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Species Diversity
• The species diversity of a community
– Is the variety of different kinds of organisms
that make up the community
–
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• Species richness
– Is the total number of different species in the
community
• Relative abundance (evenness)
–
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• Two different communities
– Can have the same species richness, but a
different relative abundance
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Simpson diversity index
• Can be used to measure and compare the
species diversity of a community/ecosystem
• Is a measure that takes into account both
richness and evenness
•
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• Biogeographic factors affect community
diversity
• Two key factors correlated with a community’s
species diversity
–
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• Species richness generally declines along an
equatorial-polar gradient (moving latitudinally
from equator towards the poles)
•
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• Climate
– Is likely the primary cause of the latitudinal
gradient in biodiversity
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• The two main climatic factors correlated with
biodiversity
–
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Area Effects
– All other factors being equal, the larger the
geographic area of a community, the greater
the number of species
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• A species-area curve of North American
breeding birds
– Supports this idea
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Island Equilibrium Model
• Species richness on islands
– Depends on island size, distance from the
mainland, immigration, and extinction
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• Studies of species richness on the Galápagos Islands
–
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Reasons for conservation of biodiversity
• Aesthetics - ensure that future generations can
experience the beauty of ecosystems such as
rainforests
• Potential source of new biopharmaceuticals,
medicines, genes for genetic engineering,
phytochemicals
•
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Reasons for conservation of biodiversity
• Economic reasons
– Farming on clear-cut rainforests has not been
successful
– Potential sources of chemicals, genes used to improve
crops
• Ecological reasons
–
– Protect against invading organisms (competition)
– More CO2 in atmosphere leading to global warming
– Soil erosion, flooding
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Reasons for conservation of biodiversity
• Ethical reasons
– Affects local populations most
– Ensure future generations can enjoy
• Aesthetics
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Arguments against conservation
• May slow down economic development of
some countries
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Introduction of alien species
• Disrupts communities
•
• Many nonnative species provide us with food,
medicine, and other benefits but a few can
wipe out native species, disrupt ecosystems,
and cause large economic losses.
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INVASIVE SPECIES
• Kudzu:deliberate
release of an alien
species
Kudzu vine was introduced in
the southeastern U.S. to
control erosion. It has taken
over native species habitats.
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Zebra mussels:accidental release of an alien species
• May have been introduced by European cargo
ships which contained mussels in ballast water
•
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Prickly pear: an alien species under control
• Introduced to Australia in mid 1800’s
• Spread rapidly
•
• Moth quickly destroyed prickly pear, and exists
in a balance today - an example of biological
control
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Impact of alien species on ecosystems
• Interspecific competition - may out-compete
native species, resulting in a loss in biodiversity
– Red squirrel/grey squirrel
• Predation - may feed on other species
– Lampreys
• Species extinction - out-compete native
species leading to their extinction
–
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INVASIVE SPECIES
• Many invasive species have been introduced
intentionally.
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INVASIVE SPECIES
• Many invasive species have been introduced
unintentionally.
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INVASIVE SPECIES
• The Argentina fire
ant was introduced
to Mobile, Alabama
in 1932 from South
America.
– Most probably
from ships.
– No natural
predators.
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INVASIVE SPECIES
• Prevention is the
best way to reduce
threats from
invasive species,
because once they
arrive it is almost
impossible to slow
their spread.
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Biological control
• Using a natural predator to control an
unwanted or invasive species
• Carries great risk of unexpected consequences
• Gallerucella beetles have been released to
attempt to control Purple Loosestrife
•
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Biomagnification
• Process by which chemical substances
become more concentrated at each trophic
level
•
• DDT caused eggs of predatory birds to have
thin shells which cracked when mother birds
sat on them - caused a decline in number of
predator birds
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Pollution
• Each year pesticides:
– Kill about 1/5th of the
U.S. honeybee
colonies.
– 67 million birds.
– 6 -14 million fish.
Example of biomagnification
of DDT in an aquatic food
chain.
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– Threaten 1/5th of the
U.S.’s endangered
and threatened
species.
Effects of ultraviolet radiation
• Non-lethal skin cancer
• Lethal skin cancers
• DNA mutations
• Sunburn
• Cataracts
• Reduced biological productivity
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OZONE DEPLETION IN THE STRATOSPHERE
• Less ozone in the stratosphere allows for more
harmful UV radiation to reach the earth’s
surface.
– The ozone layer keeps about 95% of the sun’s
harmful UV radiation from reaching the earth’s
surface.
– Chlorofluorocarbon (CFCs) have lowered the
average concentrations of ozone in the
stratosphere.
