALEOZOIC Millions of years ago 542 251 65.5
Maximum Parsimony and Maximum Likelihood • Systematists can never be sure of finding the best tree in a large data set • They narrow possibilities by applying the principles of maximum parsimony and maximum likelihood © 2011 Pearson Education, Inc.
• Maximum parsimony assumes that the tree that requires the fewest evolutionary events (appearances of shared derived characters) is the most likely • The principle of maximum likelihood states that, given certain rules about how DNA changes over time, a tree can be found that reflects the most likely sequence of evolutionary events © 2011 Pearson Education, Inc.
Figure 26.14 Human Human Mushroom Mushroom Tulip Tulip 0 0 0 30% 40% 40% 25% 15% 10% 5% 5% 15% 15% 20% (a) Percentage differences between sequences (b) Comparison of possible trees Tree 1: More likely Tree 2: Less likely
Figure 26.14a Human Human Mushroom Mushroom Tulip Tulip 0 0 0 30% 40% 40% (a) Percentage differences between sequences
Figure 26.14b 25% 15% 10% 5% 5% 15% 15% 20% (b) Comparison of possible trees Tree 1: More likely Tree 2: Less likely
• Computer programs are used to search for trees that are parsimonious and likely © 2011 Pearson Education, Inc.
Figure 26.15 Species Ι Species ΙΙ Species ΙΙΙ Three phylogenetic hypotheses:1 2 3 4 TECHNIQUE RESULTS Species Ι Species ΙΙ Species ΙΙΙ Ancestral sequence Ι ΙΙ ΙΙΙ 1 2 3 4 Site C C A A A A C C T G T T T T 1/C 1/C 1/C 1/C 1/C 3/A 2/T 4/C 3/A4/C 4/C 4/C 4/C3/A 3/A 3/A 2/T 2/T 2/T 2/T 6 events 7 events 7 events G T Ι ΙΙ ΙΙΙ Ι ΙΙ ΙΙΙ Ι ΙΙ ΙΙΙ Ι ΙΙ ΙΙΙ Ι ΙΙ ΙΙΙ Ι ΙΙ ΙΙΙ Ι ΙΙ ΙΙΙ Ι ΙΙ ΙΙΙΙ ΙΙ ΙΙΙ Ι ΙΙ ΙΙΙ Ι ΙΙ ΙΙΙ
Figure 26.15a 1 TECHNIQUE Three phylogenetic hypotheses: Species Ι Species ΙΙ Species ΙΙΙ Ι ΙΙ ΙΙΙΙ ΙΙ ΙΙΙ Ι ΙΙ ΙΙΙ
Figure 26.15b TECHNIQUE Species Ι Species ΙΙ Species ΙΙΙ Ancestral sequence 1 2 3 4 Site C C A A A A C C T G T T T TG T 2
TECHNIQUE 1/C 3 4 RESULTS 1/C 1/C 1/C 1/C 4/C 4/C 4/C 4/C 4/C 3/A 3/A 3/A 3/A 2/T 2/T 2/T 2/T 2/T3/A 7 events6 events 7 events Ι ΙΙ ΙΙΙΙ ΙΙ ΙΙΙ Ι ΙΙ ΙΙΙ Ι ΙΙ ΙΙΙΙ ΙΙ ΙΙΙ Ι ΙΙ ΙΙΙ Ι ΙΙ ΙΙΙ Ι ΙΙ ΙΙΙ Ι ΙΙ ΙΙΙ Figure 26.15c
Phylogenetic Trees as Hypotheses • The best hypotheses for phylogenetic trees fit the most data: morphological, molecular, and fossil • Phylogenetic bracketing allows us to predict features of an ancestor from features of its descendents – For example, phylogenetic bracketing allows us to infer characteristics of dinosaurs © 2011 Pearson Education, Inc.
