Introduction
The process of evolution results in genetic differences among populations and species over time and space.
Evolutionary Mechanisms
1. Mutation
Instantaneous change in genetic material (ie inherited)
Many types (gene to chromosome)
Have no to major effects on the phenotyp
Rare events (ca. 1/100,000 cell replications)
SIGNIFICANCE?
2. Migration of genes
Adult plants
don't move, but pollen
and seeds do
Wind-dispersed seeds: e.g., Betula, Alnus, Salix, Populus, Tsuga,
etc.
Animal-dispersed seeds: e.g., Quercus, Castanea, Umbellularia,
etc.
SIGNIFICANCE?
3. Chance events
Genetic
drift: rare genes disappearin small populations
Founder affect:
founding population has an unusual gene frequency
SIGNIFICANCE?
4. Natural selection
Genetic make
up of population changes because some genes are passed down at faster rate
than others because they improve the growth, survival, reproduction of individuals
that posses them.
Adaptation:
advantageous trait(s) for a particular environment.
NOTE: Very different traits can be an advantage to the same environment.
Deep snow: Drooping foliage of Chamaecyparis nootkatensis,
and short branches of Abies lasiocarpa;
fire: root suckering in Populus tremuloides and thick bark
of Pinus ponderosa and Pseudotsuga menziesii
SIGNIFICANCE?