Practical: Investigating the Distribution of Organisms (Edexcel IGCSE Biology)

Practical: Measuring Biodiversity

We can investigate biodiversity with quadrats using a similar method to the one used when investigating population size

Apparatus

• 2 tape measures

• Quadrat

• Random number generator

• Species key

Method

• Use 2 tape measures to lay out your first survey area (e.g. 10m X 10m)

• Use a random number generator to create a set of coordinates to place your first quadrat

  • E.g. for coordinates 4,5, you would place your quadrat 4m along on the x-axis and 5m along on the y-axis

• Count the number of different species found within that quadrat

• Repeat this process until you have collected the data for 10 quadrats

• Repeat these steps for the second survey area

The method for how to investigate biodiversity using a quadrat

Results

• A comparison of the number of different species found in each survey area provides an indicator of biodiversity

  • A higher level of biodiversity would be indicated by a larger number of different species found in that area

• However, this measurement doesn't tell us about the distribution or population size in either survey area

• As with species abundance, the biodiversity is likely to be influenced by biotic factors such as:

  • Competition

  • Predator-prey relationships

  • Interactions with other organisms within the food chain or food web

• Biodiversity will also be influenced by abiotic factors such as:

  • Light intensity

  • Mineral availability

  • Water availability

  • pH

  • Temperature

  • Salinity

Limitations

• As with the previous investigation (comparing abundance in 2 study areas), it can be easy to miss individual organisms when counting in a quadrat, especially if they are covered by a different species

  • Solution: Use a pencil or stick to carefully move leaves out of the way to check if there is anything else underneath

• Identifying species or distinguishing between species may be tricky

  • Solution: Use a species key to identify the species

Applying CORMS to practical work

• When working with practical investigations, remember to consider your CORMS evaluation

CORMS Evaluation

• In this investigation, your evaluation should look something like this:

  • C - We are changing the study area where we are collecting the data

  • O - We will count plant species each time (not animal, fungi etc)

  • R - We will repeat the investigation several times to ensure reliability

  • M1 - We will count the number of different plant species found across all quadrats

  • M2 -  this isn't really relevant in this scenario

  • S - We will control the size of the quadrat, the random way that quadrats are placed on the ground, the day that the results were collected