Conservation of biodiversity connects biodiversity measurement, human-driven losses, ecosystem evidence, and targeted conservation strategies for protecting species, communities, and evolutionary history.
Biodiversity is the variety of life in all its forms, levels and combinations. It includes genetic diversity within populations, species diversity in communities and ecosystem diversity across habitats and processes.
Species diversity depends on both richness (the number of species) and evenness (how evenly individuals are distributed). A community with many species can still have low diversity if nearly all individuals belong to one species.
D=N(N−1)/Σn(n−1),whereNisthetotalnumberoforganismssampledandnisthenumberbelongingtoeachspecies;alargerDindicatesgreaterdiversityforcomparablesamples.
Two fields may have the same richness, but the field whose individuals are distributed more evenly among species has the higher Simpson's reciprocal index and greater measured species diversity.
Species count alone does not measure genetic or ecosystem diversity. Compare index values only when sampling method and effort are sufficiently comparable.
This objective is assessed through structured response, commonly using State / Discuss / Calculate.
State / Discuss / Calculate / Analyse / Compare / Evaluate / Distinguish / Suggest
Build the answer around this relationship: Biodiversity includes ecosystem diversity, species diversity and genetic diversity.
Equating richness with overall biodiversity when evenness also affects diversity.
Representative question
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.
| a | use transects/quadrats; |
| b | count number of species/individuals; |
| c | measure richness and evenness; |
| d | use Simpson (reciprocal) index; |
| e | indicator species/biotic index to reflect a specific environmental condition; |
| f | changes in Simpson index/richness/evenness/indicator species indicate changes in the community biodiversity; |
Millions of living species have been discovered, named and described, and many more remain undiscovered. Fossil evidence suggests that more species may be alive now than at any earlier time in Earth's history.
Present-day surveys sample living organisms directly, whereas past biodiversity is reconstructed from fossils and dated rock layers. Fossilization is rare and uneven, so soft-bodied, small or poorly sampled organisms are underrepresented.
A fair comparison states the time interval, separates number of species from abundance, considers changes in taxonomic definitions and acknowledges unequal sampling. Speciation raises diversity through time; extinction lowers it.
A diverse fossil assemblage can establish that many lineages existed in one period, but missing fossils cannot establish that no additional species were present.
The fossil record supports a comparison but is incomplete. 'Currently more species' is an evidence-based inference, not an exact census of all past and present species.
Anthropogenic extinction occurs when human activity causes the last individuals of a species to die. The current rapid, widespread losses are described as a sixth mass extinction.
Direct killing and habitat alteration reduce abundance; small populations then become more vulnerable to reproductive failure, inbreeding and chance events. Extinction is global, whereas disappearance from one area is extirpation.
| Case | Human pressure | Evidence-based lesson |
|---|---|---|
| North Island giant moa (Dinornis novaezealandiae) | Overhunting after human arrival | Large terrestrial species with slow replacement can be removed faster than populations recover |
| Caribbean monk seal (Neomonachus tropicalis) | Human exploitation and other human pressures on a marine species | Marine range does not protect a species from sustained human-caused mortality |
For a third case from a region familiar to the learner, record the named species, verified human cause, population pathway and evidence source; do not infer global extinction from a local absence.
A plausible human pressure is not enough: the case study must connect that pressure to population decline and distinguish extinction from extirpation.
This objective is assessed through multiple choice, commonly using Identify.
Identify
Build the answer around this relationship: Anthropogenic extinction is extinction caused by human activities.
Representative question
The North Island giant moa (Dinornis novaezealandiae) went extinct some time between the arrival of humans in New Zealand and the 1800s.
What do scientists believe to be the cause of this extinction?
Deforestation
New diseases
Competition with other megafauna
Overhunting
D
Ecosystem loss is an anthropogenic reduction in habitat area, structure, species interactions or ecological function, caused directly by conversion or indirectly by environmental change.
| Ecosystem | Human drivers | Causal chain |
|---|---|---|
| Mixed dipterocarp forest, Borneo | Logging and conversion to oil-palm plantations | Tree removal and land conversion → fragmentation and altered microclimate → habitat and species loss |
| Great Barrier Reef | Greenhouse-gas-driven warming and acidification, pollution and fishing pressure | Heat stress/bleaching and reduced calcification plus local stress → coral loss → reduced reef habitat and function |
Separate direct area loss from degradation of what remains. Fragmentation increases edge effects and isolates populations; persistent pollution, invasive species or climate stress can prevent functional recovery.
Satellite images showing declining Borneo forest cover become stronger causal evidence when land-use records independently show logging and oil-palm expansion in the same places and times.
Protecting a small remnant does not by itself restore an ecosystem if connectivity, species interactions or the original abiotic conditions remain lost.
This objective is assessed through multiple choice, structured response, commonly using Outline / Explain / Describe.
Outline / Explain / Describe / Suggest
Build the answer around this relationship: Deforestation reduces biodiversity by removing habitat and essential resources.
Naming deforestation without explaining loss of habitat, food, shelter or breeding sites.
Representative question
The satellite images show changes in the area covered by forest, much of which is mixed dipterocarp forest, on the island of Borneo in Southeast Asia.
Which human activities are most likely to have caused the changes shown in the map?
Logging and palm oil plantation
Logging and rewilding
Mining and afforestation
Afforestation and palm oil plantation
A
Evidence for a biodiversity crisis comes from repeated, comparable surveys showing declines in species richness, evenness, abundance, ranges, genetic diversity or ecosystem integrity across many habitats.
