Biodiversity at three levels

• Biodiversity is the variety of life in all its forms, levels and combinations.

• The three required levels are ecosystem diversity, species diversity and genetic diversity.

• Exam answers should identify which level of biodiversity is being considered rather than treating biodiversity as species number alone.

Anthropogenic species extinction: required case studies

• Focus on anthropogenic causes of the current sixth mass extinction, not non-anthropogenic causes of previous mass extinctions.

• Study three or more brief species-extinction case studies.

• Use the North Island giant moa (Dinornis novaezealandiae) as an example of lost terrestrial megafauna.

• Use the Caribbean monk seal (Neomonachus tropicalis) as an example of a lost marine species.

• Prepare one additional example of a species extinct from an area familiar to you.

• For each case study, connect the relevant human pressure to the extinction outcome.

The North Island giant moa is one required IB species-extinction case study and represents loss of terrestrial megafauna. Use it when organizing evidence about anthropogenic extinction. Source

Evidence for the biodiversity crisis

• Evidence may come from IPBES reports and other reliable sources.

• Use reliable biodiversity surveys from a wide range of habitats around the world.

• Surveys must be repeated to demonstrate changes in species richness and evenness.

• Both expert scientists and citizen scientists can contribute useful observations.

• Verifiable evidence usually comes from published, peer-reviewed sources whose methodology can be checked.

• Citizen-science data provide benefits but also create unique methodological concerns.

Conservation requires several approaches

• No single conservation approach is sufficient; different species require different measures.

• In situ conservation protects species within their natural habitats.

• Nature reserves require active management.

• Rewilding and reclamation can address degraded ecosystems.

• Ex situ conservation includes zoos and botanic gardens.

• Germ plasm can be stored in seed banks or tissue banks.

• Effective conservation therefore combines approaches appropriate to the species and situation.

This image links practical seed-bank work with ex situ conservation. The syllabus requires germ plasm storage in seed or tissue banks as one conservation approach. Source

Biodiversity now, past and classification

• Millions of species have been discovered, named and described, but many more remain undiscovered.

• Fossil evidence suggests more species are alive on Earth today than at any previous time.

• Classification is an example of pattern recognition; the same observations can be classified differently.

• Splitters recognize more species within a taxonomic group than lumpers.

• Recorded species totals can therefore depend partly on how organisms are classified.

Anthropogenic ecosystem loss: required case studies

• Study only causes of ecosystem loss that are directly or indirectly anthropogenic.

• Prepare two ecosystem-loss case studies.

• One required case study is loss of mixed dipterocarp forest in Southeast Asia.

• The second should, where possible, be a lost ecosystem from an area familiar to you.

• For each case study, identify the human activity involved and explain its relationship to ecosystem loss.

This image visualizes a dipterocarp forest, the ecosystem type required in the Southeast Asian case study. The photograph shows the ecosystem itself, not evidence of its loss. Source

Causes of the current biodiversity crisis

• Human population growth is the overarching cause identified in the syllabus.

• Hunting and other forms of over-exploitation directly threaten biodiversity.

• Urbanization contributes to loss of natural habitats.

• Deforestation and clearance for agriculture cause natural habitat loss.

• Pollution is another major anthropogenic pressure.

• Global transport promotes the spread of pests, diseases and invasive alien species.

EDGE conservation prioritization

• EDGE conservation prioritizes species that are evolutionarily distinct and globally endangered.

• The rationale is to focus conservation effort on species combining these two characteristics.

• Choosing which species receive priority is not a purely biological decision.

• Prioritization has ethical, environmental, political, social, cultural and economic implications.

• These competing considerations mean conservation priorities need to be debated.

• Be prepared to explain the rationale for EDGE and evaluate why prioritization can be controversial.

Common exam errors and case-study checks

• Do not discuss non-anthropogenic causes of previous mass extinctions when asked about the current sixth mass extinction.

• Do not use a single survey as evidence of biodiversity change; the syllabus requires repeated surveys.

• Do not imply that one conservation method alone is sufficient.

• Do not omit the required moa, Caribbean monk seal and additional locally familiar extinction case study.

• Do not omit mixed dipterocarp forest and, where possible, a locally familiar ecosystem-loss case study.

• Do not confuse evidence for the biodiversity crisis with causes of the biodiversity crisis.