How are living things classified? Objective: Describe the system used today to classify organisms (including the seven levels of classification as well as scientific names) First things first: What IS classification and WHY do we do it (or DO we)? Classification Systems Aristotle classified organisms more than 2,000 years ago (see ex. p24). Carolus Linnaeus introduced a system based on similar structures of organisms (all have wings, six legs, etc.) Modern systems based on Linnaeus system but also on new information like fossils and DNA Binomial Nomenclature Two-word naming system Linnaeus used to name species; still used today **Written in Latin** First word identifies the genus, or group of similar species Second word identifies the species- often tells something about the organism- what it looks like, where it is found, or who discovered it Examples: Lathyrus odoratus (smelly flower), Pinus virginiana (Pine tree found in Virginia), Felis domesticus (domestic cat) Human Example: Homo sapien Three Key Points (write down!): capitalize first word (genus), lowercase second word (species), underline both words
Why use scientific names? 1.To avoid mistakes (common names can be confusing); Latin is universal 2.To show that organisms in the same genus are related 3.To describe the organism Phylogeny: the evolutionary history of an organism, or how it has changed over time Four things considered when classifying a new organism & determining its history: Fossil Record Hereditary Information- DNA Embryology Homologous Structures 4.To allow information to be organized easily Embryology- study of organisms in the early stages of development Can you tell the human from the embryo? You had a tail! Homologous Structures: structures that are similar in structure & origin These appendages do very different jobs and look very different from the outside but have all the same bones in the same order!
Homologous (similar) Structures in Plants Cladograms: a branching diagram to show relationships among organisms 10 These are all examples of leaves that are modified to do very unique jobs for a variety of plants. How we organize groups of life: Eight Levels of Classification (largest to smallest) The larger the group, the more organisms are included but the less they have in common! Today s Classification System Separates organisms into 6 kingdoms s are the most familiar category The smallest classification category is species Organisms that belong to the same species can mate and produce fertile offspring (fertile means able to reproduce) Dogs of any breed are the same species Canis (lupus) familiaris so different breeds can reproduce and those offspring ( mutts ) can also reproduce
Ferns Examples of Members of the Animal (YES, we are animals!) Moss Animalia Complex cells Many celled eat for energy no cell wall Plantae Complex cells -- Many celled Make their own food have cell walls Giant Ocean Sea Kelp Athlete s Foot is caused by fungi mold Mushrooms Pond Life (mostly microscopic) Fungi Complex cells Both one & many celled (without special structures) Eat for energy Have cell walls This kingdom is a hodge-podge- for things that are animal-like or plantlike but don t fit into either category- Protista (odds & ends) Complex cells Both one(usually) & many celled Some eat, some make food Some have cell wall, some don t
In the Dead Sea Archaea Simple & one celled Make own food Have a cell wall Live in extreme environments where nothing else can live Found in the Geysers at Yellowstone Eubacteria ( true bacteria ) Simple & one celled Some eat, some make food Have cell wall Found everywhere 20 Tools to help identify organisms Field Guide: books that describe & illustrate organisms Dichotomous Key: detailed lists of identifying characteristics Who is this?