Written for this site from the class slides, with textbook page references for each statement. The chapter is on pages 156–180 of the course textbook. Image credits are on slide 18.
Biodiversity includes ecosystem diversity, species diversity and genetic diversity. Species diversity depends on richness, the number of species, and evenness, how similar their numbers are. Simpson's reciprocal index compares communities: D = N(N − 1) / Σn(n − 1), and a higher value means higher diversity.
Millions of species have been named, and many more remain to be discovered. Fossils suggest that more species are alive now than at any time in the past, although past levels are hard to estimate.
| Species | Causes |
|---|---|
| Moa, New Zealand | Hunted, and their forest burnt and cleared, after people arrived around 1280; giant moa were gone by about 1500 |
| Caribbean monk seal | Hunted for oil and meat, and last confirmed in 1952 |
Add a third brief case study from your own region.
Causes include farming, logging, mining, dams, draining water, pollution and climate change. Mixed dipterocarp forest in South East Asia is being lost to timber and plantations such as oil palm. Your local example could be Swiss moorland or river floodplains.
Reports from IPBES and other sources draw on surveys of many habitats and groups. They include population sizes, species ranges, richness and evenness, and how degraded ecosystems are. Citizen scientists can add data too.
Human population growth is the overarching cause. Specific causes are hunting and over-exploitation, urbanization, deforestation and land clearance, pollution, and invasive species.
No single approach is enough. In situ methods include nature reserves, rewilding and reclaiming degraded land. Ex situ methods include zoos, botanic gardens and seed banks.
EDGE gives priority to species that are Evolutionarily Distinct and Globally Endangered. With limited funds, saving a species with few close relatives protects more unique evolutionary history.
Select a video to play it here. Select it again to close it.
Print this guide and complete it as you work through the slides and videos. It asks for your own explanations, so close the notes while you try each section.
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A printable worksheet covering all eight statements, from quick recall to data questions and a longer answer. It has 40 marks and takes about 40 minutes, or you can do one section at a time.
Your teacher has the mark scheme.
Questions built on realistic experimental data, in the style of Paper 1B and Paper 2. Work them on paper and show your working. 13 marks in total. Your teacher has the mark scheme.
A review of 70 long-term studies estimated how fast insect biomass is falling each year in different orders of insects.
| Insect order | Mean decline in biomass / % per year |
|---|---|
| Lepidoptera (butterflies and moths) | 3.1 |
| Coleoptera (beetles) | 2.4 |
| Hymenoptera (bees, wasps and ants) | 1.9 |
| All insects | 2.5 |
Bumblebees were fed artificial pollen with different ratios of protein to lipid, and survival was recorded after 7 days.
Large wilderness areas have very few people and are mostly undisturbed. Conservationists recorded which human activities threaten wilderness areas in five biomes. A tick means the activity threatens that biome.
| Activity | Tropical forest | Boreal forest | Tundra | Desert | Grassland |
|---|---|---|---|---|---|
| Climate change | ✓ | ✓ | ✓ | ✓ | ✓ |
| Hunting | ✓ | ✓ | ✓ | ✓ | ✓ |
| Mining | ✓ | ✓ | ✓ | ✓ | |
| Fire | ✓ | ✓ | ✓ | ||
| Logging | ✓ | ✓ | |||
| Agriculture | ✓ | ✓ | |||
| Pollution | ✓ | ✓ |
You will need: Quadrats, identification guide or app, clipboard
Safety: Check the site first. Watch for stinging plants, wash hands afterwards and consider allergies.
Carry this out with your teacher's supervision and follow your school's lab rules.
Conservation science informs international policy, yet resources are limited, so scientists and governments must choose what to protect.
Prioritising species combines data with values. Consider which parts of the decision science can and cannot settle.
Summarised in our own words. Use each code to find the exact wording in your textbook or the IB subject guide.
A4.2 has no HL-only content. SL and HL students learn the same material here.
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