Ecology and Species Interactions Notes

Species Interactions & Community Ecology

Key Concepts

• Ecosystem Interactions: The study of natural gradients in nutrient subsidies and how changes in one ecosystem affect biodiversity in another.
• Pacific Salmon (Oncorhynchus spp.): Influences nutrient loading and riparian plant communities in the Great Bear Rainforest, Canada.
• Nutrient Loading: Salmon contribute to nutrient richness, causing shifts toward nutrient-rich species and decreased diversity.

Ecological Terms

• Primary Producers: Photosynthetic autotrophs (e.g., plants, cyanobacteria) that create energy and oxygen.
• Consumers: Divided into primary (herbivores), secondary, and tertiary consumers (carnivores).
• Decomposers and Detritivores: Organisms that break down dead organic matter and contribute to nutrient recycling.

Population Interactions and Effects

• Types of Interactions (Table 27.1):
  • Predation (+/-): Predators kill prey for nutrients.
  • Parasitism (+/-): Parasites harm hosts for nutrients.
  • Herbivory (+/-): Herbivores consume plants, which may be injured or killed.
  • Competition (-/-): Both species compete for resources, reducing access.
  • Commensalism (+/0): One species benefits; the other is unaffected.
  • Mutualism (+/+): Both species benefit from the interaction.

Symbiosis and Its Types

• Symbiosis: Close ecological association between species, can be categorized into:
  • Parasitism: One benefits at the other's expense (e.g., endoparasites vs. ectoparasites).
  • Commensalism: One benefits, the other is unaffected (e.g., tree frogs for protection).
  • Mutualism: Both benefit (e.g., potato cod and cleaner wrasse).

Competition

• Types of Competition:
  • Intraspecific: Competition within the same species.
  • Interspecific: Competition between different species.
  • Interference Competition: One species harms another.
  • Exploitation Competition: Shared resource used inefficiently by multiple species.

Experimental Research on Interspecific Competition

• Gause's Experiment: Two paramecium species’ interaction exemplifies competitive exclusion principle; one species outcompetes the other.
• Competitive Exclusion Principle: Species cannot coexist indefinitely if they compete for the same resources.

Ecological Niche

• Niche: The role of a species in an ecosystem, including the resources it utilizes.
• Fundamental vs. Realized Niche: Fundamental niche encompasses all conditions under which a species can survive; realized niche includes conditions with competition and predation.

Resource Partitioning & Character Displacement

• Resource Partitioning: Differentiation in the use of resources to avoid direct competition.
• Character Displacement: Species evolve different traits to minimize competition when inhabiting the same environment.

Trophic Structure

• Trophic Levels:
  • Primary Producers: Convert sunlight into chemical energy.
  • Consumers: Include herbivores (primary), and carnivores (secondary, tertiary).
  • Decomposers: Break down dead matter, recycling nutrients in ecosystems.

Food Chains and Webs

• Illustration of Trophic Structure: Shows relationships within communities; complex food webs indicate more ecological stability.

Ecological Succession

• Types of Succession:
  • Primary Succession: Occurs in lifeless areas (e.g., post-volcanic activity).
  • Secondary Succession: Follows disruptions like fire, where soil and existing life may still be present.

Examples of Succession

• Primary Succession After Glacial Retreat: Lichens and mosses as pioneers, leading to eventual establishment of larger plants like conifers.
• Animal Succession in Ecosystems: Various bird species appearing as vegetation changes over time.

Conclusion

• Understanding species interactions, competition, community dynamics, and ecological principles is crucial for conserving biodiversity and managing ecosystems effectively.