1. Classification systems help organize the enormous diversity of life into logical groups based on evolutionary relationships and similarities between organisms. 2. Carolus Linnaeus developed the modern system of binomial nomenclature and hierarchical taxonomy that is still used today, grouping organisms into kingdoms, phyla, classes, orders, families, genera, and species. 3. Modern phylogenetic systematics connects classification to evolutionary history and phylogeny using molecular data and cladistic analysis of shared derived characteristics to construct phylogenetic trees.

1. Classification

2. The Need for Order Evolution has produced enormous diversity 1.4 million species described Scientists need a method to order organisms logically, to understand relationships between organisms Taxonomy : The science of classifying organisms on the basis of their similarities

3. Systematics The study of biological diversity in an evolutionary context. Connects classification to phylogeny Classification based on evolutionary history Traditional taxonomy employed a hierarchical system of classification Modern phylogenetic systemics is based on cladistic analysis Systematics allows us to infer phylogeny from molecular data

4. The History of Taxonomy Aristotle, a Greek philosopher, proposed one of the first systems - 350 B.C. Divided living thing into 2 groups: plants & animals Further divided animals by habitat and behavior & plants by size and structure This system was used for 2000 years Produced many errors based on what we know now By mid-1700’s naturalists were discovering many new life forms. Because different scientists used different principles to classify, understanding & communication was difficult

5. Linnaeus Carolus Linnaeus a Swedish Botanist mid 1700’s proposed a system of classification Organisms with similar structures should be placed in the same taxonomic group. We still use Linnaeus’s basic system Linnaean system has 2 main features: A 2 part name for each species A hierarchical classification into broader & broader groups.

6. Binomial Nomenclature Use of common names can lead to confusion Examples: mountain lion, puma, cougar = same animal starfish, jellyfish, silverfish = misleading relationships Linnaeus suggested use of scientific names Scientific name = genus + species genus is capitalized, species is not Called binomial nomenclature bi=2 Genus and species names are generally Latin

7. The Species Linnaeus’s smallest taxonomic group was the species Similar species were grouped in a larger category, genus . Similar genera were grouped into a family , then order , class , phylum , kingdom Example: dogs, wolves & jackals are different species, but the same genus

8. Defining a Species The most basic grouping used in biological classification. A species differs from other similar organisms in at least one characteristic Cannot interbreed freely with other species to produce fertile offspring. Species evolve and change, so definition is not always sharp

9. Linnean Taxonomy Created a hierarchy As we move from species to kingdom, each category contains more organisms, and the organisms are less similar.

10. The Linnaean Hierarchy MOST SPECIFIC FEWEST ORGANISMS Species Genus Family Order Class Phylum Kingdom [Domain] LEAST SPECIFIC MOST ORGANISMS

11. Dogs, wolves, coyotes are separate species, but have similar characteristics. All are genus Canis. Dog = Canis familiaris ; Wolf = Canis lupus ; Coyote = Canis latrans Family: Canidae also includes foxes - genus Vulpus Order: Carnivora includes other meat eaters such as cats, bears Class: Mammalia includes rodents, monkeys, many others that produce milk Phylum: Chordata all fish, birds, reptiles & other animals with a spinal cord Kingdom: Animalia all living things we think of as animals

12. The Kingdom Often the first level of classification The Domain is an even broader taxonomic level now embraced by many scientists Linnaeus proposed a system with 2 kingdoms: Autotrophs organisms that produce their own food (the plant kingdom) Hetertrophs organisms that depend on others for food (animal kingdom) As we have been able to explore the microscopic world and examine cell structure this was not sufficient

13. Cell Types All living things are made of cells Cells help us understand relationships between organisms Based on cell structure, organisms were classified as prokaryotes or eukaryotes Prokaryotes : bacteria - earliest living cells no nucleus or membrane enclosed organelles, rigid cell wall no mitosis Eukaryotes usually larger have a nucleus and other membrane enclosed organelles DNA organized in chromosomes cell division includes mitosis

14. The Five Kingdom System The first modern classification system recognized 5 kingdoms All prokaryotes were kingdom Prokaryotae (or Monera ) Eukaryotes were divided into 4 kingdoms: Plantae , Animalia , Fungi , Protista

15. The Six Kingdom System Further study of bacteria (kingdom Prokaryotae ) show there are really two distinct groups So we now use a 6 kingdom system An updated version of the 5 kingdom system Divides prokaryotes into 2 kingdoms: Archebacteria : ancient bacteria Eubacteria : true bacteria

