A4.2 Conservation of biodiversity

1. All three of the findings, because biodiversity includes ecosystem, species and genetic diversity — Biodiversity is the variety of life in all its forms, levels and combinations. The six ecosystems are ecosystem diversity, the 420 species are species diversity and the 18 alleles are genetic diversity, so all three findings describe the island's biodiversity.
2. Only the count of 420 species, because biodiversity means the variety of species — A student who carries over the GCSE definition of biodiversity as the variety of species picks this. Species diversity is one level of biodiversity; the variety of ecosystems and the variety of alleles within a species are the other two.
3. The six ecosystems and 420 species, but not the alleles, which are variation within a species — A student who treats biodiversity as differences between species picks this. Genetic diversity, the variety of alleles within a species, is a level of biodiversity in its own right, and the lizard population with 18 alleles is more diverse than the one with 4.
4. The 420 species and the 18 alleles, but not the ecosystems, which are only habitats — A student who sees ecosystems as the setting for biodiversity rather than part of it picks this. Ecosystem diversity is the third level: a region with six distinct ecosystems holds more biodiversity than one with a single ecosystem, even with the same species.

Syllabus statement A4.2.1 · Read this in Learn

1. Species numbers were at their highest before the extinction of the dinosaurs — A student who pictures a long decline since the age of the dinosaurs picks this. Fossil evidence suggests that biodiversity recovered and rose after each mass extinction, and that more species are alive today than at any time in the past.
2. Almost every species alive today has now been discovered, named and described — A student who sees classification as finished picks this. Millions of species have been described, but estimates of the total are several times higher, so there are many more species to be discovered.
3. More species are alive on Earth today than at any time in Earth's history — Evidence from fossils suggests that there are currently more species alive on Earth today than at any time in the past, even though millions of species remain undescribed.
4. The total number of species is a fixed count that all taxonomists accept — A student who treats species counts as measured facts picks this. The same observations can be classified in different ways, so splitters recognize more species than lumpers, and species totals differ between sources.

Syllabus statement A4.2.2 · Read this in Learn

1. It became extinct only after industrial fishing fleets reached the Caribbean in the twentieth century — A student who links extinction with modern technology picks this. Killing of monk seals for blubber oil began in the 1490s, and the species was reduced to scattered colonies long before industrial fishing; the last confirmed sighting was in 1952.
2. It was hunted for the oil in its blubber from the 1490s, an anthropogenic extinction of a marine mammal species — Europeans killed Caribbean monk seals for blubber oil, meat and skins from the 1490s; later, coastal settlement disturbed its colonies and fishing depleted its prey. The last confirmed sighting was in 1952 and it was declared extinct in 2008.
3. It shows that marine species are otherwise safe, since the open ocean is too large for people to affect them — A student who pictures the ocean as a refuge picks this. Marine species breed and feed at particular sites; the monk seal was killed on its beaches and its prey depleted by fishing, and it is one of many marine species threatened by human activity.
4. Its extinction counts as anthropogenic only because seals were killed; the fishing of its prey was a natural pressure — A student who counts only direct killing as a human cause picks this. Depletion of prey by fishing and disturbance of colonies by settlement are indirectly anthropogenic causes, and the guide's study of extinction includes them.

Syllabus statement A4.2.3 · Read this in Learn

1. Conversion to oil palm has replaced one kind of forest with another, so species have been lost but the ecosystem has not — A student who takes any tree cover to be forest picks this. An oil palm plantation is a crop of one species that supports a small fraction of the forest community; the dipterocarp forest ecosystem has been lost even though trees remain.
2. Droughts and forest fires that are unconnected with human activity have destroyed most of the lowland forest — A student who treats fire and drought as purely natural picks this. Intact dipterocarp forest rarely burns; the fires spread through forest opened by logging and peatland dried by drainage, and many are started to clear land, so the loss is indirectly anthropogenic.
3. Logging for hardwood timber, followed by clearance and burning of the land for oil palm and pulpwood plantations — Dipterocarp trees were logged for their valuable timber, and the logged forest was then cleared and burned to make way for oil palm and pulpwood plantations; fires during droughts spread through logged and drained land. All of these causes are directly or indirectly anthropogenic.
4. The growth of cities across the lowlands, because human population growth acts on ecosystems through urbanization — A student who equates population growth with the spread of cities picks this. Urbanization occupies little of the lowland forest; the land was taken by logging and plantation agriculture, which population growth drives through demand for timber and palm oil.

