APES — Unit 01 Module 01

🌍 Introduction to Ecosystems – Study Notes

🔑 Key Concepts

• Ecosystem: A community of interacting biotic (living) and abiotic (non-living) components.

• Ecosystems vary in size and are connected through the movement of organisms, energy, and nutrients.

📍 1-1: Defining Ecosystem Boundaries

🔸 Ecosystem boundaries:

• Can be defined scientifically (biotic/abiotic features) or artificially (e.g., national park borders).

• Examples:

  • Well-defined: Caves, lakes, ponds.

  • Poorly defined: Forests, valleys.

🔸 Abiotic factors:

• Temperature, rainfall, humidity, soil type, water availability.

🔸 Biotic factors:

• Plants, animals, fungi, bacteria interacting in complex ways.

🔸 Boundary Concepts:

• Boundaries are sometimes subjective.

• Greater Yellowstone Ecosystem example shows the need to consider broader ecological interactions.

🔸 Biosphere:

• The 20-km (12-mile) thick layer where life exists on Earth.

🥊 1-2: Competition for Limited Resources

🔸 Competition:

• Definition: Struggle between individuals/species for the same limited resource.

• Competitive Exclusion Principle:

  • Two species cannot coexist if they compete for the same resource in the same niche.

🔸 Resource Partitioning:

• Definition: Species evolve to minimize competition by using resources differently.

Types of Resource Partitioning:

1. Temporal – Using resources at different times (e.g., wolves and coyotes hunting at different times).

2. Spatial – Using different habitats (e.g., plants with shallow vs. deep roots).

3. Morphological – Evolving different traits (e.g., beak sizes in Galápagos finches).

🐾 1-3: Species Interactions Involving Consumption

🔸 Predation:

• One organism kills and eats another.

• Includes classic predators and parasitoids (e.g., wasps laying eggs inside hosts).

🔸 Prey Defenses:

• Behavioral: Hiding, fleeing.

• Morphological: Camouflage, spines.

• Chemical: Toxins, distasteful compounds.

• Mimicry: Non-toxic species mimicking toxic ones.

🔸 Parasitism:

• One organism lives on/in a host, consuming it but rarely killing it.

• Pathogens: Parasites that cause disease (e.g., viruses, bacteria, protists).

🔸 Herbivory:

• Animals consume producers (plants/algae).

• Example: Gazelles, sea urchins, deer.

• Plant defenses: Spines, toxic chemicals.

🤝 1-4: Positive or Neutral Species Interactions

🔸 Mutualism:

• Both species benefit.

• Examples:

  • Pollinators and plants.

  • Acacia trees and ants.

  • Corals and algae.

  • Lichens (fungus + algae/bacteria).

🔸 Commensalism:

• One species benefits, the other is unaffected.

• Examples:

  • Birds nesting in trees.

  • Fish hiding in coral reefs.

🌱 1-5: Invasive Species as Novel Interactions

🔸 Native vs. Exotic Species:

• Native: Found in historical range.

• Exotic (Alien): Introduced to a new area.

🔸 Invasive Species:

• Exotic species that spread rapidly and harm native ecosystems.

• Why they spread: Lack of natural predators or competitors.

🔸 Examples of Invasive Species:

• Rats on islands → bird extinctions.

• Zebra mussels in lakes.

• Kudzu vines in the U.S.

📊 Summary Table of Species Interactions

✅ Recap: Key Takeaways

• Ecosystem boundaries are not always clear but are critical for studying interactions.

• Species compete or cooperate in diverse and evolving ways.

• Human activity often introduces new species, creating unexpected and sometimes harmful interactions.

• Understanding species interactions is essential for conservation and managing biodiversity.