Questions on conservation in situ and ex situ

Question 1

A captive breeding programme has raised a large scavenging bird from 22 individuals to more than 500, over half of them flying free, but released birds are trapped and blood-tested for lead every year and treated when concentrations are high. Evaluate the claim that the programme has been a success.

Accepted Answer

B1 for: the species still exists, and the alternative when the last wild birds were taken into captivity was extinction within a few years, so on any count of individuals the outcome is a success B1 for: the captive breeding worked better than expected. Removing the first egg so that a pair lays another roughly doubled the output, and more than half the birds now fly free rather than being held in enclosures B1 against: the cause of the decline has not gone, since carcases shot with lead ammunition remain the leading source of poisoning, so without continued releases, trapping and treatment the free-flying population would fall again B1 against: the population is therefore not self-sustaining in the technical sense, and a disease outbreak in one flock can still remove a substantial part of it, so the programme is a permanent commitment rather than a finished task B1 judgement: whether this counts as success depends on the goal. It plainly succeeded in keeping the species in existence, and it has not produced a wild population living without veterinary support, with the remaining obstacle being a rule about ammunition rather than anything biological

Question 2

Describe how seed is collected, prepared and stored in a seed bank, and describe how the collection is checked for viability.

Accepted Answer

B1 seed is collected in the wild from many individuals across the population, with locality, date and habitat recorded, then cleaned and X-rayed so that empty or insect-damaged seeds are discarded B1 it is dried slowly, typically at about 15 °C and 15 per cent relative humidity, down to roughly 5 per cent moisture content B1 it is then sealed in containers and frozen, conventionally at −20 °C, and the drying has to come first because water left in the seed forms ice crystals that rupture the cell membranes B1 a sample from each accession is germinated at intervals, commonly every ten years, and if the germination percentage has fallen too far, seed is grown on to produce a fresh batch

Question 3

Explain why a captive breeding population loses genetic diversity, and explain what is done to slow that loss.

Accepted Answer

B1 a captive population is founded by a handful of individuals and held at a few hundred at most, so it passes through a bottleneck by construction and alleles that were not in the founders are simply absent B1 in a small population the alleles passed on each generation are a small sample of those present, so frequencies drift by chance and alleles are lost altogether, and only mutation or migration restores them B1 inbreeding raises the frequency of homozygous recessive genotypes, so inherited disease and reduced fertility become commoner in the herd B1 a studbook records every individual's ancestry so that the least related animals available can be paired, and animals are moved between institutions to widen the choice of mates

Question 4

Compare in situ with ex situ conservation, referring to genetic diversity, to the rest of the community and to the problems each approach cannot solve.

Accepted Answer

B1 in situ keeps the species where it lives, so the whole community and the conditions it is adapted to are conserved with it, whereas ex situ conserves the species alone and cannot conserve its habitat or the species it depends on B1 in situ can support a far larger population, so far fewer alleles are lost to drift and inbreeding, whereas an ex situ population is founded by a handful of individuals and passes through a bottleneck B1 selection continues to act in situ, so the population stays adapted to conditions that are themselves changing, whereas captivity selects for animals that breed well in enclosures and learned behaviour such as hunting or predator avoidance may never be acquired B1 ex situ offers controlled conditions, veterinary care, assisted breeding and chosen matings, and is the only option for a species already gone from the wild, whereas a boundary on a map does not stop poaching, invasive species, pollution or a changing climate

Question 5

Evaluate the claim that a frozen zoo makes the extinction of a mammal species reversible.

Accepted Answer

B1 in support: the store holds gametes and embryos carrying alleles that are otherwise gone, and in vitro fertilisation, embryo transfer and surrogacy give a route from stored material to living animals B1 against: freezing and thawing damage cells and the protocols differ between species, so success rates for wild mammals are low, and eggs and embryos are much harder to store than sperm B1 against: a stored embryo needs a female of the species or a suitable related surrogate to carry it, and a population rebuilt from a handful of samples would have very little genetic diversity and no learned behaviour B1 a judgement: a frozen zoo can slow the loss of alleles and support a population that still exists, but it does not restore the habitat the species was lost from, so it is a supplement to in situ conservation rather than a replacement for it

Question 6

Compare CITES with the Convention on Biological Diversity, referring to what each one regulates and how binding each one's provisions are.

Accepted Answer

B1 CITES regulates cross-border trade in endangered species, banning commercial trade in species listed in Appendix I entirely and requiring a permit for those in Appendix II, whereas the Convention on Biological Diversity is broader, covering conservation, sustainable use and the fair sharing of benefits from genetic resources B1 CITES controls trade specifically and does nothing about habitat loss, whereas the Convention on Biological Diversity addresses biodiversity loss more generally but through targets rather than trade rules B1 CITES depends on member states enforcing it at their own borders, whereas the Convention on Biological Diversity sets targets rather than prohibitions, and successive sets of its targets have not been met in full B1 both are international agreements that individual countries choose to join and must then implement through their own domestic law, so neither compels a non-signatory country to comply

Question 7

A conservation charity raises most of its funds by appealing to public support for large, visually appealing mammals such as tigers and pandas. Evaluate this as a strategy for funding conservation broadly.

