Microevolution revision

Microevolution Revision Session Notes

  • Purpose of the Session: Review microevolution concepts, answer questions, discuss the upcoming test, and share reminders for future classes.

Hardy-Weinberg Equilibrium vs. Nonequilibrium

  • Concept:

    • Hardy-Weinberg Equilibrium: Indicates no evolution occurring; allele frequencies remain constant.

    • Nonequilibrium: Indicates evolutionary processes at play; allele frequencies change.

    • Importance: Allows biologists to determine if a population is evolving by checking if it is in equilibrium or not.

  • Assumptions of Hardy-Weinberg:

    • No migration, random mating, no genetic drift, no mutation, no selection.

    • Violation of one or more assumptions leads to an investigation into potential evolutionary forces acting on the population.

Balancing Selection vs. Natural Selection

  • Definition:

    • Balancing selection: A form of natural selection where both alleles at a locus are maintained due to their beneficial roles in the population.

    • Discussed as part of natural selection along with positive and negative selection.

  • Negative Frequency Dependent Selection:

    • Increases diversity as rare alleles become favored, impacting gene flow.

    • Gene flow can introduce or maintain different alleles in populations, affecting selection dynamics.

Multiple Types of Natural Selection on Alleles

  • Consideration: Alleles can be subject to different types of selection over time, but likely cannot experience opposing types (e.g., neither positive nor negative selection) concurrently.

Gene Flow Equation and Population Dynamics

  • Equation Insight:

    • Changes in allele frequencies due to migration captured by the equation: Change in p = (p migrant - p focal) x migration rate.

    • Represents expected changes in the next generation based on current allele frequencies and migrant contribution.

  • Migration Duration:

    • The equation does not specify how long migration has occurred, only its immediate impact on allele frequency.

Responses of Native Species to Invasive Species

  • Understanding FST:

    • FST measures genetic differentiation between populations; invasive species impact could either decrease or increase FST depending on gene flow dynamics and the ability of native populations to exchange genes.

    • Impact of Invasive Species:

      • Can reduce genetic diversity in native species.

      • Can isolate populations leading to increased FST if gene exchange is severely limited.

  • Microevolution Evidence:

    • Native species can adapt to the presence of invasive species, altering traits or behaviors. Examples include development of new defenses, changing food sources, or creating new habitats.

Upcoming Test Information

  • Date and Format:

    • Test scheduled for next Friday, 11 AM, lasting 50 minutes with 30 marks total across 15 questions (multi-choice and short answers).

  • Preparation Tips:

    • Review all course material, labs covered, and ensure understanding of key concepts before the test.

    • Example short answer questions are provided to practice the expectations.

Laboratory and Class Reminders

  • No Classes:

    • Classes on Monday and Wednesday next week are canceled for study purposes.

  • Lab 3:

    • Will occur in MSB 022, an important change in location. Ensure to familiarize yourself with directions to avoid confusion.

  • Future Structure:

    • After test week, different instructors will pick up from where the course left off, covering macroevolution and other advanced topics.

General Advice

  • Approach to Questions:

    • Read questions carefully; break them down into parts and ensure all aspects are addressed before answering.

  • Check Moodle:

    • Always verify lecture schedules on Moodle to stay updated on any changes in the timetable.