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Classification
Classification
Classification
Classification
Classification
Classification
Classification
Classification
Classification
Classification
Classification
Classification
Classification
Classification
Classification
Classification
Classification
Classification
Classification
Classification
Classification
Classification
Classification
Classification
Classification
Classification
Classification
Classification
Classification
Classification
Classification
Classification
Classification
Classification
Classification
Classification
Classification
Classification
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Classification

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  • 1. Classification
  • 2. The Need for Order <ul><li>Evolution has produced enormous diversity </li></ul><ul><ul><li>1.4 million species described </li></ul></ul><ul><li>Scientists need a method to order organisms logically, to understand relationships between organisms </li></ul><ul><li>Taxonomy : </li></ul><ul><ul><li>The science of classifying organisms on the basis of their similarities </li></ul></ul>
  • 3. Systematics <ul><li>The study of biological diversity in an evolutionary context. </li></ul><ul><ul><li>Connects classification to phylogeny </li></ul></ul><ul><ul><li>Classification based on evolutionary history </li></ul></ul><ul><li>Traditional taxonomy employed a hierarchical system of classification </li></ul><ul><li>Modern phylogenetic systemics is based on cladistic analysis </li></ul><ul><li>Systematics allows us to infer phylogeny from molecular data </li></ul>
  • 4. The History of Taxonomy <ul><li>Aristotle, a Greek philosopher, proposed one of the first systems - 350 B.C. </li></ul><ul><li>Divided living thing into 2 groups: </li></ul><ul><ul><li>plants & animals </li></ul></ul><ul><ul><li>Further divided animals by habitat and behavior & plants by size and structure </li></ul></ul><ul><li>This system was used for 2000 years </li></ul><ul><ul><li>Produced many errors based on what we know now </li></ul></ul><ul><li>By mid-1700’s naturalists were discovering many new life forms. </li></ul><ul><ul><li>Because different scientists used different principles to classify, understanding & communication was difficult </li></ul></ul>
  • 5. Linnaeus <ul><li>Carolus Linnaeus </li></ul><ul><ul><li>a Swedish Botanist </li></ul></ul><ul><ul><li>mid 1700’s </li></ul></ul><ul><ul><li>proposed a system of classification </li></ul></ul><ul><li>Organisms with similar structures should be placed in the same taxonomic group. </li></ul><ul><li>We still use Linnaeus’s basic system </li></ul><ul><li>Linnaean system has 2 main features: </li></ul><ul><ul><li>A 2 part name for each species </li></ul></ul><ul><ul><li>A hierarchical classification into broader & broader groups. </li></ul></ul>
  • 6. Binomial Nomenclature <ul><li>Use of common names can lead to confusion </li></ul><ul><li>Examples: </li></ul><ul><ul><li>mountain lion, puma, cougar = same animal </li></ul></ul><ul><ul><li>starfish, jellyfish, silverfish = misleading relationships </li></ul></ul><ul><li>Linnaeus suggested use of scientific names </li></ul><ul><li>Scientific name = genus + species </li></ul><ul><ul><li>genus is capitalized, species is not </li></ul></ul><ul><li>Called binomial nomenclature </li></ul><ul><ul><li>bi=2 </li></ul></ul><ul><li>Genus and species names are generally Latin </li></ul>
  • 7. The Species <ul><li>Linnaeus’s smallest taxonomic group was the species </li></ul><ul><li>Similar species were grouped in a larger category, genus . </li></ul><ul><ul><li>Similar genera were grouped into a family , then order , class , phylum , kingdom </li></ul></ul><ul><li>Example: </li></ul><ul><ul><li>dogs, wolves & jackals are different species, but the same genus </li></ul></ul>
