3 three basic
assumptions in cladistics（遺傳分類學）
1.Any group of organisms is related by
descent from a common ancestor.
2.There is a bifurcating pattern of
cladogenesis. This assumption is controversial.
3.Change in characteristics occurs in
lineages over time.
• clade 【群】 is a monophyletic taxon
• taxon 【分類群】 is any named group of
organisms
but not necessarily a clade
but not necessarily a clade
• branch lengths correspond to divergence
• node is a bifurcating branch point.
Clades are groups of organisms or genes that include the most recent
common ancestor of all of its members and all
of the descendants of that most recent common
ancestor.
Clade is derived from the Greek word ‘‘klados,’’ meaning branch
or twig.
branch
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