Lecture 3: Review Lecture (Cladistic Terminologies) Flashcards
method of classifying species of organisms into groups called clades,
Cladistics
species of organisms into groups
called
clades
consist only of firstly, all the descendants of an
ancestral organism and secondly, the ancestor itself.
clades
focus on shared derived characters
(synapomorphies)
cladistic classifications (usually in the form of trees called
cladograms
are intended to reflect the relative recency of common
ancestry or the sharing of homologous features.
cladograms
In the terms of biological systematics, a clade is a single “branch” on the “tree of life”, a
monophyletic group.
a clade is a single ——– on
the ———,
branch; tree of life
originated in the work of the German entomologist
Willi Hennig, who referred to it as “phylogenetic systematics”
(also the name of his 1966 book);
Cladistics
German entomologis who referred to it as “phylogenetic systematics” (also the name of his 1966 book);
Willi Hennig
Hennig referred to his own approach as
phylogenetic systematics
The term clade was introduced in
1958
The term clade was introduced in 1958 by
Julian Huxley
the term cladistic was coined by
Cain and Harrison
year the term cladistic was coined
1960
who coined the term cladist
Mayr
year the term cladist was coined
1965
From the time of his original formulation until the end of the
———– cladistics remained a minority approach to classification.
1980s
in the —– cladistics rapidly became the dominant method of
classification in evolutionary biology
1990s
made it possible to process large quantities of data
about organisms and their characteristics.
Computers
made it possible to apply
cladistic methods of analysis to biochemical and molecular
genetic features of organisms as well as to anatomical ones.
development of effective polymerase
chain reaction (PCR) techniques
is a result of
Darwin’s discovery that the diversity and history of
life is best represented in tree-shaped diagrams.
phylogenetic nomenclature
This discovery immediately led to changes in the
existing classifications.
Cladogram
is a diagram which shows ancestral
relations between organisms, to represent the
evolutionary tree of life.
cladogram
who uses cladograms
cladists
Cladists use
cladograms
are now very commonly
used in the generation of cladograms.
DNA and RNA sequencing data and
computational phylogenetics
traditionally such cladograms were
generated largely on the basis of
morphological characters
3 types of a clade
Monophyletic, Paraphyletic, Polyphyletic
is a group of taxa consisting only
of an ancestor taxon and all of its
descendant taxa.
clade
ray-finned fishes
(Actinopterygii),
A clade is ——- to another clade if it contains that other
clade as a subset within it.
basal
(Some authors have used “basal” differently to mean a
clade that is less species-rich than a sister clade, with such a
deficit being taken as an indication of —————-
‘primitiveness’
A clade located within a clade is said to be ——— within that clade.
nested
if clades have an immediate common
ancestor.
sisters
(“close form”)
Plesiomorphy
(“close form”) or ancestral state,
Plesiomorphy
(“shared plesiomorphy”, i.e. “shared close form”),
symplesiomorphy
a characteristic that is present at the base of a tree (cladogram).
Plesiomorphy
is inherited from the common ancestor
may appear anywhere in a tree, its presence provides no evidence of relationships within the tree.
plesiomorphy
plesiomorphy
plesiomorphy
or derived state is a characteristic
believed to have evolved within the tree.
Apomorphy
can thus be used to
separate one group in the tree from the rest.
Apomorphy
Within the group which
shares the apomorphy it is a
synapomorphy
(“shared apomorphy”, i.e. “shared separate form”).
synapomorphy
is a characteristic shared by members of a tree but not present in their common ancestor.
Homoplasy
It arises by convergence or reversion.
Homoplasy
the terms ————— and ————– are relative and
their application depends on the position of a group within a tree.
(sym)plesiomorphy and (syn)apomorphy
