Transcript N - Groby Bio Page

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
 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
 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
15
Total
30
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=
2
1-(Σ(n/N) )
 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
A
12
B
7
C
2
D
6
E
5
F
8
n=
This is N
(n/N)2
n/N
(n/N)2 =
What is the species richness?
Simpson’s Index of Diversity
Species
n
A
12
B
7
C
2
D
6
E
5
F
8
n=
(n/N)2
n/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
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
(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
D = 1 - (Σ(n/N)2)
D = 1 - 0.203 = 0.797
Learning Objectives
 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)