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Chapters 10 and 15

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Chapters 10 and 15

  1. 1. Chapter 10 and 15 Classification and Viruses 0
  2. 2. PHYLOGENY AND SYSTEMATICS <ul><li>15.6 Phylogenies are based on homologies in fossils and living organisms </li></ul><ul><ul><li>Phylogeny, the evolutionary history of a group </li></ul></ul><ul><ul><ul><li>Is based on identifying homologous and molecular sequences that provide evidence of common ancestry </li></ul></ul></ul>
  3. 3. <ul><ul><li>Analogous similarities </li></ul></ul><ul><ul><ul><li>Result from convergent evolution in similar environments </li></ul></ul></ul>Figure 15.6
  4. 4. <ul><ul><li>Systematics </li></ul></ul><ul><ul><ul><li>Involves the analytical study of diversity and phylogeny </li></ul></ul></ul>
  5. 5. <ul><li>15.7 Systematics connects classification with evolutionary history </li></ul><ul><ul><li>Taxonomists assign a binomial </li></ul></ul><ul><ul><ul><li>Consisting of a genus and species name, to each species </li></ul></ul></ul><ul><ul><li>A genus </li></ul></ul><ul><ul><ul><li>May include a group of related species </li></ul></ul></ul>
  6. 6. <ul><ul><li>Genera are grouped into progressively larger categories </li></ul></ul><ul><ul><ul><li>Family, order, class, phylum, kingdom, and domain </li></ul></ul></ul>Figure 15.7A Species Genus Family Order Class Phylum Kingdom Domain Felis catus Felis Felidae Carnivora Mammalia Chordata Animalia Eukarya
  7. 7. <ul><ul><li>A phylogenetic tree </li></ul></ul><ul><ul><ul><li>Is a hypothesis of evolutionary relationships </li></ul></ul></ul>Species Felis catus (domestic cat) Mephitis mephitis (striped skunk) Lutra lutra (European otter) Canis familiaris (domestic dog) Canis lupus (wolf) Genus Family Order Felis Felidae Carnivora Mustelidae Mephitis Lutra Canis Canidae Figure 15.7B
  8. 8. <ul><li>15.8 Cladograms are diagrams based on shared characters among species </li></ul><ul><ul><li>Cladistics uses shared derived characters </li></ul></ul><ul><ul><ul><li>To define monophyletic taxa </li></ul></ul></ul>Taxa Ingroup (Mammals) Outgroup (Reptiles) Eastern box turtle Duck-billed platypus Red kangaroo North American beaver Characters Long gestation Gestation Hair, mammary glands Long gestation Gestation Hair, mammary glands Vertebral column Vertebral column Figure 15.8A 3 2 1 3 1 2
  9. 9. <ul><ul><li>Shared primitive characters </li></ul></ul><ul><ul><ul><li>Are common to ancestral groups </li></ul></ul></ul>
  10. 10. <ul><ul><li>The simplest (most parsimonious) hypothesis </li></ul></ul><ul><ul><ul><li>Creates the most likely phylogenetic tree </li></ul></ul></ul>Figure 15.8B Lizards Snakes Crocodiles Birds Common reptilian ancestor
  11. 11. <ul><li>15.9 Molecular biology is a powerful tool in systematics </li></ul><ul><ul><li>Molecular systematics </li></ul></ul><ul><ul><ul><li>Develops phylogenetic hypotheses based on molecular comparisons </li></ul></ul></ul>Brown bear Polar bear Asiatic black bear American black bear Sun bear Sloth bear Spectacled bear Giant panda Raccoon Lesser panda Pleistocene Pliocene 10 15 20 25 30 35 40 Oligocene Miocene Millions of years ago Ursidae Procyonidae Common ancestral carnivorans Figure 15.9A