16. The Prokaryote Debate More recent analysis of prokaryotes has shown that these two groups of bacteria are very different: The Eubacteria Include five clades: proteobacteria, chlamydia, spirochetes, gram-positive bacteria, cyanobacteria The Archebacteria Include euryarchaeota, crenarchaeota Confined to extreme environments Similar to early earth More closely related to eukaryotes than to modern bacteria Led to addition of a taxonomic level broader than the kingdom: the domain Three domains: bacteria, archaea, eukarya

17. The Last Common Ancestor Last universal common ancestor represents ancient divisions Archbacteria are more closely related to eukaryotes than to other prokaryotes

18. The Three Domain System An alternative to the six kingdom system Based on comparing sequences of ribosomal RNA Groups living things in 3 broad categories called domains

19. The Eubacteria formerly Prokaryotae Included blue-green algae, bacteria and other micro-organisms that lack nuclei A very diverse group

20. The Plants Plantae Autotrophic organisms that produce food through photosynthesis Multicellular Develop from an embryo that lacks a blastula

21. Divisions of the Plant Kingdom

22. The Fungi Fungi Develop directly from spores Reproduce either sexually or asexually Includes yeasts, molds, bracket fungi, mushrooms

23. The Animals Animalia All organisms we think of as animals All organisms developing from an embryo that has a blastula stage Includes vertebrates and invertebrates – insects, worms, mollusks, fish, birds, reptiles, etc.

24. The Protists Protista Remaining eukaryotes Most are single celled Includes algae, protozoa, slime molds, etc. Have characteristics that are both plant and animal like

25. Cladistic Analysis Attempts to build trees expressing phylogenetic relationships This type of tree = cladogram A tree constructed from a series of dichotomies (choices) 2-way branching points Each branch point represents the divergence of 2 species from a common ancestor Sequence of branching symbolizes chronology Each evolutionary line in cladogram = clade A monophyletic group Consists of an ancestral species and all its descendants

26. Connecting Classification & Phylogeny

27. Cladograms ~ Phylogenetic Trees A family tree that shows the evolutionary relationships among groups of organisms Can diagram divurgence of two species Can also diagram divurgence of taxa more inclusive than species (family, order, etc.) Phylogenetic trees are hypotheses

28. Cladistic Taxonomy

29. Basis of Classification Classification is based on homologies similarities that indicate related ancestry Structural homologies similarities of structure example: limb pattern of reptiles, birds, mammals. Fossil record Modern organisms Biochemical homologies similarities of body substances (e.g. blood) or molecules (e.g. DNA). These are recent tools and have helped clarify some classification problems Taxonomic classification is not permanent with new evidence, can change

30. Analogies vs. Homologies Not all structural similarities are homologies Not all similarities reflect common ancestry Convergent evolution produces similarities in unrelated species These are referred to as analogies Can confuse conventional classification

31. Shared Derived Characteristics Study of common characteristics can be used to create a cladogram Shared derived characteristics establish evolutionary relationships Derived character: a feature that evolved only within the group under consideration

32. Characteristics Shape Cladograms

33. Molecular Data Can infer phylogeny from molecular data The more recently two species branched from a common ancestor, the more similar the DNA Rates of change of DNA over evolutionary time vary from one part of the genome to another Different sequences are studied in determining closer relationships than those used for more distant relationships.

34. The Principle of Parsimony The simplest explanation that accounts for all of the available data is the best answer Occam’s razor Construct phylogentic trees that represent the smallest number of evolutionary changes

35. Phylogenetic Trees are Hypotheses Competing evidence or ideas can yield different results Tree “A” places the bird & mammal on a clade that excludes the lizard Tree “A” interprets the 4 chambered hearts of birds and mammals as homologous This is the most parsimonious hypothesis Tree “B” places the bird & lizard in a clade The 4 chambered hearts of birds and mammals are analogous Evidence actually supports “B” Birds & lizards are closer than birds & mammals

36. Analogy or Homology?

37. Taxonomy is Subject to Change Systematics and molecular evidence are changing classification In traditional vertebrate taxonomy, crocodiles snakes, lizards, and other reptiles are grouped together in the class Reptilia Birds are placed in a separate class, Aves Newer methodologies show that crocodiles are more closely related to birds than to lizards or snakes Class Reptillia in its traditional form is paraphyletic, not monophyletic

38. Changing Views