Chapter 18 Test 1 Organisms are arranged or grouped by the science of taxonomy Organizing or grouping things helps in dealing with life Ex grocery store dresser closet You organize them in similar ways by colors economical values temperature etc however they suffer from problems The organization has to be easy logistical and equally able to understand by everyone Taxonomy Taxonomy started because they needed to classify the names that biologists would use is the branch of biology concerned with naming and classifying the diverse forms of life Classifying organisms in Planet Earth Naming Have to classify things so that everyone knows what we re talking about from the beginning Classification Scheme Classification is based on characteristics that the organisms have This started before there were biologists possibly when they were cave people Classification was based on things that were in our environment around us To reconstruct evolutionary histories we name organisms and assign them to categories based on their evolutionary relationships Plants vs Animals one of the early classification systems placed the animals in 1 group and the plants in another The bacteria fungi and many protists were considered plants while some of the protists were grouped with the animals The problem with this category is that they didn t know where to classify fungi Eventually they had to make a new one Origin of Taxonomy modern classification binomial nomenclature in the 1700s It dates back to Aristotle However Linnaeus developed the foundation for Binomial Nomenclature It has 2 names When a organism is discovered if it s a like but different it gets the same first name and different last name The first name is the genus name and the second name is the species name The genus name means that organisms share characteristics with it Organisms are classified or grouped into categories These categories are further divided into smaller and smaller groupings creating an organizational hierarchy Hierarchy The lowest 2 categories of the taxonomic hierarchy genus and species make up the scientific name for an organism o Scientific Name Ex we are Homo sapiens or Homo sapiens The genus name is capitalized and the species name begins with a lowercase letter The name is usually underlined or italicized The major taxonomic categories from most inclusive biggest set to least inclusive smallest set are As you go up the categories are more broad such as plants o Domain o Kingdom o Phylum Division o Class o Order o Family o Genus o Species A HUMAN o Eukarya o Animalia o Chordate o Mammalia o Primates o Hominidae o Homo o sapiens Did King Philip Come Over For Good Spaghetti We use systematics to organize organisms A system grouping that s based on utilizing the evolutionary history phylogeny in order to classify it Evolution is the change of an evolutional species over a period of time is the part of biology practice that uses phylogeny to categorize the diversity of living Systematics organisms Phylogeny is the perceived evolutionary history of an organism Using systematic the more categories two organisms have in common the more closely related the two organisms are in their phylogeny It gives the power of inference Ex if you discover something about one organism it may also relate to an organism that s related to the organisms Systematics depict evolutionary relationships in branching phylogenetic trees see fig 18 2 But the problem is we don t know the evolutionary history so we guess Phylogenetic Trees It always starts with an ancestral parent The linages evolve into themselves The organisms that are closely related will be next to one another on the family tree Each branch point in the tree is a node that represents the divergence of species o Nodes A branch point in the tree The node will represent an evolutionary event we will only see the results of the divergence Nodes closer to the ancestral linage represent greater amounts of divergence than nodes farther from the ancestral linage Phylogenetic history can be inferred from similarities in structures both have 2 hands 4 legs ears that function same and genes when compared among organisms Generally similar morphology what they look like and similar DNA sequences closely related species None of the organisms around today are related to us Shared characters are used to construct phylogenetic trees and clades to show phylogenetic relationships o Clades are groups of species that includes the ancestral species and all its descendants It is the ancestor the node and all of the linages that come from it figure 18 2 the dark purple is a clade Frequently they represent that organizational hierarchy we now use Taxonomy systematics grouping is an inexact process All grouping methods are subject to problems We want logistical and easy to use models Plants vs animals was an imperfect system and as a result didn t last Robert Whittaker In 1969 he proposed a replacement for the plants vs animals system that had as it s largest grouping five kingdoms At this time the biggest group was the kingdom Biologists accepted it for about 16 years These five kingdoms each had observably different attributes that defined them Cell type type to characterize first kingdom monera He came up with more categories that were clear Five Kingdoms and Characteristics eukaryotic bigger have organelles prokaryotic single tinier no organelles He used cell Kingdom Monera Protista Fungi Plantae Animalia Cell Type Prokaryotic Eukaryotic Eukaryotic Eukaryotic Eukaryotic Cell Unicellular Unicellular Multicellular Multicellular Multicellular Nutritional Method Absorption photosynthesis Absorption photosyn ingestion Absorption Photosynthesis Ingestion o In this scheme each Kingdom is divided into either Phyla plural of phylum or Divisions These categories are further divided into smaller and smaller groupings creating an organizational hierarchy Problems with Whittaker s System There were 2 problems with his system that became obvious once DNA technology improved in the 1980s In the 1980s we could look at the molecules of life DNA proteins lipids more carefully Problem 1 Based on the idea that when we started looking at the organisms within a single kingdom and comparing them based on DNA Sequences we started seeing inside the individual kingdoms not all of the organisms were equally comparable The techniques of molecular biology have aided the taxonomist in the classification of organisms by allowing the
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