Figure 26.16 Lizards and snakes Crocodilians Ornithischian dinosaurs Saurischian dinosaurs Birds Common ancestor of crocodilians, dinosaurs, and birds
• Birds and crocodiles share several features: four-chambered hearts, song, nest building, and brooding • These characteristics likely evolved in a common ancestor and were shared by all of its descendents, including dinosaurs • The fossil record supports nest building and brooding in dinosaurs © 2011 Pearson Education, Inc. Animation: The Geologic Record
Figure 26.17 Front limb Hind limb Eggs (a) Fossil remains of Oviraptor and eggs (b) Artist’s reconstruction of the dinosaur’s posture based on the fossil findings
Front limb Hind limb Eggs (a) Fossil remains of Oviraptor and eggs Figure 26.17a
Figure 26.17b (b) Artist’s reconstruction of the dinosaur’s posture based on the fossil findings
Concept 26.4: An organism’s evolutionary history is documented in its genome • Comparing nucleic acids or other molecules to infer relatedness is a valuable approach for tracing organisms’ evolutionary history • 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 © 2011 Pearson Education, Inc.
Gene Duplications and Gene Families • Gene duplication increases the number of genes in the genome, providing more opportunities for evolutionary changes • Repeated gene duplications result in gene families • Like homologous genes, duplicated genes can be traced to a common ancestor © 2011 Pearson Education, Inc.
• Orthologous genes are found in a single copy in the genome and are homologous between species • They can diverge only after speciation occurs © 2011 Pearson Education, Inc.
Figure 26.18 Formation of orthologous genes: product of speciation Formation of paralogous genes: within a species Ancestral gene Ancestral gene Ancestral species Species C Speciation with divergence of gene Gene duplication and divergence Orthologous genes Paralogous genes Species A Species B Species C after many generations
rmation of orthologous genes: roduct of speciation Ancestral gene Ancestral species Speciation with divergence of gene Orthologous genes Species A Species B Figure 26.18a
• Paralogous genes result from gene duplication, so are found in more than one copy in the genome • They can diverge within the clade that carries them and often evolve new functions © 2011 Pearson Education, Inc.
Figure 26.18b Formation of paralogous genes: within a species Ancestral gene Species C Gene duplication and divergence Paralogous genes Species C after many generations
Genome Evolution • Orthologous genes are widespread and extend across many widely varied species – For example, humans and mice diverged about 65 million years ago, and 99% of our genes are orthologous © 2011 Pearson Education, Inc.
• Gene number and the complexity of an organism are not strongly linked – For example, humans have only four times as many genes as yeast, a single-celled eukaryote • Genes in complex organisms appear to be very versatile, and each gene can perform many functions © 2011 Pearson Education, Inc.
Concept 26.5: Molecular clocks help track evolutionary time • To extend molecular phylogenies beyond the fossil record, we must make an assumption about how change occurs over time © 2011 Pearson Education, Inc.
Molecular Clocks • A molecular clock uses constant rates of evolution in some genes to estimate the absolute time of evolutionary change • In orthologous genes, nucleotide substitutions are proportional to the time since they last shared a common ancestor • In paralogous genes, nucleotide substitutions are proportional to the time since the genes became duplicated © 2011 Pearson Education, Inc.
• Molecular clocks are calibrated against branches whose dates are known from the fossil record • Individual genes vary in how clocklike they are © 2011 Pearson Education, Inc.
Figure 26.19 Divergence time (millions of years) Numberofmutations 90 60 30 30 60 90 120 0
Neutral Theory • Neutral theory states that much evolutionary change in genes and proteins has no effect on fitness and is not influenced by natural selection • It states that the rate of molecular change in these genes and proteins should be regular like a clock © 2011 Pearson Education, Inc.
Problems 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 © 2011 Pearson Education, Inc.
Applying a Molecular Clock: The Origin of HIV • Phylogenetic analysis shows that HIV is descended from viruses that infect chimpanzees and other primates • HIV spread to humans more than once • Comparison of HIV samples shows that the virus evolved in a very clocklike way • Application of a molecular clock to one strain of HIV suggests that that strain spread to humans during the 1930s © 2011 Pearson Education, Inc.
Figure 26.20 Year HIV Range Adjusted best-fit line (accounts for uncertain dates of HIV sequences) 0.20 0.15 0.10 0.05 0 1900 1920 1940 1960 1980 2000 IndexofbasechangesbetweenHIVgenesequences
Concept 26.6: 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 © 2011 Pearson Education, Inc.
