IB ESS HL 2.1.15 Estimating Population Abundance Question Bank
Use sampling data to estimate abundance and interpret uncertainty in ecological populations.
- Syllabus
- First assessment 2026
- Course
- ESS HL
- Level
- HL
Exam points
- identify the population or ecosystem process in the evidence
- apply the correct interaction, growth or sampling model
- justify the conclusion using limiting factors, assumptions and uncertainty
2.1.15—Estimating population abundance question 1
[Maximum number: 9]
To what extent can the practical strategies for obtaining data for a pyramid of numbers be made reliable?
The following guide for using the markbands suggests certain features that may be offered in responses. The five headings coincide with the criteria in each of the markbands (although ESS terminology has been conflated with "understanding concepts"). This guide simply provides some possible inclusions and should not be seen as requisite or comprehensive. It outlines the kind of elements to look for when deciding on the appropriate markband and the specific mark within that band.
Answers may demonstrate:
- understanding concepts \& terminology of reliability in sampling; quadrats (including number, size, positioning, species distribution); transects; aerial photographs; traps; nets; Lincoln index; mark/release/recapture (including issues of marking technique, trap-happy and trap shy phenomena, time interval); aquatic sampling use of dragnets, kick samples); camera traps (difficulty of extrapolation); general sampling issues (including repetition; extrapolation; seasonal variation; randomisation); total census; abundance; bias; scientific expertise; etc.
- breadth in addressing and linking different sampling methodologies with varying degree of reliability for a range of different sessile and motile populations in a range of different habitats;
- examples of named sampling methods appropriate for different named species etc.
- balanced analysis evaluating extent to which sampling method can be executed to produce reliable data; practical issues hindering application of methodologies in the field.
- a conclusion that is consistent with, and supported by analysis and examples given e.g. All methods of sampling inevitably involve a degree of inaccuracy compared with a total census, but they can always be made more reliable by repeated executions.
Please see markbands on page 18
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