  • 8. Defining a Species <ul><li>The most basic grouping used in biological classification. </li></ul><ul><li>A species differs from other similar organisms in at least one characteristic </li></ul><ul><li>Cannot interbreed freely with other species to produce fertile offspring. </li></ul><ul><li>Species evolve and change, so definition is not always sharp </li></ul>
  • 9. Linnean Taxonomy <ul><li>Created a hierarchy </li></ul><ul><li>As we move from species to kingdom, each category contains more organisms, and the organisms are less similar. </li></ul>
  • 10. The Linnaean Hierarchy <ul><li>MOST SPECIFIC FEWEST ORGANISMS Species </li></ul><ul><ul><li> Genus </li></ul></ul><ul><ul><li> Family </li></ul></ul><ul><ul><li> Order </li></ul></ul><ul><ul><li> Class </li></ul></ul><ul><ul><li> Phylum </li></ul></ul><ul><ul><li> Kingdom </li></ul></ul><ul><ul><li> [Domain] </li></ul></ul><ul><li>LEAST SPECIFIC MOST ORGANISMS </li></ul>
  • 11. <ul><li>Dogs, wolves, coyotes are separate species, but have similar characteristics. </li></ul><ul><li>All are genus Canis. </li></ul><ul><ul><li>Dog = Canis familiaris ; Wolf = Canis lupus ; Coyote = Canis latrans </li></ul></ul><ul><li>Family: Canidae </li></ul><ul><ul><li>also includes foxes - genus Vulpus </li></ul></ul><ul><li>Order: Carnivora </li></ul><ul><ul><li>includes other meat eaters such as cats, bears </li></ul></ul><ul><li>Class: Mammalia </li></ul><ul><ul><li>includes rodents, monkeys, many others that produce milk </li></ul></ul><ul><li>Phylum: Chordata </li></ul><ul><ul><li>all fish, birds, reptiles & other animals with a spinal cord </li></ul></ul><ul><li>Kingdom: Animalia </li></ul><ul><ul><li>all living things we think of as animals </li></ul></ul>
  • 12. The Kingdom <ul><li>Often the first level of classification </li></ul><ul><ul><li>The Domain is an even broader taxonomic level now embraced by many scientists </li></ul></ul><ul><li>Linnaeus proposed a system with 2 kingdoms: </li></ul><ul><ul><li>Autotrophs </li></ul></ul><ul><ul><li>organisms that produce their own food (the plant kingdom) </li></ul></ul><ul><ul><li>Hetertrophs </li></ul></ul><ul><ul><li>organisms that depend on others for food (animal kingdom) </li></ul></ul><ul><li>As we have been able to explore the microscopic world and examine cell structure this was not sufficient </li></ul>
  • 13. Cell Types <ul><li>All living things are made of cells </li></ul><ul><li>Cells help us understand relationships between organisms </li></ul><ul><li>Based on cell structure, organisms were classified as prokaryotes or eukaryotes </li></ul><ul><li>Prokaryotes : </li></ul><ul><ul><li>bacteria - earliest living cells </li></ul></ul><ul><ul><li>no nucleus or membrane enclosed organelles, rigid cell wall </li></ul></ul><ul><ul><li>no mitosis </li></ul></ul><ul><li>Eukaryotes </li></ul><ul><ul><li>usually larger </li></ul></ul><ul><ul><li>have a nucleus and other membrane enclosed organelles </li></ul></ul><ul><ul><li>DNA organized in chromosomes </li></ul></ul><ul><ul><li>cell division includes mitosis </li></ul></ul>
  • 14. The Five Kingdom System <ul><li>The first modern classification system recognized 5 kingdoms </li></ul><ul><li>All prokaryotes were kingdom Prokaryotae (or Monera ) </li></ul><ul><li>Eukaryotes were divided into 4 kingdoms: </li></ul><ul><li>Plantae , Animalia , Fungi , Protista </li></ul>
