184963
Beschreibung
Mindmap von tomking304, aktualisiert more than 1 year ago
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Erstellt von tomking304
vor mehr als 10 Jahre
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DIFFICULTIES IN
PHYLOGENETIC ANALYSIS
- scoring characteristics can be hard
- anatomical characters important in systematics -
data typically only available for extinct organisms
- deciding number of independent
character differences
- DNA sequence data - changes at
several sites might be likely to evolve in
concert to preserve function
- DNA sequences must be aligned so
homologous sites can be compared
- anatomical characters important in systematics -
data typically only available for extinct organisms
- homoplasy is common
- data set may yield several different phylogenetic
estimates that are equally as good
- unwise to rely on particular phylogenetic
estimate if other hypotheses imply just a few
extra evolutionary changes
- try to get more data on other
characters instead
- try to get more data on other
characters instead
- unwise to rely on particular phylogenetic
estimate if other hypotheses imply just a few
extra evolutionary changes
- data set may yield several different phylogenetic
estimates that are equally as good
- process of evolution often
erases traces of prior
evolutionary history
- is studied taxa diverged long ago or evolved very
rapidly many characteristics will have diverged so
much that homologous characters difficult to discern
- eg teeth useful for determining relationships
between many mammals but can't use to assess
relationship of toothless anteater
- eg teeth useful for determining relationships
between many mammals but can't use to assess
relationship of toothless anteater
- earlier synapomorphies erased from
DNA sequences by multiple
substitutions occurring at a site
- evidence of common ancestry lost if
mutation occurs at site multiple times, eg
A to C then C to G
- more likely for same substitution to
occur in parallel in different lineages as
time passes
- convergent evolution & successive substitutions cause
amount of sequence divergence between taxa to level off
- is studied taxa diverged long ago or evolved very
rapidly many characteristics will have diverged so
much that homologous characters difficult to discern
- rapidly evolving DNA sequences
useful for phylogenetic analyses
of taxa that diverged recently
- slowly evolving sequences
required to assess
relationships among taxa that
diverged in distant past
- some lineages diverge so rapidly little
opportunity for ancestors of each
monophyletic group to evolve distinct
synapomorphies
- ADAPTIVE RADIATION
- evolutionary radiation associated
with marked adaptive diversification
- evolutionary radiation associated
with marked adaptive diversification
- ADAPTIVE RADIATION
- EVOLUTIONARY RADIATION
- episode of significantly
sustained excess of
cladogenesis over extinction
- CLADOGENESIS
- splitting of lineage into 2 or
more descendant lineages
- splitting of lineage into 2 or
more descendant lineages
- CLADOGENESIS
- episode of significantly
sustained excess of
cladogenesis over extinction
- HYBRIDISATION
- offspring from interbreeding from 2
different populations or species
- usually transfers genes
between populations or species
- usually transfers genes
between populations or species
- offspring from interbreeding from 2
different populations or species
- HORIZONTAL /
LATERAL GENE
TRANSFER
- usually incorporates just a few genes of one
species into the genome of another species
(contrasts to hybridisation)
- very important in evolution of bacteria - responsible
for providing genes for antibiotic resistance
- usually through viruses (natural) or
genetic modification (human
intervention)
- very important in evolution of bacteria - responsible
for providing genes for antibiotic resistance
- usually incorporates just a few genes of one
species into the genome of another species
(contrasts to hybridisation)
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