Transcript Today’s Objectives: 10/21/02

Today’s Objectives: 10/21/02
 TSW be able to write the Hardy-
Weinberg equation and explain
it.
 TSW be able to list several
evolutionary mechanisms.
 TSW be able to list several
types of speciation and discuss
the rates of evolution.
Hardy-Weinberg
Theorem
2
p
2
q
+ 2pq + = 1
Studies genetic
(allelic frequencies)
H-W Assumptions:
Large population size.
Random mating.
No migration.
No mutations or
mutational equilibrium.
Ways Evolution
Can Occur
Genetic Drift
 Neutral selection – caused allelic
frequencies to change based on chance
 Founder effect
 Bottleneck effect
Gene Flow
 Changes allelic frequencies because of
migration of individuals.
Mutation
 Random events.
 May be beneficial, harmful or
insignificant.
Natural Selection
Definition
Selection Pressure
Types of Natural Selection
 Directional selection
 Industrial
melanism in Biston betularia
 Disruptive selection
 Distinct
subpopulations
 Stabilizing selection
 Keeps
phenotypes stable for long periods
of time.
Speciation
Reproductive isolation must be
achieved!
Types of Speciation
 Allopatric
isolation – most common type
 Adaptive radiation
 Geographic
 Parapatric
 In
small, local subpopulations (demes)
 Sympatric
 Almost
always in plants
 In same population but do not interbreed
Rates of Evolution
Gradualism vs.
Punctuated Equilibrium
Mosaic Evolution
Same structure is modified
for multiple uses.