Lecture Notes: Ecological Niches (B 4.2) - Nutritional Niches

Definition of Ecological Niche

• Ecological Niche: The role a species plays in its ecosystem.
  • Dependent Factors:
    • Diet: What it eats and how it obtains food.
    • Zone of Tolerance: Determines the habitat a species can use.
    • Interactions: How it interacts with other species.

Key Terminology

• Obligate: Must occur, no choice (e.g., obligate aerobes).
• Facultative: Has a choice or flexibility.
• Aerobic: Requires oxygen.
• Anaerobic: Occurs without oxygen.

Nutritional Modes and Examples

Obligate Aerobes

• Organisms that must have oxygen.
• Includes all animals and plants.

Obligate Anaerobes

• Cannot be exposed to oxygen.
• Live in anoxic environments.
• Examples: Bacteria causing tetanus, methanogenic archebacteria.

Facultative Anaerobes

• Can live in both aerobic and anaerobic environments.
• Examples: Yeast, E. coli.

Autotrophs

• Definition: Produce their own food using photosynthesis.
• Also known as Primary Producers in ecosystems.
• Include plants, algae, and some photosynthetic bacteria.
• Photosynthesis: Converts solar energy to chemical energy (carbohydrates).

Heterotrophs

• Definition: Must consume food (consumers).
• Holozoic Nutrition: Consumption of whole food pieces, internal digestion.
  • Processes:
    • Ingestion: Eating.
    • Digestion: Chemical breakdown into smaller molecules.
    • Absorption: Uptake of molecules into bloodstream.
    • Assimilation: Incorporation into cells and tissues.
    • Egestion: Expulsion of undigested waste.

Mixotrophs

• Can obtain nutrients via both autotrophic and heterotrophic means.
• Types:
  • Obligate Mixotrophs: Must use both methods.
  • Facultative Mixotrophs: Chooses method based on environment.

Saprotrophs

• Definition: Decomposers with external digestion.
• Mechanism: Release enzymes externally to digest matter, then absorb nutrients.
• Common in fungi and some bacteria.

Archaea Nutritional Modes

• Part of the three domains of life.
• Modes:
  • Heterotrophic: Consumes organic material.
  • Phototrophic: Uses light energy (photosynthesis).
  • Chemotrophic: Oxidizes inorganic chemicals.

Summary

• Ecological niches define how organisms survive and interact in ecosystems.
• Nutritional niches illustrate the diversity of food acquisition strategies across species.
• Key groups like mixotrophs and saprotrophs highlight unique methods of obtaining energy and nutrients.