❖ Phylogenies show evolutionary relationships (26.1)
❖ Phylogenies are inferred from morphological and molecular data (26.2)
❖ Shared characters are used to construct phylogenetic trees (26.3)
❖ An organism’s evolutionary history is documented in its genome (26.4)
❖ Molecular clocks help track evolutionary time (26.5)
❖ Our understanding of the tree of life continues to change based on new data (26.6)
Concept 26.1
• Phylogeny – the evolutionary history of a species or a group of species
• Systematics – a disciple focused on classifying organisms and determining their evolutionary
relationships
• All organisms share characteristics due to a common ancestor
• Taxonomy - a discipline focused on how organisms are named and classified
• We refer to species by their Latin scientific names to avoid confusion
• Binomial – the two-part format of an organism’s scientific name
• First part of name is the genus, second part is the specific epithet
o An example is Panthera pardus, the scientific name for leopard
• The first letter is always capitalised and the whole name is italicised
• Species that appear to be closely related are put into the same genus
• The taxonomic system is named after Linnaeus (the Linnaean system)
• Family Order Class Phyla Kingdom Domain
• Example: Leopard = Felidae Carnivora Mammalia Chordata Animalia Eukarya
• The domains are Bacteria, Eukarya, and Archaea
• Taxon – the named taxonomic unit at any level of the hierarchy
o An example is that the Panthera is a taxon at the genus level, while Mammalia is a
taxon at the class level (Mammalia is not italicised since it is a taxon broader than
the genus)
• Each branch point on a phylogenetic tree represents the common ancestor of the two
evolutionary lineages diverging from it
• Sister taxa – groups of organisms that share an immediate common ancestor that is not
shared by any other group
• Example of sister taxa is chimps and humans
• Rooted tree – a tree that has a branch point that represents the most recent common
ancestor of all taxa in the tree (usually the line drawn farthest to the left)
• Basal taxon – a lineage that diverges from all other members of the group early in history
• Phylogenetic trees are intended to show patterns of descent, not phenotypic similarity
• Although, most closely related organisms resemble each other
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