Unformatted text preview: Chapter 20 Classification of Li 2 Classification of Living Outline
Taxonomy Binomial System Species Identification Classification Categories Phylogenetic Trees Systematics Systematics Today Cladistic Systematics Phenetic Systematics Classification Systems The Five Kingdom System The Three Domain Ssytem Taxonomy (naming of organisms) Classification (placing species in the proper categories) 3 Classification of Living Taxonomy Branch of biology concerned with identifying, naming, and classifying organisms Began with the ancient Greeks and Romans Aristotle classified organisms into groups such as horses, birds, and oaks John Ray (16271705) Believed that each organism should have a set name Otherwise, "men...cannot see and record accurately." Classifying Organisms 4 Taxonomy: Binomial System 5 Classification of Living Mid-eighteenth century, Linnaeus developed the binomial system of nomenclature First word is genus name Second word is specific epithet Refers to one species (of potentially many) within its genus A species is referred to by the full binomial name (Genus species) Genus name can be used alone to refer to a group of related species Carolus Linnaeus 6 Taxonomy: Distinguishing Species 7 Classification of Living Distinguishing species on the basis of structure can be difficult Members of the same species can vary in structure Attempts to demonstrate reproductive isolation is problematic because: Some species hybridize, and Reproductive isolation is difficult to observe Members of a Species 8 Hybridization between species 9 10 Classification of Living Classification Categories Modern taxonomists use the following classification: Species Genus one or more species Family one or more genera Order one or more families Class one or more orders Phylum one or more classes Kingdom one or more phyla Domain one or more kingdoms Hierarchy of Taxa for Parthenocissus quinquefolia 11 12 Classification of Living Classification Categories The higher the category, the more inclusive Organisms in the same domain have general characteristics in common In most cases, classification categories can be subdivided into additional categories Superorder Order Suborder Infraorder 13 Classification of Living Phylogenetic Trees Systematics - the diversity of organisms at all levels One goal of systematics is to determine phylogeny (evolutionary history) of a group Phylogeny often represented as a phylogenetic tree A diagram indicating lines of descent Each branching point: Is a divergence from a common ancestor Represents an organism that gives rise to two new groups Classification and Phylogeny 14 15 Classification of Living Phylogenetic Trees Classification lists the unique characters of each taxon and is intended to reflect phylogeny Primitive characters: Present in all members of a group, and Present in the common ancestor Derived characters: Present in some members of a group, but Absent in the common ancestor 16 Classification of Living Tracing Phylogeny Fossil Record Fossil record is incomplete It is often difficult to determine the phylogeny of a fossil Homology Refers to features that stem from a common ancestor Homologous structures are related to each other through common descent Analogy Similarity due to convergence Ancestral Angiosperm 17 18 Classification of Living Tracing Phylogeny Convergent Evolution The acquisition of a feature in distantly related lines of descent The feature is not present in a common ancestor Parallel Evolution The acquisition of a feature in two or more related lineages The feature is not present in a common ancestor Convergent Evolution 19 20 Classification of Living Molecular Data
Protein Comparisons Immunological techniques Degree of cross reaction used to judge relationship Amino acid sequencing Similar sequence in same protein indicates close relationship Systematics assumes: Two species with similar base-pair sequences are assumed to be closely related Two species with differing base-pair sequences are assumed to be only distantly related Use non adaptive nucleotide sequences Assumed constant rate of mutation over time RNA and DNA Comparisons Molecular Clocks Ancestry of Giant Pandas 21 Molecular Data 22 23 Classification of Living Cladistic Systematics Traces evolutionary history of the group under study Uses shared derived characters to: Classify organisms, and Arrange taxa into a cladogram A cladogram is a special type of phylogenetic tree A clade is an evolutionary branch that includes:
A common ancestor, together with its descendent species All Constructing a Cladogram 24 25 Classification of Living Parsimony Cladists are always guided by the principle of parsimony The arrangement requiring the fewest assumptions is preferred This would: Leave the fewest number of shared derived characters unexplained Minimize the number of assumed evolutionary changes The reliability of a cladogram is dependent on the knowledge and skill of the investigator Alternate, Simplified Cladograms 26 Cladistic Versus Traditional View of Reptilian Phylogeny 27 28 Classification of Living Phenetic Systematics Assumes it will never be possible to construct a truly phylogenetic classification system Species are classified according to the total number of shared similarities Disregards assumed phylogenetic considerations Ignores issues of convergent or parallel evolution 29 Classification of Living Traditional Systematics Mainly uses anatomical data Classify organisms using assumed phylogeny with emphasis on phenotype Stress both common ancestry and degree of structural difference among divergent groups Construct phylogenetic trees by applying evolutionary principles to categories Not strict in making sure all taxa are monophyletic 30 Classification of Living Classification Systems Until the middle of the twentieth century, biologists recognized only two kingdoms Plantae (plants) Animalia (animals) Protista (protists) were added as third kingdom in the 1880s Whittaker expanded to five kingdoms in 1969 by adding Fungi and Monera 31 Classification of Living Three-Domain System The Bacteria and Archaea are so different they have been assigned to separate domains Similar in that both are asexually reproducing unicellular prokaryotes Distinguishable by: Difference in rRNA base sequences Plasma membrane chemistry Cell wall chemistry 32 Classification of Living Three-Domain System Domain Eukarya Unicellular and multicellular organisms Cells with a membrane-bounded nucleus Sexual reproduction common Contains four kingdoms Kingdom Protista Kingdom Fungi Kingdom Plantae Kingdom Animalia The Three-Domain System of Classification 33 The Three Domains of Life 34 35 Classification of Living Review
Taxonomy Binomial System Species Identification Classification Categories Phylogenetic Trees Systematics Systematics Today Cladistic Systematics Phenetic Systematics Classification Systems The Five Kingdom System The Three Domain System Taxonomy (naming of organisms) Classification (placing species in the proper categories) Ending Slide Chapter 20 Classification of Li ...
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