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The Tree of Life Chapter 17.

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Presentation on theme: "The Tree of Life Chapter 17."— Presentation transcript:

1 The Tree of Life Chapter 17

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

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

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

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

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

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

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!

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

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

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

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

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

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

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

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

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

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

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

20 Phylogeny Evolutionary history for a group of species

21 Looking at Structures Convergent evolution Analogous characters
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

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

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

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

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

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

27 Cladogram Shared derived character Shared ancestral characters
Evidence that groups are closely related Ex: mammary glands Shared ancestral characters Not evidence groups are closely related Ex: Limbs Classification 12 min

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

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

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

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

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

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

34 17.4 Domains and Kingdoms Domain Recent classification group
Largest, broadest group Recent classification group 1977, Carl Woese American Prokaryotes differ fundamentally in rRNA


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

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

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

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

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

41 Review of Kingdoms Bacteria Archae Protista Fungi Plantae Animalia

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

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

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

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

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

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



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