–
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Depletion of Atmospheric Ozone
• Life on Earth is protected from the damaging
effects of UV radiation
–
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• Satellite studies of the atmosphere
– Suggest that the ozone layer has been gradually
thinning since 1975
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• The destruction of atmospheric ozone
– Probably results from chlorine-releasing
pollutants produced by human activity
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• Scientists first described an “ozone hole”
– Over Antarctica in 1985; it has increased in
size as ozone depletion has increased
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OZONE DEPLETION IN THE STRATOSPHERE
• Ozone thinning: caused by CFCs and other
ozone depleting chemicals (ODCs).
– Increased UV radiation reaching the earth’s
surface from ozone depletion in the
stratosphere is harmful to human health,
crops, forests, animals, and materials such as
plastic and paints.
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• The average area covered by the Antarctic
ozone hole this year (2012) was the second
smallest in the last 20 years, according to data
from NASA and National Oceanic and
Atmospheric Administration (NOAA) satellites.
The average size of the 2012 ozone hole was 6.9
million square miles. The Sept. 6, 2000 ozone
hole was the largest on record at 11.5 million
square miles
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Conservation of Biodiversity
• Indicator species are those that are very
sensitive to environmental change
–
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• Lichens are a common indicator species because they
are very sensitive to pollution, they can also show the
presence of metals such as lead and mercury in the
air
• Macroinvertebrates (insect larvae) are an indicator
species that can be used to determine the quality of
water
•
• Very sensitive organisms like mayfly and caddisfly
larvae require high levels of oxygen and low levels of
organic matter
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Biotic index
• As measurement that determines the quality of water
in an environment
• Measures the number of different types of organisms
in each group multiplied by a sensitivity factor
– Sensitive X 3
– Somewhat sensitive X 2
– Tolerant X 1
•
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The Passenger Pigeon - Gone Forever
• Once the most
numerous bird on earth.
• In 1858, Passenger
Pigeon hunting became
a big business.
• By 1900 they became
extinct from over-harvest
and habitat loss.
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• The Passenger Pigeon, once probably the
most numerous bird on the planet. Their flocks,
a mile wide and up to 300 miles long, were so
dense that they darkened the sky for hours and
days as the flock passed overhead. Total
populations may have reached 5 billion
individuals and comprised up to 40% of the
total number of birds in North America.
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Carolina parakeet
• Became extinct in wild
around 1900
• Settlers cleared trees
destroying habitat
• Release of honeybees
displaced parakeets
from nesting in trees
• Hunted for feathers
which were used to
make women’s hats
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SPECIES EXTINCTION
• Species can become extinct:
– Locally: A species is no longer found in an
area it once inhabited but is still found
elsewhere in the world.
– Ecologically: Occurs when so few members
of a species are left they no longer play its
ecological role.
– Globally (biologically): Species is no longer
found on the earth.
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Global Extinction
• Some animals have become prematurely
extinct because of human activities.
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Endangered and Threatened Species
• Endangered species: so few individual
survivors that it could soon become extinct.
• Threatened species: still abundant in its natural
range but is likely to become endangered in the
near future.
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SPECIES
EXTINCTION
• Some species
have
characteristics
that make them
vulnerable to
ecological and
biological
extinction.
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SPECIES EXTINCTION
• Scientists use measurements and models to
estimate extinction rates.
– The International Union for the Conservation of
Nature and Natural Resources (IUCN)
publishes an annual Red List, listing the
world’s threatened species.
– The 2004 Red List contains 15,589 species at
risk for extinction.
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SPECIES EXTINCTION
• Percentage of various species types
threatened with premature extinction from
human activities.
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IMPORTANCE OF WILD SPECIES
• We should not cause the premature extinction of
species because of the economic and ecological
services they provide.
• Some believe that each wild species has an
inherent right to exist.
–
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HABITAT LOSS, DEGRADATION, AND FRAGMENTATION
• Conservation biologists summarize the most
important causes of premature extinction as
“HIPPO”:
– Habitat destruction, degradation, and
fragmentation
– Invasive species
– Population growth
– Pollution
– Overharvest
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OVEREXPLOITATION
•
• Killing predators and pests that bother us or
cause economic losses threatens some
species with premature extinction.
• Legal and illegal trade in wildlife species used
as pets or for decorative purposes threatens
some species with extinction.
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OVEREXPLOITATION
• Rhinoceros are often
killed for their horns
and sold illegally on
the black market for
decorative and
medicinal purposes.
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•In TCM the bones of tigers have been used in manufactured medicines to treat arthritis and
other joint ailments.
•Rhinoceros horn is used in TCM to treat fever, convulsions, and delirium.
•Bear bile is used in TCM to treat a wide variety of illnesses and injuries, including liver
ailments and headaches.
