Why is sampling used to measure biodiversity rather than counting every organism?

It is impractical to count every organism in a habitat

What requirement must sampling meet to give an accurate representation of biodiversity?

Sampling must cover the range of organisms present in a habitat

What is random sampling and how is bias avoided?

Selecting sample sites using random number generators to avoid bias in site selection

What is opportunistic sampling?

A non-random sampling method where organisms are sampled based on convenience or chance encounters, rather than following a systematic approach.

Describe stratified sampling as a non-random method.

The habitat is divided into distinct sub-groups (strata) based on a particular characteristic, and samples are taken from each stratum in proportion to its size or importance.

OCR A-Level Biology H420

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Biodiversity

Sampling methods and equipment

3 things to know
Components 02 and 03

Overview

Random, opportunistic, stratified and systematic sampling and when each is appropriate, and quadrats, sweep nets, pitfall traps and pooters.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Evaluation

Why is opportunistic sampling limited?

Key term

What are quadrats and what organisms are they particularly suited for sampling?

Key term

What is systematic sampling?

Questions from this subtopic

Each one with the model answer underneath.

1
Why is sampling used to measure biodiversity rather than counting every organism?
Model answer
It is impractical to count every organism in a habitat
2
What requirement must sampling meet to give an accurate representation of biodiversity?
Model answer
Sampling must cover the range of organisms present in a habitat
3
What is random sampling and how is bias avoided?
Model answer
Selecting sample sites using random number generators to avoid bias in site selection
4
What is opportunistic sampling?
Model answer
A non-random sampling method where organisms are sampled based on convenience or chance encounters, rather than following a systematic approach.
5
Describe stratified sampling as a non-random method.
Model answer
The habitat is divided into distinct sub-groups (strata) based on a particular characteristic, and samples are taken from each stratum in proportion to its size or importance.
6
What is systematic sampling?
Model answer
A non-random sampling method where samples are taken at fixed, regular intervals, such as along a transect or using a grid pattern.

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Habitat means the physical place where an organism lives.

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