IB Biology · Theme A: Unity and diversity · SL and HL
A4.2 Conservation of biodiversity
A one-page summary of A4.2 Conservation of biodiversity, the key terms to know, and sample exam questions with answers. For the full lesson, open the illustrated revision slides or practise in the app.
Guiding questions
What factors are causing the sixth mass extinction of species?
How can conservationists minimize the loss of biodiversity?
What A4.2 covers
What biodiversity is, and how much there is
- A4.2.1Biodiversity: three levels
- A4.2.2More species than ever before
- A4.2.2 · Nature of scienceLumpers and splitters
Lost species and lost ecosystems
- A4.2.3How humans drive extinction
- A4.2.3Lost megafauna: the giant moa
- A4.2.3A lost marine species: the Caribbean monk seal
- A4.2.3A familiar case: the dodo
- A4.2.4Ecosystem loss: dipterocarp forest
- A4.2.4A second case: the tallgrass prairie
The evidence and the causes
- A4.2.5Evidence for a crisis
- A4.2.5Repeated surveys and citizen science
- A4.2.6The overarching cause: population growth
- A4.2.6The specific causes
Conservation
- A4.2.7Several approaches are needed
- A4.2.7In situ: managing nature reserves
- A4.2.7Rewilding and reclamation
- A4.2.7Ex situ: zoos and botanic gardens
- A4.2.7Storing germ plasm
- A4.2.8Choosing priorities: EDGE
A4.2 Conservation of biodiversity: summary
Biodiversity
- Ecosystem, species (richness, evenness) and genetic levels.
- More species alive today than ever; ~2.2 million described.
Extinctions
- Moa (megafauna), Caribbean monk seal (marine), dodo.
- Sixth mass extinction: tens to about 1000× background rate.
Ecosystem loss
- Dipterocarp forest → oil palm; tallgrass prairie → cropland.
- Causes are directly or indirectly anthropogenic.
Evidence
- IPBES, IUCN Red List, Living Planet Index (−73% since 1970).
- Repeated, peer-reviewed surveys; citizen science helps but has concerns.
Causes
- Overarching: human population growth.
- Over-exploitation, urbanization, land clearance, pollution, pests and invasive species.
Conservation
- In situ (reserves, rewilding) + ex situ (zoos, gardens, seed banks).
- EDGE prioritises distinct, endangered species; priorities are debated.
Key terms
- Biodiversity
- the variety of life in all its forms, levels and combinations.
- Species richness
- the number of species in a community.
- Species evenness
- how evenly individuals are shared between the species.
- Genetic diversity
- the range of alleles in a species’ gene pool.
- Anthropogenic
- caused by human activity.
- Mass extinction
- the loss of a large share of species in a geologically short time.
- In situ conservation
- protecting species in their natural habitat.
- Ex situ conservation
- protecting species outside it: zoos, gardens, banks.
- Germ plasm
- seeds, tissue or cells from which organisms can be regrown.
- EDGE species
- evolutionarily distinct and globally endangered.
Sample exam questions
Three of the 32 multiple-choice questions for A4.2. Try each one before opening the answer.
Question 1. Which term describes the range of alleles in the gene pool of a species?
- Species diversity
- Genetic diversity
- Ecosystem diversity
- Species richness
Show the answer
Answer: B. Genetic diversity is the range of alleles present in a species’ gene pool.
Question 2. Cheetahs have very little genetic variation. Why does this put the species at risk?
- Few variants may survive a new disease.
- They cannot breed with one another.
- Their habitat has low species diversity.
- They have too many alleles of each gene.
Show the answer
Answer: A. With few alleles there are few variants, so a new disease or other stress may affect almost every individual in the same way.
Question 3. Which change is a loss of ecosystem diversity without the loss of any species?
- The last individual of a species dies.
- A population loses most of its alleles.
- All the wetlands in a region are drained.
- Evenness falls as one species dominates.
Show the answer
Answer: C. Draining the wetlands removes a whole type of ecosystem from the region, even if its species survive elsewhere.
Linking questions
Questions that connect A4.2 to other parts of the course, the kind that come up in Paper 2.
- How do the interactions and stability of an ecosystem depend on its biodiversity? (see C4.1, D4.2)
- How could climate change alter species distributions and add to the current biodiversity crisis? (see D4.3)
- How does natural selection depend on the genetic diversity within a species?
- How does the classification of species help conservationists identify and prioritise biodiversity? (see A3.1)
Practise A4.2
Study notes, every question and full markschemes for A4.2 are in the app with Pro. Two lessons are completely free to try: A1.1 Water and B1.1 Carbohydrates and lipids.