2 Finding Order In Diversity – 18.1 How do we order species?Has this order changed over time?Will this order continue to change?
3 Assigning Scientific Names First step: describe and give a universally accepted name to each speciesOne of the easiest ways to classify is using a dichotomous key – following a set of steps / questions to arrive at a conclusion
4 Let’s PracticeCopy the table below and choose 4 ways to categorize the fruits with members at your tableFruit??ApplePearOrangeKiwi
5 Assigning Scientific Names Linnaeus invented a system of binomial nomenclature – scientific name consisting of Genus species
6 Assigning Scientific Names The goal of systematics is to organize living things into groups that have biological meaning – higher than Genus species
7 The Linnaean Classification System Linnaeus went from developing a system with 4 groups to one with seven hierarchical taxa:KingdomPhylumClassOrderFamilyGenusSpecies
8 The Linnaean Classification System As you down the ladder of classification, you get more specific. We go from classifying according to general similarities, to specifics and interbreeding capabilitiesKingdom looks at generalities (are you multi-cellular?) while species looks at specifics (what’s special about you?)
9 The Linnaean Classification System However, how do we decide which similarities and differences are most important?Linnaeus used only similarities and differences with other living organisms. Today, we also look at where in the evolutionary tree does the organism belong and its DNA.
10 Modern Evolutionary Classification – 18.2 Linnaean classification had some faults under Darwin’s theory of evolution… the “tree of life” did not fit under itHow do we re-organize our classification to fit molecular evidence?
11 Evolutionary Classification The goal of phylogenetic systematics (evolutionary classification) is to group species into larger categories that reflect the lines of evolutionary descent, rather than similarities or differences
12 Evolutionary Classification Common ancestors – as we go into higher taxa, we get closer to our common ancestorClades – include a common ancestor and all of its descendantsKnown as monophyletic – ‘mono’ meaning one ancestor
13 CladogramsA cladogram links groups of organisms by showing how evolutionary lines, or lineages, branched off from common ancestors
14 CladogramsWhen one species splits off into two (think the finches), we call that a node in a cladogram. That point represents the last point at which two lineages shared a common ancestor
15 CladogramsThe bottom, or “root” of the cladogram represents the common ancestorEach branching pattern gives the degree of relatedness between the organisms
16 CladogramsCladograms depend on derived characteristics (a trait that arose in a recent common ancestor in a particular lineage) while Linnaean only grouped on similaritiesSometimes traits are lost in the process of evolution, but it still links them together!
17 Interpreting Cladograms The lowest node represents the last common ancestorEach derived character listed along the main trunk of the cladogram defines a cladeEx: retractable claws are only shared by Felidae (cats)
18 Interpreting Cladograms So where do Linnaeus and cladograms meet?Remember cladograms include the common ancestor and ALL its descendantsFor example, birds do not fit into the traditional Linnaean taxonomy, but they are reptiles! (come from the same common ancestor).
19 DNA in ClassificationWhen organisms don’t have similar physical characteristics, we turn to DNA to help us classify them.In general, the more derived genetic characters two species share, the more recently they shared a common ancestor and the more closely they are related in evolutionary terms.
20 DNA in ClassificationExample: the Red Panda is more closely related to raccoons than it is to Giant Pandas and BearsCompletely different genus! All this information from DNA.
21 18.2 – Let’s Practice Study Workbook A Pgs. 205-206 Work with a buddy (one sheet of paper). Write the question AND the answerNo key conceptsDue at the end of class!
22 18.3 Building The Tree Of Life Kingdoms in the 1700’s consisted only of Plantae and Animalia. Today, we have 6 Kingdoms:EubacteriaArchaebacteriaProtistaFungiPlantaeAnimalia
23 18.3 Changing Ideas About Kingdoms As research became more readily available, the kingdoms went expanding according to different characteristics each of the cells exhibitedPg. 524, Figure should be copied in your notes!
24 18.3 Changing Ideas About Kingdoms Kingdoms were not the only ones to change – Domains changed too!Went from Eukaryotes and Prokaryotes to Eubacteria, Archaebacteria and Eukarya
25 18.3 The Tree Of LifeThe tree of life shows current hypotheses regarding evolutionary relationships among the taxa within the three domains of lifeIt is not fact or permanent, it’s constantly changing as we discover new things!
26 18.3 The Tree Of Life Domain Bacteria: Unicellular Prokaryotic Thick cell walls with peptidoglycanCan use photosynthesis or oxygen (or not)Kingdom Eubacteria
27 18.3 The Tree Of Life Domain Archaea: Unicellular Prokaryotic ExtremophilesAnaerobic (no oxygen)Cell walls with no peptidoglycanKingdom Archaebacteria
28 18.3 The Tree Of Life Domain Eukarya: Have nucleus Kingdom Protista Many different characteristics (uni / multicellular, anaerobic/aerobic) and paraphyletic (not a true clade)Kingdom FungiHeterotrophs who feed on decaying matter and have chitin in their cell wallsKingdom PlantaeAutotrophs that have cellulose in their cell walls and do photosynthesisKingdom AnimaliaMulticellular and heterotrophic with no cell walls
29 Let’s Practice! Study Workbook A Pgs. 207-209 One sheet of paper for both of you, QUESTION & ANSWERNo key conceptsDue at the end of class!