  12. 12. <ul><ul><li>Studies of ribosomal RNA sequences </li></ul></ul><ul><ul><ul><li>Have shown that humans are more closely related to fungi than to green plants </li></ul></ul></ul>Student Mushroom Tulip Common ancestor Figure 15.9B
  13. 13. <ul><li>DNA Comparisons </li></ul><ul><ul><li>Molecular comparisons of nucleic acids </li></ul></ul><ul><ul><ul><li>Often pose technical challenges </li></ul></ul></ul><ul><ul><ul><li>Can reveal the most fundamental similarities or differences between species </li></ul></ul></ul>
  14. 14. <ul><li>Molecular Clocks </li></ul><ul><ul><li>Some regions of DNA </li></ul></ul><ul><ul><ul><li>Change at a rate consistent enough to serve as molecular clocks to date evolutionary events </li></ul></ul></ul>
  15. 15. <ul><li>Genome Evolution </li></ul><ul><ul><li>Homologous genes </li></ul></ul><ul><ul><ul><li>Are found in many species </li></ul></ul></ul>Human Chimpanzee Gorilla Orangutan Common ancestor Figure 15.9C
  16. 16. <ul><li>15.10 Arranging life into kingdoms is a work in progress </li></ul><ul><ul><li>In the five-kingdom system </li></ul></ul><ul><ul><ul><li>Prokaryotes are in the kingdom Monera </li></ul></ul></ul><ul><ul><ul><li>Eukaryotes (plants, animals, protists, and fungi) are grouped in separate kingdoms </li></ul></ul></ul>Monera Protista Plantae Fungi Animalia Earliest organisms Prokaryotes Eukoryotes Figure 15.10A
  17. 17. <ul><ul><li>The domain system </li></ul></ul><ul><ul><ul><li>Recognizes the prokaryotic domains Bacteria and Archaea </li></ul></ul></ul><ul><ul><li>Eukaryotes </li></ul></ul><ul><ul><ul><li>Are placed in the domain Eukarya </li></ul></ul></ul>Bacteria Archaea Eukarya Earliest organisms Prokaryotes Eukoryotes Figure 15.10B
  18. 18. MICROBIAL GENETICS <ul><li>10.17 Viral DNA may become part of the host chromosome </li></ul><ul><ul><li>Viruses </li></ul></ul><ul><ul><ul><li>Can be regarded as genes packaged in protein </li></ul></ul></ul>
  19. 19. <ul><ul><li>When phage DNA enters a lytic cycle inside a bacterium </li></ul></ul><ul><ul><ul><li>It is replicated, transcribed, and translated </li></ul></ul></ul><ul><ul><li>The new viral DNA and protein molecules </li></ul></ul><ul><ul><ul><li>Then assemble into new phages, which burst from the host cell </li></ul></ul></ul>
  20. 20. <ul><ul><li>In the lysogenic cycle </li></ul></ul><ul><ul><ul><li>Phage DNA inserts into the host chromosome and is passed on to generations of daughter cells </li></ul></ul></ul><ul><ul><li>Much later </li></ul></ul><ul><ul><ul><li>It may initiate phage production </li></ul></ul></ul>
  21. 21. <ul><ul><li>Phage reproductive cycles </li></ul></ul>1 2 3 4 5 6 7 Lysogenic bacterium reproduces normally, replicating the prophage at each cell division Phage DNA inserts into the bacterial chromosome by recombination New phage DNA and proteins are synthesized Phages assemble Cell lyses, releasing phages Phage Attaches to cell Phage DNA Phage injects DNA Many cell divisions Prophage Lytic cycle Lysogenic cycle OR Bacterial chromosome Phage DNA circularizes Figure 10.17
  22. 22. CONNECTION <ul><li>10.18 Many viruses cause disease in animals </li></ul><ul><ul><li>Many viruses cause disease </li></ul></ul><ul><ul><ul><li>When they invade animal or plant cells </li></ul></ul></ul><ul><ul><li>Many, such as flu viruses </li></ul></ul><ul><ul><ul><li>Have RNA, rather than DNA, as their genetic material </li></ul></ul></ul>Membranous envelope RNA Protein coat Glycoprotein spike Figure 10.18A
