Taxonomy Taxonomy: field of biology that identifies and classifies organisms

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1 Taxonomy Taxonomy: field of biology that identifies and classifies organisms Why do we need it? problems with different languages common names can be confusing examples: woodchuck, groundhog crayfish, crawdad, rock lobster fish, starfish, jellyfish Linnaeus: 18 th century came up with a system that gave every organism a 2 word name called the system binomial nomenclature There are seven groupings (called taxons) in the Linnean system. 1. Kingdom 2. Phylum An organism s name 3. Class consists of the genus 4. Order and the species. Genus is 5. Family first and is capitalized. Both 6. Genus are underlined or italicized. 7. Species Recently, a change has been made to taxonomy. Instead of the kingdom being the largest taxon, taxonomists use domains, which are located above or before kingdoms on the previous list. There are 3 different domains: 1. Eukarya includes all organisms that are eukaryotic 2. Prokarya includes modern bacteria (Eubacteria) 3. Archaea includes ancient bacteria (Archaebacteria) that live in very harsh and extreme conditions

2 Examples of scientific names: Common Name Genus Species Lion Felis leo Tiger Felis tigris Housecat Felis sylvestris Human Homo sapiens We use Latin for the names. It is a dead language and will not change in meaning. Modern taxonomy uses several areas to classify organisms, such as: 1. structural similarities 2. genetic similarities 3. biochemical similarities 4. cellular structures There are 5 kingdoms used in taxonomy (although that number can vary). 1. Monera : includes all bacteria unicellular prokaryotes most are heterotrophs, some are autotrophs Please note: with the changes in taxonomy using domains, the Monera kingdom is now represented by 2 different kingdoms Eubacteria and Archaebacteria. 2. Protista : unicellular and multicellular eukaryotes most cells of multicellular protists aren t specialized some are autotrophs, some are heterotrophs

3 3. Fungi : eukaryotes, most are multicellular have cell walls heterotrophs include molds, mildews, mushrooms, yeasts 4. Plantae : multicellular, eukaryotes cell walls specialized cells tissues most are autotrophs organs 5. Animalia : multicellular, eukaryotic heterotrophs do NOT have cell walls most can move from place to place at some point in their life cycle specialized cells tissues organs

4 Viruses Virus: an infectious agent made up of a core of nucleic acid and a protein coat Viruses are NOT cells!!! do not have a n nucleus, m membrane, or organelles do not eat, respire, respond to environment Viruses are incredibly tiny. For example, 3000 polio viruses could line up across a typed period from your text. All viruses have at least 2 parts: 1. core of nucleic acid (some have DNA, some have RNA) 2. capsid: protective protein coat around the core In viruses that infect animal cells, there is another protective coating outside of the capsid called an envelope. It s made of lipid, proteins, and carbohydrates. Replication in Viruses Viruses do not reproduce (which involves cell division); they replicate. can t replicate on their own; have to have a host which is: an organism that shelters and nourishes something (in this case, a virus) Living cells act as hosts for viruses and provide all the materials that viruses need to copy themselves. When a virus enters a cell, it can immediately replicate or remain relatively inactive. Lytic Cycle: replication process that rapidly kills a host cell 1. virus invades a host cell and injects its DNA into it 2. viral DNA commands the host cell to make new viruses 3. cell splits apart and releases lots of new viruses 4. new viruses invade other host cells

5 Lysogenic Cycle: virus does not immediately kill the host cell 1. viral DNA invades the host cell and becomes part of the host cell s chromosome 2. the host cell may divide many times and every time, the viral DNA is replicated with the host s DNA 3. some viruses stay in the lysogenic cycle for a very long time; usually, some type of environmental stimulus eventually causes the viral DNA to separate from the host DNA 4. the viral DNA then enters the lytic cycle Classifying Viruses Because viruses are so diverse, classifying them can be difficult. There are several different ways of classifying viruses. 1. Shape filovirus, polyhedral, binal, helical 2. Host Since most viruses invade only a specific type of organism, you can classify them according to the host infected (ex. animal, plant, bacterial). 3. Function how a virus functions in the host Viruses in the Biosphere 1. Diseases: Many diseases are caused by viruses (colds, polio, measles, mumps, chicken pox, flu) viral diseases can NOT be cured by antibiotics (only good against bacterial cells) 2. Human Uses: vaccines: inject a harmless (weak or dead) form of a virus to get the immune system to produce cells and proteins that will kill that type of virus if it enters the body genetic engineering: viruses can be used to correct some genetic defects agriculture: control pests without chemical pesticides; create different color combinations in certain flowers (tulips)