Transcript Ch. 14 Patterns of evolution

Convergent, divergent,
parallel and co-evolution
Divergent Evolution
• When closely related species
become less like each other
over time due to different
environmental conditions or
selective pressures
• When several species diverge
from one common ancestor this
is called adaptive radiation
Divergent Evolution
Blossom bat Queensland
Eastern Horseshoe Bat - NSW
Right, large-eared variety
Fruit Bat - Victoria
Adaptive Radiation
Convergent Evolution
• When species that are not
closely related have adapted
similar features due to similar
selective pressures
• Also known as adaptive
convergence
Left: A and B, a marsupial
flying phalanger and a
placental flying squirrel; C
and D, marsupial and
placental jerboas; E and F,
marsupial and placental
moles.
Below: The marsupial
Tasmanian wolf (left) and the
familiar placental wolf (right),
with the corresponding
skulls.
Parallel Evolution
• When closely related species
develop similarities due to similar
selective pressures that they are
exposed to
Co-evolution
• When two different species have a
close relationship evolve in a way
that enhances their relationship
What type of evolution do
these diagrams show?
Speciation
• Evolution by natural selection leads
to gradual changes
• Over time, the species may change
so much that a new species forms
• This is called speciation
• Two types:
• Phyletic evolution
• Branching evolution
• When speciation occurs due to
geographical separation, this is
called allopatric speciation
Speciation
• Phyletic Evolution:
• When one population of a species
changes so much that it is no longer
able to breed with other members of
the species and produce viable
offspring
• Branching evolution:
• When a population of a species splits
into two or more groups with one of
the groups evolving separately from
the others and forming a new species
Phyletic vs. Branching
Punctuated Equilibrium
• Darwin proposed that evolution
was a very slow and gradual
process
• In 1974 – a ‘punctuated
equilibrium’ model was proposed
• Species can remain unchanged for
long periods of time and the
evolution of a species can occur
rapidly due to sudden changes
• Evidence in fossil record
Extinction
• If a species is unable to change
or evolve through natural
selection it may be unable to
survive some selective pressures
• If all of the reproductive
individuals of a species die, the
species is lost and said to be
extinct
Comparative Genomics
• Can be used to compare the entire
genome of organisms to
determine how closely related
they are
• Helps to determine whether
similar species share an
evolutionary history