  • 15. The Six Kingdom System <ul><li>Further study of bacteria (kingdom Prokaryotae ) show there are really two distinct groups </li></ul><ul><li>So we now use a 6 kingdom system </li></ul><ul><ul><li>An updated version of the 5 kingdom system </li></ul></ul><ul><li>Divides prokaryotes into 2 kingdoms: </li></ul><ul><ul><li>Archebacteria : ancient bacteria </li></ul></ul><ul><ul><li>Eubacteria : true bacteria </li></ul></ul>
  • 16. The Prokaryote Debate <ul><li>More recent analysis of prokaryotes has shown that these two groups of bacteria are very different: </li></ul><ul><li>The Eubacteria </li></ul><ul><ul><li>Include five clades: proteobacteria, chlamydia, spirochetes, gram-positive bacteria, cyanobacteria </li></ul></ul><ul><li>The Archebacteria </li></ul><ul><ul><li>Include euryarchaeota, crenarchaeota </li></ul></ul><ul><ul><li>Confined to extreme environments </li></ul></ul><ul><ul><li>Similar to early earth </li></ul></ul><ul><ul><li>More closely related to eukaryotes than to modern bacteria </li></ul></ul><ul><li>Led to addition of a taxonomic level broader than the kingdom: the domain </li></ul><ul><ul><li>Three domains: bacteria, archaea, eukarya </li></ul></ul>
  • 17. The Last Common Ancestor <ul><li>Last universal common ancestor represents ancient divisions </li></ul><ul><li>Archbacteria are more closely related to eukaryotes than to other prokaryotes </li></ul>
  • 18. The Three Domain System <ul><li>An alternative to the six kingdom system </li></ul><ul><li>Based on comparing sequences of ribosomal RNA </li></ul><ul><li>Groups living things in 3 broad categories called domains </li></ul>
  • 19. The Eubacteria <ul><li>formerly Prokaryotae </li></ul><ul><ul><li>Included blue-green algae, bacteria and other micro-organisms that lack nuclei </li></ul></ul><ul><ul><li>A very diverse group </li></ul></ul>
  • 20. The Plants <ul><li>Plantae </li></ul><ul><ul><li>Autotrophic organisms that produce food through photosynthesis </li></ul></ul><ul><ul><li>Multicellular </li></ul></ul><ul><ul><li>Develop from an embryo that lacks a blastula </li></ul></ul>
  • 21. Divisions of the Plant Kingdom
  • 22. The Fungi <ul><li>Fungi </li></ul><ul><ul><li>Develop directly from spores </li></ul></ul><ul><ul><li>Reproduce either sexually or asexually </li></ul></ul><ul><ul><li>Includes yeasts, molds, bracket fungi, mushrooms </li></ul></ul>
  • 23. The Animals <ul><li>Animalia </li></ul><ul><ul><li>All organisms we think of as animals </li></ul></ul><ul><ul><li>All organisms developing from an embryo that has a blastula stage </li></ul></ul><ul><ul><li>Includes vertebrates and invertebrates – insects, worms, mollusks, fish, birds, reptiles, etc. </li></ul></ul>
  • 24. The Protists <ul><li>Protista </li></ul><ul><ul><li>Remaining eukaryotes </li></ul></ul><ul><ul><li>Most are single celled </li></ul></ul><ul><ul><li>Includes algae, protozoa, slime molds, etc. </li></ul></ul><ul><ul><li>Have characteristics that are both plant and animal like </li></ul></ul>
  • 25. Cladistic Analysis <ul><li>Attempts to build trees expressing phylogenetic relationships </li></ul><ul><li>This type of tree = cladogram </li></ul><ul><ul><li>A tree constructed from a series of dichotomies (choices) </li></ul></ul><ul><ul><li>2-way branching points </li></ul></ul><ul><ul><li>Each branch point represents the divergence of 2 species from a common ancestor </li></ul></ul><ul><ul><li>Sequence of branching symbolizes chronology </li></ul></ul><ul><li>Each evolutionary line in cladogram = clade </li></ul><ul><ul><li>A monophyletic group </li></ul></ul><ul><ul><li>Consists of an ancestral species and all its descendants </li></ul></ul>
  • 26. Connecting Classification & Phylogeny
  • 27. Cladograms ~ Phylogenetic Trees <ul><li>A family tree that shows the evolutionary relationships among groups of organisms </li></ul><ul><li>Can diagram divurgence of two species </li></ul><ul><li>Can also diagram divurgence of taxa more inclusive than species (family, order, etc.) </li></ul><ul><li>Phylogenetic trees are hypotheses </li></ul>
