LECTURE 3A_Phylogenetic Systematics, Cladistics Flashcards
are inferred by identifying
organismal features, characters, that
vary among species.
Phylogenies
5 organismal features, characters, that
vary among species.
⚫ Morphological
⚫ Chromosomal
⚫ Molecular (genes)
⚫ Biochemistry of living organisms
⚫ Behavioral or ecological
evolutionary history or pattern
of descent of a group of organisms.
Phylogeny
representation of organisms based on and
describing evolutionary relationships.
Phylogeny
Primary goals of systematics
Phylogeny
branch of systematics concerned with
inferring phylogeny
Phylogenetic systematics/cladistics
Morphological and molecular similarities may
provide clues to
phylogeny
Similarities due to shared ancestry are called
homologies
Organisms with similar morphologies or DNA
sequences are likely to be ———————– than organisms with different
structures or sequences.
more closely related
————— between closely
related species can be small or great.
Morphological divergence
may be controlled by
relatively few genetic differences.
Morphological diversity
is concerned with grouping individual species into evolutionary categories.
Phylogenetic classification
has been made much more
facile by the invention of molecular
taxonomy:
phylogenetic
classfication
year of phylogenetic
classfication
early 1980’s (or so)
The evolutionary classification of organisms
based on the nucleotide sequence divergence at
individual loci (genes).
molecular taxonomy
can really throw a wrench between the two classification philosophies since convergent evolution,
convergent evolution
produces phenotypic similarity in the absence of close
evolutionary relatedness.
convergent evolution
The trick to solving these discrepancies is to concentrate on ——- and ———
true homologies and ignore convergence.
Similarity due to
convergent evolution
is called
analogy
it occurs when similar environmental pressures and natural selection produce similar (analogous) adaptations in organisms from different evolutionary lineages.
Convergent evolution
When constructing a phylogeny, systematists
need to distinguish whether a similarity is the
result of ——- or ——–
homology or analogy
is similarity due to shared ancestry
Homology
is similarity due to convergent evolution
Analogy
may evolve in such organisms
Similar analogous adaptations
Analogies are not due to shared
ancestry
A potential misconception in constructing
a phylogeny is similarity due to
convergent evolution,
A potential misconception in constructing
a phylogeny is similarity due to
convergent evolution, called
analogy
Analogous structures or molecular
sequences that evolved independently
are also called
homoplasies
is critical in the
reconstruction of phylogeny.
Distinguishing homology from analogy
Homology can be distinguished from
analogy
Homology can be distinguished from analogy by
comparing —————- and —————
fossil evidence and the degree of complexity
The more complex two similar structures are, the
more likely it is that they are
homologous
350 million year old
animal
first tetrapod
had limbs with one long bone (the humerus) attached to two other long bones (the radius and ulna).
the first tetrapod
Similar structures inherited
from a common ancestor are
called
homologous structures or homologies.
*Similar structures that evolved independently are called
analogous structures or analogies.
Once homologous characters have been
identified, they can be used to infer a
phylogeny
Shared characters that result from
common ancestry are
homologous
Independent evolution of similar
characters that are NOT homologous is
called
homoplasy
represents the divergence of
two species
branch point
are groups that share an immediate
common ancestor
Sister taxa
includes a branch to represent the
last common ancestor of all taxa in the tree
rooted tree
diverges early in the history of a
group and originates near the common ancestor of
the group
basal taxon
is a branch from which more than two
groups emerge
polytomy
Phylogenetic trees show
patterns of descent
Phylogenetic trees show patterns of descent, —–
phenotypic similarity
do not indicate when species
evolved or how much change occurred in a
lineage
Phylogenetic trees
provides important information about
similar characteristics in closely related species
Phylogeny
4 applications of phylogeny
⚫ Understanding evolutionary relationships
⚫ Understanding morphological evolution
⚫ Understanding bio-diversification
⚫ Understanding DNA taxonomy of Animals (for
species identification)
is a method of phylogenetic
classification which attempts to limit
comparisons within groups only to those
characters which are thought to have
evolved within a given group
Cladistics
comparisons within groups only to those
characters which are thought to have
evolved within a given group, also known as
derived characters
groups organisms by common descent
Cladistics
is a group of species that includes an
ancestral species and all its descendants
clade
Clades can be nested in
larger clades
not all
groupings of organisms qualify as
clades
Cladists consider only
homologous traits
traits shared because of a common ancestry.
