IB Biology: Biodiversity & Conservation FAQ

You need to define biodiversity at genetic, species and ecosystem levels, explain causes of biodiversity loss (habitat destruction, invasive species, climate change, overharvesting), and describe conservation strategies including in-situ and ex-situ methods. This sits under sub-topic C4.2 in the current Biology guide, first examined 2025.

Yes, if you're HL — Simpson's reciprocal index is an HL-only calculation measuring species diversity in a community, using the formula D = N(N-1) / Σn(n-1), where N is total organisms and n is organisms of each species. SL students only need to interpret given values, not calculate them from raw data.

In-situ conservation protects species within their natural habitat — national parks, marine reserves, wildlife corridors. Ex-situ conservation moves species out of their habitat — zoos, botanical gardens, seed banks, captive breeding programmes. IB examiners expect you to evaluate both, not just define them, usually with a named real-world example.

The current guide lists habitat destruction, climate change, invasive alien species, pollution and overharvesting as the main drivers examiners expect you to discuss. You should be able to link each cause to a specific mechanism — for instance, how ocean acidification from rising CO2 reduces coral reef biodiversity through impaired calcification.

CITES (the Convention on International Trade in Endangered Species) is an international agreement regulating trade in endangered plants and animals through species listings on three appendices. It appears on exams as a case study of a global conservation policy — know what it does, not just what the acronym stands for.

It can appear across all three papers — multiple-choice recall in Paper 1, data-based questions on species indices in Paper 2, and it's a classic option-adjacent topic tested through extended-response essays in Paper 2's longer answer section. HL students should also expect Simpson's index calculations as structured Paper 2 questions.

Mostly the same core content, but HL adds Simpson's reciprocal index calculations and deeper treatment of red list categorisation. SL students need to understand and interpret diversity data; HL students must calculate it themselves and justify conservation prioritisation using that data.

Expect "describe", "explain", "evaluate" and "discuss" most often. "Evaluate" questions on conservation strategies are the trickiest — examiners want strengths and limitations of a named method, not just a description of how it works.

It varies by exam session, but this sub-topic typically contributes a handful of Paper 1 marks plus a data-based Paper 2 question worth roughly 6-9 marks when it appears — more if it's combined with ecology or evolution content in a longer structured question.

Build one detailed case study you know cold — a named ecosystem with real species, real threats and a real conservation response — then practise applying it to different command terms. Examiners reward specificity: naming the actual invasive species or actual protected area beats vague general statements every time.

Confusing species richness with species diversity — richness is just the number of species present, diversity accounts for both richness and evenness of abundance. Students also frequently forget that a habitat with fewer species but more even population sizes can score a higher diversity index than one with many species dominated by one.

Practise data-based questions that give you raw species counts and ask you to calculate or interpret a diversity index — these show up regularly and combine calculation skill with conservation evaluation. On RevisionPrep, the Topical Worksheets group these by sub-topic so you can drill the Simpson's index calculation repeatedly before tackling full past papers.

Not conceptually harder, but it does demand more — HL students must calculate Simpson's index from raw data and apply it in unfamiliar contexts, while SL students only interpret given values. If your child finds data-handling straightforward, this particular sub-topic won't be the one causing HL Biology stress.

Look for resources that pair concise notes with practice questions requiring actual calculation, not just definitions to memorise — this topic rewards applied practice over passive reading. RevisionPrep's Revision Notes cover the sub-topic concisely, and the question bank includes Simpson's index practice problems with full worked solutions.