Syllabus statement A4.2.4 · Read this in Learn

1. Repeating a survey is needed only when the first survey was carried out by citizen scientists rather than experts — A student who thinks expert data need no comparison picks this. Repetition is required whoever collects the data, because a single survey, however skilled, records only one point in time and cannot show change.
2. Repeating a survey finds additional species, and so gives a higher measure of the habitat's biodiversity — A student who treats richness as the whole of biodiversity picks this. The purpose of repetition is to compare the community at different times, not to lengthen the species list; evidence of a crisis is evidence of change in richness and evenness.
3. A change in species richness or evenness can only be shown by comparing surveys made at two different times — A single survey describes a community at one moment. Evidence of a biodiversity crisis is evidence of decline, so the survey must be repeated, with the same methods, so that richness and evenness can be compared over time; reports such as those of IPBES draw on such repeated surveys.
4. A single thorough survey is sufficient, provided that it covers a wide enough range of habitats around the world — A student used to a single fieldwork sample picks this. Wide coverage of habitats is required, but breadth cannot substitute for time: without an earlier survey to compare with, even a global survey cannot show that biodiversity is falling.

Syllabus statement A4.2.5 · Read this in Learn

1. Spread of cities over natural habitat — A student who pictures population growth as the spread of cities picks this. Urbanization is one of the specific causes; the overarching cause is the growth of the human population, which drives urbanization along with every other specific cause.
2. Natural spread of invasive species — A student who thinks invasive species arrive by themselves picks this. Their spread is a specific cause of the crisis, and it is due to global transport by people, not natural dispersal; it is not the overarching cause.
3. Natural climate shifts as in past eras — A student who assumes extinction has natural causes picks this. The current crisis is anthropogenic; its causes are human activities driven by population growth, not the non-anthropogenic events behind earlier mass extinctions.
4. Growth of the human population — The guide names human population growth as the overarching cause, with hunting and over-exploitation, urbanization, deforestation and clearance for agriculture, pollution and the spread of pests, diseases and invasive alien species as the specific causes it drives.

Syllabus statement A4.2.6 · Read this in Learn

1. Nature reserves conserve species by keeping people out, so no management is needed — A student who thinks protection means exclusion picks this. Management of nature reserves is an approach in its own right: controlling invasive species, maintaining grazing or fire regimes and keeping corridors between reserves.
2. Ex situ conservation in zoos can, by itself, secure the future of an endangered animal species — A student who sees zoos as arks picks this. Captive populations are small, may lose genetic diversity and natural behaviours, and do not conserve the habitat; no single approach by itself is sufficient.
3. Rewilding restores natural processes to an area, often by reintroducing missing species — Rewilding aims to make an ecosystem self-sustaining by restoring the natural processes it has lost, for example by reintroducing large herbivores or predators and removing barriers to movement; it is one of the several approaches the guide requires.
4. Seed banks can store the germ plasm of every plant species by drying and freezing its seeds — A student who assumes seeds are uniformly hardy picks this. Many species have seeds that are killed by drying and freezing, so their germ plasm is stored in tissue banks or as living plants; different species require different measures.

Syllabus statement A4.2.7 · Read this in Learn

1. Species Y, because the most endangered species must be conserved first, whatever its relatives — A student who uses threat as the only criterion picks this. Y is as endangered as W, but it has many close relatives, so its loss would remove little unique evolutionary history; EDGE combines endangerment with distinctiveness.
2. Species X, because the most distinct lineage is the oldest and should be conserved first — A student who equates distinctiveness with age picks this. X is distinct but is not threatened, so it does not need priority; and distinctiveness measures unique evolutionary history, not how old a species is.
3. Species Z, because a species of Least Concern has the largest population and most genetic diversity — A student who judges by numbers picks this. Population size is not genetic diversity, and Z is neither threatened nor distinct, so it scores lowest on both EDGE criteria.
4. Species W, because it combines few close relatives with a high risk of extinction — EDGE prioritizes species that are both evolutionarily distinct and globally endangered. W's loss would remove a large amount of unique evolutionary history and is likely, so it receives the highest priority.

Syllabus statement A4.2.8 · Read this in Learn

1. Species diversity is low, because all the cheetahs are genetically almost identical — A student who thinks biodiversity has only one level, the number of species, picks this: with no genetic level to assign it to, the cheetah's uniformity gets labelled as low species diversity, conflating the genetic and species levels. Genetic uniformity within one species is low genetic diversity; species diversity concerns the number and relative abundance of species, which have not changed.
2. The cheetah's genetic diversity is low, although the reserve's species diversity is unchanged — The two levels are separate. Genetic diversity is the variety of alleles within a species, and the cheetah's is extremely low; species diversity depends on the species present and their abundance, which the stem says are unchanged.
3. The cheetahs' uniformity does not affect biodiversity, because the number of species present is unchanged — A student who does not count within-species variation as biodiversity picks this. Genetic diversity is one of the three levels, so a reserve whose cheetahs carry very few alleles holds less biodiversity than one whose cheetahs are genetically varied, whatever the species count.
4. The cheetah's genetic diversity must be adequate, because its population has been stable — A student who judges diversity by numbers picks this. Population size and genetic diversity are different things: a population can remain stable for decades while carrying very few alleles, which is exactly the cheetah's situation.

