1. Sampling Equipment & Methods

In brief:Ecologists use specific equipment and techniques to study habitats. These include quadrats, transects, pitfall traps, pooters, and environmental sensors.

To study an ecosystem scientifically, ecologists carry out both qualitative surveys (descriptions of what is observed) and quantitative surveys (measurements with numbers).

Key equipment:

Quadrat - a 1m × 1m square frame placed on the ground to count species within it. Used for plant surveys and slow-moving animals.
Line Transect - a rope or measuring tape laid across a habitat. Species touching the line are recorded at regular intervals.
Belt Transect - a strip (usually quadrat-width) along a transect line. All species within the belt are recorded.
Pitfall Trap - a jar sunk into the ground with a flat stone cover. Catches crawling invertebrates overnight.
Pooter - a suction device for collecting small insects without harming them.
Kestrel meter - measures abiotic factors like wind speed, temperature, and humidity.

Identification methods: Pictorial keys, dichotomous keys (branching yes/no questions), and identification apps.

Quadrat sampling — Quadrat used to sample plant populations in a habitat
Wikimedia Commons (CC)

table

Sampling Methods Comparison

Method	Used For	Data Type
Random Quadrat	Plants, slow animals	% frequency, % cover, density
Line Transect	Species distribution along gradient	Species at intervals
Belt Transect	Detailed distribution study	All species in belt width
Pitfall Trap	Ground-dwelling invertebrates	Species count
Pooter	Small insects	Species count

Key Points

1Qualitative surveys describe; quantitative surveys measure with numbers.
2Quadrats (1m²) are used for plant surveys and percentage cover.
3Line transects show species distribution along a gradient (e.g. shore to woodland).
4Pitfall traps catch crawling invertebrates; pooters collect small insects.
5Kestrel meters measure wind speed, temperature, and humidity.
6Species are identified using dichotomous keys or identification apps.

Learning Outcomes

Use primary data gathered from a chosen ecosystem to model a habitat (size, species, biotic and abiotic factors), investigate quantitatively the impact of variation in abiotic factors on distribution and abundance of a species, and explain feeding and symbiotic relationships between organisms
Design, plan and conduct investigations; explain how reliability, accuracy, precision, error, fairness, safety, integrity, and the selection of suitable equipment have been considered

2. Quantitative Data & Biodiversity Index

In brief:Ecologists collect quantitative data to measure species distribution and calculate biodiversity using Simpson's Diversity Index.

After collecting data using quadrats or transects, ecologists calculate several measures:

Percentage Frequency = (Number of quadrats containing species ÷ Total quadrats) × 100

Percentage Cover = Estimated % of quadrat area covered by a species.

Population Density = Number of individuals per unit area.

Simpson's Diversity Index (D) is used to quantify biodiversity:

D = 1 − Σ(n/N)²

Where n = number of individuals of each species, N = total number of all individuals.

A higher D value (closer to 1) = greater biodiversity. A value near 0 = low biodiversity, dominated by one species.

Analysing patterns: Look for correlations between abiotic factors (e.g. light, moisture) and species distribution. For example, more ferns may grow in shaded, damp areas of a woodland.

equation

Simpson's Diversity Index

D = 1 − Σ(n/N)²
n = individuals of one species, N = total individuals
D closer to 1 = high biodiversity

Key Points

1Percentage frequency = proportion of quadrats containing a species.
2Percentage cover = estimated area covered by a species in a quadrat.
3Simpson's Diversity Index (D) quantifies biodiversity; closer to 1 = more diverse.
4Look for correlations between abiotic factors and species distribution.
5Data should be collected systematically (random sampling or along transects).
6Compare ecosystems by comparing their D values.