From Two Kingdoms to Three Domains • Early taxonomists classified all species as either plants or animals • Later, five kingdoms were recognized: Monera (prokaryotes), Protista, Plantae, Fungi, and Animalia • More recently, the three-domain system has been adopted: Bacteria, Archaea, and Eukarya • The three-domain system is supported by data from many sequenced genomes © 2011 Pearson Education, Inc. Animation: Classification Schemes
Figure 26.21 Archaea Bacteria Eukarya COMMON ANCESTOR OF ALL LIFE Land plants Green algae Red algae Forams Ciliates Dinoflagellates Cellular slime molds Amoebas Animals Fungi Euglena Trypanosomes Leishmania Sulfolobus Thermophiles Halophiles Methanobacterium Green nonsulfur bacteria (Mitochondrion) Spirochetes Chlamydia Cyanobacteria Green sulfur bacteria (Plastids, including chloroplasts) Diatoms
Figure 26.21a Bacteria Green nonsulfur bacteria (Mitochondrion) Spirochetes Chlamydia Cyanobacteria Green sulfur bacteria (Plastids, including chloroplasts) COMMON ANCESTOR OF ALL LIFE
Figure 26.21b Sulfolobus Methanobacterium Thermophiles Halophiles Archaea
Figure 26.21c Eukarya Land plants Green algae Red algae Forams Dinoflagellates Ciliates Diatoms Cellular slime molds Amoebas Animals Fungi Trypanosomes Euglena Leishmania
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 © 2011 Pearson Education, Inc.
• 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 occurs by exchange of transposable elements and plasmids, viral infection, and fusion of organisms • Horizontal gene transfer complicates efforts to build a tree of life © 2011 Pearson Education, Inc.
Figure 26.22 Bacteria Eukarya Archaea Billions of years ago 4 3 2 1 0
• Some researchers suggest that eukaryotes arose as an fusion between a bacterium and archaean • If so, early evolutionary relationships might be better depicted by a ring of life instead of a tree of life Is the Tree of Life Really a Ring? © 2011 Pearson Education, Inc.
Figure 26.23 Archaea Eukarya Bacteria
Figure 26.UN01 A A A B B BC C C D D D (a) (b) (c)
Figure 26.UN02 Branch point Most recent common ancestor Polytomy Sister taxa Basal taxon Taxon A Taxon B Taxon C Taxon D Taxon E Taxon F Taxon G
Figure 26.UN03 Monophyletic group Polyphyletic group Paraphyletic group A B C D E F G A B C D E F G A B C D E F G
Figure 26.UN04 Salamander Lizard Goat Human
Figure 26.UN05
Figure 26.UN06
Figure 26.UN07
Figure 26.UN08
Figure 26.UN09
Figure 26.UN10
Figure 26.UN11

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26 lecture phylogeny

  • 1. LECTURE PRESENTATIONS For CAMPBELL BIOLOGY, NINTH EDITION Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson © 2011 Pearson Education, Inc. Lectures by Erin Barley Kathleen Fitzpatrick Phylogeny and the Tree of Life Chapter 26
  • 2. Overview: Investigating the Tree of Life • Legless lizards have evolved independently in several different groups © 2011 Pearson Education, Inc.
  • 4. • 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 © 2011 Pearson Education, Inc.
  • 9. Concept 26.1: Phylogenies show evolutionary relationships • Taxonomy is the ordered division and naming of organisms © 2011 Pearson Education, Inc.
  • 10. 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 © 2011 Pearson Education, Inc.
  • 11. • The two-part scientific name of a species is called a binomial • The first part of the name is the genus • The second part, called the specific epithet, is unique for each species within the genus • 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) © 2011 Pearson Education, Inc.
  • 12. Hierarchical Classification • Linnaeus introduced a system for grouping species in increasingly broad categories • The taxonomic groups from broad to narrow are domain, kingdom, phylum, class, order, family, genus, and species • A taxonomic unit at any level of hierarchy is called a taxon • The broader taxa are not comparable between lineages – For example, an order of snails has less genetic diversity than an order of mammals © 2011 Pearson Education, Inc.