Syllabus statement A4.2.1 · Read this in Learn

1. The 12-species count shows that the collection holds three times the biodiversity found by the other taxonomist — A student who equates biodiversity with the species count picks this. The beetles are the same organisms with the same variation whichever way they are classified; only the number of names has changed, not the biodiversity of the collection.
2. Only one of the counts can be valid, because the number of species in the collection is an objective fact — A student who treats a species count as a measurement picks this. Classification is pattern recognition, and how much difference counts as a species boundary is a judgement; the same observations can be classified in different ways.
3. The count that matches published lists must be right, since nearly all beetle species are already described — A student who sees classification as finished picks this. A published list is itself the product of earlier splitting or lumping decisions, and many beetle species remain undescribed, so no list settles how much consistent difference marks a species boundary; both classifications are valid.
4. The first taxonomist is a splitter and the second a lumper; both are valid classifications — Splitters recognize more species than lumpers in a taxonomic group. The same observations have been classified in different ways, which the guide gives as an example of the nature of science: classification is pattern recognition, not a fixed fact.

Syllabus statement A4.2.2 · Read this in Learn

1. Hunting of adults and taking of eggs, with burning of forest, removed moa faster than a slow-breeding population could replace them — The butchery sites show intensive hunting; a species that matured slowly, laid few eggs and had no defensive behaviour against predators could not replace the losses, and burning of forest reduced its habitat. This is the guide's example of anthropogenic loss of terrestrial megafauna.
2. A natural shift in climate at the time, of the kind behind earlier mass extinctions, removed the moa independently of the settlers — A student who assumes extinctions have natural causes picks this. The moa had survived many climate shifts over millions of years and vanished within two centuries of human arrival, with the butchery sites showing what removed it.
3. Rats and dogs brought by the settlers ate the eggs, since a few thousand people with stone tools could not hunt out so big a bird — A student who thinks extinction needs industrial scale picks this. The evidence of butchered bones points to hunting by people, and a small population can exterminate a slow-breeding species that does not flee from predators, because removal only has to exceed replacement.
4. Hunting can be ruled out because moa were abundant when the settlers arrived, so loss of forest to fire must be the only cause — A student who believes abundant species are safe from hunting picks this. Abundance delays extinction but does not prevent it: the butchery sites show that hunting was central, and burning of forest added to the pressure rather than replacing it.

Syllabus statement A4.2.3 · Read this in Learn

1. Little ecosystem loss has occurred, because canopy cover fell by only 8 percentage points and most of the region still carries trees — A student who equates tree cover with forest picks this. Canopy cover changed little because plantations replaced forest tree for tree, but the dipterocarp forest ecosystem fell from 80% to 31% of the region, a loss of 49 percentage points.
2. The forest was lost mainly to drought and fire, which are natural events and so do not count as anthropogenic ecosystem loss — A student who separates fire from human activity picks this. The data show that the lost forest area (49 percentage points) is almost matched by the growth of plantations (41 percentage points), so the land was converted; fire used in clearing is part of that conversion.
3. Human population growth explains the loss through the spread of settlements, since urban land must account for the difference — A student who equates population growth with cities picks this. The data attribute the change to plantations, which rose by 41 percentage points; population growth is the overarching cause, acting here through demand for palm oil and timber rather than through urban land.
4. Canopy cover understates the loss, because plantations keep tree cover but are not the forest ecosystem — Forest fell by 49 percentage points while canopy cover fell by only 8, and plantation rose by 41. Most of the cleared forest became plantation with a closed canopy, so a measure of tree cover hides the loss of the mixed dipterocarp ecosystem.

Syllabus statement A4.2.4 · Read this in Learn

1. Species richness was unchanged but species evenness fell, a change that only a repeated survey could reveal — Richness (8 species) is the same, but in 2020 one species made up three-quarters of the catch, so evenness has fallen and species diversity is lower. The change is only visible because the survey was repeated with the same method.
2. Biodiversity was unchanged, because both surveys recorded the same number of beetle species — A student who uses richness as the whole measure picks this. Species diversity also depends on evenness, and a community in which one species has gone from 20% to 75% of individuals has become less diverse even though every species is still present.
3. The 2020 survey alone would have shown the decline, since it recorded the dominance of one species — A student used to interpreting a single sample picks this. On its own, the 2020 survey shows only that one species is dominant; without the 2000 survey there is no evidence that this is a change rather than the woodland's normal state.
4. Species diversity rose between the surveys, because the dominant species contributed many more individuals — A student who judges diversity by numbers of individuals picks this. Diversity is a measure of variety, not abundance: more individuals concentrated in one species lowers evenness and therefore lowers species diversity.

