CARA'S TIPSPractical 6: quadrats, transects, Lincoln index, collecting apparatus and habitats
WAECNECO
What the syllabus asks
WAEC: ecology: quadrats, transects and kite diagrams, abundance calculations (density, frequency, % cover, Lincoln index), collecting apparatus and abiotic measurement, food chains, habitat adaptations, soil/humus specimens, microscope work in ecology, planning investigations; whole-paper coaching.
NECO: ecology: quadrats, transects and kite diagrams, abundance calculations (density, frequency, % cover, Lincoln index), collecting apparatus and abiotic measurement, food chains, habitat adaptations, soil/humus specimens, microscope work in ecology, planning investigations; whole-paper coaching.
What you will learn
- Explain sampling with quadrats and transects.
- Calculate density, population, frequency and percentage cover.
- Estimate populations by capture–recapture and state assumptions.
- Interpret kite diagrams and explain zonation.
- Name and describe ecological apparatus.
- Construct food chains from specimens.
- Relate adaptations to habitats.
- Plan an ecological investigation.
Key points
- Random quadrats for abundance; transects for zonation.
- Density, population, frequency, % cover formulae.
- Lincoln index and its assumptions.
- Kite diagrams and abiotic explanations.
- Apparatus and instruments named with uses.
- Food chains, trophic levels, 10% energy transfer.
- Plan: aim, method, controls, results, conclusion, reliability.
Start here: Ecology on the practical paper
Ecology appears in the practical paper as field-study questions (quadrats, transects, capture–recapture), as specimens (soil, humus, leaves from different habitats, food-chain organisms), and as data to calculate and interpret. NECO and WAEC both expect you to know the apparatus, carry out simple calculations and explain the distribution of organisms using physical (abiotic) and biotic factors.
Key terms
| Term | Meaning |
|---|---|
| Habitat | the place where an organism lives (pond, forest floor, tree bark) |
| Population | all the organisms of one species in an area |
| Community | all the populations of different species in a habitat |
| Ecosystem | a community interacting with its non-living environment |
| Abiotic factors | physical factors: light, temperature, water, pH, humidity, wind, soil type |
| Biotic factors | living factors: predators, competitors, parasites, food supply, humans |
| Abundance | how many individuals of a species are present |
| Distribution | where the individuals are found within the habitat |
Sampling, not counting everything
A field may contain millions of plants. Ecologists sample small areas and use them to estimate the whole population. To be fair, samples must be random (to estimate abundance in a uniform area) or placed systematically along a transect (to study how organisms change across a gradient, such as from a path into a bush or from dry land into a pond). Enough samples must be taken to give a reliable mean.
Qualitative and quantitative study
A qualitative study lists which species are present (a species list), using identification keys and collecting samples. A quantitative study measures how many there are, using the sampling methods in this unit. Most examination questions combine the two: identify the organisms in a habitat, then estimate their numbers and explain their distribution. When you visit a habitat for practical work, record the date, time, weather and location, because conditions change with season and time of day and examiners expect this level of detail in a field report.
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Practice questions
- plant abundance
- animal speed
- soil pH
- rainfall
Show answer
A: plant abundance
Square frame.
- save time only
- find the biggest plants
- follow a path
- avoid bias
Show answer
D: avoid bias
Random numbers.
- animals in water only
- rainfall
- changes in vegetation along a line
- only one point
Show answer
C: changes in vegetation along a line
Line or belt transect.
- area × number
- total number ÷ number of quadrats (× quadrat area)
- number of quadrats ÷ total
- percentage of quadrats with the species
Show answer
B: total number ÷ number of quadrats (× quadrat area)
Per m².
- percentage of quadrats containing the species
- total number of plants
- area covered
- number of species
Show answer
A: percentage of quadrats containing the species
Occurrence.
Key words
- Quadrat
- A square frame of known area used for sampling.
- Transect
- A line across a habitat along which samples are taken.
- Density
- Number of individuals per unit area.
- Frequency
- Percentage of samples in which a species occurs.
- Percentage cover
- Proportion of ground covered by a species.
- Lincoln index
- Capture–recapture estimate N = n₁n₂/m.
- Kite diagram
- Chart showing abundance along a transect by band width.
- Zonation
- Arrangement of species in bands along an environmental gradient.
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