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IB Biology HL B4.1.4 Range of Tolerance of Limiting Factor Questions

Explore stress, optimum and intolerance responses across abiotic gradients, then evaluate whether pH or another limiting factor explains a species’ distribution in IB Biology HL B4.1.4.

Syllabus
First assessment 2025
Course
Biology HL
Level
HL

Exam points

  • Deduce a species’ limiting-factor response over time or across a gradient, identifying stress, optimum and intolerance regions from population or range data.
  • Evaluate pH or other abiotic evidence against a hypothesis about whether water chemistry limits a species’ distribution or range.

IB Biology HL B4.1.4 Range of Tolerance of Limiting Factor Questions question 1

[Maximum number: 2]

The model describes the fundamental and realized niches of a species of microscopic marine arthropod in the Northern hemisphere with respect to two different factors ( X and Y ). The abundance of the species is shown over twelve months. The fundamental niche is separated into five zones ranging from critical to optimal conditions. The population of the species in its realized niche each month is represented by an oval. The size of each oval shows the population abundance.

Figure for Question IB Biology HL B4.1.4 Range of Tolerance of Limiting Factor Questions question 1 — IB Biology HL

Outline how factor Y affects the species from January to April.

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