Biodiversity
Dr. Manish Semwal
The Biosphere
• The sum of Earth’s ecosystems, the Biosphere
encompasses all parts of the planet inhabited by
living things.
• In 2002 about 1.7 million species had been
discovered and identified by biologists, although
estimates of the true number of species on earth
range from 3.6 to over 10 million (Wilson 2002).
• For at least 3.8 billion years, a complex web of life
has been evolving here on Earth
Biome
• The term biome refers to a major type of
terrestrial ecosystem that typifies a broad
geographical region.
Biodiversity
• Biodiversity is an abundance of different life.
• Biodiversity (biological diversity) is the
variety of all living organisms and their
interactions. Scientists often speak of three
levels of diversity - species, genetic, and
ecosystem diversity.
Earth’s Biodiversity
Insects
Protozoa
281000
69000
5800
Higher plants
Algae
26900
751000
248400
Fungi
Bacteria & viruses
Other animals
30800
• "Biological diversity is the variety and
variability among living organisms and the
ecological complexes in which they occur.
• Genetic diversity is the combination of
different genes found within a population of a
single species, and the pattern of variation
found within different populations of the
same species. Coastal populations of Douglas
fir are genetically different from Sierran
populations
• Species diversity is the variety and abundance
of different types of organisms which inhabit
an area. A ten square mile area of Modoc
County contains different species than does a
similar sized area in San Bernardino County.
• Ecosystem diversity encompasses the variety
of habitats that occur within a region, or the
mosaic of patches found within a landscape. A
familiar example is the variety of habitats and
environmental parameters in an ecosystem
and its grasslands, wetlands, rivers, estuaries,
fresh and salt water."
• Reasons human cultures value biodiversity:
The rich variety of species in biological communities
gives us food, wood, fibers, energy, raw materials,
industrial chemicals, and medicines, all of which pour
hundreds of millions of dollars into the world economy
each year.
Moreover, people have a natural affinity for nature, a
sense of “biophilia,” wherein they assign a nonutilitarian value to a tree, a forest, and wild species of
all kinds
Importance of Biodiversity
Pollination
For every third bite you take, you can thank a pollinator.
Air and Water Purification
Biodiversity maintains the air we breathe and the water we drink.
Climate Modification
By giving off moisture through their leaves and providing shade, plants
help keep us and other animals cool.
Drought and Flood Control
Plant communities, especially forests and wetlands, help control floods.
Cycling of Nutrients
The elements and compounds that sustain us are cycled endlessly through
living things and through the environment.
Importance
Habitat
Natural ecosystems provide habitat for the world’s species
(forests, wetlands, estuaries, lakes, and rivers – the world’s
nurseries).
Food
All of our food comes from other organisms.
Natural Pest Control Services
Natural predators control potential and disease-carrying
organisms in the world.
Drugs and Medicines
Living organisms provide us with many drugs and medicines.
Loss of Biodiversity
•
•
•
•
•
•
Habitat Destruction
Invasive Species
Pollution
Population
Overharvesting
Global Warming
Threats: Invasive species
• A species that is not native to a region
• Threaten native species by taking over
resources
Keystone species - a species which is
CRITICAL to the functioning of an
ecosystem
– Many different species are dependent on it
– If lost, the entire ecosystem is destroyed
Zonation
• Zonation is the classification of biomes into zones based on their
circulation or grouping in a habitat as influenced by environmental factors,
such as altitude, latitude, temperature, other biotic factors
• Supplement
• An example of ecological zonation is the vertical zonation of the pelagic
ocean:
• epipelagic zone – the zone where photosynthetic organisms (such as
planktons) thrive as they require enough light for photosynthesis
• mesopelagic zone – the zone under epipelagic zone where nektons are
abundant
• bathypelagic zone – the zone near to the deep sea floor where benthos
abound
Succession
• the gradual and orderly process of change in
an ecosystem brought about by the
progressive replacement of one community by
another until a stable climax is established
Examples of Changing Ecosystems
• A forest could have been a shallow lake a
thousand years ago.
• Mosses, shrubs, and small trees cover the
concrete of a demolished building.
Ecological Succession
• Gradual process of change and replacement of
the types of species in a community.
• May take hundreds or thousands of years.
