Lecture # 23

  An ideal population is genetically stable. 

The Hardy-Weinberg Principle 

1. No mutations occur. 

2. The population is large. 

genetic drift 

3. There is no selection of mates on the basis of
genotype.

4. Individuals of each genotype have equal
probabilities of surviving, mating and
producing offspring.

5. No migrations occur. 

Mutations are the raw material for evolution. 

The gene pool is all of the genes in all of the
organisms in a population. 

The gene pool shifts. 

1. Inorganic evolution 

      cosmology 

      Big Bang Theory 

2. Organic evolution 

Fossils
1. Solid body part
2. Impression
3. Petrification
4. Mold
5. Cast 

Reconstruction 

Catastrophism 

Georges Cuvier (1769-1832) 

Uniformitarianism 

Geologic Forces
1. erosion
2. sedimentation
3. disruption
4. uplift 

Geologic time is extremely long. 

Charles Lyell (1797-1875) 

Lamarckism

Jean Baptiste de Lamarck (1744-1829) 

Use and Disuse 

The Inheritance of Acquired Characteristics 

Natural Selection

Charles Darwin (1809-1882) 

The Beagle (1831-1836) 

flora

fauna 

“On the Origin of Species by Means
of Natural Selection” 1859 

Alfred Russell Wallace (1823-1913)   

Observations:
1. Variation is characteristic of every
group of organisms.   

2. More organisms are born than survive.   

Hypotheses:
1. The Struggle for Survival 

Competition for food and/or space 

Thomas Malthus “On Population”  1798   

2. Survival of the Fittest   

3. Inheritance of Advantageous Traits   

The population is the basic unit upon which
the forces of evolution operate.   

A species is a group of similar organisms that
actually or potentially have the ability to
interbreed. 

A population is a group of organisms of the same
species that are actually living and breeding
together. 

balanced polymorphism   

adaptive radiation 

divergent evolution   

convergent evolution