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IB ESS HL 2.1.28 Hl Fundamental and Realized Niches Questions

Prepare for IB ESS HL 2.1.28 by explaining how competition, resources, habitat and adaptations distinguish a species’ fundamental niche from its realized niche.

Syllabus
First assessment 2026
Course
ESS HL
Level
HL

Exam points

  • explain a realized niche as actual conditions shaped by competition, resource limits, habitat use and adaptation
  • compare realized niches using differences in habitat, food, nesting sites and elevation from species evidence
  • apply competition, sociality, habitat flexibility and resource breadth to explain different population recovery

IB ESS HL 2.1.28 Hl Fundamental and Realized Niches Questions question 1

[Maximum number: 3]
Figure 9(b): Round goby (Neogobius melanostomus)

Figure A:Round goby (Neogobius melanostomus)

Figure 9(b): Mottled sculpin (Cottus bairdii)

Figure B:Mottled sculpin (Cottus bairdii)

Figure:Fact file on the round goby (Neogobius melanostomus)

• An invasive species from Asia.
• First discovered in the St Lawrence River in 1990.
• Females lay eggs three times a year; up to 5000 eggs at a time.
• Young fish mature quickly.
• Can eat up to 4000 eggs of other fish in 15 minutes.
• Aggressively defend the best egg-laying sites, out-competing the native mottled sculpin (Cottus bairdii).
• Eat invasive zebra mussels.
• Eaten by native fish, such as lake trout and yellow perch.

With reference to Figure 9(a), explain why the realized niche of the mottled sculpin has changed in recent years.

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