Populations shrink when their climate shifts, when competitors arrive, when they are hunted or when their habitat is cleared. This lesson explains those threats, why biodiversity is worth keeping, and the tools of conservation, from national parks and frozen zoos to IVF in rare mammals and international law.
Populations and species become extinct when climate change shifts conditions faster than they can move or adapt, when a competitor uses their resources more efficiently, when hunting by humans removes individuals faster than they reproduce, and when habitats are degraded or lost. Small populations also lose genetic diversity. Biodiversity is worth maintaining for ecosystem stability and services, for food, medicines and genes, for economic value such as ecotourism, and for ethical reasons. Conservation protects species in national and marine parks, and away from their habitat in zoos, botanic gardens, frozen zoos and seed banks. Rare mammals can be bred by IVF, embryo transfer and surrogacy. Invasive alien species are controlled to protect native species, and internationally the IUCN assesses threat (the Red List) while CITES regulates trade.
Fig. 1: conservation of an endangered species in its own habitat, away from it, and through international agreements
Section 01
Four routes to extinction.
Start with no threat, then pick climate change, competition, hunting and habitat loss in turn. Watch the population graph, which starts at 60, and the shrinking or browning habitat.
Threat
How it drives a population down
climate change
temperature and rainfall shift, so the area with suitable conditions shrinks or moves; species that cannot migrate or adapt fast enough decline (for example mountain species with nowhere higher to go, coral bleaching in warmer seas)
competition
another species, often introduced, uses the same food, space or light more efficiently, so the native species gets fewer resources and declines
hunting by humans
animals are killed for meat, skins, ivory, horn, trophies or traditional medicine faster than they can reproduce; large, slow-breeding species are most at risk
degradation and loss of habitat
land cleared for farming, building, mining or logging, or polluted, supports fewer individuals; the habitat left is split into fragments too small for viable populations
Small populations: once numbers are low, inbreeding and the loss of alleles reduce genetic diversity, and a single disease outbreak, fire or bad season can wipe out the rest.
Why maintain biodiversity: diverse ecosystems are more stable and keep providing services (pollination, nutrient cycling, clean water, soil formation, climate regulation); wild species supply food, medicines, materials and genes for crop and livestock breeding; ecotourism brings income; and many people argue we have a moral duty to protect other species for future generations.
Examiner trap
Do not just name the threat: explain the effect on the population. For example, habitat loss reduces the food and breeding sites available, so the carrying capacity falls and fewer individuals survive and reproduce.
Section 02
Keeping endangered species safe.
Click through the conservation methods: zoos, botanic gardens, national and marine parks, frozen zoos and seed banks. For each, note what is protected and where.
Method
Role in conservation
zoos
protect animals from threats; captive breeding programmes, with stud books to avoid inbreeding; reintroduction to the wild; research; public education
botanic gardens
grow endangered plants; propagate them from seeds, cuttings and tissue culture for reintroduction; research their needs; education
national parks and marine parks
protect whole ecosystems in place, restricting building, farming, hunting or fishing; species keep their natural habitat, behaviour and interactions
frozen zoos
store sperm, eggs, embryos and tissue in liquid nitrogen at −196 °C, keeping genetic diversity for future breeding, even after the donor has died
seed banks
store dried seeds at about −20 °C for decades; conserve the genetic diversity of wild plants and crop varieties; seeds are tested for viability and regrown to make fresh stock
Examiner trap
Seed banks and frozen zoos do not stop a species declining in the wild on their own. They store genetic diversity; the habitat must still be protected for any reintroduced organisms to survive.
Stage 1 · Learn
Check what the sim just showed you
Four quick checks. Each correct answer earns XP and records this skill on your profile.
Quick check+10 XP
In the threats tab, which effect does habitat loss have on the simulated habitat?
Quick check+10 XP
In the threats tab, the competition option adds grey animals. What do they represent?
Quick check+10 XP
According to the conservation tab, at what temperature do frozen zoos store sperm, eggs and embryos?
Quick check+10 XP
Which is a role of botanic gardens shown in the conservation tab?
Section 03
Assisted reproduction, aliens and international law.
The last chips in the conservation tab cover IVF, embryo transfer and surrogacy, invasive species, and the IUCN and CITES.
IVF: eggs are collected from a female of the endangered species (after hormone treatment) and fertilised in the laboratory with sperm, fresh or thawed from a frozen zoo.
Embryo transfer: the early embryos are placed into the uterus of a female; extra embryos can be frozen.
Surrogacy: the female receiving the embryo may be a surrogate mother of the same species or a closely related, more common species, so a rare female can produce many more offspring than she could carry herself.
Benefits: more offspring from few animals, sperm can be moved between zoos instead of stressed animals, and breeding can use genetically unrelated parents to increase genetic diversity.
Invasive alien species: species introduced to an area where they did not evolve, which spread because they lack natural predators, parasites and competitors. They harm native species by competition, predation, disease and hybridisation, so they are controlled by removal, trapping, culling, biological control and border checks.
IUCN (International Union for Conservation of Nature): assesses the conservation status of species and publishes the Red List (from Least Concern through Vulnerable, Endangered and Critically Endangered to Extinct in the Wild and Extinct); this guides priorities and funding, and supports conservation projects.
CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora): an international agreement that bans trade in the most endangered species and regulates trade in others with permits, covering live organisms and products such as ivory and rhino horn.
Stage 2 · Exam
Exam-style questions
Unlocks once the four checks above are done. Worth more XP, written to A Level Paper 4 standard.
Finish the four checks above to unlock the exam questions
Exam style+20 XP
An endangered antelope female is given hormones; her eggs are fertilised in the laboratory and the embryos placed in females of a common related species. Which techniques are being used?
Exam style+20 XP
What is the main role of CITES?
Exam style+20 XP
Why are invasive alien species often so successful in a new area?
Exam style+20 XP
A population of a mountain plant has fallen to 40 individuals. Why is it now at greater risk of extinction than its numbers alone suggest?
Skill unlocked
Extinction and conservation, mastered.
This skill is now recorded on your profile. Keep the chain going.