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IB ESS HL 2.5.11 Hl R and K Strategist Species Questions

Classify r- and K-strategists from life-history evidence and explain why r-strategists colonise pioneer communities effectively.

Syllabus
First assessment 2026
Course
ESS HL
Level
HL

Exam points

  • classify a named species as an r- or K-strategist from offspring number, maturity, lifespan, parental care, growth rate or survivorship evidence
  • explain why r-strategists are suited to pioneer communities by linking rapid reproduction, dispersal, colonisation and tolerance of harsh or unstable conditions

IB ESS HL 2.5.11 Hl R and K Strategist Species Questions question 1

[Maximum number: 1]
Mottled sculpin

FigureA:Round goby

Mottled sculpin

FigureB:Mottled sculpin

Figure:Fact file on the round goby

- Figure: Mottled sculpin: Fact file on the round goby
- Round goby is invasive, first discovered in the St Lawrence River in 1990.
- Females lay eggs three times a year, up to 5000 eggs each time, and young fish mature quickly.
- Round goby can eat up to 4000 eggs of other fish in 15 minutes, defend egg-laying sites, out-compete mottled sculpin, eat zebra mussels, and are eaten by native fish.

Using Figures: Mottled sculpin and Pictures of the round goby and mottled sculpin, identify one feature of the round goby that shows it is an r-selected species.

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