homologous traits
homologous traits supply
the most information to a
cladist
Phylogenies are often presented as
cladograms
Phylogenies are often presented as cladograms
with their familiar ———- and ——-
branches and nodes
is a graphical
representation of a phylogeny.
cladogram
cladogram is a graphical
representation of a
phylogeny
Lines of a cladogram are known as —– or ——-
lineages or clades
represents the sequence of ancestral-descendant
populations through time, ultimately denoting descent.
Lineages
are organisms or species that share derived
character states and form a subset within a larger group;
Clades
group of species that includes an ancestral species and all
its descendants.
Clades
A valid clade is ———–
monophyletic
signifying that it consists of the
ancestor species and all its
descendants
monophyletic
A group that includes an immediate common ancestral species (known or hypothesized) and all of its descendants
Holophyletic group
is a good taxon in an evolutionary
sense, meaning that no members which ought to be a
part of the taxon
monophyletic taxon
in terms of ancestor-descendant
relationships, are excluded.
monophyletic taxon
is a grouping that consists of an ancestral species and some, but not all, of the descendants.
paraphyletic clade
all of whose members are descended from a common ancestor, but which does not include all of the known or considered descendants of that common ancestor.
phylogenetic group
is a monophyletic taxon in which a member, other than the most recent common ancestor, is excluded.
paraphyletic taxon
represent the improper exclusion
of members on the basis of phenotypic differences rather than
on the basis of ancestor-descendant relationships.
paraphyletic taxa
grouping includes numerous types of organisms that lack a common ancestor.
polyphyletic
A grouping that does not
include a most recent
common ancestor
polyphyletic
the most recent common ancestor is assigned to some other group and not to the group itself.
polyphyletic
is essentially an
erroneously compiled taxonic grouping.
polyphyletic taxon
It means that two unrelated taxa have been
lumped into one.
polyphyletic taxon
polyphyletic taxa can only be done if one
includes the common ancestor, but then the
resulting taxon would be either ———— or ———–
monophyletic or paraphyletic
2 types of derived characteristics
Apomorphy
synapomorphy
is an evolutionary
novelty unique to a
particular clade.
shared derived character
is a derived condition
Apomorphy
is a
derived character shared
by the members of the
clade;
synapomorphy
a derived chracteristic that unites 2 or more lineages
apomorphy
evolutionary novelty
unique to a particular clade
Shared Derived Characteristics
character that originated in an
ancestor of the taxon
Shared Primitive/Ancestral:
Is a homologous structure that predates the branching of a particular clade from other members of that clade
shared primitive character
Is shared beyond the
taxon we are trying to
define.
shared primitive character
2 types Shared Primitive/Ancestral Characteristics
plesiomorphic
symplesiomorphy
Ancestral character states for a taxon are
called
plesiomorphic
Sharing these ancestral characters is
called
symplesiomorphy
do not provide information on nesting of clades – groups with derived characters get left out
Symplesiomorphies
A character can be both ———— and ————,
depending on the context
ancestral and derived
one
that occurs within a
single lineage
Autapomorphy
corresponds to
a unit of evolutionary
common descent.
clade
is
formed by the derived
states of all characters
in a study group.
nested hierarchy
4 kinds of clades
monophyletic
holophyletic
paraphyletic
polyphyletic
more complex two similar structures are, the
more likely it is that they are ———-
homologous
Similar structures that evolved independently are called
analogous or analogies
corresponds to
a unit of evolutionary
common descent
clade
