Ch 3 · 18.3 Conservation · AS & A Level Biology 9700

Topic 3 of 3 in Classification, biodiversity and conservation — AS & A Level Biology 9700 — 88 lessons.

Introduction

Human activity is reducing biodiversity faster than it can be replaced by evolution, so conservation strategies aim to maintain species, genetic and habitat diversity. Cambridge examiners set "discuss" questions in this topic, requiring balanced, well-organised points rather than single facts, and expect named examples of organisations, sites and techniques rather than vague statements. (Syllabus section 18.3.)

Key ideas — Why species become extinct

A population becomes extinct when its death rate stays above its birth rate until no individuals are left. The syllabus names four causes:

🧑‍🏫 Teacher's explanation

Imagine a game of musical chairs where the number of chairs is constantly shrinking while the number of players stays the same. Eventually, there are no chairs left, and the game ends. In biology, extinction is the ultimate 'end of the game' for a species. It happens when the death rate consistently exceeds the birth rate until the population hits zero.

📖 Definitions

🔍 Worked example — Easy

A population of 500 birds has a birth rate of 0.2 per year and a death rate of 0.3 per year. Calculate the percentage change in the population size after one year.

🔍 Worked example — Standard

A conservationist uses a seed bank to preserve a rare plant species. Explain why storing seeds is a more effective method for preserving plant biodiversity than simply protecting a small patch of land.

🔍 Worked example — Exam-style

Compare the roles of the IUCN and CITES in conservation.

⚠️ Common errors

🧠 Quick check 1

🧠 Quick check 2

🎯 Exam question

Key ideas — Reasons for maintaining biodiversity

Biodiversity must be maintained for several linked reasons. Ecological reasons: species interact in food webs and nutrient cycles, so losing one species can destabilise an ecosystem and reduce the services it provides, such as pollination, soil formation and climate regulation. Economic reasons: wild species and their genetic diversity are sources of new medicines, crop varieties, and genes for breeding disease resistance or stress tolerance into existing crops; many habitats also generate income through sustainable ecotourism. Ethical and aesthetic reasons: many people consider other species to have intrinsic value and a right to exist, independent of any use to humans, and value habitats for their beauty and recreational value. Scientific reasons: undiscovered species and unstudied genetic variation are a resource for ongoing research into evolution, ecology and physiology.

🧑‍🏫 Teacher's explanation

Think of biodiversity like a complex game of Jenga. Each species is a wooden block. If you have a huge tower with hundreds of blocks (high biodiversity), removing one or two won't make the tower fall. But if you have a tiny tower with only a few blocks (low biodiversity), removing just one can cause the whole structure to collapse.

📖 Definitions

🔍 Worked example — Easy

A researcher identifies that a specific orchid species is declining due to the loss of its only pollinator, a specific bee species. Explain how this loss affects the ecosystem stability.

🔍 Worked example — Standard

Compare the roles of a seed bank and a 'frozen zoo' in conservation.

🔍 Worked example — Exam-style

An invasive species is introduced to an island. Explain why controlling this species is vital for the conservation of the native fauna.

⚠️ Common errors

🧠 Quick check 1

🧠 Quick check 2

🎯 Exam question

(a) Outline two reasons why maintaining the biodiversity of this ecosystem is important. [2] (b) Describe how assisted reproduction techniques, such as IVF, could be used to help prevent the extinction of this species. [2] [4 marks]

Key ideas — In situ conservation

In situ conservation protects species within their natural habitat in conserved areas: national parks, marine parks (where fishing, anchoring and other damaging activities are restricted) and nature reserves. Organisms continue to interact naturally with other species and with their physical environment, allowing natural selection and adaptation to continue, and large numbers of species can be protected simultaneously at relatively low cost. Limitations include continued vulnerability to poaching, disease, natural disasters and habitat-level threats such as climate change, which in situ measures alone cannot always prevent.

🧑‍🏫 Teacher's explanation

Imagine you are trying to protect a rare species of orchid. You have two choices: you can take the orchid out of the forest and keep it in a temperature-controlled greenhouse (ex situ), or you can protect the entire forest so the orchid can live where it belongs (in situ). In situ conservation is like protecting the whole forest. It is much more efficient because by saving the forest, you automatically save the insects, birds, and fungi that live there too.