  • 14. Linking Classification and Phylogeny • Systematists depict evolutionary relationships in branching phylogenetic trees © 2011 Pearson Education, Inc.
  • 15. Figure 26.4 Order Family Panthera pardus (leopard) Genus Species Canis latrans (coyote) Taxidea taxus (American badger) Lutra lutra (European otter) Canis lupus (gray wolf) Felidae Carnivora PantheraTaxidea Mustelidae Lutra Canidae Canis
  • 16. • Linnaean classification and phylogeny can differ from each other • Systematists have proposed the PhyloCode, which recognizes only groups that include a common ancestor and all its descendents © 2011 Pearson Education, Inc.
  • 17. • 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 © 2011 Pearson Education, Inc.
  • 18. • A rooted tree includes a branch to represent the last 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 polytomy is a branch from which more than two groups emerge © 2011 Pearson Education, Inc.
  • 19. 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. Sister taxa Basal taxon Taxon A Taxon B Taxon C Taxon D Taxon E Taxon F Taxon G
  • 20. 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 © 2011 Pearson Education, Inc.
  • 21. Applying Phylogenies • 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 © 2011 Pearson Education, Inc.
  • 22. Minke (Southern Hemisphere) Unknowns #1a, 2, 3, 4, 5, 6, 7, 8 Minke (North Atlantic) Humpback (North Atlantic) Humpback (North Pacific) Gray Blue Unknowns #10, 11, 12 Unknown #13 Unknown #1b Unknown #9 Fin (Mediterranean) Fin (Iceland) RESULTS Figure 26.6
  • 23. Concept 26.2: Phylogenies are inferred from morphological and molecular data • To infer phylogenies, systematists gather information about morphologies, genes, and biochemistry of living organisms © 2011 Pearson Education, Inc.
  • 24. Morphological and Molecular Homologies • Phenotypic and genetic similarities due to shared ancestry are called homologies • Organisms with similar morphologies or DNA sequences are likely to be more closely related than organisms with different structures or sequences © 2011 Pearson Education, Inc.
  • 25. 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 © 2011 Pearson Education, Inc.
  • 26. • Convergent evolution occurs when similar environmental pressures and natural selection produce similar (analogous) adaptations in organisms from different evolutionary lineages © 2011 Pearson Education, Inc.
  • 28. • Bat and bird wings are homologous as forelimbs, but analogous as functional wings • Analogous structures or molecular sequences that evolved independently are also called homoplasies • Homology can be distinguished from analogy by comparing fossil evidence and the degree of complexity • The more complex two similar structures are, the more likely it is that they are homologous © 2011 Pearson Education, Inc.
  • 29. Evaluating Molecular Homologies • Systematists use computer programs and mathematical tools when analyzing comparable DNA segments from different organisms © 2011 Pearson Education, Inc.
  • 34. • It is also important to distinguish homology from analogy in molecular similarities • Mathematical tools help to identify molecular homoplasies, or coincidences • Molecular systematics uses DNA and other molecular data to determine evolutionary relationships © 2011 Pearson Education, Inc.
  • 36. Concept 26.3: Shared characters are used to construct phylogenetic trees • Once homologous characters have been identified, they can be used to infer a phylogeny © 2011 Pearson Education, Inc.
  • 37. 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 © 2011 Pearson Education, Inc.
  • 38. • A valid clade is monophyletic, signifying that it consists of the ancestor species and all its descendants © 2011 Pearson Education, Inc.
  • 39. Figure 26.10 (a) Monophyletic group (clade) (b) Paraphyletic group (c) Polyphyletic group Group Ι Group ΙΙ Group ΙΙΙ A B C D E F G A B C D E F G A B C D E F G
  • 40. Figure 26.10a (a) Monophyletic group (clade) Group Ι A B C D E F G
  • 41. • A paraphyletic grouping consists of an ancestral species and some, but not all, of the descendants © 2011 Pearson Education, Inc.
  • 42. Figure 26.10b (b) Paraphyletic group Group ΙΙ A B C D E F G
  • 43. • A polyphyletic grouping consists of various species with different ancestors © 2011 Pearson Education, Inc.
