Classification of Living Things—Taxonomy Pima Medical Institute Veterinary Technician Program VTT 200 General Sciences

Taxonomy Taxonomy: The science of classification of all known life forms from the most simple single-cell bacteria to the most complex animal Linnaen System developed by Swedish botanist Carolu Linnaeus Originally classified organisms by 7 designations: Kingdom, Phylum, Class, Order, Family, Genus, species In past 20 years as scientists have furthered research, a more general designation has been added at top: Domain

Taxonomy Many biology students have memorized the system with this pneumonic device: Darn King Philip Came Over From Great Spain Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species

Taxonomy Linnaeus made sure every organism had an independent name that would differentiate it from all other organisms Binomial nomenclature was developed: First word is Genus (Capitalized & italicized) Second word is species (italicized, but not capitalized) EX: Homo sapiens; Canis familiares, Felis domesticus

Domains Two Main Domains are: Prokaryote and Eukaryotes All living things are classified under one of these domains—there are several differences All Prokaryotes are single-celled organisms with no true nucleus—just a simple strand of DNA Eukaryotes can be either single-celled or multi-cellular and have a true nucleus See 6 Kingdoms Handout RE: special classification of Domain Archaebacteria

Size Organelles Life Cycle Prokaryotes Eukaryotes Size 1-10m 10-100m Organelles Non-membrane bound Membrane bound & used to compartmentalize Life Cycle Binary Fission Complete life cycle with mitosis and meiosis

Cell Wall Nuclear Region Prokaryotes Eukaryotes Cell Wall Eubacteria have a cell wall made of peptidoglycan (amino acids and sugars) Plants- yes- cellulose Fungi-yes- Chitin Archaebacteria wall is mainly Lipid based Animals- no wall, but cell membrane Nuclear Region Nucleoid Region with no nuclear membrane True nucleus with membrane & envelope

Kingdoms There are Six Kingdoms Kingdoms Archaebacteria and Eubacteria are classified under Domain Prokaryotes The other four Kingdoms fall under Eukaryote: Protista Fungi Plantae Animalia NOTE: Organisms will increase in complexity as we move across the Taxonomy chart: Eubacteria>Archaebacteria > Protista > Fungi > Plantae > Animalia There is a general description of all Kingdoms and evolutionary history in your handout

Taxonomy & Evolution The development of organisms is a study that has caused much controversy and debate In the late 1700’s British scientists hypothesized that similar species descended from the same common ancestor Certain traits were not handed down by genes, but acquired during an organism’s life because of their experiences or behavior as they tried to cope with a changing environment In the mid-1800’s Charles Darwin and Alfred Wallace proposed the theories of Natural Selection Darwin had studied creatures on the isolated Galapagos Islands off S. America and had seen little change in these animals because of their isolation and no natural predators

Taxonomy & Evolution Darwin proposed: Theory # 1—Descent with Modification: newer forms of life are actually modified descendents of older species, these similar organisms would arise in the same geographic area Theory # 2—Modification by Natural Selection: Darwin proposed that organisms best suited to their environment reproduce more successfully and will survive more readily than organisms that do not adapt as well

Taxonomy & Evolution Basics of Natural Selection: Some organisms have traits that make them more suitable for coping with changing environmental conditions; these organisms will then hand down such traits to offspring who will be better suited to survive Species change over long periods of time Darwin called these changes Mutations IMPORTANT NOTE: Natural Selection is NOT an active process—Organisms don’t purposely acquire these traits. The environment “selects” the organisms with the traits that will make them better to cope as environments change EX: Dinosaurs could not cope with the changing earth and were wiped out; smaller creatures were able to survive