Ecosystem Structure and Biodiversity Notes

ECOSYSTEM STRUCTURE, PATTERNS IN BIODIVERSITY AND LAND SUCCESSION

KEYSTONE SPECIES

  • Definition: Species that other species in an ecosystem depend on heavily.
  • Impact: Removal of a keystone species leads to drastic changes in ecosystem structure.

PACIFIC COAST KELP BED

  • Historical Context: Kelp ecosystems in Alaska collapsed in the 1990s, raising concerns about ecological balance.

IMPORTANCE OF KELP FOREST

  • Function: Serves as a critical nursery for fish, supporting biodiversity and overall marine life.

FOOD WEB DYNAMICS

  • Sea Urchins: Primary grazers of kelp.
  • Sea Otters: Predators of sea urchins, crucial for kelp forest health.
  • Sea Lions: Eat fish that rely on kelp environments.
  • Orcas: Apex predators feeding on sea lions and potentially otters.

IMPACT OF INCREASED FISHING PRESSURE

  • Result: More fishing boats lead to a potential decline in fish populations and disruptions in the food web.
  • Predictive Model: Assess effects with arrows indicating increase (↑), no change (↔), decrease (↓), or uncertainty (?).

COMBINED IMPACTS ON KELP ECOSYSTEMS

  • Stressors:
    • Increased Fishing Pressure
    • Sea Star Wasting Disease
    • Elevated Temperatures

CONSEQUENCES OF OVERFISHING

  • Overview: Climate warming and other human impacts lead to severe declines in species diversity and abundance.
  • Statistical Impacts:
    • Top predators decreased by 90%.
    • Primary predators down 100-fold or more.
    • Zooplankton declines by 80%.
    • 50% decrease in species diversity over 50 years.

EXTREMOPHILES

  • Definition: Organisms thriving in extreme physical or geochemical conditions.
  • Types of Extremes & Examples:
    • High Temperature: Pyrolobus fumarii
    • Low Temperature: Synechococcus lividus
    • High Pressure: Mariana Trench organisms
    • High Salinity: Halobacteriaceae
    • UV Radiation: Deinococcus radiodurans

TARDIGRADES

  • Remarkable Resilience: Known as the toughest creatures on Earth, capable of surviving extreme environments.
  • Role: Act as pioneer species, colonizing new habitats.

BIODIVERSITY

  • Definition: The variety and variability of life on Earth, encompassing all species and genetic differences.
  • Greatest Threats:
    • Overexploitation
    • Habitat Destruction
    • Invasive Species
    • Pollution
    • Global Warming

PATTERNS IN BIODIVERSITY

  • Species Richness: Number of different species in an ecosystem.
  • Factors Influencing Species Richness on Islands:
    • Size of the island
    • Distance from other populations
    • Isolation duration
    • Environmental factors (currents, winds)

HABITAT FRAGMENTATION

  • Impacts: Fragmented habitats can have severe effects on native populations, leading to decreased biodiversity.
  • Example: Effects of forest fragmentation in England.

HABITAT DESTRUCTION

  • Overview of Tropical Rainforests:
    • Cover only 6% of Earth but host 50% of all species.
    • Deforestation causes significant species loss due to farming, logging, and cattle ranching.

DISTURBANCE & DIVERSITY

  • Role of Disturbances: Moderate disturbances can increase species diversity by creating new niches.
  • Secondary Succession: Faster recovery in previously disturbed areas where soil remains.

INTERMEDIATE DISTURBANCE HYPOTHESIS

  • Insights: Moderate disturbance levels promote higher species diversity compared to low or high disturbance levels.

RECOVERY EXAMPLES

  • Primary Succession: Observed in newly created land, such as after volcanic eruptions in Hawaii.
  • Secondary Succession: Analyzed through the recovery of ecosystems post-disturbance, with particular reference to Mt. St. Helens.

MODERN VIEW OF NATURE

  • Concept: Nature is characterized by constant flux and change, with disturbance being a regulatory factor rather than a state.