  • 44. Figure 26.10c (c) Polyphyletic group Group ΙΙΙ A B C D E F G
  • 45. Shared Ancestral and Shared Derived Characters • In comparison with its ancestor, an organism has both shared and different characteristics © 2011 Pearson Education, Inc.
  • 46. • 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 © 2011 Pearson Education, Inc.
  • 47. Inferring Phylogenies Using Derived Characters • When inferring evolutionary relationships, it is useful to know in which clade a shared derived character first appeared © 2011 Pearson Education, Inc.
  • 48. 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 CHARACTERS Lancelet (outgroup) Lamprey Bass Frog Turtle Leopard 0 0 0 0 0 1 0 0 0 0 1 1 0 0 0 1 1 1 0 0 1 1 1 1 0 1 1 1 1 1
  • 49. Figure 26.11a TAXA Vertebral column (backbone) Four walking legs Hinged jaws Amnion Hair (a) Character table CHARACTERS Lancelet (outgroup) Lamprey Bass Frog Turtle Leopard 0 0 0 0 0 1 0 0 0 0 1 1 0 0 0 1 1 1 0 0 1 1 1 1 0 1 1 1 1 1
  • 51. • An outgroup is 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 © 2011 Pearson Education, Inc.
  • 52. • Characters shared by the outgroup and ingroup are ancestral characters that predate the divergence of both groups from a common ancestor © 2011 Pearson Education, Inc.
  • 53. 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 © 2011 Pearson Education, Inc.
  • 55. • In other trees, branch length can represent chronological time, and branching points can be determined from the fossil record © 2011 Pearson Education, Inc.
  • 57. Maximum Parsimony and Maximum Likelihood • Systematists can never be sure of finding the best tree in a large data set • They narrow possibilities by applying the principles of maximum parsimony and maximum likelihood © 2011 Pearson Education, Inc.
  • 58. • Maximum parsimony assumes that the tree that requires the fewest evolutionary events (appearances of shared derived characters) is the most likely • The principle of maximum likelihood states that, given certain rules about how DNA changes over time, a tree can be found that reflects the most likely sequence of evolutionary events © 2011 Pearson Education, Inc.
  • 59. Figure 26.14 Human Human Mushroom Mushroom Tulip Tulip 0 0 0 30% 40% 40% 25% 15% 10% 5% 5% 15% 15% 20% (a) Percentage differences between sequences (b) Comparison of possible trees Tree 1: More likely Tree 2: Less likely
  • 61. Figure 26.14b 25% 15% 10% 5% 5% 15% 15% 20% (b) Comparison of possible trees Tree 1: More likely Tree 2: Less likely
  • 62. • Computer programs are used to search for trees that are parsimonious and likely © 2011 Pearson Education, Inc.
  • 63. Figure 26.15 Species Ι Species ΙΙ Species ΙΙΙ Three phylogenetic hypotheses:1 2 3 4 TECHNIQUE RESULTS Species Ι Species ΙΙ Species ΙΙΙ Ancestral sequence Ι ΙΙ ΙΙΙ 1 2 3 4 Site C C A A A A C C T G T T T T 1/C 1/C 1/C 1/C 1/C 3/A 2/T 4/C 3/A4/C 4/C 4/C 4/C3/A 3/A 3/A 2/T 2/T 2/T 2/T 6 events 7 events 7 events G T Ι ΙΙ ΙΙΙ Ι ΙΙ ΙΙΙ Ι ΙΙ ΙΙΙ Ι ΙΙ ΙΙΙ Ι ΙΙ ΙΙΙ Ι ΙΙ ΙΙΙ Ι ΙΙ ΙΙΙ Ι ΙΙ ΙΙΙΙ ΙΙ ΙΙΙ Ι ΙΙ ΙΙΙ Ι ΙΙ ΙΙΙ
  • 64. Figure 26.15a 1 TECHNIQUE Three phylogenetic hypotheses: Species Ι Species ΙΙ Species ΙΙΙ Ι ΙΙ ΙΙΙΙ ΙΙ ΙΙΙ Ι ΙΙ ΙΙΙ
  • 65. Figure 26.15b TECHNIQUE Species Ι Species ΙΙ Species ΙΙΙ Ancestral sequence 1 2 3 4 Site C C A A A A C C T G T T T TG T 2
  • 66. TECHNIQUE 1/C 3 4 RESULTS 1/C 1/C 1/C 1/C 4/C 4/C 4/C 4/C 4/C 3/A 3/A 3/A 3/A 2/T 2/T 2/T 2/T 2/T3/A 7 events6 events 7 events Ι ΙΙ ΙΙΙΙ ΙΙ ΙΙΙ Ι ΙΙ ΙΙΙ Ι ΙΙ ΙΙΙΙ ΙΙ ΙΙΙ Ι ΙΙ ΙΙΙ Ι ΙΙ ΙΙΙ Ι ΙΙ ΙΙΙ Ι ΙΙ ΙΙΙ Figure 26.15c
  • 67. Phylogenetic Trees as Hypotheses • The best hypotheses for phylogenetic trees fit the most data: morphological, molecular, and fossil • Phylogenetic bracketing allows us to predict features of an ancestor from features of its descendents – For example, phylogenetic bracketing allows us to infer characteristics of dinosaurs © 2011 Pearson Education, Inc.
