Lec 6 Systematic Notes Flashcards Preview

Fishes > Lec 6 Systematic Notes > Flashcards

Flashcards in Lec 6 Systematic Notes Deck (12):


The discovery, recognition, definition, and naming of groups of organisms



The study of biological diversity; or, more specifically, the ordering of the diversity of nature through construction of a classificationthat can serve as a General Reference System



The orderingof plants and animals into groups based on their similarityand relationship



Concise listsof organisms, grouped or ranked according to the pattern of branching seen in the branching diagram, a product of systematic research


Branching diagrams

Graphic views of the sequence of evolutionary divergenceof groups of organisms through time, another product of systematic research. Along the horizontal axis, they show the relative primitivenessof organisms; along the vertical axis, they show how groups of organisms have evolved from one another, that is, the pattern of branchingthrough time



The major criteria are: 1.Based onOverall similarity 2. Numerous charactersare used, as many as can be found, and all are given 3. Equal weight; the resulting branching diagram (tree) is 4. Computer generated; and the branching diagram (tree) that is produced is called a 5.Phenogram(from the Greek “phenomen,” that which is seen), a branching diagram that links organisms by estimates of overall similarity as evidenced by an analysis of characters



Sometimes called Phylogenetic Systematics, the major criteria are: 1. One criterion for classification: recencyof common descent. 2.The method allows only the use of specializedor derived character states, character states that we call apomorphic(primitive characters states are calledplesiomorphic). So, in this sense, characters, or more precisely, character states, are more heavily weighted over others. 3.Taxa that share derived or apomorphiccharacters statesare said to be related. Shared apomorphiccharacter states are called synapomorphic, whereas shared plesiomorphiccharacter states are called symplesiomorphic. 4.Grouping and ranking are given simultaneously by branching points in a diagram called a cladogram(from the Greek “clad” or “klados,” meaning to branch



Cladisticsystematics, or Cladisticsfor short, was first articulated in a formal way by a German entomologist


Donn E. Rosenand GarethNelson

primary proponents of cladisticsin the fish world



Sometimes called the Synthetic Method, because in some ways it combines the criteria of pheneticsand cladistics. Evolutionary systematicsrelies on: 1.Two criteria for classifying and ranking organisms: recencyof common descentand the amount and nature of evolutionary change between branching points. 2.The method allows the use of plesiomorphic(primitive) character states as well as apomorphic(specialized or derived) character states. Characters states thought to be more evolutionarily or functionally significant are often heavily weightedover others. 3. Grouping and ranking are given simultaneously by branching points in a diagram called a Phylogenetic Tree



One of the criticisms is that it totally ignores the possibility of evolutionaryconvergence


Robert R. Sokaland Peter H. A. Sneath

The phenetic methodwas all the rage in the early and midsixties, popularized primarily by two individuals