Lecture Notes on Genetic Selection and Biogeography

Genetic Selection and Equilibrium

Stable Equilibrium

• Stable Equilibrium Example: Sickle cell anemia showing heterozygote advantage
• Heterozygote Advantage: Maintains relative performance of alleles.

Gene Selection and Variation

• Negative Frequency Dependent Selection: Maintains variation by increasing rare allele's genetic risk.

Unstable Equilibrium

• Heterozygote Disadvantage: Results in unstable equilibrium. Allele becomes fixed based on initial frequencies.

Genetic Drift

• Small Population Effects: In absence of mutation and selection, genetic drift occurs leading to fixation of an allele.

Phenotypic Selection

Disruptive Selection

• Phenotypic Selection: Increases range of trait variability by selecting extremes.

Quantitative Traits

• Description: Focus on far ends of distribution.

Biogeography and Species Distribution

Endemic Species

• Definition: Species restricted to a specific location, not found elsewhere.

Biogeographic Realms

• Characteristics: Do not share species between realms, different orders, and families.
• Examples: Lady slipper orchids, koalas, alligators, and starlings illustrate distributions.

Dispersal and Vicariance

• Panama Land Bridge: Example of jump dispersal leading to range expansion.
• Vicariance: Suggests similar historical geological and climatic influences on species divergence.

Genetic Concepts

Coalescence

• Definition: Concept that traces current population to a single ancestor.

Heterozygosity

• Autozygosity: Individual with alleles identical by descent.

Evolutionary Processes

Natural Selection vs. Genetic Drift

• Adaptation: Results from natural selection, not genetic drift.
• Genetic Drift: Random process, weaker evolutionary force than natural selection.

Speciation

• Vicarious: Often drives speciation, closely linked to extinction.

Phylogenetic Analysis

• Child Dispersal: Evidence from phylogenetic analysis supports it.

Exam Questions

• Review: Discussed various genetic selection and biogeography examples as basis for exam questions.

Additional Points

• Self-Breeding: Decreases heterozygosity by half, not by one quarter.
• Kingdom Classification: True that kingdoms are classified by names.

Note: Clarification and further study needed on specific genetic selection examples and biogeographic evidence.