  • 69. • Birds and crocodiles share several features: four-chambered hearts, song, nest building, and brooding • These characteristics likely evolved in a common ancestor and were shared by all of its descendents, including dinosaurs • The fossil record supports nest building and brooding in dinosaurs © 2011 Pearson Education, Inc. Animation: The Geologic Record
  • 70. Figure 26.17 Front limb Hind limb Eggs (a) Fossil remains of Oviraptor and eggs (b) Artist’s reconstruction of the dinosaur’s posture based on the fossil findings
  • 71. Front limb Hind limb Eggs (a) Fossil remains of Oviraptor and eggs Figure 26.17a
  • 72. Figure 26.17b (b) Artist’s reconstruction of the dinosaur’s posture based on the fossil findings
  • 73. Concept 26.4: An organism’s evolutionary history is documented in its genome • Comparing nucleic acids or other molecules to infer relatedness is a valuable approach for tracing organisms’ evolutionary history • 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 © 2011 Pearson Education, Inc.
  • 74. Gene Duplications and Gene Families • Gene duplication increases the number of genes in the genome, providing more opportunities for evolutionary changes • Repeated gene duplications result in gene families • Like homologous genes, duplicated genes can be traced to a common ancestor © 2011 Pearson Education, Inc.
  • 75. • Orthologous genes are found in a single copy in the genome and are homologous between species • They can diverge only after speciation occurs © 2011 Pearson Education, Inc.
  • 76. Figure 26.18 Formation of orthologous genes: product of speciation Formation of paralogous genes: within a species Ancestral gene Ancestral gene Ancestral species Species C Speciation with divergence of gene Gene duplication and divergence Orthologous genes Paralogous genes Species A Species B Species C after many generations
  • 77. rmation of orthologous genes: roduct of speciation Ancestral gene Ancestral species Speciation with divergence of gene Orthologous genes Species A Species B Figure 26.18a
  • 78. • Paralogous genes result from gene duplication, so are found in more than one copy in the genome • They can diverge within the clade that carries them and often evolve new functions © 2011 Pearson Education, Inc.
  • 79. Figure 26.18b Formation of paralogous genes: within a species Ancestral gene Species C Gene duplication and divergence Paralogous genes Species C after many generations
  • 80. Genome Evolution • Orthologous genes are widespread and extend across many widely varied species – For example, humans and mice diverged about 65 million years ago, and 99% of our genes are orthologous © 2011 Pearson Education, Inc.
  • 81. • Gene number and the complexity of an organism are not strongly linked – For example, humans have only four times as many genes as yeast, a single-celled eukaryote • Genes in complex organisms appear to be very versatile, and each gene can perform many functions © 2011 Pearson Education, Inc.
  • 82. Concept 26.5: Molecular clocks help track evolutionary time • To extend molecular phylogenies beyond the fossil record, we must make an assumption about how change occurs over time © 2011 Pearson Education, Inc.
