The Tree of Life Chapter 17 1
17.1 Taxonomy The science of naming and classifying organisms 2000 years ago Aristotle Grouped plants and animals Based on structural similarities Greeks and Romans included categories Genus = Latin for group 2
Taxonomy Mid 1700 s Naming organisms Polynomials Descriptive phrases European honeybee Apis pubescens thorace subgriseo abdomine fusco pedibus posticis glabis untrinque margine ciliatus 3
Simpler System Carl Linnaeus Swedish biologist Developed binomial nomenclature Two-part naming system Ex: European honeybee Apis mellifera 4
Scientific Names Unique two-part name for a species Genus - First name Taxonomic category of similar organisms Organisms have common important characteristics 5
Scientific Names Species = Second name One specific kind of living thing Identifies the particular type of organism Most specific and basic naming unit 6
Rules for Scientific Names Genus Always first Capitalized 1 st letter Species Always second NOT capitalized Both Italicized or underlined Based on Latin language 7
Scientific Names Conform to rules established No two the same Gives biologist common way of communicating Common names have problems Ex: Robin Different bird in US and England! 8
Classifying Organisms Carl Linnaeus Classification system Ranked system of groups Large groups subdivided into smaller groups Increasingly similar 7 groups total Now we have one more group = Eight group levels 9
Classifying Organisms Groups Domain Kingdom Phylum Class Order Family Genus Species Definition Group of similar kingdoms Group of similar phyla Group of similar classes Group of similar orders Group of similar families Group of similar genera Group of similar species 10
Classifying Organisms Groups Domain Kingdom Phylum Class Order Family Genus Species Danish Kings Play Chess On Fine Green Silk Biggest Diverse Smallest Similar 11
Identifying Organisms Field Guides Use: Image Description General info Range Common name Scientific name 12
Identifying Organisms Dichotomous Keys Use: Pairs of descriptions OR a question that can be answered in ONLY 2 ways Read both descriptions or question Choose one Follow directions for next step End up with a scientific name Ex: 1a. This organism has an exoskeleton - go to number 2 1b. This organism has an endoskeleton or no skeleton - go to number 3 13
Identifying Organisms Species Unique Differences in appearance and structure Ex: Paramecium syngens Once thought to be a single species Look similar, but other differences 14
Species Biological species Defined by 1942 Ernst Mayr: A group of organisms that can reproduce only among themselves and are usually contained in a geographic region 15
Hybrids Hybrids Offspring produced by different species interbreeding Reproductive barriers not complete Some are fertile! Ex: Dogs and wolves Dogs = Canis familiaris Wolves = Canis lupus 16
Biological Species Concept Reproduction: Most of kingdom Animalia = limited Strong barriers Species only fails in: Organisms that reproduce asexually Ex: prokaryotes Transfer genes outside of reproduction Still working on how to classify them 17
17.2 Classification of Species Put into groups based on similarities and differences More similar = closely related Suspect common ancestor 18
Classification of Species Similarity of structure can be misleading Not all characteristics inherited by offspring Ex: Wings Both birds and insects have... 19
Phylogeny Evolutionary history for a group of species 20
Looking at Structures Convergent evolution Converge = Come together When similarities develop in organisms not closely related b/c Live in similar habitats thus have similar adaptations Analogous characters Arise through convergent evolution 21
Characters in Groups Ancestral character Feature in common ancestor of both groups Ex: Backbone Birds and mammals 22
Characters in Groups Derived character Found in only some members of a group More shared = more closely related Ex: Feathers Birds but Not mammals 23
Cladistics Classification based on common ancestry Clade - group of species that shares a common ancestor 24
Cladogram Cladogram Branching diagram Shows hypothesized evolutionary relationships Tips represent groups of descendent taxa Nodes represent common ancestors 25
Cladistics Outgroup shares no derived characters with other groups being studied 26
Cladogram Shared derived character Evidence that groups are closely related Ex: mammary glands Shared ancestral characters Not evidence groups are closely related Ex: Limbs Classification 12 min 27
Cladograms Strengths Objectivity Either character exists or doesn t Weakness Each character treated the same Character impact or importance ignored 28
Phylogenetic Tree Taxonomist assign importance to characters Branching tree-like diagram Shows evolutionary relationships inferred 29
Molecular Evidence Uses DNA to show relationships Often considered the last word by scientists Usually agrees with classification that was based on physical appearances Reclassification sometimes necessary 30
17.3 Molecular Clocks Models that use mutation rates to estimate evolutionary time Hypothesized that changes in DNA add up Rate of mutations = ticking of time More mutations = less closely related 31
Mitochondrial DNA mtdna Found only in mitochondria Only inherited from mother Sperm loses mitochondria after fertilization Mutation rate ~10x faster than nuclear DNA Often used as molecular clock Help classify closely related organisms 32
Ribosomal RNA rrna Useful when comparing different species that may be very distantly related Lots of time has passed Lower mutation rate Was used to reclassify Archaea and Bacteria into different domains 33
17.4 Domains and Kingdoms Domain Largest, broadest group Recent classification group 1977, Carl Woese American Prokaryotes differ fundamentally in rrna 34
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Domain Bacteria Contains kingdom Bacteria Unicellular prokaryotes Contains autotrophs and heterotrophs Classified by: Shape Need for oxygen Whether the cause disease 36
Domain Archaea Contain kingdom Archaea Unicellular prokaryotes Some autotrophic, some heterotrophic 37
Domain Archaea Cell walls do NOT contain peptidoglycan Live in extreme environments Salt lakes Antarctic waters Deep sea vents Hot geysers 38
Domains Archaea and Bacteria No true species Genes are shared outside of typical reproduction Still trying to decide how to classify Used to be classified together in one kingdom: Monera 39
Domain Eukarya Includes kingdoms: Protista Plantae Fungi Animalia Eukaryotic cells Unicellular or multicellular 40
Review of Kingdoms Bacteria Archae Protista Fungi Plantae Animalia 41
Kingdom Bacteria Cell wall made of peptidoglycan Web-like carbohydrate strands and peptide bridges 42
Kingdom Archaea Cell wall No peptidoglycan Cell membrane Different lipids than bacteria or eukaryotes 43
Kingdom Protista Many unicellular Some have cell walls Heterotrophs or autotrophs Many move Most reproduce asexually 44
Kingdom Fungi Most multicellular Except yeasts Cell walls contain chitin Tough carbohydrate Heterotrophic 45
Kingdom Plantae Multicellular Cell walls Cellulose (complex carb) Eukaryotic Autotrophic 46
Kingdom Animalia Multicellular Heterotrophs Eukaryotic Mostly diploid cells No cell wall Organized cells Motility 47
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