A forest or a fishery can supply people for ever, as long as no more is taken each year than grows back. When species do decline, conservationists monitor, protect, educate and breed them in captivity, and store seeds of plants. Managing forests and fish stocks, the reasons for conservation, AI and IVF, and the risk of losing genetic variation are Extended content.
A sustainable resource is one which is produced as rapidly as it is removed from the environment, so that it does not run out. Forests and fish stocks can be conserved and managed sustainably. Organisms become endangered or extinct through climate change, habitat destruction, hunting, overharvesting, pollution and introduced species. They can be conserved by monitoring and protecting species and habitats, education, captive breeding programmes and seed banks.
Fig. 1: a fish stock managed sustainably stays steady; with overfishing it collapses
Section 01
Sustainable resources: fish and forests.
Set the fishing effort, choose any conservation measures and press Fish for 30 years. The graph shows the fish stock and the catch as a percentage of the original stock.
Sustainable resource: produced as rapidly as it is removed from the environment, so it does not run out. Forests and fish stocks can be conserved and managed sustainably.
In the sim: at the starting effort with no measures, fish are caught faster than they reproduce and the stock falls to under a fifth of its original size. Switching on quotas keeps the stock high.
Extended.Fish stocks are conserved by education (fishers and consumers), closed seasons (no fishing during the breeding season), protected areas (no fishing, so fish can breed), controlled net types and mesh size (young fish escape and grow to breed), quotas (a maximum catch) and monitoring stock sizes to set the rules.
Extended.Forests are conserved by education, protected areas such as national parks, quotas on the number of trees felled, and replanting to replace the trees cut down.
Examiner trap
A larger mesh size lets young, small fish escape, so they survive to reproduce. It does not mean catching bigger fish to make more money.
Section 02
Endangered species and how to save them.
The conservation tab starts with a healthy wild population of 40 animals; the colours stand for different alleles. Press Population crashes, then Captive breeding, then AI / IVF with animals from another zoo, and watch the number of different alleles.
Why species become endangered or extinct
How endangered species are conserved
climate change; habitat destruction; hunting; overharvesting; pollution; introduced species (predators or competitors brought in by humans)
monitoring and protecting species and their habitats; education; captive breeding programmes; seed banks storing seeds of endangered plants
Captive breeding: animals are bred in zoos or reserves to increase their numbers, and some are released back into protected habitats.
Seed banks: seeds are dried and kept cold so they stay alive for many years and can be used to grow plants if the species declines in the wild.
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 fish stocks sim at the starting fishing effort with no measures, what happens over 30 years?
Quick check+10 XP
In the fish stocks sim, which single measure keeps the stock close to its starting size?
Quick check+10 XP
In the conservation sim, what happens to the number of different alleles when the population crashes?
Quick check+10 XP
In the conservation sim, which button increases the number of different alleles?
Section 03
Why conserve, and genetic variation.
Extended. A small population is at risk even if its numbers are rebuilt, because so much of its genetic variation has been lost.
Reasons for conservation programmes: maintaining or increasing biodiversity; reducing extinction; protecting vulnerable ecosystems; maintaining ecosystem functions, such as nutrient cycling and resource provision (food, drugs, fuel and genes).
Risks of a small population: fewer individuals carry fewer different alleles, so genetic variation is reduced. The species is less able to adapt to a change in the environment, a new disease could kill all of them, and inbreeding makes harmful recessive conditions more likely.
In the sim: captive breeding brings the numbers back up, but every new animal inherits alleles from the few survivors, so the number of different alleles does not increase.
Artificial insemination (AI): sperm collected from a male, perhaps in another zoo or the wild, is placed in a female, so animals do not have to be moved. In vitro fertilisation (IVF): eggs are fertilised outside the body and the embryos placed into a female, possibly a surrogate. Both bring in new alleles and increase genetic variation.
Examiner trap
Increasing the number of animals does not restore genetic variation on its own. New alleles must come from unrelated animals, for example by AI or IVF with animals from other populations.
Stage 2 · Exam
Exam-style questions
Unlocks once the four checks above are done. Worth more XP, written to IGCSE Paper 2 and Paper 4 standard.
Finish the four checks above to unlock the exam questions
Exam style+20 XP
Which describes a sustainable resource?
Exam style+20 XP
Extended: why does controlling the mesh size of fishing nets help to conserve fish stocks?
Exam style+20 XP
Extended: which is a reason for conservation programmes that refers to ecosystem functions?
Exam style+20 XP
Extended: a rhino population falls to 20 animals. Why is the species still at risk if the population then increases to 200?
Skill unlocked
Conservation, mastered.
This skill is now recorded on your profile. Keep the chain going.