Diversity of LifeClassification - an organized scheme for grouping organisms- a tool for communication -Hierarchical - a series of successive and inclusive rankings• Domain - the highest rank - contains one or more kingdoms• Kingdom - contains one or more phyla• Phylum - contains one or more classes• Class - contains one or more orders• Order - contains one or more families• Family - contains one or more genera• Genus - contains one or more species• Species - a group of potentially interbreeding organisms that are reproductively isolated from all other organismsHierarchies can be represented as trees:Trees and classifications can be based on estimates ofevolutionary relatedness.The modern method bases estimates on shared derivedcharacteristics (synapomorphies).This methodassumes thatcomplexcharacteristicsevolve rarely.Thus, the presenceof characteristicslike amnioticdevelopment orlungs is anindication ofdescent from theoriginal species thatpossessed them.A tree that represents an estimate (hypothesis) of evolutionaryrelatedness is called a phylogenyClassifications can be based on groupings within a phylogenyGroupings can be categorized• monophyletic - a group that includes all of the descendants ofa single common ancestor• paraphyletic - a group that includes some, but not all, of thedescendants of a single common ancestor• polyphyletic - a group that is not based on common ancestryThe trend in modern classification is to create cladistic classifications.Cladistic classifications include only monophyletic groups.Some rearrangements of long-established groups will result:Classifications through time:Relationships among the three domainsBacteria and Archaeans are both prokaryotic:• generally small and simple,• lacking membrane bound organelles,• no nuclear membrane,• if present, flagella consist of a single fiber,• genetic recombination occurs through•transformation, conjugation, or transductionBacteria and Archeans differ • First amino acid in protein synthesis• presence of introns in genes• membrane lipid structure• number of RNA polymerases• peptidoglycan in cell wall• response to some antibioticsBacteriaArchaeaf-Met MetNo someunbranched branchedone severalyes nosensitive insensitiveBacteria• source of many diseases in plants, fungi, and animals• some are photosynthetic - purple sulfur bacteria, cyanobacteria• some are anaerobes• important decomposers in every habitat on earthArchaea• many obligate anaerobes• many live in extreme environments (extremophiles)• thermophiles• halophiles• methanogensArchaeans share many characteristics with the Eukarya• First amino acid is Met• Genes with introns• Several RNA polymerases• Lack peptidoglycan in cell wall• Insensitive to antibioticsDomain Eukarya - consists of four kingdomsKingdom Protista - diverse single celled organisms -some colonial or with primitive multicellularity nutrionally diverse - autotrophic - photosyntheticheterotrophic - both saprobes and ingestersKindom Fungi - mushrooms, rusts, molds, etc. - multicellular saprobes - use extracellular digestion cell walls made of chitin immobileKingdom Plantae - plantsmulticellular, cell walls made of cellulose photosynthetic using chlorophyll a & b immobileKingdom Animalia - animalsmulticellularlack cell wallsusually mobileheterotrophic ingestersSex is the hallmark of the Eukarya- the combination of genetic information from two different sources - through syngamy- life cycle consists of both a diploid stage and a haploid stage- either stage may be multicellular or single celledSeen inFungi andalgaeSeen inAnimalsSeen
View Full Document
Unlocking...