Determining Evolutionary Relationships | Phylogenies and the History of Life

Описание: Chapter: Determining Evolutionary Relationships
Collection: Phylogenies and the History of Life
Unit 4. Evolutionary Processes
Book: Biology


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To build phylogenetic trees, scientists must collect accurate information that allows them to make evolutionary connections between organisms. Using morphologic and molecular data, scientists work to identify homologous characteristics and genes. Similarities between organisms can stem either from shared evolutionary history (homologies) or from separate evolutionary paths (analogies). Newer technologies can be used to help distinguish homologies from analogies. After homologous information is identified, scientists use cladistics to organize these events as a means to determine an evolutionary timeline. Scientists apply the concept of maximum parsimony, which states that the order of events probably occurred in the most obvious and simple way with the least amount of steps. For evolutionary events, this would be the path with the least number of major divergences that correlate with the evidence.


00:00 Determining Evolutionary Relationships
00:28 Two options for similarities
01:48 Misleading appearances
03:27 Molecular comparisons
04:52 Evolution connection
06:13 Building phylogenetic trees
07:36 Shared characteristics
09:36 Choosing the right relationships
11:31 Section summary

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