Lecture Notes: Using Quadrats and Transects to Study Ecosystems
Introduction
- Objective: Learn to use quadrats and transects to determine species abundance and distribution in an ecosystem.
- Importance: Organisms' distribution is affected by abiotic factors (e.g., light intensity, temperature, moisture levels).
Sampling Techniques
Scientists use sampling to determine the number of organisms in an area. Two main methods:
1. Random Sampling
- Purpose: Compare organism numbers in different areas.
- Tool Used: Quadrat (a wooden or plastic square).
- Procedure:
- Place the quadrat on the ground.
- Count the number of organisms inside the quadrat.
- Suitable for sampling plants or slow-moving animals.
- Example Hypothesis: Fewer ferns are found in light conditions than dark conditions.
- Compare two different areas (light vs. dark conditions) using random sampling.
- Randomly place quadrats numerous times to ensure valid results.
- Use random numbers to select locations for quadrats.
- Importance: Sampling multiple locations provides a representative sample of the area.
- Estimating Population Size:
- Equation: Total population size = (Total area / Area sampled) × Number of organisms counted in sample.
2. Sampling Along a Transect
- Purpose: Investigate how species numbers change across a habitat.
- Tool Used: Transect line (tape measure or rope).
- Procedure:
- Place transect across the habitat.
- Use quadrat to count organisms at intervals along the transect.
- Example: Sand Dune Ecosystem
- As you move inland from the sea, plant species change.
- Use transect to measure changes: sea to beach to dune.
- Species Types: Grasses, bushes, flowers, trees.
- Process:
- Place tape measure from beach inland.
- Place quadrat at start, count plants.
- Move quadrat at set intervals (e.g., every 2 meters).
- Repeat transect multiple times for valid results.
Additional Resources
- Practice Questions: Available in the revision workbook linked in the video.
These notes summarize the techniques used to analyze species distribution and abundance, focusing on practical applications of quadrats and transects in different ecosystems.