Learning Outcomes

Model species diversity in ecosystems using the Simpson's Diversity Index equation
Use primary data gathered from a chosen ecosystem to model a habitat (size, species, biotic and abiotic factors), investigate quantitatively the impact of variation in abiotic factors on distribution and abundance of a species, and explain feeding and symbiotic relationships between organisms

3. Irish Ecosystems

In brief:Ireland has diverse ecosystems including woodlands, rocky seashores, and hedgerows, each with characteristic species and abiotic conditions.

Three important Irish ecosystems to study:

1. Woodland Ecosystem

Trees form a canopy; understory includes ferns, mosses, ivy
Abiotic: shaded, damp, sheltered from wind, humus-rich soil
Animals: woodlice, spiders, birds, foxes, badgers

2. Rocky Seashore Ecosystem

Intertidal zone with zonation from splash zone to low tide
Abiotic: high salinity, wave action, tidal exposure, rock type
Species: barnacles, limpets, seaweed, anemones, crabs

3. Hedgerow Ecosystem

Linear habitat acting as wildlife corridor connecting larger habitats
Abiotic: more exposed, varied soil, seasonal light changes
Species: hawthorn, blackthorn, robin, hedgehog, field mice

Adaptations: Every organism has physical and behavioural adaptations to survive in its habitat. For example, limpets have a muscular foot to cling to rocks against wave action.

Key Points

1Woodlands: shaded, damp, rich biodiversity in canopy and understory layers.
2Rocky seashores: zonation from splash zone to low tide, organisms adapted to wave action and tidal exposure.
3Hedgerows: linear habitats acting as wildlife corridors between larger ecosystems.
4Every organism has physical and behavioural adaptations to its habitat.
5Climate change is a major threat, especially to coastal and exposed ecosystems.

Learning Outcomes

Illustrate how limiting factors determine the carrying capacity for species in Irish ecosystems
Consider, using population curves, how the carrying capacity for species in Irish ecosystems varies depending on limiting factors
Use primary data gathered from a chosen ecosystem to model a habitat (size, species, biotic and abiotic factors), investigate quantitatively the impact of variation in abiotic factors on distribution and abundance of a species, and explain feeding and symbiotic relationships between organisms

4. Random Sampling & Study Design

In brief:For quadrat and transect data to represent an ecosystem fairly, sampling must be random or systematic, and repeated enough times to be reliable.

An ecological survey is only as good as the way its samples are chosen. If a student places every quadrat in the same sunny patch of grass, the results describe that patch - not the field.

Random sampling removes personal bias. A common method:

Lay two long measuring tapes at right angles along the edges of the study area to create x/y axes.
Use a random number generator to pick pairs of coordinates.
Place a 1 m × 1 m quadrat at each coordinate and record the species inside.
Repeat for at least 10-20 quadrats so patterns are not down to chance.

Systematic sampling is used when there is a clear environmental gradient - such as up a rocky shore or from a woodland edge into open field. A line transect is laid along the gradient and quadrats are placed at fixed intervals (e.g. every 2 m). This shows how species distribution changes with abiotic factors.

Reliability & fairness:

Take enough samples - one quadrat is not a survey.
Sample at the same time of day and in similar weather where possible.
Measure abiotic factors at every quadrat (light, soil moisture, temperature) so any correlation with species distribution can be tested.
Follow safety and ethics guidelines - return specimens to their habitat, avoid trampling sensitive areas.

comparison

Random vs Systematic Sampling

Random sampling

Quadrat positions chosen with random numbers
Best for uniform habitats (e.g. a lawn)
Measures overall abundance and diversity

Systematic sampling (transects)

Quadrats placed at fixed intervals along a line
Best when there is a gradient (shore, hedge, slope)
Shows how species change with an abiotic factor

Key Points

1Random sampling removes bias by choosing quadrat positions with random numbers.
2Systematic sampling (transects) is best when studying a gradient of abiotic factors.
3Repeat sampling (10-20+ quadrats) improves reliability of results.
4Record abiotic factors at each quadrat so correlations can be tested.
5Return any collected specimens to their habitat after identification.