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
