AQA A-level Environmental Science (7447) · The Living Environment
Mini-Lesson
The Living Environment
Life on Earth is organised into ecosystems and measured by its biodiversity. This lesson covers types of diversity, how we quantify it with Simpson’s Index, energy flow through ecosystems, and conservation.
You will do two real calculations — a diversity index and an energy-transfer efficiency. Answer the questions and collect ⭐.
Biodiversity
Types of biodiversity
Biodiversity is the variety of life. It has three levels:
Genetic diversity — variation of alleles within a species;
Species diversity — the number (richness) and relative abundance (evenness) of species;
Habitat / ecosystem diversity — the range of habitats in an area.
Measuring
Simpson’s Index of Diversity
Species diversity combines richness and evenness. AQA uses Simpson’s Index of Diversity:
D = 1 − ( Σ n(n−1) ) / ( N(N−1) ) where n = number of organisms of one species and N = total number of organisms of all species.
D ranges from 0 to 1; a value closer to 1 means higher diversity.
Calculate
Your turn — Simpson’s Index
1A sample contains three species with counts of 3, 4 and 5 organisms (N = 12). Calculate Simpson’s Index of Diversity D to 2 decimal places.
An ecosystem is a community of organisms plus their abiotic (non-living) environment. Energy enters through producers (photosynthesis) and passes along trophic levels (producer → primary consumer → secondary consumer…).
Only about 10% of the energy at one trophic level is passed to the next; the rest is lost in respiration, movement and as heat. This limits food-chain length.
Calculate
Your turn — energy transfer
2Producers fix 20 000 kJ m⁻² yr⁻¹. The primary consumers receive 1 800 kJ m⁻² yr⁻¹. Calculate the percentage efficiency of energy transfer.
%
Hint: efficiency = (energy to next level ÷ energy at this level) × 100 = (1800 ÷ 20000) × 100.
Check
Reading the index
1A woodland has Simpson’s Index D = 0.85 and a nearby plantation has D = 0.20. This means:
Conservation
Conservation
Conservation protects biodiversity for ecological, economic, aesthetic and ethical reasons.
In situ conservation protects species in their natural habitat — e.g. national parks, nature reserves, marine protected areas.
Ex situ conservation protects species outside their habitat — e.g. seed banks, botanic gardens and captive breeding in zoos.
Check
In situ or ex situ?
2Storing seeds in a refrigerated seed bank is an example of:
Sort it
Classify each item
Sort each item into the correct category.
🧬 Type of diversity
🏞️ In situ conservation
🏛️ Ex situ conservation
Match
Term to meaning
Match each term to its meaning.
Statement
Answer
Recap
The big ideas to know
Biodiversity: Genetic, species and habitat diversity
Simpson’s Index: D = 1 − Σn(n−1)/N(N−1); closer to 1 = more diverse
Energy flow: Producers → consumers; roughly 10% passes between levels
Conservation: In situ (habitat) vs ex situ (seed banks, zoos)
Always show your working in index and efficiency calculations. Press Finish.
🏆
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