Population Dynamics and Genetic Diversity

Variation in Populations

  • Definition of Variation: Refers to the different combinations of alleles or genotypes and phenotypes found within a population.
  • Source of Variation: Arises from random mutations and crossing over during meiosis.
  • Impact on Phenotypes: Genotypes, combined with environmental factors, determine an individual's phenotype.

Genetic Diversity and Population Dynamics

  • Importance of Genetic Diversity:
    • Influential in a population's ability to respond to environmental changes.
    • Populations with low genetic diversity are at greater risk of extinction.
Example: California Condor
  • Threats to Population: Habitat loss, poaching, and lead poisoning have historically threatened condor populations.
  • Population Recovery: Last 27 wild condors were captured for breeding which produced a low genetic diversity population.
  • Current Status: Today's condor population is descended from only 14 birds from captivity, resulting in reduced resilience to environmental changes.
  • Conservation Efforts: Current maintenance of condors through captive breeding programs.

Resilience of Diverse Populations

  • Advantage of Genetic Diversity:
    • Genetically diverse populations have a variety of adaptations that increase resilience.
    • Survival Through Environmental Changes: Some individuals may not be adapted to changes; however, diversity increases the likelihood of having individuals that can adapt
    • Examples of Environmental Pressures: Climate change, habitat loss, and changes in food sources or predation.
Example: Antibiotic Resistance in Bacteria
  • Natural Variation in Bacteria: Some bacteria have natural resistance to antibiotics due to genetic variation.
  • Impact of Antibiotics: Antibiotics kill susceptible bacteria but can leave drug-resistant bacteria behind, which can proliferate and pass on resistance traits.
  • Implication: This demonstrates population resilience since not all individuals in a diverse population succumb to disease outbreaks.

Traits and Survival

  • Adaptive vs. Deleterious Traits:
    • Adaptive Traits: Increase the chances of survival in specific environments (e.g., darker coloration in a dark environment).
    • Deleterious Traits: Traits that reduce survival chances (e.g., lighter coloration in a dark environment).
    • Selective Pressures: The environment determines the advantage of traits, indicating that genes are not inherently good or bad but context-dependent.

Key Takeaways

  • Populations with low genetic diversity are at heightened risk of extinction.
  • Genetically diverse populations can better withstand environmental pressures, as some individuals are likely to have adaptive traits.
  • Selective pressures of the environment critically influence survival outcomes for individuals in a population.