198944
Descripción
Mapa Mental por tomking304, actualizado hace más de 1 año
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Creado por tomking304
hace más de 10 años
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SPECIATION 6
- several conditions - self-fertilisation, vegetative
propagation, higher fitness than the diploid, or niche
separation from the diploid - may enable new polyploidy
to increase & form a viable population
- because polyploidy apparently confers new physiological &
ecological capabilities it may play important role in plant evolution
- their increased number of genes
may enhance their adaptability
- their increased number of genes
may enhance their adaptability
- polyploidy doesn't confer major new
morphological characteristics eg
differences in structure of flowers or fruits,
so seems unlikely to cause evolution of
new genera or other higher taxa
- because polyploidy apparently confers new physiological &
ecological capabilities it may play important role in plant evolution
- recombination speciation - arises when hybrid
genotypes, that are fertile but reproductively
isolated from the parent species, increase in
frequency forming a distinct population (aka hybrid
speciation) - more common in plants than animals
- hybridisation, by generating diverse gene combinations on
which selection can act, can be source of new species with
novel morphological & ecological features
- hybridisation, by generating diverse gene combinations on
which selection can act, can be source of new species with
novel morphological & ecological features
- speciation rates
vary greatly:
- expected to be very
slow if it proceeds by
mutation & drift of
neutral alleles
- expected to be faster
if driven by ecological
or sexual selection
- expected to be
accelerated if
reinforcement plays
a role
- expected to be very
slow if it proceeds by
mutation & drift of
neutral alleles
- allopatric speciation could be
slow or very rapid, depending on
strength of divergent selection &
on genetic variation in relevant
traits
- polyploidy, recombination speciation & sympatric speciation
should be very rapid when they occur - but may occur rarely,
resulting in long intervals between speciation events
- ecological speciation
can be very rapid
- ecological speciation
can be very rapid
- polyploidy, recombination speciation & sympatric speciation
should be very rapid when they occur - but may occur rarely,
resulting in long intervals between speciation events
- characteristics that
seem most likely to
increase speciation rate
include:
- pollination
by animal
(rather than
wind) in
plants
- features that
indicate
intense
sexual
selection in
animals
- these observations suggest diversification in some groups of
animals owes more to simple evolution of reproductive isolation
(due to sexual selection) than to ecological diversification
- pollination
by animal
(rather than
wind) in
plants
- MOST IMPORTANT
CONSEQUENCE OF
SPECIATION IS THAT
ITS THE SINE QUA
NON (ESSENTIAL
CONDITION OR
PREREQUISITE) OF
DIVERSITY
- for sexually reproducing organisms,
every branch on phylogenetic tree
represents a speciation event
- speciation stands at border between microevolution - genetic
changes within & among populations - & macroevolution - evolution
of higher taxa in all their diversity
- speciation stands at border between microevolution - genetic
changes within & among populations - & macroevolution - evolution
of higher taxa in all their diversity
- evidence that speciation contributes to both rates
of molecular & morphological evolution, based on
expected differences between patterns of
divergence expected under models of phyletic
gradualism vs punctuated equilibrium
- in gradual
model, rate
of evolution
of lineage
is
unaffected
by number
of
speciation
events
- in contrast,
evolutionary
change
requires
speciation &
increases with
number of
speciation
events, in
pure
punctuated
equilibrium
model
- in contrast,
evolutionary
change
requires
speciation &
increases with
number of
speciation
events, in
pure
punctuated
equilibrium
model
- in gradual
model, rate
of evolution
of lineage
is
unaffected
by number
of
speciation
events
- agreed no
reason to think
speciation
triggers
morphological
evolution
- nevertheless,
morphological
change might be
associated with
speciation
because
reproductive
isolation enables
morphological
differences
between
populations to
persist in the long
term
- nevertheless,
morphological
change might be
associated with
speciation
because
reproductive
isolation enables
morphological
differences
between
populations to
persist in the long
term
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