Biodiversity and sampling
Introduced| English | Meaning |
|---|---|
| ecosystem/ˈiːkəʊsɪstəm/ | A community of organisms interacting with each other and with their physical environment. |
| niche/niːʃ/ | A species' particular role and place within it. |
| biodiversity/ˌbaɪəʊdaɪˈvɜːsɪti/ | The variety of life, including genetic diversity, species diversity and ecosystem diversity. |
| abundance/əˈbʌndəns/ | The amount or relative frequency of a particular entity, such as a species or an isotope. |
| quadrat/ˈkwɒdræt/ | A frame marking a known area used to sample the abundance or distribution of organisms. |
| transect/trænˈsekt/ | A line or strip along which observations or samples are taken to study changes across a habitat. |
| mark-release-recapture/mɑːk rɪˈliːs rɪˈkæptʃə/ | For moving animals: mark and release some, then see what fraction of a later catch is marked. |
| Simpson's index/ˈsɪmpsnz ˈɪndeks/ | Higher = more diverse (and usually more stable). |
The variety of life
- An ecosystem 生态系统 is all the living things in an area plus their non-living surroundings.
- A niche 生态位 is a species' particular role and place within it.
- Biodiversity 生物多样性 measures the variety of life — at three levels.
Biodiversity sampling lab
Choose the sampling method or index that matches the field question.
An ecosystem is:
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An ecosystem includes the living community and the abiotic surroundings; a niche is a species' role within it.
Three levels of biodiversity
- the number and range of different ecosystems and habitats.
- the number of species and their abundance 丰度 (how common each is).
- the genetic variation within each species.
Biodiversity is measured at three levels: ecosystems, species, and the genes within a species
Biodiversity is measured at three levels: ecosystems/habitats, species/abundance, and:
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The three levels are ecosystem diversity, species diversity (and abundance), and genetic diversity.
Sampling an area
- You can't count everything, so you take samples. Random sampling avoids bias.
- quadrats 样方 — square frames to count species inside them.
- transects 样带 — counting along a line across the area.
- mark-release-recapture 标志重捕法 — for moving animals: mark and release some, then see what fraction of a later catch is marked.
Quadrats, transects and mark-release-recapture
Why is random sampling used?
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Choosing positions by chance avoids bias, so the sample fairly represents the whole area.
Random sampling is used so the sample is not biased and fairly represents the whole area.
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Picking spots by chance (e.g. with coordinates) stops you only choosing the interesting-looking places.
Match each sampling method to what it is for.
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Quadrats and transects sample plants/slow organisms; mark-recapture estimates mobile animals; Simpson's index summarises diversity.
You mark 20 woodlice and release them. Later you catch 25, of which 10 are marked. Estimate the population (first catch × second catch ÷ marked in the second).
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Population ≈ (20 × 25) ÷ 10 = 50. The marked fraction of the second catch (10/25) reflects the marked fraction of the whole population (20/N).
Measuring diversity
- Simpson's index 辛普森指数 of diversity turns biodiversity into a single number.
- A higher value means more diverse — and usually more stable.
A higher Simpson's index of diversity means the area is:
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Simpson's index gives a single diversity number; higher means more diverse and generally more stable.
You've got it
- ecosystem = living + non-living; niche = a species' role
- biodiversity has three levels: ecosystems/habitats, species + abundance, genetic variation
- sample with quadrats & transects (fixed organisms) and mark-release-recapture (moving animals); use random sampling
- Simpson's index: higher = more diverse (and usually more stable)