Classifying the Diversity of Organisms TEK 8A: Define taxonomy and recognize the importance of a standardized taxonomic system to the scientific community. TEK 8B: Categorize organisms using a hierarchical classification system based on similarities and differences shared among groups. TEK 8C: Compare characteristics of taxonomic groups including archae, bacteria, protists, fungi, plants, and animals. 1

Why classify organisms?  To study the diversity of life, biologists use a classification system to name organisms and group them in a logical manner. 2

Taxonomy  Taxonomy is the branch of biology that groups organisms based on studies of their different characteristics.  Some characteristics are structure, behavior, development, genetic makeup (DNA), nutritional needs, and methods of obtaining food.  Biologists who study taxonomy are called taxonomists. 3

Aristotle’s System of Classification  The Greek philosopher, Aristotle ( B.C.) developed the first widely developed system of biological classification.  He used two groups: plants and animals. Marble bust of Aristotle 4

Aristotle’s System of Classification  Plants were subdivided into three groups: Herbs, shrubs, and trees.  Plant groups depended on the plant’s size and structure.  Animals were grouped according to various characteristics such as habitat and physical differences. 5

Common name vs. Scientific name  By the 18 th century, scientists realized that common names were confusing because the names varied among different regions and languages. They can also be misleading.  Here are some common names: spider monkey, sea horse, sea monkey, gray wolf, horned toad, ringworm, mud puppy, jellyfish.  Is a sea horse really a horse? 6

Linnaeus’ System of Classification  In the late 18 th century, Swedish botanist, Carolus Linnaeus ( ) developed a method of grouping organisms that is still used by scientists today.  He developed a two-word naming system called binomial nomenclature.  The name written using binomial nomenclature is the scientific name. 7

Binomial nomenclature  The first part of the name is the genus.  The first letter should be capitalized.  The second part of the name is the species.  The first letter should be lowercased.  Both parts of the name should be italicized in print and underlined when handwritten.  Scientific names are often abbreviated using the first letter of the first name, a period, and the whole second name. 8

Examples of binomial nomenclature Ailuropoda melanoleuca ( giant panda bear ) A. melanoleuca (abbreviated) Ursus maritimus (polar bear) U. maritimus (abbreviated) Ursus arctos (grizzly bear) U. arctos (abbreviated) 9

What is wrong with each of the following incorrectly written scientific names? 1. Prunus Avium ( second word should be lowercased) 2. prunus serrula ( first word should be capitalized) 3. Ulmus minor (both words should be italicized) 4. Sorbus aria (should be italicized, not underlined since it is printed, not handwritten) 10

Linnaeus’ Hierarchal System of Classification  Linnaeus’ system divides all living things into hierarchical groups based on their characteristics.  “Hierarchical” means that living things are divided into groups, the groups are then divided into smaller groups and so on until every living thing has a distinct name due to their distinct characteristics  Each level is called a taxon (plural: taxa), or taxonomic category. 11

Linneaus’ Hierarchical System of Classfication  The seven groups can be put in order from the most inclusive (biggest group) to the most exclusive (smallest group):  Kingdom  Phylum  Class  Order  Family  Genus  Species 12

Categories of Organisms  KINGDOM (KING)  PHYLUM(PHILLIP)  CLASS(CAME)  ORDER (OVER)  FAMILY (FOR)  GENUS (GOOD)  SPECIES(SPAGHETTI) 13

HumanLionTigerPintail Duck KingdomAnimalia Phylum/DivisionChordata ClassMammalia Aves OrderPrimateCarnivora Anseriformes FamilyHomindaeFelidae Anatidae GenusHomoPanthera Anas Speciessapiensleotigrisacuta 14

Phylogeny  Phylogeny is the study of the evolutionary relationships among organisms.  Biologists now group organisms into categories that represent lines of evolutionary descent, or phylogeny, not just physical similarities. 15

Kingdoms and Domains  As biologists learned more about the natural world, they realized that Linnaeus’ two kingdoms, Animalia and Plantae, did not adequately represent the diversity of life.  There have been several changes in classification groups since Linnaeus and now we use either Kingdoms or Domains. 16

The Six-Kingdom System of Classification KingdomExamples EubacteriaStreptococcus, E. coli ArchaebacteriaMethonogens, halophiles ProtistaAmoeba, Paramecium, slime molds, giant kelp FungiMushrooms, yeasts PlantaeMosses, ferns, flowering plants AnimaliaSponges, worms, insects, fishes, mammals 17

The three-domain system of classification  A domain is a more inclusive category than any other-larger than a kingdom.  The three domains are:  Bacteria (Kingdom: Eubacteria)  Archae (Kingdom: Archaebacteria)  Eukarya (Kingdoms: Protista, Fungi,Plantae, Animalia) 18

Dichotomous Key (Biological Key)  One tool used to identify unfamiliar organisms is a dichotomous, or biological key.  A dichotomous key is a series of paired statements that describe physical characteristics of different organisms. 19

Example of a Dichotomous Key 20

Characteristics of Kingdoms  Kingdom placement is decided by three factors; Cell Structure, Cellular Organization and Trophic Function. 21

KingdomCell StructureCellular Organization Trophic Function AnimaliaEukaryoticMulticellularHeterotrophic PlantaeEukaryoticMulticellularAutotrophic ProtistsEukaryoticUnicellularHeterotrophic FungiEukaryoticUnicellular or Multicellular Heterotrophic EubacteriaProkaryoticUnicellularAutotrophic or Heterotrophic ArchaeProkaryoticUnicellularAutotrophic Characteristics of Kingdoms 22