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.