lesson_9.2_changes_in_species

  • Unique Species Populations: Islands often host unique species populations due to isolation and adaptation to different environmental conditions.

  • Evidence of Change: Environmental changes can lead to the emergence of new species and extinction of others.

  • Silversword Alliance: Example of over 30 related Hawaiian plant species descended from one tarweed species. Showcases remarkable diversity despite close relation.

  • Mechanisms of Speciation:

    • Definition: Speciation is the rise of new species from an existing species, driven by genetic and environmental changes.
    • Experiment with Fruit Flies: Divided into maltose vs. starch diets; led to distinct mating preferences and potential reproductive isolation over generations.

  • Reproductive Isolation: Occurs when gene flow is interrupted between populations, leading to divergence and adaptations that prevent successful mating.

    • Physical Isolation Example: Isthmus of Panama caused speciation in snapping shrimp due to separation and divergent adaptation to different environments.

  • Behavioral & Temporal Isolation:

    • Example: Eastern and western meadowlarks have different mating songs, leading to behavioral isolation.
    • Red-legged and yellow-legged frogs have different mating seasons, causing temporal isolation.

  • Adaptive Radiation:

    • Definition: Rapid speciation from one ancestor into diverse forms, typically under reduced competition or new niches (e.g., Darwin’s finches in the Galápagos Islands).

  • Expansion of Species: Climate change and human activity can facilitate range expansions for certain species, like the barred owl moving west due to habitat changes.

    • Hybridization: As species expand into new territories, they may hybridize, potentially leading to the loss of distinct species.

  • Extinction:

    • Definition: Extinction occurs when a species cannot adapt to environmental changes.
    • Background vs. Mass Extinction: Background extinctions happen continuously, while mass extinctions can wipe out many species suddenly due to catastrophic events.
    • Current Threats: Human-induced changes are causing a sixth mass extinction with accelerated rates.

  • Coevolution: Species may evolve together through mutual interactions or competitive pressures, leading to adaptations that benefit one or both.

    • Example: The relationship between acacia trees and stinging ants shows mutual benefits and evolutionary adaptations.

  • Patterns of Speciation: Include gradualism