Biology Sampling Techniques

Introduction

• Goal: Describe sampling techniques used in biology.
• Context: Used to determine species richness and species evenness by sampling organisms within a habitat.

Sampling Techniques for Animals

Sweeping Net

• Use: Sample insects in fields or meadows.
• Method:
  • Sweep the net over plants multiple times.
  • Traps insects present in the area.

Pooter

• Use: Catch small insects directly.
• Components:
  • Container with two tubes.
  • Trapping tube and mouthpiece tube.
• Method:
  • Place the trapping tube near the insect.
  • Inhale gently through the mouthpiece.
  • Insect is sucked into the container.
  • Cloth in mouthpiece prevents insects entering the mouth.

Pitfall Trap

• Use: Trap ground-level animals (e.g., insects, snails).
• Method:
  • Container sunk into the ground.
  • Covered to prevent rainwater entry.
  • Animals fall in and cannot crawl out.

Tullgren Funnel

• Use: Sample tiny animals in soil.
• Method:
  • Soil placed in a funnel above a container.
  • Light bulb heats the soil surface.
  • Animals move downwards to avoid heat, fall into the container.

Kick Sampling

• Use: Sample bottom-dwelling riverbed animals.
• Method:
  • Net placed downstream.
  • Scientist kicks the riverbed.
  • Dislodged organisms are caught in the net.

Sampling Techniques for Slow-Moving or Static Animals and Plants

Frame Quadrat

• Use: Sample animals on a seashore or plants in a habitat.
• Method:
  • Place on the ground.
  • Sample animals or plants within the quadrat.

Density per Meter Squared

• Use: Count actual number of a plant species (e.g., dandelions).
• Measure: Highly accurate sampling method.

Percentage Frequency

• Use: For plants difficult to count (e.g., moss, grass).
• Method:
  • Count small squares within quadrat that contain the plant.
  • Report as percentage frequency.
  • Example: 20/100 squares containing moss = 20% frequency.

Percentage Cover

• Use: For plants occupying a large proportion of the quadrat.
• Method: Estimate by eye the percentage of quadrat area covered.
• Note: Rapid but least accurate method.

Point Quadrat

• Use: Alternative to frame quadrat.
• Components: Wooden bar with holes.
• Method:
  • Position over ground, insert metal pins into holes.
  • Count plants touched by pins.

Increasing Reliability

• Place quadrat in multiple positions.
• Calculate a mean to enhance reliability.