Accepted Answer

B1 for: people value and are willing to pay to see and protect landscapes and charismatic animals, and ecotourism and public donations turn that valuation into real income that can pay directly for protection B1 for: a well-known species can act as a flagship that draws in funding and attention which then also supports conservation of the habitat, and of the many less visible species that share it B1 against: public valuation of species is measurably uneven, favouring large mammals and birds over invertebrates, fungi and plants, which is close to the reverse of where most of the planet's species diversity actually lies B1 judgement: funding driven mainly by public appeal will systematically under-fund the groups that hold most of the diversity, so it is a genuine source of income for conservation but a poor basis for deciding which species most need it

Question 8

The caterpillar of the large blue butterfly feeds on wild thyme for about three weeks, then is carried by one particular species of red ant into its nest, where it eats the ant grubs for about ten months before pupating. That ant thrives only in short turf, where the sun warms the soil; in taller turf the soil is cooler and a related ant, which does not rear the caterpillars, replaces it. Grazing rabbits kept the turf short until myxomatosis killed most of Britain's rabbits in the 1950s. The butterfly's sites were protected from development and collectors, but it became extinct in Britain in 1979. Explain why protecting the sites did not prevent the extinction, and suggest what had to be done before the butterfly could be reintroduced.

Accepted Answer

B1 the butterfly depends on the one ant species for most of its larval life, so it cannot survive where that ant is absent, however much thyme there is B1 without grazing the turf grew taller and the soil cooler, so the host ant declined and was replaced by the related species that does not rear the caterpillars B1 protection kept people from damaging the sites but did nothing to keep the turf short, so the conditions the ant needs were lost on protected land B1 the turf had to be kept short again, by grazing with livestock or by cutting, until the host ant was common, and only then could butterflies be reintroduced

Question 9

Explain what artificial insemination, in vitro fertilisation and embryo transfer each contribute to captive breeding, and explain when a surrogate mother is used instead.

Accepted Answer

B1 artificial insemination moves semen to a female without moving the male, which matters where the two animals are kept on different continents or where a pair will not mate naturally B1 in vitro fertilisation takes eggs from a female and fertilises them with collected semen in the laboratory, allowing the resulting embryos to be assessed before any is used B1 embryo transfer places an embryo into a female that did not produce the egg, so that a single genetically valuable female can become the mother of far more offspring than she could carry herself B1 a surrogate, a female of a closely related species, is used to carry a pregnancy where no female of the endangered species itself is available to do so

Question 10

A student says that if a species is in trouble, the answer is to breed it in a zoo and put it back. Discuss whether this is generally an adequate conservation strategy.

Accepted Answer

B1 what is right: captive breeding has restored some species that would otherwise have gone extinct, and it is the only option remaining once a species is already extinct in the wild B1 against: a captive population is founded by a handful of individuals and held at a few hundred at most, so it loses genetic diversity to a bottleneck and to inbreeding, and captivity can select for behaviour unsuited to survival outside it B1 against: releasing bred animals does nothing about the cause of the original decline; if that cause, such as habitat loss, poaching or lead poisoning, is still present, a released population will simply decline again or require permanent, continued intervention such as trapping and treatment, as with the California condor B1 judgement: breeding and releasing a species can rescue it from extinction, but 'put it back' understates what is needed; a self-sustaining wild population usually also requires the original cause of decline to be addressed, which captive breeding on its own does not do

Question 11

The seeds of many tropical rainforest trees are shed with a high water content and die if they are dried. Suggest why such species cannot be held in a conventional seed bank, and suggest two other ways of conserving them outside their habitat.

Accepted Answer

B1 the seed cannot be dried to about 5 per cent moisture, and freezing it while wet would form ice crystals that rupture the cell membranes, so the method depends on a step these seeds do not survive B1 they can be kept as a living collection of plants in a botanic garden, which takes far more space and labour and holds far fewer individuals, and therefore far fewer alleles B1 embryos can be excised and frozen in liquid nitrogen, or the plants maintained in tissue culture, both of which are more expensive and less secure than a seed store

Question 12

Describe what a frozen zoo stores and explain one advantage it has over keeping the same species as living animals in a zoo.

Accepted Answer

B1 it stores gametes, embryos and tissue samples from endangered animals in liquid nitrogen at about minus one hundred and ninety six degrees Celsius B1 at that temperature metabolism stops, so the material keeps for decades without ageing or being selected on B1 it holds far more genetic variation in far less space and at far lower cost, and semen stored decades ago can put alleles back into a population that has since lost them

Question 13

Explain the economic case for maintaining biodiversity, giving a named example, and explain the standard objection made to this argument.

Accepted Answer

B1 wild species are a stock of potentially useful material; for example, vincristine and vinblastine, still used to treat childhood leukaemia and Hodgkin lymphoma, were derived from the Madagascar periwinkle B1 wild relatives of crop species can also carry disease resistance that plant breeders need, such as the wild rice from India that supplied resistance to grassy stunt virus bred into cultivated rice B1 the objection is that the argument applies in both directions: if a species is worth conserving because it may prove useful, a species assessed as having no use has no claim under this argument, and the great majority of species will never be assessed for usefulness at all

Question 14

Explain the ethical case for maintaining biodiversity, and explain the standard objection made to it.

Accepted Answer

B1 a species is the product of a very long evolutionary history, and the ethical case holds that it should not be ended by human action regardless of whether it is useful, with an obligation owed by the present generation to future ones B1 this argument does not depend on a species being useful or conspicuous, unlike the economic or aesthetic cases B1 the objection is that it gives no basis for choosing between species when a fixed budget cannot fund every one: an argument that every species has an equal and absolute claim cannot say which of two species should be funded when only one can be

Question 15

State what is meant by in situ conservation and what is meant by ex situ conservation.

Accepted Answer

B1 in situ: conserving a species in its natural habitat, so that the community and the conditions it is adapted to are conserved along with it B1 ex situ: conserving a species outside its natural habitat, in a zoo, a botanic garden, a seed bank or a captive breeding centre