Lecture Topic # 7 Evolutionary Processes / Microevolution:

I. Present Research Directions

-Documenting HOW evolution occurs, not whether it has occurred

II. Where does Evol. occur?

A. Artificial selection example

- local population

B. Structure in species

Example: Clematis fremontii

Evolution occurs in demes or interbreeding populations

III. Variation in populations

A. Environment

B. Genetic Variation

1. segregation of alleles and

2. independent assortment of loci

C. Observation

1. many traits show bell-shaped distribution

2. envir. and genetic variation

3. many loci segregating alleles

IV. Tenet of NeoDarwinian Theory

A. Evolution = change in gene frequency in a population through time/ across generations (microevolution)

1. Processes

a. mutation

b. gene flow or migration

c. genetic drift or random fluctuation of gene frequencies

d. natural selection

B. Macroevolution

1. Continuation of microevolution

2. processes acting within populations leads to:

Macroevolution = large changes; differences between species, genera, families, etc.

V. Population Genetics

A. Importance

1. need to understand how gene frequencies change in populations

2. thus need a theory which can describe transmission of genes on a population level

3. analogous to Mendelian genetics (parent --> offspring)

VI. Take Home Message

A. Evolution occurs at the population level, or deme

B. Genetic variation high within populations

C. Change in gene frequencies within a population over time = Evolution

D. Change occurs via: mutation, gene flow, drift and/or natural selection

E. Changes over longterm = Macroevolution

F. Need a theory that describes changes in gene frequencies at level of popln = Population Genetics

Next: Examination of Hardy Weinberg Equilibrium

B. Review:

1. Meiosis

Aa

A ...............a

A ..........A......... a............ a

(these dots don't mean anything, they're just spacers for the web page program)

50% of gametes: A

50% of gametes: a

Aa (male) x Aa (female)

Eggs:

1/2 A

1/2 a

sperm:

1/2 A

1/2 a

1/4 of progeny = AA

1/4 aa

1/2 Aa

Population????

AA AA AA AA AA

AA Aa Aa aa aa Aa

Aa Aa AA AA Aa Aa

Aa AA AA

10 AA, 8 Aa, 2 aa = 28 copies of A

12 a

2. Maintenance of variation

a. Blending inheritance

b. Loss of recessives

c. High mutation rates ??