Georgia Performance Standards: Classification: Georgia Performance Standards: Compare how structures and functions vary between the six kingdoms (archaebacteria, eubacteria, protests, fungi, plants, and animals). Examine the evolutionary basis of modern classification systems Essential Questions: How does the evidence of evolution contribute to modern classification systems? Why classify? 3. On what criteria do Taxonomists base their classification of organisms? 4. In what way does scientific discovery lead to the development of a new classification group?

Why Classify? To study the diversity of life, biologists use a classification system to name organisms and group them in a logical manner. In taxonomy, scientists classify organisms and assign each organism a universally accepted name. By using a scientific name, biologists can be certain that everyone is discussing the same organism.

Early Efforts at Naming Organisms The first attempts at standard scientific names often described the physical characteristics of a species in great detail. Results in long names Difficult to standardize the names of organisms Different scientists described different characteristics.

Binomial Nomenclature  Carolus Linnaeus developed a two-word naming system called binomial nomenclature. In binomial nomenclature, each species is assigned a two-part scientific name. The scientific name is always written in italics. The first word (the genus) is capitalized The second word (the species) is lowercased.

Linnaeus's System of Classification A group or level of organization is called a taxonomic category, or taxon The are 7 taxonomic categories. (from smallest to largest) species genus family order class Phylum kingdom.

The 7 taxonomic categories Species - a group of organisms that breed with one another and produce fertile offspring. Genus - a group of closely related species. Family - genera that share many characteristics. Order - is a broad taxonomic category composed of similar families. Class - is composed of similar orders. Phylum- several different classes that share important characteristics. Kingdom - largest taxonomic group, consisting of closely related phyla

Checkpoint Questions: 1.  How are living things organized for study? 2. Describe the system for naming species that Linnaeus developed. 3. What are the seven taxonomic categories of Linnaeus’s classification system? 4. Why do scientists avoid using common names when discussing organisms? 5.   Which category has more biological meaning—all brown birds or all hawklike birds? Why?

Modern Evolutionary Classification Organisms are grouped into categories that represent lines of evolutionary descent, not just physical similarities This strategy of grouping organisms together based on their evolutionary history is called evolutionary classification. Modern classification systems are based upon biochemical and genetic evidence that indicates evolutionary relationships

Classification Using Cladograms Cladistic analysis identifies and considers only the 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. Derived characters can be used to construct a cladogram, a diagram that shows the evolutionary relationships among a group of organisms.

Traditional Classification Versus Cladogram TRADITIONAL CLASSIFICATION Section 18-2 Appendages Conical Shells Crustaceans Gastropod Crab Barnacle Limpet Crab Barnacle Limpet Molted exoskeleton Segmentation Tiny free-swimming larva TRADITIONAL CLASSIFICATION CLADOGRAM Go to Section:

Modern Evolutionary Classification Similarities in DNA and RNA The genes of many organisms show important similarities at the molecular level that can be used as criteria to help determine classification.

Modern Evolutionary Classification Molecular Clocks Comparisons of DNA can also be used to mark the passage of evolutionary time. A model known as a molecular clock uses DNA comparisons to estimate the length of time that two species have been evolving independently. Comparison reveals more DNA in common, the more recent the common ancestor

Checkpoint Questions: How is information about evolutionary relationships useful in classification? How are genes used to help scientists classify organisms? 3. What is the principle behind cladistic analysis? 4. Describe the relationship between evolutionary time and the similarity of genes in two species. 5. How have new discoveries in molecular biology affected the way in which we classify organisms compared with the system used by Linnaeus? Constructing a Chart  

Kingdoms and Domains  The six-kingdom system of classification includes the following kingdoms: Eubacteria Archaebacteria Protista Fungi Plantae Animalia.

The Three-Domain System The domain is the most inclusive taxonomic category; larger than a kingdom    The three domains are: Bacteria : kingdom Eubacteria Archaea,: kingdom Archaebacteria; Eukarya :Kingdom protists, fungi, plants, and animals.

Cladogram of Six Kingdoms and Three Domains Section 18-3 DOMAIN ARCHAEA DOMAIN EUKARYA Kingdoms Eubacteria Archaebacteria Protista Plantae Fungi Animalia DOMAIN BACTERIA Go to Section:

Classification of Living Things Key Characteristics of Kingdoms and Domains Classification of Living Things Eukarya DOMAIN KINGDOM CELL TYPE CELL STRUCTURES NUMBER OF CELLS MODE OF NUTRITION EXAMPLES Bacteria Eubacteria Prokaryote Cell walls with peptidoglycan Unicellular Autotroph or heterotroph Streptococcus, Escherichia coli Archaea Archaebacteria Prokaryote Cell walls without peptidoglycan Unicellular Autotroph or heterotroph Methanogens, halophiles Protista Eukaryote Cell walls of cellulose in some; some have chloroplasts Most unicellular; some colonial; some multicellular Autotroph or heterotroph Amoeba, Paramecium, slime molds, giant kelp Plantae Eukaryote Cell walls of cellulose; chloroplasts Multicellular Autotroph Mosses, ferns, flowering plants Fungi Eukaryote Cell walls of chitin Most multicellular; some unicellular Heterotroph Mushrooms, yeasts Animalia Eukaryote No cell walls or chloroplasts Multicellular Heterotroph Sponges, worms, insects, fishes, mammals Go to Section:

Section 18-3 Living Things Eukaryotic cells Prokaryotic cells are characterized by Important characteristics and differing which place them in Domain Eukarya Cell wall structures such as which is subdivided into which place them in Kingdom Plantae Kingdom Protista Kingdom Fungi Kingdom Animalia Domain Bacteria Domain Archaea which coincides with which coincides with Kingdom Eubacteria Kingdom Archaebacteria Go to Section:

Checkpoint Questions: What are the six kingdoms of life as they are now identified?  What are the three domains of life? 3. Why was the kingdom Monera divided into two separate kingdoms? 4. Why might kingdom Protista be thought of as the “odds and ends” kingdom? 5. Which kingdoms include only prokaryotes? Which kingdoms include only heterotrophs?