410 likes | 523 Vues
Chapter 18. Classification. Evolution has lead to a large variety of organisms. Biologists have identified and named about 1.5 million species so far. They estimate anywhere between 2 and 100 million additional species have yet to be discovered. Taxonomy.
E N D
Chapter 18 Classification
Evolution has lead to a large variety of organisms. Biologists have identified and named about 1.5 million species so far. They estimate anywhere between 2 and 100 million additional species have yet to be discovered.
Taxonomy • The science of classifying and naming organisms. • This ensures that everyone is talking about the same organism. • Uses accepted names and common criteria to group things. • “Teacher” or “Mechanic” • “Biology Teacher” or “Auto Mechanic”
Assigning Scientific Names • 18th century- European scientists recognized that referring to organisms by common names was confusing. • Common names vary among regions within a country. • In UK buzzard refers to a hawk • In the US buzzard refers to a vulture
Mountain Lion Cougar
Early Efforts at Naming Organisms First attempts at standard scientific names often described physical characteristics. As a result, these names could be 20 words long! The English translation of the scientific name of a particular tree might be “Oak with deeply divided leaves that have no hairs on their undersides and no teeth around their edges.”
Linnaeus’s System of Classification • Carolus Linnaeus (18th Century) • Hierarchical system that consists of 7 levels. • Currently there are now 8 levels.
Linnaeus’s system of classification uses seven taxonomic categories Largest / LeastSpecific Taxon :A group or level of organization Smallest / Most Specific Domain Kingdom Phylum Class Order Family Genus species
Mnemonic Device Domain Kingdom Phylum Class Order Family Genus species • Did • King • Phillip • Come • Over • For • Good • Soup
Binomial Nomenclature • Developed by Linnaeus. • Two-word naming system. • Assigns a two-part scientific name. • Universally accepted • Written in Greek and Latin • Written in italics • First word is capitalized • Second word is lowercased • Composed of a genus and species • Example: • Canislupis • C. lupis
Problems with Traditional Classification Organisms determine who belongs to their species by choosing with whom they will mate! Taxonomic groups above species are “invented” by researchers. Sometimes, due to Convergent Evolution organisms that are quite different from each other evolve similar body structures. Example: Crab, limpet, barnacle
Evolutionary Classification • Darwin’s theory of evolution changed the entire way that biologists thought about classification. • Biologists now group organisms into categories that represent lines of evolutionary descent, not just physical similarities. • Phylogeny • Species within a genus are more closely related then species within another genus.
Classification Using Cladograms Many biologists now prefer a method called cladisticanalysis. This method of classification identifies and considers only those newcharacteristics that arise as lineages evolve over time. Derived characteristics - Characteristics that appear in recent parts of a lineage but not in its older members.
Classification using a CLADOGRAM CLADOGRAM- a diagram which shows evolutionary relationships among a group of organisms. Things to know: -Location of “circles” represent when a characteristic first appeared. -Derived traits determine the grouping of organisms. -Help scientists understand how one lineage might have branched from another.
Similarities in DNA and RNA Suppose you were trying to compare diverse organisms such as yeast and humans. It wouldn’t make sense to try to classify anatomical similarities. The genes of many organisms show important similarities at the molecular level. These similarities can be used as criteria to help determine classification. Example: Myosin in humans & yeast
Stork and vultures • American vultures have a behavior similar to storks. • Urinate on legs when overheated. • Evaporative cooling • Scientists analyzed DNA. • Share more similarities in DNA. • Common ancestor
Molecular Clocks Use DNA comparison to estimate the length of time that two species have been evolving independently. Mutations happen all the time at about the same rate. A comparison of DNA sequences in two species can reveal how dissimilar the genes are. The degree of dissimilarity is an indication of how long ago the two species shared a common ancestor.
The Tree of Life Evolves Before Linnaeus’s time, the only two Kingdoms that existed were Plants andAnimals. As scientists discovered new organisms that didn’t fit into the plant or animal category, they made new categories. Microorganisms got the kingdom - Protista Mushrooms, yeast and mold were separated from plants – and made into Fungi.
3 Domains 1. Bacteria • Kingdom Eubacteria 2. Archaea • Kingdom Archaebacteria 3. Eukarya • Kingdom Protists, fungi, plantae, animalia (Everything with a nucleus)
Domain ArchaeaKingdom Archaebacteria • Unicellular • Prokaryotic • Live in Extreme environments • Volcanic Hot springs • Some need oxygen (Aerobic), others live in oxygen deprived (Anaerobic) environments • Cell walls lack peptidoglycan • Autotroph or Heterotroph • Asexual reproduction- binary fission
Domain BacteriaKingdom Eubacteria Unicellular Prokaryotic - no nucleus, no membrane bound organelles. Cell walls with peptidoglycan. Some autotrophic/some heterotrophic. Important decomposers. Asexual reproduction. Found in soil, water, on / inside humans. Some cause disease, others help make chemicals to help humans fight disease causing bacteria.
Domain Eukarya • Consists of all organisms that have a nucleus. • The four kingdoms include: • Protista • Fungi • Plantae • Anamalia
The Old 5 Kingdom System • Monera - Bacteria • Protist • Fungi • Plants • Animals
The New 6 Kingdom System • Recently, biologists come to recognize that the Monera (bacteria) were composed of two distinct groups • Eubacteria and Archaebacteria
Kingdom Protista Small - Mostly unicellular! Wide variety! Eukaryotic – has a nucleus, and membrane bound organelles Cannot be classified as animals, plants or fungi, but share many characteristics with plants (algae), animals (protozoan) and fungi (slime molds) Cellulose cell walls and some have chloroplast. Most- asexual reproduction- binary fission Can be photosynthetic or heterotrophic
Kingdom Fungi • Mostly multicellular • Mushroom, yeast • Eukaryote • Chitin cell walls • Heterotrophs- decomposers • Feed on decaying organic matter • Secrete digestive enzymes into food source then absorb nutrients • Unicellular (yeast) or multicellular (mushrooms) • Sexualand asexualreproduction • Spread and reproduce by spores
Kingdom Plantae Eukaryote Multicellular Photosynthetic autotrophs – make their own food by photosynthesis Non-motile Cell walls (cellulose) Cone bearing, flowering plants & mosses and ferns. Sexual and asexual reproduction (Algae = Protist- Not in this kingdom!!!)
Kingdom Animalia Eukaryote Multicellular Heterotrophic No cell walls Most move - mobile Incredible diversity Most = Sexual reproduction