BIO 221 CM 12 - L

Cemetery Demography Review

  • Focused on contrasting lifespans between two birth cohorts and males vs. females.

  • No significant lifespan differences observed between cohorts for all individuals, females, or males.

  • Surprising finding: no lifespan differences between females and males in both cohorts.

  • Possible reasons include:

    • Sample may not demonstrate clear signals.

    • Caution against blaming methodology for results.

    • Potential sample errors due to duplicate entries in data.

    • Legibility issues with headstone engravings from earlier cohorts.

Monte Carlo Tera Competition Model and Niche Concepts

  • Introduced fundamental niche vs. realized niche:

    • Fundamental Niche: Potential conditions for survival and reproduction.

    • Realized Niche: Actual conditions where the organism is found.

    • Example: Red-winged blackbirds' nesting in marshes, limited by competition with yellow-headed blackbirds.

Empirical Outcomes of Competition

Key Concepts:

  • Competition can lead to varied ecological outcomes:

    • Spatial Exclusion: One species excludes another from a habitat.

    • Temporal Exclusion: Species segregate by time of activity.

    • Resource Partitioning: Species evolve to utilize different resources to minimize competition.

    • Character Displacement: Phenotype differences occur between species in sympatric vs. allopatric settings.

Examples of Outcomes:

Spatial Exclusion

  • Barnacles Example:

    • Cohabitants: Semibalanus (more competitive) and Chthamalus (less competitive).

    • Semibalanus occupies lower intertidal zones due to superior competition.

    • Chthamalus exists in upper zones where it is less competitive.

Temporal Exclusion

  • Rodent Study:

    • Species Studied: Clomys carinus (Nocturnal) vs. Rosatus (Diurnal).

    • Behavior: Clomys captures peak during the night; Rosatus primarily active during the day.

    • Lab Findings: Clomys displays nocturnal behavior in absence of competition.

Resource Partitioning

  • Sunfish Species:

    • Species: Bluegill and Pumpkin Seed.

    • Examined dietary composition indicates specialization in resources.

    • Example: Bluegills consume more vegetation-dwelling prey; Pumpkin Seeds rely on plankton (less overlap in dietary habits).

Character Displacement

  • Darwin’s Finches:

    • Based on beak size differentiation in areas of sympatry vs. allopatry.

    • Sympatric sizes show separation without overlap due to competitive pressures.

  • Spadefoot Toads:

    • Tadpole morphology changes based on diet; omnivorous vs. carnivorous conditions vary by population overlap.

    • Sympatric populations exhibit more carnivore morphology due to competitive dynamics.

Conclusion and Future Topics

  • Upcoming topics: predation and parasitism.

  • Discussion will condense empirical and theoretical insights.

  • Crayfish labs will be returned for review.