IGCSE · Practice questions · Conservation

Numbers and alleles.

Six original Cambridge-style questions on sustainable resources, endangered species and conservation methods, including fish stock data and (Extended) captive breeding with AI and IVF.

Original questions All questions on this page are original work, written in the Cambridge IGCSE style. They are not from past papers. They test the same concepts and skills the syllabus rewards.

Keep these straight

Replace what you remove.

Sustainable: produced as rapidly as it is removed, so it does not run out.
Fish (Extended): education, closed seasons, protected areas, net types and mesh size, quotas, monitoring.
Forests (Extended): education, protected areas, quotas, replanting.
Small populations (Extended): low genetic variation; AI and IVF bring in new alleles.

Recall

[4 marks]

Give four reasons why organisms become endangered or extinct.

Habitat destruction (for example deforestation). ✓
Hunting or overharvesting. ✓
Pollution, or climate change. ✓
Introduced species that prey on or compete with them. (Any four of: climate change, habitat destruction, hunting, overharvesting, pollution, introduced species.) ✓

Explain

[4 marks]

Describe how endangered species can be conserved.

Monitoring population numbers and protecting the species and its habitat, for example in reserves, with laws against hunting. ✓
Education, so people understand why the species matters and do not harm it. ✓
Captive breeding programmes in zoos, then releasing animals into protected habitats. ✓
Seed banks that store seeds of endangered plants so they can be grown again. ✓

Data

[4 marks]

The table shows the estimated mass of adult cod in a sea area.

Year	1970	1980	1990	2000	2010	2020
Mass of adult cod / thousand tonnes	250	160	90	60	95	140

Quotas and a larger mesh size were introduced in 2000. (a) Calculate the percentage decrease from 1970 to 2000. (b) Describe and explain the change after 2000.

(a) (250 − 60) ÷ 250 × 100 = 76%. ✓
(b) After 2000 the stock rose from 60 to 140 thousand tonnes. ✓
Quotas limited the number of fish removed each year. ✓
A larger mesh let young fish escape, grow and breed, so fish were replaced faster than they were removed. ✓

Explain

[4 marks]

Extended. Explain how forests can be conserved.

Education about the importance of forests and sustainable timber, so people buy from managed forests. ✓
Protected areas such as national parks or reserves where felling is not allowed. ✓
Quotas that limit the number of trees that can be felled. ✓
Replanting, so new trees replace those cut down and the forest is produced as fast as it is removed. ✓

Explain

[4 marks]

Extended. A zoo has a small group of an endangered antelope. Explain the risks to the species of the small population size, and how AI and IVF can be used in a captive breeding programme.

A small population carries few different alleles, so genetic variation is reduced. ✓
The species is less able to adapt to environmental change and one disease could kill them all; inbreeding increases harmful recessive conditions. ✓
AI: sperm from a male in another zoo or the wild is placed in a female, so new alleles are introduced without moving animals. ✓
IVF: eggs are fertilised with sperm outside the body and the embryos implanted into a female (perhaps a surrogate), increasing numbers and genetic variation. ✓

Analysis

[4 marks]

Extended. Describe the reasons for conservation programmes.

To maintain or increase biodiversity. ✓
To reduce extinction of species. ✓
To protect vulnerable ecosystems. ✓
To maintain ecosystem functions such as nutrient cycling and resource provision: food, drugs, fuel and genes. ✓

Mark this once you have attempted all six and checked your working. It records a Practiced badge on the topic and adds a one-time bonus. Revealing the solutions alone does not count.