Test 2 Chapter 26 relationships Phylogeny and The Tree of Life The discipline of systematics classifies organisms based on shared Systematics is the analytical study of the diversity and relationships of organisms both present day and extinct Use fossil molecular and genetic data to infer these relationships Organizing or grouping things together helps in dealing with them If organisms or any items are to be grouped them they need a name In biology this begins with taxonomy Taxonomy is the branch of biology concerned with naming and classifying the diverse forms of life The origins of taxonomy date back to Aristotle There are many ways that organisms may be grouped o Plants vs animals One of the early classification systems placed the animals in one group an the plants in the another The bacteria fungi and many protists were considered plants while some of the protists were grouped with the animals Systematics is an inexact process All grouping methods are subject to problems Plants vs Animals was an imperfect system and as a result didn t last Naming The foundation for modern classification binomial nomenclature was developed by Linnaeaus in the 1700 s Linnaeaus also developed a scheme where organisms are classified or grouped into categories These categories are further divided into smaller groupings creating an organizational hierarchy The lowest two categories of the taxonomic hierarchy make up the scientific name for the organism o Homo sapiens The genus name is capitalized and the species name begins with a lowercase letter The scientific name is usually underlined or italicized Major taxonomic categories o Domain o Kingdom o Phylum Division o Class o Order o Family o Genus o Species Do Knowledge Political Candidates Often Forget General Subjects Many criteria are used by biologists to group organisms o Morphology Size shape structure o Anatomy Organs tissues o Developmental stage Compare the embryos o Cell structure Chromosome number and structure Does it fly Swim Quack o Behavior o Lifecycle o Ecology How long does it live How often does it reproduce Where does it live o Using systematic the more categories two organisms have in common the more closely related they are o The more closely related two organisms are the smaller the difference between them This often means very small anatomical differences are used to distinguish between two species o Some of these criteria can be misleading because very different organisms can have similar characteristics which are the result of convergent evolution Shark vs dolphin Kingdoms In 1969 Robert Whittaker proposed a means for easily determining which of the five kingdoms an organism is based on observably different attributes that define them The Five kingdoms and their defining characteristics Kingdom Cell Type Cell Method Nutritional Monera Prokaryotic Unicellular Absorption photosynthesis Protista Eukaryotic Unicellular Absorption photosynthesis ingestion Fungi Eukaryotic Multicellular Absorption Plantae Eukaryotic Multicellular Photosynthesis Animalia Eukaryotic Multicellular Ingestion In this scheme each kingdom is divided into either Phyla plural of phylum or divisions There were two problems with Whittaker s system that became obvious once DNA technology improved in the 1980 s The techniques of molecular biology have aided the taxonomist in the classification of organisms by allowing the DNA sequences from two organisms to be compared The ability to examine the DNA sequences and genes of different organisms resulted in the kingdom Monera being separated into two distinct groups which are polyphyletic o Polyphyletic groups derived from more than one common evolutionary ancestor or ancestral group an therefore not suitable for placing in the same taxon o Carl Woese prosed that these two groups of prokaryotes are as different from each other as they are from the eukaryotes and that these difference arose very early in the process of o In orderin order to accommodate these differences and place them in the appropriate evolutionary context Woese and others proposed an evolutionary tree with three main evolution brances 2 prokaryotic domains Bacteria Archaea Eukaryotic Domain Eukarya Branches into separate eukaryotic kingdoms o Some kingdoms are polyphyletic Linking systematics and phylogeny Phylogeny describes a taxon whose members were denied from two or more ancestral forms not common to all ancestors o Grouping based on perceived evolution o Systematics depict evolutionary relationships in branching phylogenetic trees o Each branch point node represents the divergence of species o Nodes closer to the ancestral lineage represent greater amounts of divergence than nodes further from the ancestral o A node with multiple lineages is a polytomy that requires more data to be resolved o lineage A B C D E F G A B C E and F share characteristic 1 D E and F share characteristic 2 A is the only one that has characteristic 3 C and b share characteristic 4 Characteristic 5 is shared by D E and F 1 2 3 4 5 o Phylogenic history can be inferred from similarities in homologous structure and genes when compared among o Generally similar morphology and similar DNA sequences organisms result on closely related Chapter 27 Test 2 Bacteria and Archaea The organisms that make up the two prokaryotic domains bacteria and archaea were the first organisms to arise on earth Some General Characteristics Unicellular grow in colonies No membrane bound organelle Circular chromosomes Most prokaryotes range in size from 2 5 micrometers in diameter The two domains appear similar in many respects however they are different in some very basic ways One main distinction between the bacteria and the archaea is the type of a semi rigid permeable cell wall The bacterial wall is composed of peptidoglycan o Peptidoglycan is a type of polymer in bacterial cell walls consisting of modified sugars cross linked by short The cell wall of bacterium gives characteristic shapes polypeptides o Bacilli o Cocci o Spirilla the peptidoglycan cell wall of bacteria can be stained by a specific stain the Domain Bacteria can be divided into two groups based on the ability to known as Gram stain be stained with Gram stain Gram positive bacteria have the cell wall exposed to the environment Gram negative bacteria are not stained by Gram stain o These bacteria still have a peptidoglycan cell wall but they also have an extra outer membrane About half the prokaryotic species are capable of
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