Primary Succession
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M-DCC / PCB 2340C
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• Newer communities
make it harder for the
older ones to survive.
• Example: Younger birch
trees will have a harder
time competing with
taller, older birch trees
for sun, but a shade
loving tree may replace
the smaller birch trees.
Primary Succession
• Type of succession that
occurs where there was
no ecosystem before.
• Occurs on rocks, cliffs,
and sand dunes.
• Primary succession is very slow.
• Begins where there is no soil.
• Takes several hundred years to produce fertile
soil naturally.
• First species to colonize bare rock would be
bacteria and lichens.
Lichens
• Do not require soil.
• Colorful, flaky patches.
• Composed of two species, a fungi and an
algae.
• The algae photosynthesize and the fungi
absorbs nutrients from rocks and holds water.
• Over time, they break down the rock.
• As the rocks breaks apart, water freezes and
thaws on the cracks, which breaks up the
rocks further.
• When the lichens die, they accumulate in the
cracks.
• Then mosses begin to grow and die, leading to
the creation of fertile soil.
• Fertile soil is made up of the broken rocks,
decayed organisms, water, and air.
Mosses on rocks
• Primary succession can
be seen happening on
the sidewalks.
• If left alone, even NYC
would return to a
cement filled woodland.
Secondary Succession
• More common
• Occurs on a surface where an ecosystem has
previously existed.
• Occurs on ecosystems that have been
disturbed or disrupted by humans, animals, or
by natural processes such as storms, floods,
earthquakes, and volcanoes.
Secondary Succession: Mt. St. Helens
• Erupted in 1980.
• 44,460 acres were
burned and flattened.
• After the eruption, plants
began to colonize the
volcanic debris.
• Pioneer species: the first
organism to colonize any
newly available area and
begin the process of
ecological succession.
• Over time, the pioneer species makes the area habitable
by other species.
• Today, Mt. St. Helens in the process of secondary
succession.
• Plants, flowers, new trees and shrubs have started to
grow.
• If this continues, over time they will form a climax
community.
• Climax community: the final and stable
community.
• Climax community will continue to change in
small ways, but left undisturbed, it will remain
the same through time.
Fire and Secondary Succession
• Natural fire caused by lightening are a
necessary part of secondary succession.
• Some species of trees (ex: Jack pine) can only
release their seeds after they have been
exposed to the intense heat of a fire.
• Minor forest fires remove brush and
deadwood.
Fire and Secondary Succession
• Some animals depend on fires because they
feed on the newly sprouted vegetation.
• Foresters allow natural fires to burn unless
they are a threat to human life or property.
Old-field Succession
• Occurs in farmland that
has been abandoned.
• Grasses and weeds
grow quickly, and
produce many seeds
that cover large areas.
• Over time, taller plants grow in the area,
shading the light and keeping the pioneer
species from receiving any light.
• The longer roots of the taller plants deprive
the pioneer species from water.
• The pioneer species die.
• Taller trees begin to
grow and deprive the
taller plants of water
and light.
• Followed by slow
growing trees (oaks,
maples) takeover the
area.
• After about a century,
the land returns to a
climax community.
Measuring Biodiversity
• The simplest measure of biodiversity is the number of
species – called species richness.
– Usually only count resident species, and not accidental or
temporary immigrants
• Another concept of species diversity is heterogeneity:
Community 1 Community 2
Species A
99
50
Species B
1
50
Heterogeneity is higher in a community where there are more
species and when the species are more equally abundant.
Diversity Indices
• A mathematical measure of species diversity
in a community.
• Reveals important information regarding rarity
and commonness of species in a community.
Simpson’s Diversity Index
• Attempts to quantify the diversity (variety) of
an ecosystem.
• There are two components:
Evenness
Richness
Evenness
• Evenness is a measure of the relative
abundance of the different species within an
area.
• When the numbers of each type of species is
even, the value for the Simpson Diversity
Index will be larger.
Species richness
• Richness is a measure of the variety of the
species
• More species is “richer” so the value for the
index will be higher.
The equation
D = N(N - 1)
 n(n -1)
D = diversity index
N = total number of organisms of all species
found
n = number of individuals of a particular species
The Simpson Diversity Index
• A high value of D suggests a stable and ancient
site
• A low value of D could suggest pollution, recent
colonization or agricultural management.
