VII. Macroevolution
Resources:
 Bozeman—
 Speciation
http://www.bozemanscience.com/speciation
 Campbell Textbook—
 Ch. 24
VII. Macroevolution (Explained by
Evolutionary Theory)
A.Definition– evolutionary change above the
species level
B.Species
i. Definition– group of organisms that produce
freely in nature and produce fertile offspring
VII. Macroevolution
ii.
Why organisms don’t reproduce
1. Prezygotic Barriers– before zygote
a. Temporal Isolation– timing of
reproduction
b. Habitat Isolation– location provides no
contact
c. Behavioral Isolation– behaviors wrong
d. Mechanical Isolation– parts don’t match
e. Gametic Isolation– egg/sperm won’t
fertilize
VII. Macroevolution
2. Postzygotic Barriers– after
fertilization/zygote
a. Hybrid Inviability– zygote won’t mature
b. Hybrid Sterility– non-fxn gametes in
offspring
c. Hybrid Breakdown– weak/infertile
offspring– reproduction not prolific
enough to be viable
VII. Macroevolution
C.Allopatric Speciation– Geographic
Isolation
 Population separated geographically
 New environment in new area (open niches)
 Enough change that no longer reproduce with
original population
VII. Macroevolution
D.Sympatric Speciation–
Genetic/Reproduction Isolation
 Example: Plants that are polyploidy (extra set
of chromosomes) are genetically different and
can’t reproduce with parental population
VII. Macroevolution
VII. Macroevolution
E. Patterns of Speciation–
i.
Divergent
ii. Convergent
iii. Adaptive Radiation
F. Models of Evolution
i. Gradual– slow and steady– describes relatively
short periods of time in earth’s history
ii. Punctual– abrupt changes– fits geological evidence
and best describes long periods of time
VII. Macroevolution
VII. Macroevolution
E. Extinction—90% of all known organisms
are now extinct
 Many extinct due to single events
 Some mass extinction events
Why– No potential to migrate; Lack of diversity
within population; Small population size; Rapid
environmental change
**Extinction is the rule!**