A single survey provides a snapshot; repeated standardized sampling reveals change. IPBES assessments combine many published datasets and lines of evidence, so their broad conclusions are stronger than one isolated observation.
Check the baseline, time span, sampling effort, method, geographic and taxonomic coverage, uncertainty and alternative explanations. Richness and evenness—and, where appropriate, Simpson's reciprocal index—allow communities to be compared through time.
Citizen scientists can supply frequent observations over a wide area, but training, validation, repeated sites and correction for changing observer effort are needed before a decline is inferred.
Peer review permits methods and analysis to be checked but does not make a dataset flawless. A crisis claim should report scale and uncertainty rather than imply that every species declines equally.
Human population growth is an overarching driver of the biodiversity crisis because it increases demand for food, housing, land, energy and materials.
Demand is translated into habitat loss through urbanization, deforestation, agriculture and mining; direct mortality through hunting, fishing and other overexploitation; and environmental stress through pollution and climate change.
Global transport spreads pests, diseases and invasive alien species. These drivers interact: fragmented native populations may be less able to withstand pollution, warming, a new pathogen or an introduced competitor.
Water hyacinth can spread rapidly as an invasive alien plant, block waterways and reduce light or oxygen available to native aquatic organisms.
Do not stop at a list of threats. Link each human activity to the mechanism that changes survival, reproduction, habitat or species interactions.
This objective is assessed through structured response, commonly using Outline / State.
Outline / State
Build the answer around this relationship: Urbanization and agricultural land clearance reduce habitat and fragment ecosystems.
Representative question
List human actions that could threaten populations of insect pollinators such as bees.
a. use of pesticides/insecticides (which may kill/harm pollinators);
b. urbanization;
c. loss of habitat/change of land use (monocultural/intensive farming practices);
d. use of herbicide or removal of "weeds" reducing food sources;
e. introduction of alien species;
For a. or d. the mention of a specific pesticide or herbicide would be ok.
3
Marking guidance:
max
No single conservation method is sufficient because species, ecosystems and threats differ. Effective plans combine approaches and monitor whether populations and ecological functions recover.
| Approach | Main role | Examples |
|---|---|---|
| In situ | Protect species in natural habitats and retain interactions/evolution | Nature reserves, corridors, anti-poaching and active habitat management |
| Ecosystem recovery | Restore lost processes and habitat | Rewilding and reclamation of degraded ecosystems |
| Ex situ | Protect organisms or genetic material outside the threatened habitat | Zoos, captive breeding, botanic gardens, seed banks and tissue/germ-plasm banks |
In-situ conservation retains natural selection and food webs but may not control an immediate threat. Ex-situ programmes can protect a very small population, yet require genetic management and a safe habitat before reintroduction.
A threatened amphibian may need a protected and restored wetland, disease control, connected habitat and a carefully managed captive-breeding population rather than one isolated action.
A reserve without enforcement, connectivity or threat removal may protect only a map boundary; captive breeding without genetic management and a viable release site cannot restore a wild population.
This objective is assessed through essay response, structured response, commonly using Discuss / Outline / Distinguish.
Discuss / Outline / Distinguish / Explain / Suggest
Build the answer around this relationship: In situ conservation protects species within their natural habitats and communities.
Defining in situ and ex situ without linking each approach to its conservation advantages and limits.
Representative question
Discuss in situ and ex situ conservation of endangered species.
a. both methods ensure continuing survival of species/recover endangered species;
b. in situ (conservation) occurs in natural habitat;
c. ex situ (conservation) takes place outside original/natural habitat/occurs in artificial/controlled habitat;
d. in situ not as disruptive;
e. in situ encourages conservation of natural habitat;
f. ex situ may be last chance for survival / increase breeding
OR
needed if species too rare to be left in the wild;
g. one example of either type of conservation;
Marking guidance:
Max 3 marks if only in situ or ex situ discussed;
Or converse for marking points d and e
4 max
The EDGE of Existence approach prioritizes species that are both evolutionarily distinct and globally endangered.
Evolutionary distinctiveness estimates how much unique evolutionary history a species represents; global-endangerment status estimates extinction risk. Combining them directs limited conservation resources toward irreplaceable branches and urgent threats. Use the evidence scale and context before drawing a broad conclusion.
Interpret an EDGE priority:
Protecting a highly distinct, critically endangered mammal can preserve more unique evolutionary history than protecting a common close relative.
EDGE ranking does not mean other species have no value; it is a prioritization tool under limited resources.
This objective is assessed through structured response, multiple choice, commonly using Outline / Describe.
Outline / Describe
Build the answer around this relationship: EDGE species are both evolutionarily distinct and globally endangered.
Explaining EDGE only by expanding the initials without linking distinctiveness to extinction risk.
Representative question
Outline the importance of the EDGE of Existence programme.
a. estimates the expected loss of evolutionary history (per unit time) / helps maintain the evolutionary history
OR
focuses on species that belong to small clades (few or no close relatives);
b. focuses on species with populations in danger of extinction;
c. conservation actions can be taken for EDGE species
OR
EDGE lists inform/inspire/suggest priorities for conservation;
Marking guidance:
Do not award marking points for just repeating what ED and GE stand for.
2
max
A strong conservation answer follows a chain: define biodiversity, measure evidence of decline, identify human drivers, then justify conservation action. Biodiversity includes ecosystem, species, and genetic diversity; species diversity uses richness and evenness. Evidence comes from estimates, fossils, repeated surveys, IPBES reports, and indices. Drivers include extinction pressure, ecosystem conversion, population-driven resource demand, pollution, and invasive species. Responses include in situ, ex situ, and EDGE prioritization.