• The value of D indicates the richness and
evenness of the species found within the area
sampled.
Predict the value for D for the
following: (high or low)
• Tropical rainforest
• Desert
• A wheat field
• A polluted river
• A tall grass prairie
How to Calculate D:
D = N(N – 1)
 n(n -1)
1.
2.
3.
4.
Record the numbers of each species
Calculate n-1 for each species
Find the total number of organisms, N
Calculate the Simpson Diversity Index
Values for D
• What is the lowest possible value?
• What does a higher value indicate?
The values for D
• The lowest possible value is 1. When there is
only one kind of species.
• This is a monoculture or an area that has been
disturbed by pollution, a flood, or another big
event
• A high value for D indicates stability,
complexity and an older ecosystem.
Calculate the Simpson’s Diversity Index
for each sample
Comment on the evenness and richness of each sample.
Answers
• Sample One: 2.99
• Sample Two: 1.15
• Both have the same richness as there are
three species in each area.
• Sample One is more diverse because the
species are more even.
Sampling Methods
• Transects and Quadrants
– Plants and Non-motile animals
• Lincoln Index
• Capture –Mark- Recapture
– Small animals
• Aerial observations
– Large trees and animals
Average Size
• Measure all trees in a transect or quadrat.
• Produce a size-frequency histogram to show
the size distribution.
• Can also calculate the average size tree.
Quadrat Sampling
Quadrat
1
1
1
1
1
1
2
2
2
2
2
2
Species
BoxElder
Button Bush
Chinese Tallow
Cottonwood
Maple
Willow
BoxElder
Button Bush
Chinese Tallow
Cottonwood
Maple
Willow
No.
0
2
1
9
0
62
4
0
0
1
2
60
• Randomly select plots and
count all individuals in that
plot.
• Each quadrat = 200m2.
• Can calculate density as
#/m2 then multiply by total
area to estimate the total #
of trees.
• 60,703 m2 = 15 acres
Transect Sample
Transect
1
1
1
1
2
2
2
2
3
3
3
3
Species
BoxElder
Cottonwood
Maple
Willow
BoxElder
Cottonwood
Maple
Willow
BoxElder
Cottonwood
Maple
Willow
No.
1
1
2
27
2
1
0
37
2
4
0
44
• Randomly select a transect
of known area and count
every tree in that transect.
• Each transect = 90m2.
• Can calculate density for
each tree species.
• 60,703 m2 = 15 acres
Sampling along Transects
• Samples taken at fixed intervals
• Set up along an environmental gradient (e.g.
high to low on a mountain)
Line transect method
• A measured line laid across the area in the
direction of the environmental gradient
• All species touching the line are be recorded
along the whole length of the line or at specific
points along the line
• Measures presence or absence of species
Belt transect method
• Transect line is laid out and a quadrant is placed
at each survey interval
• Samples are identified and abundance is
estimated
– Animals are collected
– For plants an percent coverage is estimated
• Data collection should be completed by an
individual as estimates can vary person to
person
Quadrats
• Used to measure coverage and abundance of
plants or animals
• A grid of known size is laid out and all the
organisms within each square are counted.
Lincoln Index
• Capture-Mark-Recapture
– Animals are captured,counted, tagged and released.
– After a period of time another capture occurs.
– Previously tagged animals are counted and unmarked
organisms are marked.
– Abundance is calculated using the following formula:
n 1 x n2
n3
n1=total marked after catch 1
n2=total marked after catch 2
n3=total caught in catch 2 but
marked in catch 1
Measurements
• Sampling methods measure
–
–
–
–
–
Density
Coverage
Frequency
Biomass
Diversity
Measuring Biodiversity
• The simplest measure of biodiversity is the number of
species – called species richness.
– Usually only count resident species, and not accidental or
temporary immigrants
• Another concept of species diversity is heterogeneity:
Community 1 Community 2
Species A
99
50
Species B
1
50
Heterogeneity is higher in a community where there are more
species and when the species are more equally abundant.
Diversity Indices
• A mathematical measure of species diversity
in a community.
• Reveals important information regarding rarity
and commonness of species in a community.