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Chapter 18 Classification

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1 Chapter 18 Classification

2 18.1 Finding Order in Diversity SC.912.L.15.4 and SC.912.N.1.1
Assigning Scientific Names Key Question: What are the goals of binominal nomenclature and systematics? The first step in understanding and studying diversity is to describe and name each species. In the eighteenth century, European scientist agreed to assign Latin or Greek names to each species.

3 Binomial Nomenclature
Binomial nomenclature is a two part scientific name given to a species. For example, the polar bear’s binomial nomenclature is Ursus maritimus. Ursus is the genus of the organism and maritimus is the species.

4 Classifying Species Into Larger Groups
The goal of systematics is to organize living things into groups that have biological meaning. They group species into larger groups with organisms that are similar to them.

5 The Linnaean Classification System
Key Question: How did Linnaeus group species into larger taxa? Over time, Linnaeus’ original classification system expanded to include seven hierarchical taxa: species, genus, family, order, class, phylum, and kingdom. Organisms are grouped by their characteristics within each taxa.

6 Problems with Traditional Classification
Systematics over time have emphasized a variety of characteristics, and some of these groups have been defined differently. Sometimes problems come about when species are classified by observable traits.

7 18. 2 Modern Evolutionary Classification SC. 912. L. 15. 5, SC. 912. N
18.2 Modern Evolutionary Classification SC.912.L.15.5, SC.912.N.1.1, SC.912.L.15.4 Evolutionary Classification Key Question: What is the goal of evolutionary classification? The goal of phylogenetic systematics, or evolutionary classification, is to group species into larger categories that reflect lines of evolutionary descent, rather than overall similarities and differences. Phylogeny is the evolutionary history of lineages.

8 Common Ancestors Phylogenetic systematics places organisms into higher taxa whose members are closely related to another member of the taxa. In the past, all members in a large taxon shared a common ancestry and is true to even the largest taxa.

9 Clades Classifying organisms according to the rules places them into groups called clades. A clade has to be a monophyletic group which includes a single common ancestor and all of its descendants.

10 Cladograms Key Question: What is a cladogram?
A cladogram links groups of organisms by showing how evolutionary lines, or lineages, branch off from common ancestors. Cladistic analysis compares carefully selected traits to determine the order in which groups of organisms branch off their common ancestors.

11 Building Cladograms A speciation event, where one ancestral species splits into two new ones, and creates two branch points. The node represents the last point at which the two lineages shared a common ancestor.

12 Derived Characters A derived character is a trait that arose in the most recent common ancestor of a particular lineage and was passed along to its descendants. Whether or not a character is derived depends on the level at which the organisms are grouped.

13 Losing Traits Somewhere in a lineage there is a trait that can be lost. For example, snakes lost the trait of having four legs.

14 Interpreting Cladograms
The lowest node represents the last common ancestor of the group being represented. Then each new node is a derived characteristic of the specie.

15 Clades and Traditional Taxonomic Groups
True clades must be monophyletic, which means that it contains an ancestral species and all of its descendants. Some groups do not form valid clades.

16 DNA in Classification Key Question: How are DNA sequences used in classification? Some organisms are similar but have no physical similarities. DNA can be used to show the common ancestor between two species.

17 Genes as Derived Characters
The more derived genetic characteristics two species share, the more recently they shared a common ancestor and the more closely they are related in evolutionary terms. Genetic information is stored in DNA, it can be used to trace back to previous generation or lineages.

18 New Techniques Suggest New Trees
The use of DNA characteristics in cladistic analysis has helped to make evolutionary trees more accurate. Scientists use DNA evidence when anatomical traits alone can’t be provide clear answers.

19 18.3 Building the Tree of Life SC.912.L.15.6, SC.912.N.1.1, SC.912.N.1.6, SC.912.L.15.4, SC.912.L.15.5, MA.912.S.3.2 Changing Ideas About Kingdoms Key Question: What are the six kingdoms of life as they are now identified? During Linnaeus’ time, the only known difference among living things were the fundamental characteristics that separated animals from plants. In time, biologist learned more about the natural world, and they realized that Linnaeus’ two kingdoms did not reflect the full diversity of life.

20 Five Kingdoms When researchers began to study microorganisms, they discovered that single celled organisms were completely different from plants and animals, and were placed in a new kingdom called Protista. Yeasts and molds, along with mushrooms went into their own kingdom known as Fungi. Bacteria was also put into a new kingdom called Monera.

21 Six Kingdoms In the 1990s, researchers learned more about genetics and biochemistry of bacteria, and made it clear that the kingdom Monera was actually made up of two genetically and biochemically different groups. The six kingdom system of classification includes the kingdoms Eubacteria, Archaebacteria, Protista, Fungi, Plantae, and Animalia.

22 Three Domains A domain is a larger, more inclusive category than a kingdom. There are three domains: Domain Bacteria, corresponding with kingdom Eubacteria, Domain Archaea, corresponding with kingdom Archaebacteria, and Domain Eukarya, corresponding with kingdom Fungi, Plantae, Animalia, and Protista.

23 The Tree of All Life Key Question: What does the tree of life show?
Cladograms are visual presentations of hypotheses about relationships. The tree of life shows current hypotheses regarding evolutionary relationships among the taxa within the three domains of life.

24 Domain Bacteria The members in this domain have to be unicellular and prokaryotic. This domain corresponds with the kingdom Eubacteria.

25 Domain Archaea Members of this domain are unicellular and prokaryotic, but live in extreme conditions. For example, in a volcano or on mount Everest.

26 Domain Eukarya Members of this domain are multicellular and eukaryotic. This domain consists of four of the major kingdoms of the six-kingdom system: Protists, Fungi, Plantae, and Animalia.

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