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 25 Phylogeny and Systematics

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

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Systematics is an analytical approach to understanding the diversity and relationships of organisms, both present-day and extinct Systematists use morphological, biochemical, and molecular comparisons to infer evolutionary relationships

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Fossil Record Sedimentary rocks are the richest source of fossils Sedimentary rocks are deposited into layers called strata Video: Grand Canyon Video: Grand Canyon Rivers carry sediment to the ocean. Sedimentary rock layers containing fossils form on the ocean floor. Over time, new strata are deposited, containing fossils from each time period. As sea levels change and the seafloor is pushed upward, sedimentary rocks are exposed. Erosion reveals strata and fossils. Younger stratum with more recent fossils Older stratum with older fossils

LE 25-4 Dinosaur bones being excavated from sandstone Casts of ammonites, about 375 million years old Boy standing in a 150-million-year-old dinosaur track in Colorado Tusks of a 23,000-year-old mammoth, frozen whole in Siberian ice Petrified trees in Arizona, about 190 million years old Insects preserved whole in amber Leaf fossil, about 40 million years ago

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Morphological and Molecular Homologies Organisms with very similar morphologies or similar DNA sequences are likely to be more closely related than organisms with vastly different structures or sequences

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

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Convergent evolution occurs when similar environmental pressures and natural selection produce similar (analogous) adaptations in organisms from different evolutionary lineages

LE Deletion Insertion

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 today: two-part names for species and hierarchical classification

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Binomial Nomenclature 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 latinized Both parts together name the species (not the specific epithet alone)

LE 25-8 Species Panthera pardus Panthera Genus Family Felidae Carnivora Order Mammalia Class Phylum Chordata Kingdom Animalia Eukarya Domain Linnaeus introduced a system for grouping species in increasingly broad categories

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 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) Species Genus Family Order FelidaeMustelidaeCanidae PantheraMephitisLutraCanis

LeopardDomestic cat Common ancestor LeopardDomestic catWolf Common ancestor Each branch point represents the divergence of two species

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 25.3: Phylogenetic systematics informs the construction of phylogenetic trees based on shared characteristics A cladogram depicts patterns of shared characteristics among taxa A clade is a group of species that includes an ancestral species and all its descendants Cladistics studies resemblances among clades

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cladistics Clades can be nested in larger clades, but not all groupings or organisms qualify as clades A valid clade is monophyletic, signifying that it consists of the ancestor species and all its descendants

LE 25-10a Grouping 1 Monophyletic

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A paraphyletic grouping consists of an ancestral species and some, but not all, of the descendants

LE 25-10b Paraphyletic Grouping 2

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A polyphyletic grouping consists of various species that lack an immediate common ancestor

LE 25-10c Polyphyletic Grouping 3

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Shared Primitive and Shared Derived Characteristics In cladistic analysis, clades are defined by their evolutionary novelties

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A shared primitive character is a character that is shared beyond the taxon we are trying to define A shared derived character is an evolutionary novelty unique to a particular clade

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Outgroups An outgroup is a species or group of species that is closely related to the ingroup, the various species being studied Systematists compare each ingroup species with the outgroup to differentiate between shared derived and shared primitive characteristics

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Outgroup comparison assumes that homologies shared by the outgroup and ingroup must be primitive characters that predate the divergence of both groups from a common ancestor It enables us to focus on characters derived at various branch points in the evolution of a clade

LE Hair Amniotic (shelled) egg Four walking legs Hinged jaws Vertebral column (backbone) Character table CHARACTERS TAXA Lancelet (outgroup) LampreyTunaSalamander TurtleLeopard Turtle Leopard Hair Amniotic egg Four walking legs Hinged jaws Vertebral column Salamander Tuna Lamprey Lancelet (outgroup) Cladogram

LE Drosophila Lancelet Fish Amphibian Bird Human Rat Mouse Cenozoic Mesozoic Paleozoic Neoproterozoic Millions of years ago

LE Human 0 Mushroom 30% 0 Tulip 40% Human Mushroom 0Tulip Percentage differences between sequences Comparison of possible trees 15% 20% 5% 10% 15% 25% Tree 1: More likelyTree 2: Less likely

LE LizardBirdMammal Four-chambered heart Mammal-bird clade LizardBirdMammal Four-chambered heart Four-chambered heart Lizard-bird clade