  • 83. Molecular Clocks • A molecular clock uses constant rates of evolution in some genes to estimate the absolute time of evolutionary change • In orthologous genes, nucleotide substitutions are proportional to the time since they last shared a common ancestor • In paralogous genes, nucleotide substitutions are proportional to the time since the genes became duplicated © 2011 Pearson Education, Inc.
  • 84. • Molecular clocks are calibrated against branches whose dates are known from the fossil record • Individual genes vary in how clocklike they are © 2011 Pearson Education, Inc.
  • 85. Figure 26.19 Divergence time (millions of years) Numberofmutations 90 60 30 30 60 90 120 0
  • 86. Neutral Theory • Neutral theory states that much evolutionary change in genes and proteins has no effect on fitness and is not influenced by natural selection • It states that the rate of molecular change in these genes and proteins should be regular like a clock © 2011 Pearson Education, Inc.
  • 87. Problems 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 © 2011 Pearson Education, Inc.
  • 88. Applying a Molecular Clock: The Origin of HIV • Phylogenetic analysis shows that HIV is descended from viruses that infect chimpanzees and other primates • HIV spread to humans more than once • Comparison of HIV samples shows that the virus evolved in a very clocklike way • Application of a molecular clock to one strain of HIV suggests that that strain spread to humans during the 1930s © 2011 Pearson Education, Inc.
  • 89. Figure 26.20 Year HIV Range Adjusted best-fit line (accounts for uncertain dates of HIV sequences) 0.20 0.15 0.10 0.05 0 1900 1920 1940 1960 1980 2000 IndexofbasechangesbetweenHIVgenesequences
  • 90. Concept 26.6: 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 © 2011 Pearson Education, Inc.
  • 91. From Two Kingdoms to Three Domains • Early taxonomists classified all species as either plants or animals • Later, five kingdoms were recognized: Monera (prokaryotes), Protista, Plantae, Fungi, and Animalia • More recently, the three-domain system has been adopted: Bacteria, Archaea, and Eukarya • The three-domain system is supported by data from many sequenced genomes © 2011 Pearson Education, Inc. Animation: Classification Schemes
  • 92. Figure 26.21 Archaea Bacteria Eukarya COMMON ANCESTOR OF ALL LIFE Land plants Green algae Red algae Forams Ciliates Dinoflagellates Cellular slime molds Amoebas Animals Fungi Euglena Trypanosomes Leishmania Sulfolobus Thermophiles Halophiles Methanobacterium Green nonsulfur bacteria (Mitochondrion) Spirochetes Chlamydia Cyanobacteria Green sulfur bacteria (Plastids, including chloroplasts) Diatoms
  • 93. Figure 26.21a Bacteria Green nonsulfur bacteria (Mitochondrion) Spirochetes Chlamydia Cyanobacteria Green sulfur bacteria (Plastids, including chloroplasts) COMMON ANCESTOR OF ALL LIFE
  • 95. Figure 26.21c Eukarya Land plants Green algae Red algae Forams Dinoflagellates Ciliates Diatoms Cellular slime molds Amoebas Animals Fungi Trypanosomes Euglena Leishmania
  • 96. 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 © 2011 Pearson Education, Inc.
  • 97. • 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 occurs by exchange of transposable elements and plasmids, viral infection, and fusion of organisms • Horizontal gene transfer complicates efforts to build a tree of life © 2011 Pearson Education, Inc.
  • 99. • Some researchers suggest that eukaryotes arose as an fusion between a bacterium and archaean • If so, early evolutionary relationships might be better depicted by a ring of life instead of a tree of life Is the Tree of Life Really a Ring? © 2011 Pearson Education, Inc.
  • 101. Figure 26.UN01 A A A B B BC C C D D D (a) (b) (c)
  • 102. Figure 26.UN02 Branch point Most recent common ancestor Polytomy Sister taxa Basal taxon Taxon A Taxon B Taxon C Taxon D Taxon E Taxon F Taxon G
  • 103. Figure 26.UN03 Monophyletic group Polyphyletic group Paraphyletic group A B C D E F G A B C D E F G A B C D E F G

Editor's Notes

  • #4: Figure 26.1 What is this organism?
  • #6: Figure 26.2 An unexpected family tree.
  • #7: Figure 26.2 An unexpected family tree.
