Classification: Taxonomy & Cladistics – Flashcards
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Taxonomy
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The naming of organisms based on a system
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Goal of modern taxonomy
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Describe phylogeny
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Phylogenetic Systematics
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Taxonomy based on phylogeny
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Why study phylogenies?
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1. Knowledge about one group allows for inferences to be made about related groups. Photosynthesis first worked out in a single cell green algae. 2. Medical Considerations: If you want to develop new types of antibiotics what sort of microbe should you explore?
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Taxon
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Group of related organisms
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The only taxon with a biological bases is
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the species
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Hierarchical arrangement of taxons
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Domain, kingdom, phylum, class, order, family, genus, species.
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Binomial Nomenclature
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The scientific name of a species. Humans are called Homo sapiens.
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Phylogenetic Trees
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Graphical presentation of phylogeny ex. evolutionary relatedness. Phylogenetic systematics established the rolling tree for life on Earth.
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Henning Principle: Homologous Traits
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are due to descent from a common ancestor ex. forelimbs of fish and mammals
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Henning Principle: Synapomorphies
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Homologous traits that differ between groups are due to divergent evolution. ex. forelimbs vs. legs. Thus, the evolutionary most related species will share the greatest number of homologous traits.
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What creates synapomorphies between homologous traits?
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Divergent evolution. Homologs: forelimbs Synapomorphies: fins vs. legs
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Homologous Traits used include:
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1. Morphology -skeletal arrangements -flower parts -embryonic or larval developmental patterns 2. Biochemistry -DNA sequences -Protein sequences -Metabolism
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Characters used to infer phylogeny
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Assumptions: 1. most closely related species share the greatest number of traits. 2. traits are shared because homologous (common ancestry) Traits to use should be: 1. under genetic control 2. show variation between talons (synapomorphy) and similar within taxon. 3. traits being studied are independent of each other.
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Homoplasy:
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apparent homology not consistent with other homologies.
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Convergent evolution
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similar traits arising independently in not closely related organisms.
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Revertance:
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mutation and selection back to the ancestral form ex. antibiotic resistance in bacteria.
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Making phylogenetic trees Phenetics:
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derived from phenotype, relationships among a group of organisms based on their similarity ex. the most similar organisms are grouped together. -resulting trees are called phonograms.
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cladistics
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identifying groups based on a shared derived characteristics. ex. identifying the pathway of evolution. -resulting trees are called cladograms
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phenograms and cladograms
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-sometimes phonograms are cladograms produce identical looking trees -sometimes phenograms and cladograms produce different looking trees ex. similar organisms produced are in different groups.
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Parsimony
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adoption of the simplest assumption in the formulation of a hypothesis -parsimonious cladograms produce a phylogenetic tree with the fewest number of evolutionary changes.
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Taxon Domain:eukaryote
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synapomorphy: nucleus and organelle
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Taxon kingdom: animalia
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synapomorphy: multicellular, eukaryotic heterotrophs, embryos
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Taxon phylum: chordata
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synapomorphy: closed circulatory system
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Taxon class: mammalia
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synapomorphy hair, mammary glands
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Taxon order: Primate
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synapomorphy forward facing eyes, nails, hands, feet
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Taxon family: hominid
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synapomorphy bipedal walk by two feet
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Taxon genus: homo
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synapomorphy smaller face, larger brain
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Taxon species: Homo sapiens
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reproduction
