Finding Order in Diversity: Classification and Evolutionary Relationships

1. Chapter 18

2. Finding Order in Diversity • Biologist have found and named over 1.5 million species so far • It is estimated that there are between 2 and 100 million species left to be discovered • To study the diversity of life, biologist use a classification system to name organism and group them in a logical manner

3. Finding Order in Diversity • Scientist discovered early that they could not use common names to name organisms… • Buzzard • In the UK meansHawk • In the US meansVulture • Cougar in the Mountain means: • Lion, Puma, Panther • Because early 18th century scientist all understood Latin and Greek, this was the language that was used to name organisms

4. Binomial Nomenclature • A 2 word naming system • Each species is assigned a 2 part scientific name • Always written italics • 1st part of the name is capitalized, 2nd part of the name is lowercase • Ursus arctos – grizzly bear

5. Binomial Nomenclature • The 1st part of the name is the genus • A group of closely related species • The 2nd part of the name is unique to a particular species within a genus • A Latinized word often describing a physical trait of the organism or a location where it lives • Ursus maritimus refers to the sea where polar bears live or pack ice in sea

6. Binomial Nomenclature

7. Taxon (pl. Taxa) • A group or level of organization • Linnaeus’ system of classification uses 7 Taxonomic Categories from smallest to largest • Species • Genus • Family • Order • Class • Phylum • Kingdom

8. Species • A population of organisms that can breed with one another and produce fertile offspring

9. Genus • A group of closely related species • Family • A group of genera that share many characteristics • Order • A broad taxonomic category that is composed or similar families • Class • Composed of similar orders

10. Phylum • Composed of many different classes…includes many different organism that nevertheless share important characteristics • Kingdom • The largest of all taxons, i.e the kingdom Animalia

11. A good aid for remembering these categories is the mnemonic device:  • Keep Plates Clean Or  Family Gets Sick.

12. Modern Evolutionary Classification • Originally, organism were grouped and classified according to body structure • There were problems with this method though, i.e dolphins --fish or mammals; and convergent evolution made it difficult to distinguish between related organism and unrelated organism with similar body structures

13. Modern Evolutionary Classification • Scientist began to understand that organism share certain traits because they share an evolutionary history • Biologist now group organisms into categories that represent lines of Evolutionary Decent, not just physical similarities– this is called Evolutionary Classification

14. Many biologist now use Cladistic Analysis • Identifies and considers only those characteristics of organisms that are Evolutionary Innovations: • New characteristics that arise as lineages evolve • Derived characters are characteristics that appear in recent parts of the lineage but not in its older members

15. Claydogram • A diagram that shows the evolutionary relationships among groups of organisms • Uses Derived Characters to mark the evolutionary change of a trait on the diagram • A useful tool to help us understand how one lineage branched from another in the course of evolution

16. Claydogram

17. Similarities in DNA & RNA • All organism use DNA & RNA to pass on information and to control growth and development • DNA & RNA provide an excellent way of comparing organism at a genetic (gene) level • The genes of many organism show important similarities at the molecular level. These similarities can be used as criteria to help determine classification • i.e … genes of humans and yeast even show similarities because both have a gene that codes for Protein Myosin • In humans causes muscle constrictions • In yeast enables internal cell part to move

18. Similarities in DNA & RNA • DNA comparisons have shed light on classification questions regarding just how closely related 2 species are .. • i.e… the American Vulture and the Stork • American Vulture has peculiar habits • When they get over-heated they urinate on their legs so that evaporative cooling removes some body heat

19. Similarities in DNA & RNA • Storks also behave in the same manner as American Vulture, but Storks looks quite different from vultures and have always been in a separate family • Scientists analyzed the DNA of these three(African Vultures, American Vultures, & Storks) birds revealed that American vultures are indeed more closely related to storks than they are to other vultures

21. Molecular Clocks • A model known as a Molecular Clock uses DNA comparisons to estimate the length of time that 2 species have been evolving independently • Relies on a repeating process to mark time--Mutations

22. Molecular Clocks • Mutations occur and accumulate in genes at a steady rate causing slight changes in the structure of DNA • Some mutations cause a change in phenotype while others do not • The one that do affect phenotype are under pressure form National Selection • The one that do not affect phenotype are accumulated in DNA at about the same rate

23. Molecular Clocks • A comparison of the DNA of 2 species can reveal how dissimilar the genes are • The degree of dissimilarity is an indication of how long ago the 2 shared a common ancestor • Molecular Clocks are complex while one gene may be at one rate, another at a different rate, etc like hands on clock –second, minute, hour, day, week, month, year, etc • Researchers would use a different Molecular Clock to compare modern bid species than they would to estimate the age of the common ancestor of yeasts and humans

25. Kingdoms and Domains • At first, there were only 2 kingdoms: Plantae and Animalia • As scientist learned more about the natural world, they realized that more kingdoms were needed and added • Eubacteria • Archaebacteria • Protista • Fungi • These are the 6 Kingdoms use today

26. Three Domain System • Using a Molecular Clock based on ribosomal RNA, scientist have grouped modern organisms according to how long they have been evolving independently • The Taxon that they are using for this broad group is called the Domain • The Domain is more inclusive than any other category– even larger than the Kingdom

27. The 3 Domain • Bacteria • Corresponds to kingdom Eubacteria • Archaea • Corresponds to kingdom Archaebacteria • Eukarya • Corresponds to kingdoms Protista, Fungi, Palantae, and Animalia

28. Eukarya • The kingdom Animalia is in this domain • Members of this kingdom (Animals) are Multicellular and Heterotrophic • The cells of animals have no cell walls • Most animals move about for at least some part of their life

29. Eubacteria • Have three basic shapes. • round • rod • spiral

30. Archaebacteria • Archaebacteria are found in extreme condition. • Some are autotrophic • Photoautotrophs • Chemoautotrophs

31. Plantae • Multicellular • Photosynthetic • Cell walls contain cellulose • Non-motile

32. Protista • Mostly single celled • Very diverse group • Some multicellular (Seaweeds) • Eukaryotes • Many are autotrophic

33. Fungi • Heterotrophic • Have cell wall • Eukaryotes • Very diverse

34. Animalia • Heterotrophic • Eukaryotic • Motile

35. Chapter 18 Questions • What is taxonomy? • Explain Binomial Nomenclature • What are the 7 Taxonomic categories form smallest largest? • What is evolutionary classification? • What are derived characters? • How and why do scientist use Cladograms?

36. Chapter 18 Questions 7. How can genes be used in classification? 8. What is a molecular clock? 9. What are the 6 kingdoms used in modern classification? 10. What are 3 domains and which kingdoms do they correspond with?

37. Chapter 18 Questions 11. What are 4 characteristics of the domain Bacteria 12. What are 4 characteristics of the domain Archaea? 13. What are the 4 kingdoms of Eukarya and what are 2 characteristics of each?