Topic 20.4 · Core + Supplement
Conserving Endangered Species
A small surviving population is not automatically safe just because it still exists. Cambridge wants you to see conservation working on several different fronts at once — the species itself, its habitat, human behaviour, and, at Supplement level, its genetics.
Core conservation methods
Monitoring tracks population size, distribution and breeding success over time, so conservationists have real evidence of whether a population is growing or shrinking, and where action is most needed. Protecting species directly reduces killing, capture or disturbance, while protecting habitats preserves the food, shelter, breeding sites and physical conditions a species actually depends on — protecting the animal without protecting where it lives rarely solves the underlying problem on its own. Education explains why a species is threatened and how human behaviour affects it, which matters because long-term conservation usually needs cooperation from the people living in or using that ecosystem, not enforcement alone.
Captive breeding programmes breed endangered animals under managed, protected conditions to increase numbers, and in suitable cases the offspring can later support wild populations. Seed banks do the equivalent job for plants, storing seeds under controlled conditions so genetic material is preserved and can be germinated again even if wild populations decline severely.
Supplement: artificial insemination
Artificial inseminationintroduces sperm into a female’s reproductive tract without natural mating taking place. In a captive breeding programme this allows reproduction between carefully selected individuals even when they’re kept apart or natural mating is difficult, letting sperm from a chosen male be used strategically across a breeding plan.
Supplement: in vitro fertilisation
In vitro fertilisationfollows three steps: egg cells and sperm are collected; fertilisation happens outside the female’s body; and the resulting embryo is transferred into a suitable female for development to continue. Like artificial insemination, IVF lets conservationists carry out carefully planned breeding when natural reproduction between selected individuals is difficult, and makes fuller use of the limited gametes available from a very small population.
Neither technique creates new genetic variation on its own — both help conservationists manage breeding and make better use of the variation a population already has, not generate variation it doesn’t.
Supplement: genetic variation in small populations
When a population becomes very small, fewer individuals remain to breed, so fewer different alleles remain in circulation and genetic variation falls. That matters because a genetically varied population is more likely to include individuals with traits that help them survive a new disease or a changing environment — with little variation left, a single environmental change or disease can affect nearly every individual in much the same way, which raises the population’s overall risk of extinction. This relationship between population size and genetic variation is required; the mechanism of genetic drift itself is not, and needn’t be part of an answer at this level. The underlying concept of genetic variation is built up fully in Chapter 18 — what’s new here is applying it specifically to the risks facing a shrinking, endangered population.
Why conservation programmes matter
Conservation isn’t only about the survival of one species in isolation. It maintains or increases overall biodiversity, reduces the risk of extinction — which, once it happens, can’t be reversed — and protects ecosystems that would otherwise be seriously damaged by comparatively small additional disturbances. It also maintains ecosystem functions that other species, including humans, depend on: nutrient cycling, and the ongoing provision of biological resources such as food, drugs, fuel and genes. Genes matter here in their own right, because the genetic variation held within a species can supply useful traits for future breeding, disease resistance or other biological applications — meaning a species that disappears can represent the loss of a genetic resource, not only the loss of the organism itself.
Where this leads
The methods above apply to a species wherever it’s found. Two specific resources get their own, more detailed sustainable-management approach because of how they’re commercially harvested: see sustainable forests and fish stocks.