  23. 23. <ul><ul><li>Some animal viruses </li></ul></ul><ul><ul><ul><li>Steal a bit of host cell membrane as a protective envelope </li></ul></ul></ul><ul><ul><ul><li>Can remain latent in the host’s body for long periods </li></ul></ul></ul>Glycoprotein spike Envelope Protein coat Viral RNA (genome) VIRUS Plasma membrane of host cell Viral RNA (genome) Template New viral genome Exit mRNA 7 New viral proteins Figure 10.18B Entry 1 Uncoating 2 RNA synthesis by viral enzyme 3 Protein synthesis 4 RNA synthesis (other strand) 5 Assembly 6
  24. 24. CONNECTION <ul><li>10.19 Plant viruses are serious agricultural pests </li></ul><ul><ul><li>Most plant viruses </li></ul></ul><ul><ul><ul><li>Have RNA genomes </li></ul></ul></ul><ul><ul><ul><li>Enter their hosts via wounds in the plant’s outer layers </li></ul></ul></ul>Protein RNA Figure 10.19
  25. 25. CONNECTION <ul><li>10.20 Emerging viruses threaten human health </li></ul>Colorized TEM 50,000  Colorized TEM 370,000  Figure 10.20A, B
  26. 26. <ul><li>10.21 The AIDS virus makes DNA on an RNA template </li></ul><ul><ul><li>HIV, the AIDS virus </li></ul></ul><ul><ul><ul><li>Is a retrovirus </li></ul></ul></ul>Envelope Glycoprotein Protein coat RNA (two identical strands) Reverse transcriptase Figure 10.21A
  27. 27. <ul><ul><li>Inside a cell, HIV uses its RNA as a template for making DNA </li></ul></ul><ul><ul><ul><li>To insert into a host chromosome </li></ul></ul></ul>1 2 3 4 5 6 Viral RNA RNA strand Double- stranded DNA Viral RNA and proteins CYTOPLASM NUCLEUS Chromosomal DNA Provirus DNA RNA Figure 10.21B
  28. 28. <ul><li>10.22 Bacteria can transfer DNA in three ways </li></ul><ul><ul><li>Bacteria can transfer genes from cell to cell by one of three processes </li></ul></ul><ul><ul><ul><li>Transformation, transduction, or conjugation </li></ul></ul></ul>DNA enters cell Fragment of DNA from another bacterial cell Bacterial chromosome (DNA) Phage Fragment of DNA from another bacterial cell (former phage host) Phage Sex pili Mating bridge Donor cell (“male”) Recipient cell (“female”) Figure 10.22A–C
  29. 29. <ul><ul><li>Once new DNA gets into a bacterial cell </li></ul></ul><ul><ul><ul><li>Part of it may then integrate into the recipient’s chromosome </li></ul></ul></ul>Recipient cell’s chromosome Recombinant chromosome Donated DNA Crossovers Degraded DNA Figure 10.22D
  30. 30. <ul><li>10.23 Bacterial plasmids can serve as carriers for gene transfer </li></ul><ul><ul><li>Plasmids </li></ul></ul><ul><ul><ul><li>Are small circular DNA molecules separate from the bacterial chromosome </li></ul></ul></ul>
  31. 31. <ul><ul><li>Plasmids can serve as carriers </li></ul></ul><ul><ul><ul><li>For the transfer of genes </li></ul></ul></ul>Plasmids Colorized TEM 2,000  Cell now male Plasmid completes transfer and circularizes F factor starts replication and transfer Male (donor) cell Bacterial chromosome F factor (plasmid) Recombination can occur Only part of the chromosome transfers F factor starts replication and transfer of chromosome Origin of F replication Bacterial chromosome Male (donor) cell F factor (integrated) Recipient cell Figure 10.23A–C

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