Organism Tolerance and Niche Quiz

Organism Tolerance and Abiotic Factors

• Organisms need specific abiotic factors (e.g., temperature, sunlight) to survive, reproduce, and develop.
• Organism tolerance describes its ability to withstand variations in abiotic factors.
• Each organism has a specific tolerance range for each abiotic factor.
• Optimal conditions fall within an organism's tolerance range, promoting survival and reproduction.
• Stressful conditions are near the tolerance limits; survival is possible but reproduction may be reduced.
• Extreme conditions exceed tolerance limits, resulting in organism death.
• An abiotic factor's variation creates a bell-shaped curve. Optimal conditions are centered, and survival decreases towards the tails (stressful conditions), and ceases beyond the tolerance limits.

Fundamental and Realized Niches

• An organism's fundamental niche encompasses all environmental conditions where it could survive, based on its tolerance ranges for abiotic factors.
• Competition, predation, and resource availability can restrict an organism's use of its environment.
• This leads to a realized niche, representing the actual portion of the fundamental niche the organism occupies.
• The realized niche is a reduced subset of the fundamental niche, often due to interactions with other species.
• For example, predation risk or competition at higher dissolved oxygen levels or temperatures might limit the realized niche.

Specialist and Generalist Species

• Specialist species have narrow niches, with limited tolerance ranges for abiotic factors, specific resource requirements, and a restricted geographic range. Examples include the Kirtland's warbler.
• Generalist species have broad niches, with wide tolerance ranges, use various resources, and possess a wide geographic distribution. Examples include raccoons.
• An organism's niche may change during its lifespan. For example caterpillars feed on plants and butterflies feed on nectar.