CHAPTER 18 CLASSIFICATION

1. CHAPTER 18 CLASSIFICATION

2. SECTION 1 FINDING ORDER IN DIVERSITY

3. KEY CONCEPT QUESTIONS: • How are living things organized for study? • What is binomial nomenclature? • What is Linnaeus’s system of classification?

4. How are living things organized for study? • To study the diversity of life, biologists use a classification system to name organisms and group them in a logical manner • TAXONOMY • discipline of classifying organisms and assigning each organism a universally accepted name

5. Classification • System to organize all living creatures • plants • animals • microbes • etc.

6. Why do you classify anything? • to be certain everyone is talking about the same thing • Using common names can be confusing • In the United Kingdom, the word buzzard refers to a hawk, whereas in many parts of the United States, buzzard refers to a vulture. • Woodchuck and ground hog are the same animal

7. Why not use common names? • Misleading • starfish • dragonfly • Confusing • blue jay, blue coat, corn thief • dog, perro, chien I swim,but I’m stilla bird!

8. Why not use common names? • But they all have only one scientific name! Pisaster ochraceus Pyrrhosoma nymphula Cyanocitta cristata

9. A more universal way of scientifically classifying came about • BINOMIALNOMENCLATURE • classification system in which each species is assigned a two-part scientificname

10. Carolus Linnaeus • The Linnean system • proposed in 1700s • each species has a 2 part name • genus • species Homo sapiens

11. Latin binomial • 2 part scientific name • Genus — larger group to which organism belongs • always capitalized • species — specific name for that organism • always lowercase • example: Linnaeus named humans Homosapiens • means “wise man”— perhaps in a show of hope & optimism

12. The grizzly bear is called Ursus arctos. • The first part of the scientific name—in this case, Ursus—is the genus to which the organism belongs • The second part of a scientific name—in this case, arctos—is unique to each species within the genus (this is usually a Latin name)

13. GENUS • a group of closely related species • Linnaeus’s System of Classification • TAXON • a group or level of organization; aka: taxonomic category

14. Genus groupings • Classify organisms into broader groups • Species that are closely related are grouped into the same genus • Leopard Pantherapardus • African lion Pantheraleo • Tiger Pantheratigris

15. Classification • Kingdom • Phylum • Class • Order • Family • Genus • species

16. Orders & families

17. KEY CONCEPT QUESTIONS: • How are living things organized for study? • Taxonomic categories • What is binomial nomenclature? • 2-part universal naming system • What is Linnaeus’s system of classification? • each species has a 2 part name • genus • species

18. SECTION 2 MODERN EVOLUTIONARY CLASSIFICATION

19. KEY CONCEPT QUESTIONS: • How are evolutionary relationships important in classification? • How can DNA and RNA help scientists determine evolutionary relationships?

20. Darwin's ideas about descent with modification have given rise to the study of PHYLOGENY, or evolutionary relationships among organisms. • evolutionary history of a species • based on common ancestries inferred from • fossil record • morphological & biochemical resemblances • molecular evidence

21. With the help of newer technology scientists have found more accurate ways of classifying organisms • Biologists now group organisms into categories that represent lines of evolutionary descent, not just physical similarities. • In other words, species placed within the same genus should be more closely related to one another than to species of any other genus

22. EVOLUTIONARY CLASSIFICATION • method of grouping organisms together according to their evolutionary history • To refine the process of evolutionary classification, many biologists now prefer a method called cladistic analysis

23. Cladistic analysis identifies and considers only those characteristics of organisms that are evolutionary innovations—new characteristics that arise as lineages evolve over time. Characteristics that appear in recent parts of a lineage but not in its older members are called DERIVED CHARACTERS.

24. Illustrating phylogeny • Cladograms • patterns of shared characteristics • diagram that shows the evolutionary relationships among a group of organisms Classify organisms according to the order in time at which branches arise along a phylogenetic tree

25. How is a cladogram constructed? • Procedure : pg. 453 in textbook • Identify the organism in the table that is least closely related to the others. • Use the information in the table to construct a cladogram of these animals.

