Required practical 9: abundance and distribution
הוצג| English | משמעות |
|---|---|
| quadrat/ˈkwɒdræt/ | רבעון |
| transect/trænˈsekt/ | שדרה |
What would explain this observation?
- Placing every quadrat 样方 beside the easiest path can bias a population estimate. A sampling method must match the question and represent the habitat.
Build the model
- A quadrat samples a known area.
- For a population estimate, generate random coordinates across the defined accessible study area, count the target species using a consistent boundary rule and repeat.
- Mean count per quadrat divided by quadrat area estimates density; multiply by habitat area for estimated abundance.
- A transect 样带 with systematic sampling helps examine distribution along an environmental gradient.
- quadrat: A frame defining an area for ecological sampling.
- transect: A defined line or route along which distribution is sampled.
Which method best estimates abundance across a defined habitat?
רמת קושי 1/5 · 100 מטבעות + בונוס קטן בהשלמה הראשונה היום
Random quadrat positions give every patch an equal chance, so the estimate represents the whole habitat. Choosing the crowded patch or the door-side overestimates or distorts abundance.
Match each technical term to its precise meaning.
רמת קושי 2/5 · 140 מטבעות + בונוס קטן בהשלמה הראשונה היום
Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- Required practical 9 measures a common species and investigates a factor affecting its distribution.
- Measure the factor, such as light intensity, at comparable sampling locations.
- Random sampling estimates the wider population; a single gradient transect is not automatically representative of the whole habitat.
- Mean, median and mode describe different properties of the recorded counts.
In the lab: Complete actual school-supervised fieldwork with teacher-approved access, sensible weather precautions and minimal disturbance. Record coordinates, quadrat area, counts and factor measurements. Repeat sufficient samples, keep effort and species identification consistent, plot labelled axes and explain uncertainty from patchiness and restricted access.
Which two habits make the investigation or model in this case more defensible?
רמת קושי 2/5 · 140 מטבעות + בונוס קטן בהשלמה הראשונה היום
Stating the conditions and assumptions lets others repeat the work exactly, and recording the supporting evidence lets them check the conclusion. Hiding disagreeing results removes the evidence that could challenge a wrong conclusion, and one measurement can never establish a wider claim.
Work from known quantities
- Known: five 0.25 m² quadrats contain 2, 4, 4, 5 and 5 plants.
- Mean = 20/5 = 4; density = 4/0.25 = 16 plants/m².
- A 30 m² habitat estimate is 480 plants.
- Median is 4; the data are bimodal at 4 and 5.
- This is an estimate conditional on representative sampling.
Your turn: Mean count is 3 plants per 0.25 m² quadrat. Estimate the number in a 40 m² habitat.
Mean count is 3 plants per 0.25 m² quadrat. Estimate the number in a 40 m² habitat.
רמת קושי 2/5 · 140 מטבעות + בונוס קטן בהשלמה הראשונה היום
The result is 480 plants. Known: mean 3 plants per 0.25 m^2 quadrat; habitat 40 m^2. Density = 3/0.25 = 12 plants per m^2. Estimate = 12 x 40 = 480 plants. Never multiply the quadrat count by area without first dividing by quadrat area.
Check the conclusion and its limits
- Do not multiply a quadrat count directly by habitat area without accounting for quadrat area.
- A transect measures a pattern along a route, not proof of causation.
- Destroying plants to count them is unnecessary.
- A written worksheet supports but does not replace field experience.
Not true: A population estimate from sampling is an exact census. Sampling extrapolates from a few quadrats to the whole area, so it carries uncertainty - it is an estimate, not a census. Different random samples give somewhat different estimates.
- A quadrat samples a known area.
- Required practical 9 measures a common species and investigates a factor affecting its distribution.
- Watch for: do not multiply a quadrat count directly by habitat area without accounting for quadrat area.
Sampling extrapolates from a few quadrats to the whole area, so it carries uncertainty - it is an estimate, not a census.
רמת קושי 1/5 · 100 מטבעות + בונוס קטן בהשלמה הראשונה היום
True. Sampling extrapolates from a few quadrats to the whole area, so it carries uncertainty - it is an estimate, not a census. Different random samples give somewhat different estimates.
A frame defining an area for ecological sampling: write the technical term.
רמת קושי 1/5 · 100 מטבעות + בונוס קטן בהשלמה הראשונה היום
quadrat means A frame defining an area for ecological sampling.