📖 Definitions

🔍 Worked example — Easy

A conservationist manages a marine park. In the park, there are 500 individuals of Species A. Due to successful in situ conservation, the population increases to 750 individuals. Calculate the percentage increase in the population of Species A.

🔍 Worked example — Standard

Explain why in situ conservation is often considered more cost-effective than ex situ conservation for protecting an entire ecosystem.

🔍 Worked example — Exam-style

A population of mammals is declining due to the presence of an invasive alien species. Explain why controlling this invasive species is a priority for conservationists.

⚠️ Common errors

🧠 Quick check 1

🧠 Quick check 2

🎯 Exam question

Key ideas — Ex situ conservation

Ex situ conservation protects species away from their natural habitat, for example in zoos, botanic gardens, seed banks and gene banks. It is used when a species' population or habitat has declined so severely that in situ protection alone is insufficient, allowing controlled breeding, close monitoring and protection from the original causes of decline. Limitations include the cost and space needed to maintain viable populations, the loss of natural behaviours and adaptation to captivity, and the difficulty of ever successfully reintroducing organisms to the wild.

🧑‍🏫 Teacher's explanation

Imagine you have a rare, ancient book that is falling apart because the library it is kept in is flooding and the roof is leaking. If you leave it there, it will be lost forever. 'Ex situ' conservation is like taking that book out of the flood zone and putting it in a climate-controlled museum vault. You save the object, but you have to work hard to make sure it still functions like a book and can eventually be used in a library again.

📖 Definitions

🔍 Worked example — Easy

A conservationist uses a seed bank to store seeds from a rare orchid. If the seed bank successfully preserves 500 seeds, but only 15\% germinate successfully when planted in a controlled environment, calculate the number of viable plants produced.

🔍 Worked example — Standard

Compare the use of in situ and ex situ conservation for a critically endangered mammal species.

🔍 Worked example — Exam-style

A conservation program uses IVF and embryo transfer to increase the population of a rhino species. Explain why this is considered 'assisted reproduction' and state one potential risk of relying solely on this method for long-term survival.

⚠️ Common errors

🧠 Quick check 1

🧠 Quick check 2

🎯 Exam question

(a) Outline one reason why in situ conservation might be failing for this species. [1] (b) Describe how ex situ conservation could be used to prevent the extinction of this bird. [2] (c) Explain one limitation of the ex situ conservation method described in part (b). [1] [4 marks]

Key ideas — Botanic gardens, seed banks and frozen zoos

Botanic gardens maintain living collections of plant species, including rare and endangered ones, for propagation, horticultural research and public education, and can supply plants for habitat restoration projects. Seed banks (e.g. the Millennium Seed Bank in the UK, the Svalbard Global Seed Vault) store seeds from many plant species under cold, dry conditions, which greatly extends seed viability and allows the genetic diversity of a species to be preserved in a very small physical space at low cost; stored seeds are periodically tested for germination and regrown to refresh stocks, and can be used to restore populations after a local extinction.

🧑‍🏫 Teacher's explanation

Imagine a massive library that stores not just books, but the actual blueprints for life. If a forest burns down or a species is hunted to near extinction, we lose the 'instruction manuals' for those organisms. Conservation techniques like seed banks and frozen zoos act as a biological backup drive. Instead of keeping the whole animal or plant, which requires massive space and food, we store only the essential genetic code.

📖 Definitions

🔍 Worked example — Easy

A botanic garden is used to restore a population of a rare orchid. The garden currently holds 500 seeds. If the germination rate is 25\%, calculate the number of viable plants expected from this batch.

🔍 Worked example — Standard

Compare the advantages of using a seed bank versus a living collection in a botanic garden for the purpose of long-term conservation.

🔍 Worked example — Exam-style

An endangered mammal population is suffering from a loss of genetic diversity due to a bottleneck effect. Describe how 'frozen zoo' technology and assisted reproduction could be used to mitigate this loss.

