BIOLOGY Chapter 19 Phylogeny and Systematics

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Phylogeny is the evolutionary history of a group of organisms. Phylogenies are based on common ancestries inferred from fossil, morphological, and molecular evidence. Systematics is utilizing an analytical approach to understanding the diversity and relationships of organisms, both present day and extinct. Phylogenetic trees strive to represent evolutionary history

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Morphological and molecular homologies Morphological and molecular similarities are often used to determine phylogenetic histories. Organisms that share similar morphologies or similar DNA sequences are likely to be closely related. However, morphological differences can be great, while genetic divergence is small. Human46 gorilla, chimpanzee48 common fruit fly8 domestic pig38 lab mouse40 Plant10 Roundworm12 Yeast32

20 Tracing Phylogeny Fossil Record Fossil record is incomplete It is often difficult to determine the phylogeny of a fossil Homology Refers to features that stem from a common ancestor Homologous structures are related to each other through common descent Analogy Similarity due to convergence

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Homology vs. Analogy Homologous structures suggest shared ancestry. Analogy is the result of convergent evolution. Similar environmental pressures produce analogous adaptations.

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings CONVERGENT EVOLUTION and Analogous structures

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings DIVERGENT EVOLUTION and Homologous structures

10 Phylogenetic Trees Systematics is the study of diversity of organisms using information from cellular to population levels One goal of systematics is to determine phylogeny (evolutionary history) of a group Phylogeny is the evolutionary history of a group of organisms. Phylogeny often represented as a phylogenetic tree A diagram indicating lines of descent Each branching point: Is a divergence from a common ancestor Represents an organism that gives rise to two new groups

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings An unexpected family tree Molecular systematics has revealed that- despite appearances- animals, including humans, and fungi, such as mushrooms are more closely related to each other than either are to plants.

Classification and Phylogeny Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. monkeysapes common ancestor (mobile limbs) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. reindeermonkeysapes common ancestor (placental mammal)

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings PHYLOGENY PHYLOGENETIC TREE

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure SPECIES Felis catus (domestic cat) Mephitis mephitis (striped skunk) Lutra lutra (European otter) Canis familiaris (domestic dog) Canis lupus (wolf) Felis GENUS FAMILY ORDER MephitisLutraCanis CanidaeMustelidaeFelidae Carnivora

13 Phylogenetic Trees Classification lists the unique characters of each taxon and is intended to reflect phylogeny Primitive characters: Present in all members of a group, and Present in the common ancestor Derived characters: Present in some members of a group, but Absent in the common ancestor

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Members of a species share quite specific characters. A character is any structural, chromosomal, or molecular feature that distinguishes one group from another Patterns of shared characteristics can be depicted in a cladogram. Within a phylogenetic tree, a clade is defined as a group of species that includes an ancestral species and all its descendants. The analysis of how species are grouped into clades is called cladistics. Cladistics

19 Terms Used in Cladistics

14 Cladistic Systematics Cladistics analyze primitive and derived characters and constructs cladograms on the basis of shared derived characters. Arrange taxa into a cladogram A cladogram is a special type of phylogenetic tree A clade is an evolutionary branch that includes: A common ancestor, together with All its descendent species It traces the evolutionary history of the group being studied. Constructing a Cladogram First step: construct a table of characters of the taxa being compared. Any character found in the outgroup as well is a shared primitive character. Homologies shared by certain lineages are shared derived characters.

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings A valid clade is monophyletic (“single tribe”) Paraphyletic and polyphyletic clades lack information. The ancestral species (B) and all of its descendants are included in this clade. Consists of an ancestor (A) and some, but not all, of the descendants. Lacks the common ancestor (A) of the species in the group.

15 Constructing a Cladogram Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. chimpanzeedogfinchcrocodilelizardfrogtuna lancelet (outgroup) Species Traits mammary glands gizzard epidermal scales amniotic egg four limbs vertebrae hair ingroup notochord in embryo Outgroup is a species that is closely related to the ingroup, but is less closely related than any of the ingroup members are to each other.

16 Constructing a Cladogram: Phylogenetic Tree vertebrae four limbs feathers gizzard hair, mammary glands long canine teeth enlarged brain chimpanzee tuna frog lizard crocodile finch terrier lancelet (outgroup) common ancestor epidermal scales Amniotic egg common ancestor Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

17 Parsimony Cladists are guided by the principle of parsimony—the minimum number of assumptions is most logical. The best cladogram is one in which the fewest number of shared derived characters are left unexplained or that minimizes the number of assumed evolutionary changes. Reliability of cladograms is dependent on the knowledge and skill of a investigator.

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Aristotle classified life into 14 groups (e.g., mammals, birds, etc.), Ray grouped animals and plants according to how he thought they were related. Systematics dates back to the 18 th century with Linnaeus, and his taxonomic classification of plants and animals. Taxonomists assign a two-part name to each species (binomial nomenclature) –The first name, the genus, covers a group of related species –The second name refers to a species within a genus Phylogenetic systematics connects classification with evolutionary history SYSTEMATICS AND PHYLOGENETIC BIOLOGY

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Hierarchical classification Table 15.10

29 Three-Domain System Domain Eukarya Unicellular and multicellular organisms Cells with a membrane-bounded nucleus Sexual reproduction common Contains four kingdoms Kingdom Protista Kingdom Fungi Kingdom Plantae Kingdom Animalia

30 Tree of Life Showing The Three Domains Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. common ancestor ARCHAEA BACTERIA EUKARYA animalsfungi plants cyanobacteria protists heterotrophic bacteria

31 Major Difference of Three Domains

32 The Three Domains of Life Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. (Bacteria): © David M. Phillips/Visuals Unlimited; (Archaea): © Ralph Robinson/Visuals Unlimited; (Flower): © Ed Reschke/Peter Arnold, Inc.; (Paramecium): © M. Abbey/Visuals Unlimited; (Mushroom): © S. Gerig/Tom Stack & Associates; (Wolf): © Art Wolf/Stone/Getty Images Domain Eukarya Protists Paramecium, Paramecium Domain Eukarya Kingdom Fungi Mushroom, Hygrocybe Domain Eukarya Kingdom Plantae Black-eyed Susan, Rudbeckia Domain Bacteria Escherichia Domain Archaea Methanosarcina Domain Eukarya Kingdom Animalia Grey wolf, Canis