IB Biology SL A4.2 Conservation of biodiversity Questions

Practise IB Biology SL A4.2 with questions on biodiversity, conservation priorities, threats, ecosystem change and sustainable decisions.

32 questions in this syllabus scope, with question parts counted together.

Syllabus
First assessment 2025
Course
Biology SL
Level
SL

Exam analysis

SL · 2010–2025
Papers with this topic28 / 141in the analysed sample
Latest appearanceNovember 2025
Tagged question parts41
Paper types5

Most tested objectives

  1. A4.2.7—Conservation approaches12 papers
  2. A4.2.1—Biodiversity definition11 papers
  3. A4.2.4—Ecosystem loss causes3 papers
  4. A4.2.3—Anthropogenic species extinction2 papers
  5. A4.2.6—Causes of biodiversity crisis2 papers

Common question formats

  • Definition or recall
  • Calculation
  • Data analysis
  • Evaluation
  • Process explanation
  • Extended response

Recent exam appearances

November 2025Paper 2 SL · TZ3Q6(b)[ 3 ]
November 2025Paper 1A SL · TZ3Q22[ 1 ]
May 2025Paper 2 SL · TZ3Q3(a)[ 2 ]

141 papers analysed · Tagging incomplete

Exam points

  • Distinguish species richness from evenness and calculate Simpson’s reciprocal diversity index from community counts, showing the working.
  • Interpret Simpson’s reciprocal index together with richness and evenness, using quadrats or transects and counts to quantify biodiversity change over time.
  • Identify a named anthropogenic extinction cause and explain how habitat conversion removes food, shelter and breeding sites.
  • Explain how forest fragmentation and environmental pressure such as temperature change biodiversity and reef or community condition.
  • Identify urbanisation, land clearance, agriculture, pollution and overexploitation as human drivers of biodiversity loss.
  • Compare in situ and ex situ conservation using reserves, zoos, captive breeding, botanical gardens and seed banks.
  • Explain protected-area management, threat control and reintroduction as in situ conservation actions.
  • Evaluate biological control by naming target and control organisms and weighing selectivity, food-web risk and spread.
  • Explain how EDGE combines evolutionary distinctiveness with extinction risk to justify conservation priorities.

Covered syllabus points

A4.2.1—Biodiversity definitionA4.2.2—Current vs. past biodiversityA4.2.3—Anthropogenic species extinctionA4.2.4—Ecosystem loss causesA4.2.5—Evidence for biodiversity crisisA4.2.6—Causes of biodiversity crisisA4.2.7—Conservation approachesA4.2.8—EDGE of Existence programme

Exam points

  • Identify ecosystem, species and genetic diversity as forms or levels of biodiversity.
  • Distinguish species richness from evenness when describing community diversity.
  • Use Simpson’s reciprocal index to compare species diversity between communities.

Question 1

[Maximum number: 4]

Entire communities need to be conserved in order to preserve biodiversity.

Suggest different quantitative methods to measure changes in biodiversity in a community over time.

Exam points

  • State the estimate of about 9 million species and note that many remain undescribed.
  • Use fossil and radiometric evidence to reconstruct past biodiversity, noting that the record is incomplete.
  • Compare present and past species diversity cautiously because fossil gaps create uncertainty.

Question 1

[Maximum number: 2]

Knowledge of deep-water fish is important for fisheries and marine reserve management. Scientists analysed data from scientific trawls made from 1977 to 1989 (early period) and from 1997 to 2002 (late period). These were at depths from 800 m to 4800 m in the Porcupine Seabight and Porcupine Abyssal Plain area southwest of Ireland. The graphs represent the abundance of fish and the number of species for each of these trawls.

Key: ○ 1977 to 1989 (early period) - 1997 to 2002 (late period)

Key: ○ 1977 to 1989 (early period) - 1997 to 2002 (late period)

Discuss the evidence in these data for a decline in the biodiversity of fish between the early period and the late period.

Exam points

  • Describe human activity as a driver of the current sixth mass extinction.
  • Link hunting, habitat change or resource use to the extinction of the North Island giant moa.
  • Explain how loss of the Caribbean monk seal as a top predator can change food webs.

Question 1

[Maximum number: 1]

Outline one reason for the extinction of a named animal species.

Exam points

  • Explain how logging and oil-palm plantations cause ecosystem loss in Borneo’s mixed dipterocarp forests.
  • Explain how climate, pollution and fishing contribute to ecosystem loss on the Great Barrier Reef.

Question 1

[Maximum number: 1]

Data from the International Union for Conservation of Nature (IUCN) indicates that the population numbers of many mammal species are decreasing. The chart shows reasons for the decrease and the number of species in each category of danger.

Figure for Question 1 — IB Biology SL

Outline how deforestation can affect the richness of biodiversity in an ecosystem.

Exam points

  • Use richness, evenness and Simpson’s reciprocal index to compare disturbed and undisturbed habitats.
  • Interpret IPBES reports and repeated biodiversity surveys as evidence of a biodiversity crisis.
  • Assess reliability checks when using peer-reviewed studies and citizen-science data.

Question 1

[Maximum number: 2]

The sinking of the tanker Eurobulker off the coast of Greece in September 2000 resulted in a spill of 700 tonnes of crude oil. The sands in the oil spill region were categorized according to the level of pollution and the presence of indicator species.

The graph shows the trends in richness of all species in the five ecological quality status categories in sands after the oil spill.

Figure for Question 1 — IB Biology SL

Analyse the data to show that pollution affects biodiversity.

Exam points

  • Link population growth to rising demand for food, housing, energy and land.
  • Identify overexploitation, urbanisation, deforestation, agriculture, mining and pollution.
  • Explain how invasive lionfish or water hyacinth can outcompete or disrupt native species.

Question 1

[Maximum number: 1]

What are causes for a global reduction in biodiversity?

I. Increase in size of towns and cities
II. Reclamation of degraded ecosystems
III. Clearance of land for agriculture

A

I and II only

B

I and III only

C

II and III only

D

I, II and III

Exam points

  • Choose conservation approaches to match the species and the threats it faces.
  • Describe in situ protected areas, reserve design, corridors, active management and rewilding.
  • Describe ex situ zoos, captive breeding, botanic gardens, seed banks and tissue banks.

Question 1

[Maximum number: 3]

The diagram shows a simplified Black Sea food web.

Figure for Question 1 — IB Biology SL

In the Black Sea, invasive comb jellies, Mnemiopsis leidyi, have been blamed for a significant disruption in the food web. The accidental introduction of Beroe ovata, a different species of comb jelly, drastically reduced the population of M. leidyi.

Discuss whether biological control measures, such as introducing B. ovata into the Black Sea ecosystem, should be used.

Exam points

  • Combine IUCN extinction risk and phylogenetic distinctiveness when identifying EDGE priorities.
  • Relate EDGE conservation priorities to preventing disproportionate loss of evolutionary history.

Question 1

[Maximum number: 1]

The dark areas of the map show the distribution of some species included in the EDGE of Existence programme.

Figure for Question 1 — IB Biology SL

What is the reason these species have been included in the EDGE of Existence programme?

A

They occupy similar niches threatened by invasive species.

B

Their risk of extinction is higher as they live at the edge of ecosystems.

C

Their populations are decreasing and there are few or no closely related species.

D

They are keystone species in their ecosystems.

Question 1

[Maximum number: 2]

Question (a)

(a)

Outline one reason for the extinction of a named animal species.

[ 1 ]

Question (b)

(b)

State one use of the Simpson index in ecology.

[ 1 ]
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