Random quadrats, transects, population estimates, capture-recapture and efficiency of biomass transfer.
What you will learn
- Estimate a population from quadrats
- Explain random sampling and transects
- Calculate the efficiency of a transfer
From a few squares to a whole field
- five 1 m² quadrats: 3, 5, 4, 6, 2 daisies
- mean = 20 ÷ 5 = 4 per m²
- field of 500 m²: about 4 × 500 = 2000 daisies
Counting cells works the same way: 12 cells in a square that holds 0.0004 cm³ is 12 ÷ 0.0004 = 30 000 = 3.0 × 10⁴ cells per cm³, so 20 cm³ holds about 6.0 × 10⁵ cells.
Place quadrats at random coordinates to avoid bias. Use a transect (quadrats along a line) to see how a species changes from one place to another.
population ≈ (number marked × number caught second time) ÷ number marked in the second catch
efficiency = biomass at the next level ÷ biomass at this level × 100
The rest of this lesson and its 9 practice questions are locked.
In this lesson
- From a few squares to a whole field
9 practice questions, marked as you go; about 20 minutes in all.
Key terms
Transect
In this unit: Required practicals and maths skills
The skills behind every biology practical: units and magnification, means and percentages, rates and graphs, sampling, ratios and planning.