Chapter 26 1 Terms a Phylogeny evolutionary relationships between organisms evolutionary history i Patterns of relatedness ii Animals are grouped together based on shared characteristics b Systematics the study of biological diversity in an evolutionary context scientific study of classification of organisms c Taxonomy naming and classification or organisms i Taxon group of organisms treated as a unit in a classification scheme ii Taxa plural iii Most people use taxonomy and systematics interchangeably 2 Linnaean system of classification a Carolus Linnaeus Swedish biologist i Described his classification scheme classified species by their morphology 200 years ago males and females may have been separated into different species sexual dimorphic Juvenile and adult stages 3 Scientific names Latin names a Each species has one scientific name only regardless of whether it is found in different b Why not use common names Problematic same name can apply to many different locations species depending on location i Pickerel applies to one species in Great Lakes and another in Ontario ii Pickerel also refers to this flowering plant c Blue Bells numerous unrelated species have this name based on blue flower i One species may have different common names depending on location leads ii Many types of scientists rely on taxonomists allows scientists to share results in to confusion a meaningful way 4 Binomial Nomenclature a The scientific name of a species has two parts b Two species can be in the same genus or can have the same species ending i 1st Genus name the genus it belongs to ii 2nd species name trivial name or epithet iii No two species can have the same name 1 The same genus species combination i Same genus ii Same ending 1 Homo erectus or homo sapiens Lysmata californica a shrimp 1 2 Eurylepta Californica a flatworm iii You can write a species name with underlining or italics 5 Taxonomic Levels a Domain kingdom phylum class order family genus species i Can get more complicated than the basic levels 6 Goal classify organisms based on phylogenetic relationship 7 Branch point a Where lineages diverge b This branch point represents the common ancestor of taxa A G i This branch point forms a polytomy an unresolved pattern of divergence 8 Phylogenetic tree is drawn to show patterns of relatedness a How Compare extant not extinct species b Compare with fossils 9 Phylogeny Methods of systematics a Main types cladistics verses phonetics b Terms i Phenetics number of traits looked at the number of traits that were shared by organisms species with the most traits in common were assumed to be the closest relatives 1 Traits were not weighted each trait had the same value ii Cladistics based on the presence of derived traits traits are weighted some traits are thought to be more important than others 1 Form a cladogram to show relationships i Analogous traits traits that serve similar functions are shared between two organisms due to convergent evolution 1 Example tail autotomy in lizards and salamanders ii Convergence in body shape 1 Rodents and ungulates in south America and Africa 2 Australian marsupial mole and north American eutherian mole iii Analogous structure 1 Wings of bats birds insects even flying squirrels are analogous wings perform similar functions but they evolved independently in each of these groups iv Analogous Character also called Homoplasies 1 Bioluminescence chemical production of light in insects ctenophores protists fish mollusks c Homologous traits traits that are shared between two organism because they were derived from a common ancestor includes ancestral and derived traits i Ancestral trait a trait that is shared with a common ancestor 1 For mammals having 4 limbs is an ancestral trait because their ancestor ii Derived trait a trait that differs from that of the ancestor can be development had four limbs or loss of a structure 1 Mammals derived traits include hair mammary glands d Outgroup a species or group of species that is closely related to the species that we are studying but known to be less closely related than any study group members are to each other i Evolutionary relationships between various vertebrate groups e Monophyly polyphyly paraphyly i Monophyletic group clade 1 All taxa share a common ancestor all descendants from that ancestor are included in that taxon 1 All taxa share a common ancestor but all descendants are not included ii Paraphyletic group in the taxon iii Polyphyletic group 1 All taxa do not share a common ancestor but all descendants from that ancestor are included in the taxon a Example Paraphyletic group polyphyletic group 10 Differences between cladistics and traditional classification a Traditional birds reptiles mammals b Cladistic birds and crocodiles reptiles mammals cladistics are shared derived traits 11 Classifying organisms a Traits used to construct phylogenies i The fossil record 1 Types of fossils mineralized fossils animal is buried minerals in groundwater replace organic material Mineralization Impressions the organism decays but its impression is left 2 a Sometimes organic material is left behind like leaves or pollen 3 Whole organisms rarest preserved in amber or ice 4 Trace fossils footprints burrow or other impression left in sediments by the activities of animals 5 Fossils appear in layers strata a Sedimentation process will vary over time lake may dry up etc b Why is it difficult to use fossils i Fossil record is incomplete 1 Organism has to die at exactly the right place at the right time conditions that favor fossilization thought to be rare 2 rock layer with the fossil must escape processes that destroy or distort rock e g heat erosion 3 fossil has to be exposed at some point 4 someone has to find it ii Fossil record is thought to be biased 1 organisms with wide distribution favored 2 those present for long periods of time 3 hard skeletons preserve better 12 Traits used to construct phylogenies a From living organisms i Gross morphology sizes and shapes of body parts ii Developmental data 1 Stages passed through during development often reflect patterns of relatedness can look at number of stages morphology of stages etc 2 Behavior similar courtship rituals etc 13 Molecular traits a Proteins structure of proteins b DNA hybridization more popular 20 years ago can compare DNA from different strands without knowing the sequences i At what temperature does it take to separate a hybrid DNA combination ii Human and