Measuring biodiversity

Starter - Key Term Definitions Species A group of organisms whose members are similar to each other in morphology, physiology, biochemistry and behaviour; who can interbreed to produce fertile offspring Habitat Place where an organism or population lives Biodiversity Number and variety of living things to be found in the world/ecosystem/habitat

Learning Objectives Success criteria To understand how to calculate diversity and what is all means Success criteria Describe how to measure species richness and species evenness in a habitat Use Simpson’s Index of Diversity (D) to calculate the biodiversity of a habitat, using the formula D = 1-(Σ(n/N)2) Outline the significance of both high and low values of Simpson’s Index of Diversity (D)

Key Term Definitions Species richness Species evenness Number of species present in habitat Species evenness Measure of abundance of individuals in each species (ACFOR) The greater the species richness and evenness the higher the biodiversity

Measuring Species Richness Number of species present in habitat Qualitative survey Use sampling techniques best suited to habitat (e.g. transect, quadrats) Walk round see if any species you’ve missed

Measuring Species Evenness Measure of abundance of individuals in each species Quantitative surveying Plants - use sampling techniques measuring species per unit area or percentage ground cover With large animals use observation With small animals can use mark and recapture method C1: number on first capture; C2 number on second capture; C3 number of already marked animals on second capture Total population = (C1 x C2) / C3

Species richness and evenness Habitat X Habitat Y Species 1 28 15 Species 2 2 Total 30 What can you deduce about species richness and evenness for these 2 habitats? Species richness (2) is the same for both habitats Habitat Y has a greater species evenness

Simpson’s Index of Diversity Measure biodiversity of a habitat taking into account species richness and species evenness D = 1-(Σ(n/N)2) n = number of individuals of a particular species (or percentage cover for plants) N = total number of all individuals of all species (or percentage cover for plants)

Simpson’s Index of Diversity Simpson’s index is always a value between 1 and 0. Significance of high values of D (close to 1) Diverse habitat Small change in habitat may only affect one species Habitat stable and can withstand change Significance of low values of D (close to 0) Habitat dominated by just a few species Small change in habitat may effect one of the key species and damage whole habitat

Simpson’s Index of Diversity Species n n/N (n/N)2 A 12 B 7 C 2 D 6 E 5 F 8 n= This is N (n/N)2 = What is the species richness?

Simpson’s Index of Diversity Species n n/N (n/N)2 A 12 B 7 C 2 D 6 E 5 F 8 n= (n/N)2 = Work out n (sum of all the species present) Then work out n/N for all species

Simpson’s Index of Diversity Species n n/N (n/N)2 A 12 0.300 B 7 0.175 C 2 0.050 D 6 0.150 E 5 0.125 F 8 0.200 n= 40 (n/N)2 = Work out (n/N)2 for all species Then add them all up for (n/N)2

Simpson’s Index of Diversity Species n n/N (n/N)2 A 12 0.300 0.09 B 7 0.175 0.031 C 2 0.050 0.003 D 6 0.150 0.023 E 5 0.125 0.016 F 8 0.200 0.040 n= 40 (n/N)2 = 0.203 WHAT’S WRONG WITH THE TABLE? (3DP) D = 1 - (Σ(n/N)2) D = 1 - 0.203 = 0.797

Learning Objectives Success criteria To understand how to calculate diversity and what is all means Success criteria Describe how to measure species richness and species evenness in a habitat Use Simpson’s Index of Diversity (D) to calculate the biodiversity of a habitat, using the formula D = 1-(Σ(n/N)2) Outline the significance of both high and low values of Simpson’s Index of Diversity (D)