  • 28. Cladistic Taxonomy
  • 29. Basis of Classification <ul><li>Classification is based on homologies </li></ul><ul><ul><li>similarities that indicate related ancestry </li></ul></ul><ul><li>Structural homologies </li></ul><ul><ul><li>similarities of structure </li></ul></ul><ul><ul><li>example: limb pattern of reptiles, birds, mammals. </li></ul></ul><ul><ul><li>Fossil record </li></ul></ul><ul><ul><li>Modern organisms </li></ul></ul><ul><li>Biochemical homologies </li></ul><ul><ul><li>similarities of body substances (e.g. blood) or molecules (e.g. DNA). </li></ul></ul><ul><ul><li>These are recent tools and have helped clarify some classification problems </li></ul></ul><ul><li>Taxonomic classification is not permanent </li></ul><ul><ul><li>with new evidence, can change </li></ul></ul>
  • 30. Analogies vs. Homologies <ul><li>Not all structural similarities are homologies </li></ul><ul><li>Not all similarities reflect common ancestry </li></ul><ul><li>Convergent evolution produces similarities in unrelated species </li></ul><ul><li>These are referred to as analogies </li></ul><ul><li>Can confuse conventional classification </li></ul>
  • 31. Shared Derived Characteristics <ul><li>Study of common characteristics can be used to create a cladogram </li></ul><ul><li>Shared derived characteristics establish evolutionary relationships </li></ul><ul><li>Derived character: </li></ul><ul><ul><li>a feature that evolved only within the group under consideration </li></ul></ul>
  • 32. Characteristics Shape Cladograms
  • 33. Molecular Data <ul><li>Can infer phylogeny from molecular data </li></ul><ul><li>The more recently two species branched from a common ancestor, the more similar the DNA </li></ul><ul><li>Rates of change of DNA over evolutionary time vary from one part of the genome to another </li></ul><ul><li>Different sequences are studied in determining closer relationships than those used for more distant relationships. </li></ul>
  • 34. The Principle of Parsimony <ul><li>The simplest explanation that accounts for all of the available data is the best answer </li></ul><ul><li>Occam’s razor </li></ul><ul><li>Construct phylogentic trees that represent the smallest number of evolutionary changes </li></ul>
  • 35. Phylogenetic Trees are Hypotheses <ul><li>Competing evidence or ideas can yield different results </li></ul><ul><li>Tree “A” places the bird & mammal on a clade that excludes the lizard </li></ul><ul><ul><li>Tree “A” interprets the 4 chambered hearts of birds and mammals as homologous </li></ul></ul><ul><ul><li>This is the most parsimonious hypothesis </li></ul></ul><ul><li>Tree “B” places the bird & lizard in a clade </li></ul><ul><ul><li>The 4 chambered hearts of birds and mammals are analogous </li></ul></ul><ul><li>Evidence actually supports “B” </li></ul><ul><ul><li>Birds & lizards are closer than birds & mammals </li></ul></ul>
  • 36. Analogy or Homology?
  • 37. Taxonomy is Subject to Change <ul><li>Systematics and molecular evidence are changing classification </li></ul><ul><li>In traditional vertebrate taxonomy, crocodiles snakes, lizards, and other reptiles are grouped together in the class Reptilia </li></ul><ul><li>Birds are placed in a separate class, Aves </li></ul><ul><li>Newer methodologies show that crocodiles are more closely related to birds than to lizards or snakes </li></ul><ul><li>Class Reptillia in its traditional form is paraphyletic, not monophyletic </li></ul>
  • 38. Changing Views

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