Tolerance and Ecological Niche

Introduction to topic: Tolerance and ecological niche.
Example of barnacles:
- They are filter feeders, using their gills to capture food and breathe underwater.
- Require submersion for respiration and protection from predators.
- Relies on secure surfaces (e.g., rocks) to thrive.
- Preference for low tide regions for better access to food due to constant submersion.

Question raised: Why don't barnacles inhabit the entire rocky shore?
Importance of tolerance and niche in understanding barnacle distribution.
Every species has a range of tolerance - the conditions they can survive under.
- Example factors: pH, temperature, light intensity, and air exposure.
Optimum range: Ideal conditions where species thrive (e.g., specific pH or temperature).
- Movement out of this zone leads to physiological stress - in this state, organisms struggle, affecting their survival and reproduction.

Visual representation: bell curve for organism abundance in relation to environmental factors.
- Organisms thrive in optimum range, while numbers drop in physiological stress zone and fall to zero in the zone of death.
Example: Flies in winter - fewer observed due to temperature dropping below their optimum range (15-23 degrees Celsius).
Physiological stress in colder temperatures leads to reduced reproductive rates.

Barnacles can tolerate wide air exposure, allowing some to survive in high tide zones.
Different species have varying tolerances; e.g., snails prefer lower air exposure.
Every organism has upper and lower tolerance ranges affecting their distribution on the rocky shore.

Definition of niche: An organism's way of life, including habitat, resource acquisition, and biotic/abiotic interactions.
Fundamental niche: Ideal theoretical conditions for a species.
Realized niche: Actual living conditions considering competition and other species.

Two barnacle species: red (wide fundamental niche) and blue (narrow niche).
Scenario: If red barnacles are alone, they could occupy the entire rocky shore, while blue barnacles have limited range due to their tolerance levels.

Competition's role in niche differentiation:
- If red barnacles were removed, they could expand due to high tolerance.
- Blue barnacles occupy a niche that red cannot reach without competition.

Gore's Principle:
- Overlap in niches leads to competition; one organism outcompetes the other.
Possible outcomes: One species could thrive while the other is eliminated or forced to move.
Example: The adaptive strengths of each species determine their success in different tidal zones.

Summary: Importance of understanding tolerance and niche to excel academically.
Encourage students to engage in discussions about these concepts and ask questions for clarification.
Invitation for collaboration in tackling uncertainties about ecological niches and tolerance ranges in class activities.