17.617-18 · Selection, Evolution, Classification and Conservation

Conservation — Cambridge AS & A Level Biology 9700 Revision Notes & Topical Questions

5 min read 9 parts Lesson 19 of 36 1 quiz

📚 Cambridge AS & A Level Biology 9700 Hub / Topical Revision

0%read

Lesson summary

17.6 Conservation — CAMBRIDGE AS & A LEVEL BIOLOGY 9700 — REVISION NOTES notes: Explain why species become extinct, why biodiversity matters and how species are conserved.Extinction — a species comes to an end and dies out; it is a natural process, but current rates are raised by…

National parks
Marine parks
Botanic gardens
Frozen zoos
Seed banks
Embryo transfer

Part 1 of 7Causes of extinction

Extinction

Extinction a species comes to an end and dies out;
- it is a natural process, but current rates are raised by humans.

Main causes:

Habitat degradation and loss (the main cause): deforestation, draining wetlands and pollution.
Climate change from fossil fuel burningwarming, rising seas, ocean acidity and melting ice.
Competition and introduced non-native species with no natural predators or pathogens.
Hunting by humans, especially for rare species.

Small populations are more vulnerable because inbreeding and genetic drift reduce genetic variation and fitness.

Part 2 of 7Reasons for maintaining biodiversity

Reason	Explanation
Ecological	Diverse ecosystems are more stable; keystone species such as elephants maintain the ecosystem
Economic	Medicines (e.g. paclitaxel from yew), ecotourism, enzymes such as Taq polymerase from hot-spring bacteria
Aesthetic and social	Beauty and inspiration; recreation such as walking and birdwatching
Moral and ethical	Humans have a duty not to cause extinctions
Environmental	Services: carbon dioxide absorption, decomposition, water and nutrient cycles, producers
Agricultural	Wild relatives supply alleles to rescue uniform crops, e.g. wild potatoes of the Andes

Part 3 of 7In situ conservation

Keeps species in their natural habitat, where the support systems already exist.

National parks

National parks government-controlled land with legislation protecting wildlife.
Human access is controlled, industry and building are regulated, and hunting is limited or banned.

Marine parks

Marine parks protected water with restrictions to prevent overfishing and pollution.

Parks gain support from tourism income, local jobs and community benefits.

Part 4 of 7Ex situ conservation

Zoos

Zoos captive breeding for release, research and education.
Problemsreduced genetic diversity, some species will not breed, not all zoos can meet needs.
The oryx was saved by zoos; pandas have not been reintroduced despite 60 years of breeding.

Botanic gardens

Botanic gardens grow endangered plants from seeds and cuttings, use tissue culture, do research and educate.

Frozen zoos

Frozen zoos store eggs, sperm and tissue at about −196 °C.

Seed banks

Seed banks dried seeds in temperature-controlled stores, grown on periodically to renew them.
Svalbard Global Seed Vault holds almost 1 million samples; seeds of coffee and cacao cannot be frozen.

Conservation fails if there is no habitat to return to, so conserving whole ecosystems is essential.

Part 5 of 7Assisted reproduction

Small isolated populations suffer inbreeding depression and difficulty finding mates.

IVF

IVF eggs are removed from the ovaries, mixed with semen outside the body, and the embryos are cultured then transferred.

Embryo transfer

Embryo transfer an embryo from a rare female is transferred to a surrogate, sparing the female the risks of pregnancy.
The surrogate can be of another, non-vulnerable species if closely related.
The surrogate has hormone treatment to prepare the uterus.

Artificial insemination

Artificial insemination semen is injected into the uterus, avoiding transport of animals.

Part 6 of 7Controlling invasive species

Invasive species

Invasive species species that move into an ecosystem where they were previously unknown, mostly due to humans.

They have no natural predators or competitors, so numbers rise rapidly.

They compete with and displace natives, over-predate, and bring new diseases.
They reduce biodiversity and productivity and cost economies money.

Control methods include prevention at borders, physical removal, chemical control and biological control.

Biological control agents must be host-specific or they may become invasive themselves.

Part 7 of 7IUCN and CITES

IUCN

IUCN assesses the conservation status of species and publishes the Red List.
Categories depend on population numbers and threats, and are reviewed continually.

CITES

CITES agreement signed by over 150 countries to control trade in endangered species.
Appendix I — greatest risk of extinction; all trade banned.
Appendix II — not endangered yet but will be unless trade is controlled; export permits needed.
Appendix III — listed at the request of one country; permits needed but easier to obtain.

Banning trade can raise the price and so encourage illegal trade.

Key terms

Term	Meaning
Extinction	The dying out of a species.
In situ conservation	Protecting species in their natural habitat.
Ex situ conservation	Protecting species outside their natural habitat, e.g. in zoos or seed banks.
Invasive species	A species that has spread into an ecosystem where it was previously unknown.
IVF	Fertilisation of an egg outside the body.
Seed bank	Facility storing dried seeds to conserve plant diversity.
CITES	Convention controlling international trade in endangered species.
IUCN Red List	List of conservation status of species.

Avoid these mistakes

Saying all extinction is caused by humans — extinction is also natural, but human activity has greatly increased the rate.

Saying zoos alone can save species — habitat must still exist for release.

Forgetting that small populations lose fitness through inbreeding and genetic drift.

Saying biological control is always safe — the agent must be specific or it may itself become invasive.

Saying CITES Appendix II bans trade — it allows trade with permits.

Last updated: 18 October 2026