Transcript macroevolution involves evolution at the large scale as species

› A group of organisms
that interbreed with each
other and share the
same gene pool.
› A group of organisms
that produce fertile
offspring.
*Simplified: A species is a group
of organisms that can have
children. Also their children can
have children.
Reproductive barriers can be
PREZYGOTIC or POSTZYGOTIC.
Prezygotic isolating mechanisms prevent
reproduction and make fertilization
unlikely
geographic isolation
 Gamete isolation
 temporal isolation
 behavioral isolation
 mechanical isolation

Geographic
Temporal Isolation
Isolation
 Organisms can not
mate because
 Organisms can
not mate because they reproduce in
different seasons
they are
or different times
separated by
of day.
geographic
barriers.
Mechanical
Behavioral
Isolation
Isolation
 Organisms don’t  Organisms can
not mate
mate because
because their
they have
genitalia is
different mating
unsuitable for one
rituals.
another.
Gamete
Isolation
Organisms
can not
mate
because
their sperm
and egg will
not fuse.
Postzygotic Isolating Mechanisms
take place once organisms have
mated.
 Zygote
mortality
 Hybrid Sterility
 Hybrid Inviability
Hybrid Sterility
A hybrid
offspring is
produced, but
is sterile.
Hybrid
Inviability
The
offspring
survives,
but is weak
and sickly.
Zygote
Mortality
Fertilization
occurs, but
the zygote
does not
survive.
ALLOPATRIC
SPECIATION
SYMPATRIC SPECIATION
ADAPTIVE RADIATION
In ALLOPATRIC
SPECIATION, an
ancestral population is
geographically isolated,
resulting in the evolution
of separate species.
 Populations begin to
diverge when gene
flow between them is
restricted and
variations accumulate
until the populations
are reproductively
isolated.
In SYMPATRIC SPECIATION, an
ancestral population is isolated,
resulting in the evolution of
separate species.
 Sympatric speciation involves
speciation without a geographic
barrier.
Adaptive radiation involves the
evolution of several new species from
an ancestral species.
 Adaptive radiation occurs as natural
selection drives members of the
ancestral species to adapt to several
different environments.

Evolution through Natural Selection is not
random. Although mutations and
Genetic Drift can not be predicted and
are random themselves, Natural
Selection acting upon these changes is
not random at all…….the best suited for
their environment are still the ones most
likely to survive and reproduce. How the
actual “Evolution” takes place is up for
some debate.
Convergent Evolution…..Unrelated
species growing more and more alike
due to adapting to their
surroundings….Analogous Structures is an
example of Convergent Evolution
 Divergent Evolution ……When closely
related species grow less and less alike
due to adapting to their
surroundings….ie) Darwin's Finches

Coevolution ….When two or more
species evolve in response to changes in
the other.
 Extinction ….The elimination of a species
on Earth….happens when a species is
unable to adapt to its surroundings
