Transcript Chapter 18
Chapter 18 Finding Order in Diversity Biologist have found and named over 1.5 million species so far It is estimated that there are between 2 and 100 million species left to be discovered To study the diversity of life, biologist use a classification system to name organism and group them in a logical manner Finding Order in Diversity Scientist discovered early that they could not use common names to name organisms… Buzzard In the UK means Hawk In the US means Vulture Cougar in the Mountain means: Lion, Puma, Panther Because early 18th century scientist all understood Latin and Greek, this was the language that was used to name organisms Binomial Nomenclature A 2 word naming system Each species is assigned a 2 part scientific name Always written italics 1st part of the name is capitalized, 2nd part of the name is lowercase Ursus arctos – grizzly bear Binomial Nomenclature The 1st part of the name is the genus A group of closely related species The 2nd part of the name is unique to a particular species within a genus A Latinized word often describing a physical trait of the organism or a location where it lives Ursus maritimus refers to the sea where polar bears live or pack ice in sea Binomial Nomenclature Taxon (pl. Taxa) A group or level of organization Linnaeus’ system of classification uses 7 Taxonomic Categories from smallest to largest Species Genus Family Order Class Phylum Kingdom Species A population of organisms that can breed with one another and produce fertile offspring Genus A group of closely related species Family A group of genera that share many characteristics Order A broad taxonomic category that is composed or similar families Class Composed of similar orders Phylum Composed of many different classes…includes many different organism that nevertheless share important characteristics Kingdom The largest of all taxons, i.e the kingdom Animalia A good aid for remembering these categories is the mnemonic device: Keep Plates Clean Or Family Gets Sick. Modern Evolutionary Classification Originally, organism were grouped and classified according to body structure There were problems with this method though, i.e dolphins --fish or mammals; and convergent evolution made it difficult to distinguish between related organism and unrelated organism with similar body structures Modern Evolutionary Classification Scientist began to understand that organism share certain traits because they share an evolutionary history Biologist now group organisms into categories that represent lines of Evolutionary Decent, not just physical similarities– this is called Evolutionary Classification Many biologist now use Cladistic Analysis Identifies and considers only those characteristics of organisms that are Evolutionary Innovations: New characteristics that arise as lineages evolve Derived characters are characteristics that appear in recent parts of the lineage but not in its older members Claydogram A diagram that shows the evolutionary relationships among groups of organisms Uses Derived Characters to mark the evolutionary change of a trait on the diagram A useful tool to help us understand how one lineage branched from another in the course of evolution Claydogram Similarities in DNA & RNA All organism use DNA & RNA to pass on information and to control growth and development DNA & RNA provide an excellent way of comparing organism at a genetic (gene) level The genes of many organism show important similarities at the molecular level. These similarities can be used as criteria to help determine classification i.e … genes of humans and yeast even show similarities because both have a gene that codes for Protein Myosin In humans causes muscle constrictions In yeast enables internal cell part to move Similarities in DNA & RNA DNA comparisons have shed light on classification questions regarding just how closely related 2 species are .. i.e… the American Vulture and the Stork American Vulture has peculiar habits When they get over-heated they urinate on their legs so that evaporative cooling removes some body heat Similarities in DNA & RNA Storks also behave in the same manner as American Vulture, but Storks looks quite different from vultures and have always been in a separate family Scientists analyzed the DNA of these three (African Vultures, American Vultures, & Storks) birds revealed that American vultures are indeed more closely related to storks than they are to other vultures Molecular Clocks A model known as a Molecular Clock uses DNA comparisons to estimate the length of time that 2 species have been evolving independently Relies on a repeating process to mark time--Mutations Molecular Clocks Mutations occur and accumulate in genes at a steady rate causing slight changes in the structure of DNA Some mutations cause a change in phenotype while others do not The one that do affect phenotype are under pressure form National Selection The one that do not affect phenotype are accumulated in DNA at about the same rate Molecular Clocks A comparison of the DNA of 2 species can reveal how dissimilar the genes are The degree of dissimilarity is an indication of how long ago the 2 shared a common ancestor Molecular Clocks are complex while one gene may be at one rate, another at a different rate, etc like hands on clock –second, minute, hour, day, week, month, year, etc Researchers would use a different Molecular Clock to compare modern bid species than they would to estimate the age of the common ancestor of yeasts and humans Kingdoms and Domains At first, there were only 2 kingdoms: Plantae and Animalia As scientist learned more about the natural world, they realized that more kingdoms were needed and added Eubacteria Archaebacteria Protista Fungi These are the 6 Kingdoms use today Three Domain System Using a Molecular Clock based on ribosomal RNA, scientist have grouped modern organisms according to how long they have been evolving independently The Taxon that they are using for this broad group is called the Domain The Domain is more inclusive than any other category– even larger than the Kingdom The 3 Domain Bacteria Corresponds to kingdom Eubacteria Archaea Corresponds to kingdom Archaebacteria Eukarya Corresponds to kingdoms Protista, Fungi, Palantae, and Animalia Eukarya The kingdom Animalia is in this domain Members of this kingdom (Animals) are Multicellular and Heterotrophic The cells of animals have no cell walls Most animals move about for at least some part of their life Eubacteria Have three basic shapes. round rod spiral Archaebacteria Archaebacteria are found in extreme condition. Some are autotrophic Photoautotrophs Chemoautotrophs Plantae Multicellular Photosynthetic Cell walls contain cellulose Non-motile Protista Mostly single celled Very diverse group Some multicellular (Seaweeds) Eukaryotes Many are autotrophic Fungi Heterotrophic Have cell wall Eukaryotes Very diverse Animalia Heterotrophic Eukaryotic Motile Chapter 18 Questions 1. What is taxonomy? 2. Explain Binomial Nomenclature 3. What are the 7 Taxonomic categories form smallest largest? 4. What is evolutionary classification? 5. What are derived characters? 6. How and why do scientist use Cladograms? Chapter 18 Questions 7. How can genes be used in classification? 8. What is a molecular clock? 9. What are the 6 kingdoms used in modern classification? 10. What are 3 domains and which kingdoms do they correspond with? Chapter 18 Questions 11. What are 4 characteristics of the domain Bacteria 12. What are 4 characteristics of the domain Archaea? 13. What are the 4 kingdoms of Eukarya and what are 2 characteristics of each?