•Musk from the musk deer is the basis of some 300 TCM prescriptions, of various remedies
in Western homeopathic medicine, and of some perfumes. It is used to promote circulation
and to treat skin infections and abdominal pain
•The seahorse, used as a treatment for kidney ailments, circulatory problems, and
impotence.
•Alligator meat is promoted as a way to cure the common cold and to prevent cancer, and
alligator organs are also said to have medicinal properties.
Asian elephants are killed for their meat, hide, tusks and other body parts. In Myanmar, for
example, small pieces of elephant foot are turned into a paste to treat hernias.
The sun bear is just one of several bear species killed for its gallbladder, which is used for
treating everything from burns to asthma to cancer.
Zebra’s meat and fat are used to treat diseases such as tuberculosis.
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Case Study:Rising Demand for Bushmeat in Africa
• Bushmeat hunting
has caused the
local extinction of
many animals in
West Africa.
• Can spread
disease such as
HIV/AIDS and
ebola virus.
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PROTECTING WILD SPECIES: LEGAL AND
ECONOMIC APPROACHES
• International treaties have helped reduce the
international trade of endangered and
threatened species, but enforcement is difficult.
– One of the most powerful is the 1975
Convention on International Trade of
Endangered Species (CITES).
•
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Case Study: The U.S. Endangered Species Act
• One of the world’s most far-reaching and
controversial environmental laws is the 1973
U.S. Endangered Species Act (ESA).
– ESA forbids federal agencies (besides defense
department) to carry out / fund projects that
would jeopardize an endangered species.
–
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Case Study: The U.S. Endangered Species Act
• Biodiversity hotspots in relation to the largest
concentrations of rare and potentially
endangered species in the U.S.
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Endangered Species
• Because of
scarcity of
inspectors,
probably no
more than 1/10th
of the illegal
wildlife trade in
the U.S. is
discovered.
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Endangered Species
• Congress has amended the ESA to help
landowners protect species on their land.
• Some believe that the ESA should be
weakened or repealed while others believe it
should be strengthened and modified to focus
on protecting ecosystems.
• Many scientists believe that we should focus
on protecting and sustaining biodiversity and
ecosystem function as the best way to protect
species.
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PROTECTING WILD SPECIES: THE
SANCTUARY APPROACH
• The U.S. has set aside 544
federal refuges for wildlife, but
many refuges are suffering
from environmental
degradation.
Pelican Island was the
nation’s first wildlife refuge.
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PROTECTING WILD SPECIES: THE
SANCTUARY APPROACH
• Gene banks, botanical gardens and using
farms to raise threatened species can help
prevent extinction, but these options lack
funding and storage space.
• Zoos and aquariums can help protect
endangered animal species by preserving
some individuals with the long-term goal of
reintroduction, but suffer from lack of space
and money.
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Features of nature reserves which promote biodiversity
• Size of the reserve
– Larger reserves sustain larger populations which are
safer from extinction from unexpected factors like fire,
also have less edge area
• Edge effect
– Edge between ecosystem and disturbed habitat and
center of ecosystem differ
– Organisms at edge of ecosystem suffer from more
predation and competition from invasive species
–
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• Corridors
–
–
Corridors may expose animals to predation,
allow invasive species to enter and may
negatively impact human activity
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Management of conservation areas
• Restoration - return land to natural state
• Recovery of threatened species -restoration
and protection of habitat for endangered
species
•
• Legal protection against development or
pollution
• Funding and prioritizing
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In situ conservation methods
• Keeping organisms “in situ” or in place in
situation where they belong
• Organisms adapted to the conditions they live
in, nature reserves protect endangered species
by maintaining habitat and prevent competition
by removing invasive species
• Defend against predators, poaching
•
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Ex situ conservation methods
• Used as a last resort when natural habitat is
not safe or population is too small to sustain
itself
– Captive breeding in zoos
– Botanical gardens
– Seed banks
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Black-footed ferret
• In 1987 last of wild ferrets captured
• Numbered 18
• Through captive-breeding programs, 2008
estimates put population at 750 in the wild and
250 captive animals
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California condor
• 1982 - 22 birds remaining in wild
• 1987 last bird captured from wild
• 2000 - 157 condors/62 released into wild
• 2005 - 270 condors/125 released into wild
• 2008 - 332 condors/156 released into wild
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What Can You Do?
Protecting Species
• Do not buy furs, ivory products, and other
materials made from endangered or threatened
animal species.
• Do not buy wood and paper products
produced by cutting remaining oldgrowth forests in the tropics.
• Do not buy birds, snakes, turtles, tropical fish,
and other animals that are taken from the wild.
• Do not buy orchids, cacti, and other plants that
are taken from the wild.
• Spread the word. Talk to your friends and
relatives about this problem and what they can
do about it.
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