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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.

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Presentation on theme: "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."— Presentation transcript:

1 The Tree of Life Chapter 17 1

2 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

3 Taxonomy  Mid – 1700’s  Naming organisms  Polynomials  Descriptive phrases  European honeybee  Apis pubescens, thorace subgriseo, abdomine fusco, pedibus posticis glabis, untrinque margine ciliatus 3

4 Simpler System  Carl Linnaeus  Swedish biologist  Developed binomial nomenclature  Two-part naming system  Ex: European honeybee  Apis mellifera 4

5 Scientific Names  Unique two-part name for a species  Genus - First name  Taxonomic category of similar organisms  Organisms have common important characteristics 5

6 Scientific Names  Species = Second name  One specific kind of living thing  Identifies the particular type of organism  Most specific and basic naming unit 6

7 Rules for Scientific Names  Genus  Always first  Capitalized 1 st letter  Species  Always second  NOT capitalized  Both  Italicized or underlined  Base on Latin language Apis mellifera 7

8 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

9 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

10 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

11 Classifying Organisms  Groups  Domain  Kingdom  Phylum  Class  Order  Family  Genus  Species Diverse Similar Biggest Smallest Danish Kings Play Chess On Fine Green Silk 11

12 Identifying Organisms  Field Guides Use:  Image  Description  General info  Range  Common name  Scientific name 12

13 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

14 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

15 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

16 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

17 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

18 17.2 Classification of Species  Put into groups based on similarities and differences  More similar = closely related  Suspect common ancestor 18

19 Classification of Species  Similarity of structure can be misleading  Not all characteristics inherited by offspring  Ex: Wings  Both birds and insects have... 19

20 Phylogeny  Evolutionary history for a group of species 20

21 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

22 Characters in Groups  Ancestral character  Feature in common ancestor of both groups  Ex:  Backbone  Birds and mammals 22

23 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

24 Cladistics  Classification based on common ancestry  Clade - group of species that shares a common ancestor 24

25 Cladogram  Cladogram  Branching diagram  Shows hypothesized evolutionary relationships  Tips represent groups of descendent taxa  Nodes represent common ancestors 25

26 Cladistics  Outgroup – shares no derived characters with other groups being studied 26

27 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 Classification 12 min Classification 12 min 27

28 Cladograms  Strengths  Objectivity  Either character exists or doesn’t  Weakness  Each character treated the same  Character impact or importance ignored 28

29 Phylogenetic Tree  Taxonomist assign importance to characters  Branching tree-like diagram  Shows evolutionary relationships  inferred 29

30 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

31 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

32 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

33 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

34 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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36 Domain Bacteria  Contains kingdom Bacteria  Unicellular prokaryotes  Contains autotrophs and heterotrophs  Classified by:  Shape  Need for oxygen  Whether the cause disease 36

37 Domain Archaea  Contain kingdom Archaea  Unicellular prokaryotes  Some autotrophic, some heterotrophic 37

38 Domain Archaea  Cell walls do NOT contain peptidoglycan  Live in “extreme” environments  Salt lakes  Antarctic waters  Deep sea vents  Hot geysers 38

39 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

40 Domain Eukarya  Includes kingdoms:  Protista  Plantae  Fungi  Animalia  Eukaryotic cells  Unicellular or multicellular 40

41 Review of Kingdoms  Bacteria  Archae  Protista  Fungi  Plantae  Animalia 41

42 Kingdom Bacteria  Cell wall made of peptidoglycan  Web-like carbohydrate strands and peptide bridges  42

43 Kingdom Archaea  Cell wall  No peptidoglycan  Cell membrane  Different lipids than bacteria or eukaryotes 43

44 Kingdom Protista  Many unicellular  Some have cell walls  Heterotrophs or autotrophs  Many move  Most reproduce asexually 44

45 Kingdom Fungi  Most multicellular  Except yeasts  Cell walls contain chitin  Tough carbohydrate  Heterotrophic 45

46 Kingdom Plantae  Multicellular  Cell walls  Cellulose (complex carb)  Eukaryotic  Autotrophic 46

47 Kingdom Animalia  Multicellular  Heterotrophs  Eukaryotic  Mostly diploid cells  No cell wall  Organized cells  Motility 47

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