  • #8: Figure 26.2 An unexpected family tree.
  • #9: Figure 26.2 An unexpected family tree.
  • #14: Figure 26.3 Linnaean classification.
  • #16: Figure 26.4 The connection between classification and phylogeny.
  • #20: Figure 26.5 How to read a phylogenetic tree.
  • #23: Figure 26.6 Inquiry: What is the species identity of food being sold as whale meat?
  • #28: Figure 26.7 Convergent evolution of analogous burrowing characteristics.
  • #31: Figure 26.8 Aligning segments of DNA.
  • #32: Figure 26.8 Aligning segments of DNA.
  • #33: Figure 26.8 Aligning segments of DNA.
  • #34: Figure 26.8 Aligning segments of DNA.
  • #36: Figure 26.9 A molecular homoplasy.
  • #40: Figure 26.10 Monophyletic, paraphyletic, and polyphyletic groups.
  • #41: Figure 26.10 Monophyletic, paraphyletic, and polyphyletic groups.
  • #43: Figure 26.10 Monophyletic, paraphyletic, and polyphyletic groups.
  • #45: Figure 26.10 Monophyletic, paraphyletic, and polyphyletic groups.
  • #49: Figure 26.11 Constructing a phylogenetic tree.
  • #50: Figure 26.11 Constructing a phylogenetic tree.
  • #51: Figure 26.11 Constructing a phylogenetic tree.
  • #55: Figure 26.12 Branch lengths can represent genetic change.
  • #57: Figure 26.13 Branch lengths can indicate time.
  • #60: Figure 26.14 Trees with different likelihoods.
  • #61: Figure 26.14 Trees with different likelihoods.
  • #62: Figure 26.14 Trees with different likelihoods.
  • #64: Figure 26.15 Research Method: Applying parsimony to a problem in molecular systematics
  • #65: Figure 26.15 Research Method: Applying parsimony to a problem in molecular systematics
  • #66: Figure 26.15 Research Method: Applying parsimony to a problem in molecular systematics
  • #67: Figure 26.15 Research Method: Applying parsimony to a problem in molecular systematics
  • #69: Figure 26.16 A phylogenetic tree of birds and their close relatives.
  • #71: Figure 26.17 Fossil support for a phylogenetic prediction: Dinosaurs built nests and brooded their eggs.
  • #72: Figure 26.17 Fossil support for a phylogenetic prediction: Dinosaurs built nests and brooded their eggs.
  • #73: Figure 26.17 Fossil support for a phylogenetic prediction: Dinosaurs built nests and brooded their eggs.
  • #77: Figure 26.18 Two types of homologous genes.
  • #78: Figure 26.18 Two types of homologous genes.
  • #80: Figure 26.18 Two types of homologous genes.
  • #86: Figure 26.19 A molecular clock for mammals.
  • #90: Figure 26.20 Dating the origin of HIV-1 M with a molecular clock.
  • #93: Figure 26.21 The three domains of life.
  • #94: Figure 26.21 The three domains of life.
  • #95: Figure 26.21 The three domains of life.
  • #96: Figure 26.21 The three domains of life.
  • #99: Figure 26.22 The role of horizontal gene transfer in the history of life.
  • #101: Figure 26.23 A ring of life.
  • #102: Figure 26.UN01 Concept Check 26.1, question 3
  • #103: Figure 26.UN02 Summary figure, Concept 26.1
  • #104: Figure 26.UN03 Summary figure, Concept 26.3
  • #105: Figure 26.UN04 Test Your Understanding, question 5
  • #106: Figure 26.UN05 Test Your Understanding, question 9
  • #107: Figure 26.UN06 Appendix A: answer to Figure 26.5 legend question
  • #108: Figure 26.UN07 Appendix A: answer to Figure 26.21 legend question
  • #109: Figure 26.UN08 Appendix A: answer to Concept Check 26.1, question 4
  • #110: Figure 26.UN09 Appendix A: answer to Concept Check 26.3, question 3
  • #111: Figure 26.UN10 Appendix A: answer to Concept Check 26.6, question 3
  • #112: Figure 26.UN11 Appendix A: answer to Test Your Understanding, question 9