Chapter 18: Classification Dichotomous Key A way to identify unknown organisms Contains major characteristics of groups of organisms Pairs of CONTRASTING descriptions 4. After each description key either directs use to another pair of descriptions or identifies an object Section 1: The Importance of Classification Taxonomy: Genus: Binominal Nomenclature: a system for giving each organism a twoword scientific name that consists of the genus name followed by the species name I. The Need for Systems A. About million species have been named and described by scientists B. C. Practice of naming and classifying organisms is taxonomy D. E. Systems attempt to provide consistent ways to name and categorize organisms F. May be confusing because common names are different in different places 1
G. Biologists group organisms into large categories Then smaller, more specific categories II. Scientific Nomenclature A. Various naming systems were invented in the early days of European biology Names for taxa were inconsistent between these systems The only consistent taxon was genus B. Carlos Linnaeus Developed simpler and more consistent system 4. Two-word naming system called 5. Genus name and a single descriptive word for each species 6. 7. C. Naming Rules All scientific names are made up of two Latin or Latin-like terms 2
4. The second term is called the species identifier, and is often descriptive 5. When you write the scientific name, the genus name should be capitalized and the species identifier should be lowercase 6. 7. Example Apis mellifera is the European honeybee 1) The term mellifera derives from the Latin word for honey III. The Linnaean System A. Devised a system to classify all plants and animals that were known B. Organisms grouped at successive levels of the hierarchy based on similarities in form and structure C. Eight basic levels of modern classification 4. 5. 6. 7. 8. D. Classification of Man Domain Kingdom Phylum 3
4. Class 5. Order 6. Family 7. Genus 8. species D. Each taxon is identified based on shared traits. E. Similar species are grouped into a genus Similar genera are grouped into a family And so on up to the level of domain F. Domain Recognizes most basic differences among cell types All living things grouped into one of three domains G. Kingdom H. Phylum I. Class J. Order K. Family 4
L. Genus (plural, genera) M. species Subgroup within Genus 4. Defined as a unique group of organisms united by heredity or the ability to interbreed 5. Scientists tend to define species based on unique features 6. Example Homo sapiens Section 2: Modern Systematics Phylogenetic Tree: shows the evolutionary relationships among organisms I. Evolutionary Relationships A. Phylogenetic Tree: Fossil Record Used Comparative to family members 4. Spirochetes are most closely related to what organisms? 5. Name two organisms that are distantly related 6. 5
7. II. Physical Structures A. Linnaeus based his classification on B. Moderns scientists base classification on III. Problems in Classification A. As new evidence is discovered and new research is done scientists are having to reclassify organisms Section 3: Kingdoms and Domains Bacteria: extremely small, single-celled organisms that usually have a cell wall and that usually reproduce by cell division: members of the domain Bacterial Archaea: 6
Eukaryote: an organism made up of cells that have a nucleus enclosed by a membrane, multiple chromosomes, and a mitotic cycle; members of the domain Eukarya I. Updating Classification Systems A. When Linnaeus created his system he recognized two kingdoms: B. Biologists have added complexity and detail to classification systems as they have learned more C. Microscopes allowed scientists to study sponge cells c. Scientists learned that sponge cells are much more like animal cells, so today sponges are classified as animals D. Then noticed differences between prokaryotic and eukaryotic cells Scientists created Kingdom Monera for prokaryotes E. By the 1950s, Kingdoms Monera, Protista, Fungi, Plantae, and Animalia were used F. In the 1990s, genetic data suggested two major groups of prokaryotes Kingdom Monera split into Kingdoms 7
II. The Three-Domain System A. Divide all organisms into three domains B. Major taxa are defined by major characteristics, including Cell Type Cell Walls Body Type 4. Nutrition 5. Related groups of organisms have similar 8
C. Bacteria Strong exterior walls and a unique genetic system Same kind of cell membrane lipid as most eukaryotes do 4. All bacteria are similar in structure, no internal compartments 5. Classified according to Nature of their cell wall c. Their type of metabolism d. 6. Most abundant organisms on Earth 7. D. Archea Unique genetic system Share some similarities with those of eukaryotes that they do not share with those of prokaryotes Scientists think that archea evolved in a separate lineage from bacteria early in Earth s history 4. Scientists also believe that some archea eventually gave rise to eukaryotes 5. First found in extreme environments c. d. These archaea are called extremophiles. 9
e. E. Eukarya is made up of Kingdoms 4. 5. 6. Cells have a complex inner structure that enabled cells to become larger than the earliest cells 7. Complex inner structure enabled the evolution of multicellular organisms 8. True multicellularity and sexual reproduction 9. Major groups of eukaryotes are defined by F. Plantae The process that makes food, photosynthesis, occurs in chloroplasts More than 350,000 known species of plants exist G. Animalia 10
Their bodies may be simple collections of cells or complex networks of organ systems 4. More than 1 million known species of animals exist H. Fungi More than 70,000 known species of fungi exist I. Protista Any eukaryote that is not a plant, animal, or fungi can be called a protist Did not descend from a single common ancestor 4. Biologists recognize four major groups of protists: c. d. 5. Recently, biologists have proposed to replace Protista with several new kingdoms 11
Natural Selection Review I. Define natural selection. A. B. List the four parts of natural selection 4. 12
Use the table below to answer questions the following questions. Level Dog Wolf Human House Cat Octopus Anteater Kingdo m Animalia Animalia Animalia Animalia Animalia Animalia Phylu m Chordat a Chordat a Chordat a Chordata Molluska Chordata Class Mammal Mammal Mammal Mammali Cephalopo Mammalia ia ia ia a da Order Carnivor Carnivor Primate Carnivor Octopoda Edentata a a a Family Canidae Canidae Hominid ae Felidae Octopodid ae Myrmecophagi dae Genus Canis Canis Homo Felis Octopus Myramecophag a Specie s familiari s lupus sapiens domestic us vulgaris tridactyla Which organisms on the table are most closely related? Which level of classification is your answer based on? c. Which organism on the table is the most distantly related to the others? d. Which level of classification is your answer based on? 13