Transcript Patterns of Evolution

Patterns of Evolution
EQ: What patterns can be observed in
evolution?
PATTERNS OF EVOLUTION
These are models of evolution:
A. Mass Extinctions
B. Adaptive Radiation
C. Convergent Evolution
D. Coevolution
E. Gradualism
F. Punctuated Equilibrium
A. MASS EXTINCTIONS
●
Event in which many types of living things became extinct at
the same time.
●Huge numbers of species disappeared.
●Whole ecosystems were wiped out.
Resulted in burst of evolution of new species in new habitat
●Disrupted energy flow throughout the biosphere and caused
food webs to collapse
●
(Possible Causes: Asteroids, volcanic eruptions, continental
drifts, changing sea levels)
●
B. ADAPTIVE RADIATION
(DIVERGENT EVOLUTION)
The evolution of an ancestral species,
which was adapted to a particular way of
life, into many diverse species, each
adapted to a different habitat
●Many new species diversify from a
common ancestor .
●The branching out of a population
through variation.
●The new species live in different ways
than the original species did.
●
ADAPTIVE RADIATION
C. CONVERGENT EVOLUTION
Opposite of divergent evolution (adaptive
radiation)
●Unrelated organisms independently evolve
similarities when adapting to similar
environments, or ecological niches
●Analogous structures are a result of this process
●Example: penguin limb/whale flipper/fish fin
●The wings of insects, birds, pterosaurs, and bats
all serve the same function and are similar in
structure, but each evolved independently
●
CONVERGENT EVOLUTION
D. COEVOLUTION
The mutual evolutionary influence between two
species
●When two species evolve in response to changes in
each other
●They are closely connected to one another by
ecological interactions (have a symbiotic
relationship) including:
●Predator/prey
●Parasite/host
●Plant/pollinator
●Each party exerts selective pressures on the other,
thereby affecting each others' evolution
●
COEVOLUTION
Bumblebees and the flowers the they pollinate
have co-evolved so that both have become
dependent on each other for survival.
E. GRADUALISM
The evolution of new species by gradual
accumulation of small genetic changes
over long periods of time
●Emphasizing slow and steady change in
an organism
●Occurs at a slow but constant rate
●Over a short period of time it is hard to
notice
●
GRADUALISM
Current living zebras (top), extinct quaggas (bottom)
F. PUNCTUATED EQUILIBRIUM
Stable periods of no change (genetic
equilibrium) interrupted by rapid changes
involving many different lines of descent
●Opposite of gradualism
●It is rare, rapid events of branching
speciation
●Characterized by long periods of virtual
standstill ("equilibrium"), "punctuated" by
episodes of very fast development of new
forms
●
PUNCTUATED EQUILIBRIUM
Horseshoe crabs have changed little since
their first appearance in the fossil record.
●They are in a state of equilibrium
●
GRADUALISM VS
PUNCTUATED EQUILIBRIUM