⚠️ Common errors

🧠 Quick check 1

🧠 Quick check 2

🎯 Exam question

Key ideas — Captive breeding and assisted reproduction

Zoos run captive breeding programmes for endangered animals, using studbooks that record each animal's ancestry so that unrelated animals are paired and inbreeding is avoided. The aim is often reintroduction to the wild, which is difficult: captive-bred animals may lack survival skills, and the original threats must be removed first. Zoos also carry out research and educate the public.

🧑‍🏫 Teacher's explanation

Imagine you are trying to save a rare, ancient book that is falling apart. If you only have one copy, and it gets damaged, the story is lost forever. To save it, you might make photocopies (assisted reproduction) to ensure there are many versions, or you might store digital files in a safe place (seed banks/frozen zoos) so you can print them later if the original is lost.

📖 Definitions

🔍 Worked example — Easy

A zoo manages a population of 50 rhinos. To prevent inbreeding, they use a studbook to select mates. If the current genetic diversity is measured by the number of different alleles at a specific locus, and the population size increases from N=50 to N=100 through successful captive breeding, explain why this is beneficial for long-term survival.

🔍 Worked example — Standard

Compare the use of Artificial Insemination (AI) and In Vitro Fertilisation (IVF) in a conservation programme.

🔍 Worked example — Exam-style

A conservationist uses embryo transfer to save a species of rare antelope. The procedure involves: (i) collecting eggs from a rare female, (ii) fertilizing them in a lab, and (iii) placing the embryo into a domestic cow. Identify the specific method being used and explain the advantage of using a surrogate mother.

⚠️ Common errors

🧠 Quick check 1

🧠 Quick check 2

🎯 Exam question

(a) Describe the process of embryo transfer. [2] (b) Explain why increasing the population size through assisted reproduction is important for the survival of the species. [2] [4 marks]

Key ideas — International and local organisations

The International Union for Conservation of Nature (IUCN) assesses the conservation status of species worldwide and publishes the Red List, categorising species from "least concern" to "critically endangered" or "extinct", which guides global conservation priorities. The Convention on International Trade in Endangered Species (CITES) is an international agreement that regulates or bans trade in listed endangered species and their products between member countries, reducing the incentive for poaching. Local and national organisations, including government agencies, community groups and non-governmental organisations, manage specific reserves, run captive breeding or reintroduction projects, and educate local communities, often addressing the particular social and economic pressures that threaten biodiversity in that area.

🧑‍🏫 Teacher's explanation

Think of biodiversity as a massive, complex web of interconnected threads. If you pull out too many threads—due to habitat loss or climate change—the whole web loses its strength and eventually collapses. Conservation is the effort to patch those holes and stop people from pulling more threads out.

📖 Definitions

🔍 Worked example — Easy

A student is asked to list three reasons why a population might become extinct. Provide three distinct biological or human-induced causes.

🔍 Worked example — Standard

Compare the roles of a seed bank and a 'frozen zoo' in conservation.

🔍 Worked example — Exam-style

An invasive species is introduced to an island. Explain why controlling this species is vital for the local ecosystem.

⚠️ Common errors

🧠 Quick check 1

🧠 Quick check 2

🎯 Exam question

(a) Outline two reasons why maintaining the biodiversity of this area is important. [2] (b) Describe how assisted reproduction techniques, such as IVF, could be used to help increase the population size of this mammal. [2] [4 marks]

Key ideas — Controlling invasive alien species

An invasive alien species is one that has been introduced, deliberately or accidentally, to an area outside its natural range and spreads rapidly, harming native species. Reasons to control them:

🧑‍🏫 Teacher's explanation

Imagine a busy, balanced community garden where every plant and insect has a specific role. Now, imagine someone accidentally drops a handful of extremely aggressive, fast-growing weeds into that garden. These weeds don't have any local insects to eat them, so they grow uncontrollably, stealing all the sunlight and water from the original flowers.

Ch 3 · 18.3 Conservation · AS & A Level Biology 9700

All chapters in Classification, biodiversity and conservation