26. Analyze and Conclude:  • What trait separates the least closely related organism from the other animals? • Lack of backbone • List the animals in your cladogram in order of distance from the least closely related organism. • Trout, lizard, and human

27. Does your cladogram indicate that lizards and humans share a more recent common ancestor than either does with an earthworm? Explain. • Yes, lizards and humans shared an ancestor that had legs and a backbone and that evolved after the earthworm’s lineage branched off on another evolutionary pathway • Where would you insert a frog if you added it to the cladogram? Explain your answer • A frog would occupy a branch between the trout and the lizard, because it has the derived characteristic of legs. Another derived characteristic, such as dry skin, would then have to be added for the lizard.

28. How are genes used to help scientists classify organisms? • The genes of many organisms show important similarities at the molecular level. • The similarities can be used to help determine classification • Scientists compare the DNA of different organisms to establish similarities between them and reconstruct possible evolutionary relationships

29. Of Mice and Men… • Evolving genomes • now that we can compare the entire genomes of different organisms, we find… • humans & mice have 99% of their genes in common • 50% of human genes have a close match with those of yeast! • the simplest eukaryote

30. The more similar the DNA sequences of two species, the more recently they shared a common ancestor, and the more closely they are related in evolutionary terms • Comparisons of DNA can also be used to mark the passage of evolutionary time.

31. A model known as a MOLECULAR CLOCK uses DNA comparisons to estimate the length of time that two species have been evolving independently. • To understand molecular clocks, think about a pendulum clock. It marks time with a periodically swinging pendulum. • A molecular clock also relies on a repeating process to mark time—mutation.

32. Molecular clocks HIV-1M samples were collected from patients between early 1980s & late 1990s. The gene evolved at a relatively constant rate. Concluded that HIV-1M strain first infected humans in 1930s. • Trace variations in genomes to date evolutionary changes • Rate of change is calculated and then extrapolate back

33. Simple mutations occur all the time, causing slight changes in the structure of DNA • Some mutations have a major positive or negative effect on an organism's phenotype. • These mutations are under powerful pressure from natural selection. • Other mutations have no effects on phenotype. These neutral mutations accumulate in the DNA of different species at about the same rate.

34. A comparison of such DNA sequences in two species can reveal how dissimilar the genes are. • The degree of dissimilarity is, in turn, an indication of how long ago the two species shared a common ancestor.

35. Evaluating molecular homologies • Aligning DNA sequences • more bases in common = more closely related • analyzed by software beware of molecular homologies

36. Modern Systematics • Shaking up some trees! Crocodiles are now thought to be closer to birds than other reptiles

37. KEY CONCEPT QUESTIONS: • How are evolutionary relationships important in classification? • evolutionary history of a species based on common ancestries inferred from • fossil record • morphological & biochemical resemblances • molecular evidence • How can DNA and RNA help scientists determine evolutionary relationships? • The more similar the DNA sequences of two species, the more recently they shared a common ancestor, and the more closely they are related in evolutionary terms

38. SECTION 3 KINGDOMS AND DOMAINS

39. KEY CONCEPT QUESTIONS: • What are the six kingdoms of life as they are now identified?  • What is the three-domain system of classification?

40. Since Linnaeus’s time kingdom classification has changed. • he had two kingdoms – plantae and animalia • now there are six • eubacteria, archaebacteria, protista, fungi, plantae, and animalia

41. There is also a level higher than kingdom called Domains • The three domains are: • Bacteria • kingdom Eubacteria • Archaea • kingdom Archaebacteria • Eukarya • Kingdom protists, fungi, plants, and animals.

42. Universal Tree of Life • 3 Domains • Bacteria • Eukarya • Archaea

43. KEY CONCEPT QUESTIONS: • What are the six kingdoms of life as they are now identified?  • eubacteria, archaebacteria, protista, fungi, plantae, and animalia • What is the three-domain system of classification? • Bacteria • Archea • Eukarya