What you need to know
- 4.21Evaluate zoo and seed-bank methods: research, captive breeding, reintroduction and education.
- 4.15Human activity threatens the variety of life, which is why conservationProtecting and managing species and habitats to maintain biodiversity. is attempted.
Evaluate means give strengths and limitations, not write a slogan. In situ habitat protection is the necessary context; it is not a substitute for discussing the specified ex situ methods. These notes are not fundraising, travel advice or a ranking of named zoos.
By the end, you should be able to…
- Describe research, captive breeding, reintroduction and education.
- Explain how seed bankA store of seeds kept dry and cold so that they stay viable for many years. store genetic diversityThe variety of alleles in a population or species..
- Give a balanced evaluation of each approach.
Build your understanding
Why ex situ methods exist
When a wild populationAll the individuals of one species living in one area at the same time. is tiny or its habitatThe place where an organism lives. is disappearing, keeping organisms or their gameteA haploid sex cell, such as a sperm or an egg cell. and seeds off-site can prevent immediate extinction. Zoos, botanic gardens and seed bankA store of seeds kept dry and cold so that they stay viable for many years. are ex situDescribes conservation away from the natural habitat, such as in a zoo or a seed bank.: they work away from the original nicheThe role of a species in its habitat: how it uses biotic and abiotic resources and interacts with other organisms.. They cannot replace that niche. Specification 4.21 asks you to evaluate how they conserve endangered speciesA group of organisms that can interbreed to produce fertile offspring. and genetic diversityThe variety of alleles in a population or species..
Genetic diversity is the point as much as headcount. A dozen related animals are a weaker insurance policy than a larger, carefully paired group. heterozygosityA measure of genetic diversity: H = number of heterozygotes ÷ number of individuals, for one gene locus. and gene-pool ideas from 4C 2 and 4C 4 belong in this evaluation.
Zoos: four named roles
Scientific research can record breeding biology, disease and genetics that are hard to study in the wild. Captive breeding aims to increase numbers while avoiding inbreeding, often using studbooks and transfers between collections. Reintroduction programmes release animals if threats in the habitat have been reduced and if the animals can survive. Education can change public behaviour and funding for in situDescribes conservation in the species’ natural habitat, such as a nature reserve. work.
Limitations: small groups lose diversity and may inbreed; animals can lose wild skills; reintroduction fails if hunting, habitat loss or disease remain; welfare and cost are real; a zoo cannot hold an ecosystemA community together with the non-living (abiotic) parts of its environment, interacting.. Success stories exist, but they do not make zoos sufficient on their own.
Seed banks: cold stores of alleles
Seed banks dry and freeze seeds from many parent plants so a wide sample of the gene poolAll the alleles of all the genes in a population. is kept for decades. Collections can support research, breeding and later restoration. Svalbard, for example, stores duplicate samples from genebanks around the world as a backup. Wild-species banks similarly try to sample many populations, not one convenient field.
Limitations: not all plants produce orthodox seeds that survive drying and freezing; some need living collections or cryopreservation of other tissues; stored seeds do not experience ongoing selection in the wild; pollinators, soil and habitat still have to exist for restoration. A vault without habitat work is a library with no town left to use it.
| Method | A strength for genetic diversity | A limitation |
|---|---|---|
| Scientific research | Measures variation, health and breeding systems | Knowledge alone does not restore habitat |
| Captive breeding | Can raise numbers of a rare animal | Small groups inbreed; wild skills may be lost |
| Reintroduction | Returns genes to a wild population if it works | Fails if the original threat remains |
| Education | Can protect habitat through people and policy | Hard to measure; not a substitute for breeding or land |
| Seed banks | Many genotypes stored compactly for decades | Not all species bank well; habitat still required |
Make your reasoning visible
Always pair a strength with a limit
“seed bankA store of seeds kept dry and cold so that they stay viable for many years. store diversity” scores less than “they store many genotypes, but restoration still needs habitatThe place where an organism lives. and not all seeds survive freezing”.
Name genetic diversity
4.21 includes diversity, not only “save the speciesA group of organisms that can interbreed to produce fertile offspring.”. Mention inbreeding or sampling many parents.
Avoid this misconception
The claim: If a species is in a zoo, it is conserved.
The correction: A small captive group can lose genetic diversityThe variety of alleles in a population or species. and cannot play its wild ecological role. Evaluate numbers, breeding design and habitat, not presence in a cage.
Check your understanding
Try each question before opening the suggested answer.
Practice question
Retrieval and explanation · suggested answer
Name the four zoo or seed-bank methods listed in specification 4.21.
