Edexcel A (SNAB) A Level Biology:复习笔记4.1.3 Comparing Biodiversity Between Habitats

Comparing Biodiversity Between Habitats

• Once the abundance of different species in an area has been recorded, the results can be used to calculate the species diversity for that area
• Species diversity looks at the number of different species in an area but also the abundance across the different species
• An index of diversity is a measurement that describes the relationship between the number of species present and how each species contributes to the total number of organisms that are present in that community

The index of diversity formula

• The formula is:

• Where:
• n = total no. of organisms for a single species in the community
• N = total no. of organisms in the community
• Σ = sum of
•  The larger the number obtained, the higher the level of diversity

Calculating the index of diversity

• To calculate:
• Step 1: Calculate N(N-1) to find value A
• Step 2: Calculate n(n-1) for each species and add all these numbers together to find value B
• Step 3: Divide value A by value B

Worked Example

Samples of different insect species in a back garden were collected using sweep nets and identification keys. Use the data recorded to calculate the index of diversity.

The total number of organisms(N) in this community would be: 7 + 34 + 6 + 21 + 12 + 37 + 7 + 19 + 59 = 202

The formula is:

Step one:       Calculate N(N-1) to find value A

N(N-1) = 202(202-1)

N(N-1)= 202(201)

N(N-1) = 40602

Step two:       Calculate n(n-1) for each species and add all of these numbers together to find value B

See table below

Step three:      Divide value A by value B to calculate the index of diversity (D)

D = 40602÷ 6884

D = 5.90

• The higher the value of D, the greater the level of biodiversity in that area
• It is useful to compare the species diversity in different habitats by calculating the diversity index for each of them

Exam Tip

Even though you are not expected to memorise the formulae for calculating the heterozygosity index and index of diversity, you will be expected to know how to use them and understand what the values mean that you calculate with them.