Teacher sheet · Ages 15–16 · about 45–50 minutes
Biodiversity: measuring it and losing it
Lesson page: echoesof.science/school/biodiversity/ages-15-16/ · Pupil worksheet: echoesof.science/school/biodiversity/ages-15-16/print/
Learning aims
- Describe genetic, species and ecosystem diversity, including richness and relative abundance.
- Interpret Red List and Living Planet Index data correctly, with calculations.
- Explain why species totals and extinction rates are uncertain.
- Use a Tullgren funnel to compare invertebrate diversity and evaluate the method.
Lesson plan
| Time | Activity |
|---|---|
| 5 min | Starter: two woods each have 10 species. Are they equally diverse? (Introduce relative abundance.) |
| 10 min | Read the text; Red List and extinction-rate calculations. |
| 20 min | Collect litter and set up the funnels (lesson 1). |
| 5 min | Quiz on interpreting the Living Planet Index. |
| 5 min | Days later: sort, count, compare and evaluate (lesson 2). |
Materials for the experiment
- Two Tullgren funnels (funnel, perforated disc or wire mesh, collecting pot) and two desk lamps
- Leaf litter from two contrasting areas (e.g. under a hedge and under a mown-grass edge or a single-species plantation), same volume each
- Small quadrat or a beaker to measure equal volumes
- Damp tissue for the collecting pots
- White tray, hand lens, simple invertebrate key
- Gloves
Safety: Lamps get hot: keep them at a safe distance from the litter, never leave flammable material touching the bulb, and switch off when unattended overnight if the school's risk assessment requires it. Wear gloves when collecting litter, wash hands afterwards, handle live animals gently and return them. Collect only small amounts and from areas where it is allowed.
Common misconceptions
| Pupils may think… | Actually… |
|---|---|
| A 73% fall in the Living Planet Index means 73% of animals have gone. | It is the average proportional change in monitored vertebrate populations. |
| Scientists know exactly how many species exist. | Totals such as 8.7 million are expert best guesses; perhaps less than 20% of species are described. |
| Biodiversity is just the number of species. | Relative abundance, genetic diversity and ecosystem diversity also count. |
Worksheet answers
- Richness = number of different types found; relative abundance = how many individuals of each type compared with the total (e.g. 30 of 60 animals were springtails = 50%).
- 48,646 ÷ 172,620 = 0.282; × 100 ≈ 28%.
- Any two: many species are not yet described; estimates of totals are expert best guesses; most extinctions probably happen without being observed; methods such as the species–area relationship are questioned.
- Limitations e.g. one sample per habitat; some animals not extracted (slow, flying or killed by drying); identification only to type; litter volume not exactly equal. Improvement e.g. 10–30 samples per habitat chosen randomly; same funnel conditions; use a key to a finer level.
Quiz answers
- Which level of biodiversity is described as the raw material for evolution and adaptation? Genetic diversity. Genetic variation within a species allows adaptation.[3]
- 48,646 of 172,620 Red List species are threatened. What percentage is that, to the nearest whole number? 28%. 48,646 ÷ 172,620 × 100 ≈ 28.2%.[4]
- If the current extinction rate is 100 E/MSY, how many times faster is it than the background rate? 100 times. The background rate is about 1 E/MSY.[3]
- What does the 73% fall in the Living Planet Index mean? The average monitored population shrank by 73%. It is an average proportional change in population size.[5]
- Which populations fell most steeply in the Living Planet Index? Freshwater. Freshwater populations fell by 85%.[5]
- Why does a Tullgren funnel work? Animals move away from the heat and drying of the lamp. They move down and fall into the collecting pot.[7]
Going further
Collect the class's data from several groups and compare the two habitats with a statistical test, or calculate a diversity index that combines richness and relative abundance and discuss what it adds.
Sources used in this lesson
- [1] What is biodiversity and why does it matter to us? (Natural History Museum, London): reliability High
- [2] Biodiversity (OLogy card) (American Museum of Natural History): reliability High
- [3] Biology 2e, 47.1 The biodiversity crisis (OpenStax (Rice University)): reliability High
- [4] Arctic seals threatened by climate change, birds decline globally – IUCN Red List (International Union for Conservation of Nature (IUCN)): reliability High
- [5] Catastrophic 73% decline in the average size of global wildlife populations in just 50 years (WWF (Living Planet Report 2024)): reliability Medium-high
- [6] Diversity: terrestrial method (Field Studies Council): reliability High
- [7] Invertebrates in leaf litter and soil (Field Studies Council): reliability High
Full list with links and a note on each source's reliability: echoesof.science/school/biodiversity/sources/
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