Syllabus statement A4.2.5 · Read this in Learn

1. The species has become about seven times more common over the ten years, because its records rose from 40 to 300 sightings — A student who reads raw records as abundance picks this. Records depend on how many people are looking: 40 records from 5 000 participants is 0.008 per participant, and 300 from 60 000 is 0.005, so records per participant have fallen.
2. Records per participant fell from 0.008 to 0.005, so the rise in records reflects effort, not evidence of an increase — 40 ÷ 5 000 = 0.008 and 300 ÷ 60 000 = 0.005. Once the twelve-fold rise in participants is accounted for, the rate of records has fallen, so the raw totals give no evidence that the species has increased. Correcting for effort is one of the methodological concerns unique to citizen science.
3. The results became verifiable evidence as soon as the scheme published its yearly totals on its website — A student who equates 'published' with 'verifiable' picks this. To be verifiable, evidence usually has to come from a peer-reviewed source that allows the methodology, including how effort and identification were handled, to be checked.
4. A single year's count would have shown the trend equally well, because so many people took part in the scheme — A student who draws conclusions from a single snapshot picks this. However many people take part, one year's count gives no information about change; a trend can only be shown by repeating the survey and comparing years.

Syllabus statement A4.2.5 · Read this in Learn

1. It is an invasive alien species whose spread is a consequence of global transport, one of the specific causes of the crisis — The mussel was carried outside its natural range in ships' ballast water, established and now harms native species: an invasive alien species spread by global transport, which the guide lists among the specific causes of the biodiversity crisis.
2. It reached the Great Lakes by natural range expansion, so its spread is not a human cause of biodiversity loss — A student who takes 'invasive' to mean self-propelled picks this. The mussel crossed an ocean in ballast water; without human transport it could not have reached the Great Lakes, so its presence is anthropogenic.
3. Its spread results from urbanization along the lake shores, the route by which population growth affects biodiversity — A student who equates population growth with cities picks this. The mussel arrived through shipping, which population growth drives through trade; urbanization is a separate specific cause and did not transport the mussel.
4. Native mussels are not at risk, since populations as large as theirs cannot be eliminated by a competing species — A student who believes abundant species are safe picks this. Abundance does not prevent extinction when removal exceeds replacement; native mussel populations in invaded lakes have collapsed as zebra mussels smother them.

Syllabus statement A4.2.6 · Read this in Learn

1. Dry and freeze its seeds in a seed bank, because seed banks can preserve the germ plasm of any species of plant — A student who assumes all seeds can be banked picks this. The stem states that this species' seeds are killed by drying and freezing, so a seed bank would destroy the germ plasm it was meant to store.
2. Store its germ plasm as cultured tissue in a tissue bank, alongside protection of the remaining forest in situ — Species whose seeds cannot survive seed banking are conserved as tissue cultures or living plants, and because no single approach is sufficient, ex situ storage is combined with in situ conservation of the habitat. Different species require different measures.
3. Grow the tree in a botanic garden alone, so that its natural forest habitat no longer needs to be protected — A student who treats ex situ conservation as sufficient picks this. A botanic garden holds few individuals and limited genetic diversity and does not conserve the forest ecosystem or the species' ecological role; in situ protection is still needed.
4. Fence off the remaining forest and leave it unmanaged, since a reserve protects a species by itself — A student who thinks in situ conservation means excluding people picks this. A reserve needs active management against logging, fire and invasive species, and for a species this threatened ex situ storage of germ plasm is also needed as insurance.

Syllabus statement A4.2.7 · Read this in Learn

1. The EDGE rationale favours the amphibian, but the choice also has ethical, economic and cultural implications that need to be debated — The amphibian is evolutionarily distinct and globally endangered, so EDGE would prioritize it. The guide's NOS point is that such decisions also carry ethical, environmental, political, social, cultural and economic implications, so scores inform a debate rather than replace it.
2. The decision is purely scientific: the species' scores settle the matter, so there is nothing left to debate — A student who expects data to make the decision picks this. EDGE scores identify which loss would remove the most unique evolutionary history, but livelihoods from tourism, cultural value and ethics are also at stake, and the guide says such issues need to be debated.
3. The mammal must be chosen, because conservation effort should go to the species that people care about most — A student who uses appeal as the criterion picks this. Popularity is one consideration in the debate, but the mammal has many close relatives and its loss would remove little unique evolutionary history; the EDGE rationale exists to stop such species crowding out distinct ones.
4. The amphibian must be chosen, because having no close relatives makes it the older and more primitive species — A student who reads distinctiveness as age picks this. The amphibian's priority under EDGE comes from the unique evolutionary history it represents and its endangerment, not from being older; and even then the decision is not automatic.

Syllabus statement A4.2.8 · Read this in Learn