1. 20-1 Chapter 20 Lecture Outline See PowerPoint Image Slides for all figures and tables pre-inserted into PowerPoint without notes.

2. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-2 The Classification of Organisms The problem with common names – Different in every language – Different names can be used to identify the same organism. Organisms must have names that all scientists can identify. Naming organisms involves two different activities. – Taxonomy The naming of organisms – Phylogeny Demonstrating how organisms are related evolutionarily

3. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-3 Garden Snake or Gardner Snake?

4. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-4 Taxonomy The science of naming organisms and grouping them into logical categories – Taxis = arrangement Scientific names of organisms are in Latin.

5. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-5 Taxonomy Organism names follow the binomial system of nomenclature. – Introduced by Linnaeus – Uses two Latin names The genus and the specific epithet A genus is a group of closely related organisms. A specific epithet identifies the particular species to which the organism belongs. Binomial names are italicized or underlined. The first letter of the genus is capitalized; the specific epithet is not. Thamnophis sirtalis

6. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-6 Taxonomy Three sets of rules determine how organisms are named. – International Rules for Botanical Nomenclature – International Rules for Zoological Nomenclature – International Bacteriological Code of Nomenclature Organisms are organized into logical groups. – These groups are hierarchical. – Domain, kingdom, phylum, class, order, family, genus, species

7. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-7 The Three Domains of Life

8. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-8 Classification of Humans

9. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-9 Phylogeny The science that explores the evolutionary relationships among organisms – Seeks to reconstruct evolutionary history Taxonomists use phylogeny to classify organisms whenever possible. Phylogenists use a variety of data to establish evolutionary relationships. – Fossils – Comparative anatomy studies – Life cycle information – Biochemical and molecular studies

10. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-10 Fossils Different types of fossils – Whole organisms that have been preserved intact – Bones embedded in rock – Impressions left in rock – Found in sedimentary rock, not igneous or metamorphic Some organisms fossilize more easily than others. – Those with hard parts vs. those with soft bodies – Those that live in water and can be buried in sediment

11. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-11 Fossils Fossils can be placed in a time sequence. – Established by the order that the organisms appear in the layers of sediment Deeper layers were laid down first. – Rocks can be aged by analyzing radioactive isotopes. Older rocks have fewer radioactive isotopes.

12. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-12 Comparative Anatomy Studies The anatomy of fossilized organisms can be compared to that of living organisms. – Allows for the classification of fossils – Those organisms that have similar structures are presumed to be related. – Examples Plants with flowers are related. Animals with hair and mammary glands are related.

13. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-13 Life Cycle Information Larval stages can provide clues about the relatedness of organisms. – Barnacles and shrimp The anatomy of eggs also provides clues. – Birds and reptiles The anatomy of seeds can be used as well. – Peas, peanuts and lima beans

14. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-14 Biochemical and Molecular Studies New DNA technologies have allowed phylogenists to use DNA sequence comparisons to determine relatedness. These analyses have clarified phylogenetic relationships that previously could not be confirmed. – Storks, flamingoes and geese – Green algae and plants

15. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-15 A Current Phylogenetic Tree

16. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-16 A Brief Survey of the Domains of Life Eubacteria, Archaea and Eucarya – Eubacteria and Archaea are prokaryotic. – Eucarya is eukaryotic. Order of appearance – Eubacteria evolved first. – Gave rise to Archaea – Eucarya evolved most recently.

17. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-17 Domain Eubacteria “True bacteria” Unicellular Small (1-10  m) Prokaryotic (no nucleus) – Contain a single, circular chromosome – Reproduce asexually

18. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-18 Domain Eubacteria Cell walls made of peptidoglycan – One component, muramic acid, is only found in bacteria. Can be rods, spheres or spirals Move via slime or flagella Varied metabolic requirements – Some are aerobic, some are anaerobic. – Some are decomposers, others are parasites; some are commensals. – Some are autotrophs, others are chemosynthetic.

19. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-19 Domain Archaea Unicellular Prokaryotic – Single circular chromosomes – Have several genes that are different from eubacteria and eucarya No peptidoglycan in their cell walls Have unique cell membranes Can be spheres, spirals, filaments or flat plates

20. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-20 Domain Archaea Metabolically labeled as extremophiles – Methanogens Produce methane Found in sewage, guts of ruminants, intestines of humans – Halobacteria Live in extremely salty environments Photosynthetic – Thermophiles Live in high temperatures or areas with high sulfur concentrations

21. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-21 Habitat for Thermophilic Archaea

22. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-22 Domain Eucarya Eukaryotic Appear to have evolved through endosymbiosis of prokaryotic cells Larger than prokaryotes Contain specialized membranous organelles

23. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-23 Kingdom Protista Diverse – 60,000 species Live in freshwater, marine, terrestrial Some are parasitic, commensalistic or mutualistic. Some reproduce asexually via mitosis. Some are autotrophic, others are heterotrophic. May not be a cohesive phylogenetic unit Include algae, protozoa and slime molds – Amoeba, Paramecium

24. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-24 A Diversity of Protista

25. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-25 Kingdom Fungi Most are non-motile Have a thin, rigid cell wall composed of chitin Heterotrophic – Most are saprophytes that secrete enzymes that break down the material they live on. – Decomposers – Some are parasitic, others are mutualistic. – Can form lichens

26. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-26 Kingdom Fungi Most are multicellular. – A few are unicellular. Yeast Made up of filaments Include – Athlete’s foot – Plant pathogens – Ringworm

27. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-27 Examples of Fungi

28. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-28 Kingdom Plantae Photosynthetic – Green because of chlorophyll Non-motile Terrestrial Likely evolved from green algae – Non-vascular plants first – Then vascular Cone-bearing Flowering

29. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-29 Kingdom Plantae Multicellular Contain a cellulose cell wall Exhibit alternation of generations – Multicellular gametophyte stage produces gametes via mitosis. – Multicellular sprorophyte stage produces spores via meiosis. – Able to reproduce sexually and asexually

30. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-30 Plant Evolution

31. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-31 Kingdom Animalia Are thought to have evolved from protozoa Over a million species identified Range from microscopic to very large Common traits – Heterotrophs – Multicellular – Motile – Can reproduce sexually

32. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-32 Animal Diversity

33. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-33 Acellular Infectious Particles Living organisms are made of cells. – Have cell membranes – Use nucleic acids as genetic material – Have cytoplasm – Contain enzymes – Contain ribosomes – Use ATP as their source of energy Particles that show some of these characteristics, but not all, are called acellular. – Most of these cause disease. – Viruses, viroids and prions

34. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-34 Viruses An infectious particle consisting of a nucleic acid core surrounded by a coat of protein. Are obligate intracellular parasites – Because they cannot live outside of a living cell Not technically “living” Some cause disease, some do not Vary in size and shape – Rod-shaped, spherical, coil, helix – Most are extremely small.

35. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-35 Typical Viruses

36. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-36 Viral Disease

37. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-37 How Viruses Cause Disease Viruses are host-specific. – Only infect one type of cell that has specific receptor sites on the cell membrane This is where the virus attaches. Is usually a glycoprotein Viruses must get their nucleic acids into the cell. – Once attached, viruses either enter the cell whole, or inject their nucleic acid into the cytoplasm.

38. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-38 How Viruses Cause Disease Viruses don’t have many enzymes. – They depend on their hosts to replicate their DNA and make their proteins. After viruses are replicated they leave the cell. – Frequently, this process kills the cell.

39. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-39 Viral Invasion of a Bacterial Cell

40. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-40 Viroids: Infectious RNA Infectious particles – Simply single strands of RNA Only found to infect plants Viroid infections cause stunted growth May cause plant death

41. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-41 Prions: Infectious Proteins Infectious proteins All prion diseases cause brain tissue to become “spongy”. – Cause spongiform encephalitis – Mad cow (BSE), scrapie (sheep), Creutzfeld- Jakob and Kuru (human) Can be transmitted from one animal to another

42. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-42 How Prions Cause Disease How do prions form and how do they multiply? – Normal prion proteins exist in the brain. – Infectious prions come in contact with normal prions and cause them to change shape. Called conversion Makes the normal prions infectious – The infectious proteins aggregate and form plaques. These plaques disrupt brain function and kill brain cells. Where cells die, a hole is formed. Causes infected brain tissue to look “spongy” Some people are more resistant to prion disease than others.