Show suggested answer
Scientific research, captive breeding programmes, reintroduction programmes and education.
Practice question
Retrieval and explanation · suggested answer
How do seed banks conserve genetic diversity?
Show suggested answer
They store seeds from many parent plants in cold, dry conditions, keeping a wide sample of alleles ex situ.
Practice question
Retrieval and explanation · suggested answer
Give one reason a reintroduction can fail after successful captive breeding.
Show suggested answer
The original threat, such as habitat loss or hunting, may remain, or released animals may lack skills needed in the wild.
Take the idea further
Apply the same specification knowledge to an unfamiliar problem. Any extra assumptions are supplied in the question.
Stretch question
A zoo has 40 animals of an endangered bird, all descended from four founders, and a popular education exhibit. The wild habitat is still being cleared. Evaluate this as conservation of the species and its genetic diversity.
Show a hint
Separate education, numbers and the gene pool from in situ threat.
Explore the reasoning
Education may build support, and 40 birds are more than four. The gene pool is still a bottleneck from four founders, so inbreeding and lost alleles remain likely. Clearing the habitat means reintroduction cannot succeed yet. This is partial insurance, not completed conservation.
Recall this lesson
Lesson recall questions
Question 1 of 5: Name two human activities that threaten biodiversity.
Variety of life under threat
Practice question
Retrieval and explanation · suggested answer
Name two human activities that threaten biodiversity.
Lesson: 4C 1: Biodiversity and Endemism
Try this from memory first.
Put your biology to work
Explore where these ideas appear in the world. Enrichment, not extra required recall.
A backup of backups
4C · Conservation: Why and How?The Crop Trust describes the Svalbard Global Seed Vault as a backup of seed collections from genebanks around the world, held in permafrost as insurance against loss of…Specification 4.21Read & use the scienceClose article
Why this matters
The Crop Trust describes the Svalbard Global Seed Vault as a backup of seed collections from genebanks around the world, held in permafrost as insurance against loss of those collections. It is not a zoo, and it is not a wild habitat. It is one designed answer to the genetic-diversity half of 4.21, with the usual limit that frozen seed does not replace living ecosystems. Seed banks protect samples of genetic diversity, while zoos can coordinate breeding of living animals. Neither method is a substitute for protecting the conditions in which a species survives. The Svalbard backup illustrates why copies of seed collections are useful after accident or conflict, but viability, regeneration and access still require active management. In an evaluation, compare a method with the actual conservation goal: keeping alleles, restoring a wild population, or educating people. Each demands different evidence of success.
Back to the specification
Pearson Edexcel IAL Biology · Issue 2, February 2021 · Unit 2, pp. 21–24. The application extends beyond required recall.
- 4.21 be able to evaluate the methods used by zoos and seed banks in the conservation of endangered species and their genetic diversity, including scientific research, captive breeding programmes, reintroduction programmes and education
Use the science
Why does duplicating samples in Svalbard not by itself restore a vanished farmland variety to farmers?
Explore a possible response
Someone must still grow, select and share the seed under suitable conditions. The vault reduces the chance the last samples are lost.
Explore the source
- Crop Trust: Svalbard Global Seed VaultCrop Trust
From breeding programme to wild survival
4C · Conservation: Why and How?The US Fish and Wildlife Service says the California condor recovery programme brought the remaining wild birds into captive breeding and later released captive-bred birds. That does not…Specification 4.21Read & use the scienceClose article
Why this matters
The US Fish and Wildlife Service says the California condor recovery programme brought the remaining wild birds into captive breeding and later released captive-bred birds. That does not end the evaluation: conservation staff monitor survival, reproduction and ongoing threats after release. A zoo population can preserve individuals and genetic diversity, while habitat protection and threat reduction determine whether a wild population can persist. This offers a concrete way to weigh the benefits and limits of captive breeding in the specification. In an exam answer, identify an outcome that demonstrates conservation, rather than equating the number of animals in care with success in nature.
Back to the specification
Pearson Edexcel IAL Biology · Issue 2, February 2021 · Unit 2, pp. 21–24. The application extends beyond required recall.
- 4.21 be able to evaluate the methods used by zoos and seed banks in the conservation of endangered species and their genetic diversity, including scientific research, captive breeding programmes, reintroduction programmes and education
Use the science
Why would many chicks born in captivity not by itself prove successful reintroduction?
Explore a possible response
Chicks must survive after release, breed in the wild and face manageable threats. Captive births measure only one stage of recovery.
Explore the source
- California condor recovery programmeUS Fish and Wildlife Service