Download Hardy- Weinberg Equilibrium - Fort Thomas Independent Schools

HardyWeinberg
Equilibrium
WHAT HAPPENS IF IT DOESN’T
Hardy -Weinberg
Under
certain conditions
the frequency of an
allele will remain the
same
Hardy -Weinberg
No
Mutation
No immigration or
emigration
Large population
No Natural Selection
Random Mating
Hardy -Weinberg
 Use
p & q to represent allele
frequency
p
(%) + q (%) = 1.00 (100%)
 P2
+2pq + q2 = 1.00 (100%)
Disruptions to Equilibrium
 Mutations
Could
produce new alleles
(spontaneous)
Hard
If
to eliminate harmful
recessives
helpful become part of
population
Disruptions to Equilibrium
Migration
Emigration
– exit
Immigration – into
Disruptions to Equilibrium
 Genetic
drift
Allele frequencies
change
Happens in small
population
Leads to no variation &
possible extinction
Disruptions to Equilibrium
Non
random mating
Geographic
proximity
Many species
have mate
selection
Disruptions to Equilibrium
 Natural
selection
 stabilizing – selects for the
average
directional – selects for extreme
disruptive–selects
sexual

for either end
– choose mates
Concepts of species
morphological
based on looks

- what look like 2
different species can
breed & produce
fertile off spring
Concepts of species
biological –
populations
of organisms
that can
breed &
produce
fertile
offspring, but
do not breed
with other
groups
Concepts of species
Modern –
single type of
organism that are
morphologically
similar, can
interbreed &
produce fertile
offspring
Types of speciation
 Allopatric
speciation
Results because a physical barrier is
present
Types of speciation
 Sympatric
Speciation
Results when there are no
barriers, from natural selection,
mutation and genetic drift
Isolation Mechanism
1.
geographic –
physical separation
(island & rivers)
2. Reproductive –
unsuccessful breeding
Reproductive isolation
Post- zygotic –
after fertilize
offspring can’t
reproduce
Ex: mule, seedless grape
Reproductive isolation
Pre – zygotic
before fertilize
Ex: mating times
Rates of Speciation
gradual –
slow shift in the forms
that are seen
punctuated –
sudden shift in the
forms seen in the
fossil record