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Chapter 5 – Evolution of
Biodiversity
Module 14
The Biodiversity of Earth
It is difficult to estimate the number
of species on Earth
Species – group of organisms that is distinct
from other groups in terms of size, shape,
behavior, or biochemical properties and can
interbreed with other individuals in its group to
produce viable or fertile offspring.
Pond
Lawn
Common measure of Biodiversity
= # of species in any given place
What about the # of species on Earth? (easy or
challenging?
It is challenging because;
- hard to find
- nocturnal species
- live in inaccessible locations (deep
ocean)
- microscopic
- species are uniformly distributed
Unknown Diversity
2M species : identified
Sample method of estimating the
# of species
•
•
•
•
Fumigate a tree
Collected dead insects
Sort them out by species (ex: beetle)
Count the # of each species in one (1) tree and
multiplied it with the # of tropical trees.
Result: 8M (canopy alone)
30M total estimate (including the ones in
the bottom ground.
We can measure biodiversity in terms
of Species Richness and Evenness
- Two (2) measures for species diversity at local
or regional scales.
Species richness = the number of species in a
given area such as a pond, canopy of a
tree, or a plot of grassland.
= is used by scientists to give an
approximate sense of the biodiversity of a
particular place.
Species evenness = is the relative proportion of
individuals within the different species in a
location.
= it tells us whether a
particular ecosystem is dominated by one
species or whether all of its species have
similar abundances.
Species richness and evenness
• Decline after a human disturbance
• Gives scientists a baseline that they can use to
determine how much that ecosystem has
changed.
Evolutionary relationship among species can be
illustrated using a phylogeny
Phylogeny = the branching pattern of
evolutionary relationships.
= can be describes using a diagram
known as phylogenetic tree
(cladogram).
Scientists used the following to measure similarity
- Morphology
- Behavior
- Genetics
* The more similar traits of two (2) species, the more closely related they are
Measuring Biodiversity
(Richness and Evenness)
• a) Simpson’s Diversity Index
Where: 0 = no diversity
1 = infinite diversity
D = diversity index
N = total number of organisms of all species
found in the sample
Σ = the sum of
n = number of individuals of a particular
species in the sample
• b) Shannon’s Diversity Index
where:
H = the Shannon diversity index
Pi = fraction of the entire population
made up of species i
S = numbers of species encountered
∑ = sum from species 1 to species S
Note: The power to which the base e (e
= 2.718281828.......) must be raised to
obtain a number is called the natural
logarithm (ln) of the number.
Simpson’s Diversity Index
Macroinvertebrates
# of Organisms in Each
Group (n)
n(n-1)
Mayflies
1
1(1-1) = 0
Stoneflies
3
3(3-1) = 6
Caddisflies
5
Midges
6
Craneflies
1
Dragonflies
3
Scuds
6
Pouch Snails
6
Tubifex worms
8
Leeches
5
Total
N=
Ʃn(n-1) =
Simpson’s Diversity Index
Macroinvertebrates
# of Organisms in Each
Group (n)
n(n-1)
Mayflies
1
1(1-1) = 0
Stoneflies
3
3(3-1) = 6
Caddisflies
5
5(5-1) = 20
Midges
6
6(6-1) = 30
Craneflies
1
1(1-1) = 0
Dragonflies
3
3(3-1) = 6
Scuds
6
6(6-1) = 30
Pouch Snails
6
6(6-1) = 30
Tubifex worms
8
8(8-1) = 56
Leeches
5
5(5-1) = 20
Total
N=
Ʃn(n-1) = 198
b) Shannon’s Diversity Index
Area 1
Order
description # of
individuals
Orthoptera
(grasshopper)
Green with
red legs
6
Orthoptera
(grasshopper)
Brown with a
yellow stripe
5
Lepidoptera
(buttefly)
Large, blue
1
Lepidoptera
(buttefly)
Small, blue
3
Coleoptera
(beetle)
Red and blue
12
N = 27
n/N
pi
In pi
pi In pi
Ʃpi In pi =
Calculate the diversity of Area 2 in your WS and compare the 2 areas.
b) Shannon’s Diversity Index
Area 1
Order
description # of
individuals
n/N
pi
In pi
pi In pi
Orthoptera
(grasshopper)
Green with
red legs
6
6/27
0.222
-1.505
-0.334
Orthoptera
(grasshopper)
Brown with a
yellow stripe
5
5/27
0.185
-1.687
-0.312
Lepidoptera
(buttefly)
Large, blue
1
1/27
0.037
-3.297
-0.122
Lepidoptera
(buttefly)
Small, blue
3
3/27
0.111
-2.198
-0.244
Coleoptera
(beetle)
Red and blue
12
12/27
0.444
-0.812
-0.360
N = 27
Ʃpi In pi =
Calculate the diversity of Area 2 in your WS and compare the 2 areas.