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BIODIVERSITY
A P E N V I R O N M E N TA L S C I E N C E
3 . 6 B I L L I O N Y E A R S O F E V O L U T I O N O N P L A N E T E A R T H H A S C R E AT E D
T H E M I L L I O N S O F S P E C I E S T H AT I N H A B I T T H E E A R T H T O D AY
THE ELEMENTS OF BIODIVERSITY
Species Diversity: the number or variety of different species in a particular region
 Species Richness
 the total number of different
species in an ecosystem
 Species Evenness
 the extent to which each
species is well represented in
the ecosystem
WORLD WIDE SPECIES RICHNESS
• In a study, ecologist Holger Kreft of the University of California, San Diego and
his colleagues looked at what they termed “endemism richness”, or the
number of unique species combined with the overall number of species
around the world.
• The researchers were surprised to find that islands from Micronesia to the
Atlantic—just 3.6 percent of the surface of the planet—boasted plant
endemism richness 9.5 times higher than the continents and more than 8
times higher for vertebrates.
SPECIES RICHNESS OF LARGE MAMMALS IN
NORTH AMERICA
GENETIC DIVERSITY
• The variation in DNA
composition among
individuals within a
species.
GENETIC DIVERSITY
 Provides the crucial
raw material for
adaptation to local
conditions.
 Populations with low
genetic diversity are
vulnerable to
environmental
change, disease, and
ultimately to
extinction.
ECOSYSTEM DIVERSITY
• Ecosystem diversity
refers to variety at
levels above the species
level, such as
ecosystems,
communities, habitats,
or landscapes.
• A coral reef contains far
more biodiversity than
the same area of an
agricultural farm.
HOW MANY SPECIES ARE THERE?
Good Question – Hard to
Know
Currently there are about
1.5 million described.
The highest estimate is
around 100 million.
The lowest around 5 million.
The best estimate might be
around 10 million.
It means we've only known
about a small fraction of
what is presently there.
HOW MANY SPECIES ARE THERE?
Estimates of
biodiversity are
incomplete because
Difficulty of estimating
certain groups
 microbes, nematodes,
fungi, protists, and soildwelling arthropods.
Many areas of Earth still
remain little explored
Deep ocean
Tropical rainforest
HOW MANY SPECIES ARE THERE?
To illustrate: In a famous
study conducted in
Panama, 19 trees were
"fogged" with insecticide
and the dead were
collected as they fell
through the canopy.
Nearly 1,200 species of
beetles alone were
collected. Of those, 80
percent were not known
to science.
HOW MANY SPECIES ARE THERE?
Many of the species that are
currently being discovered live in
areas that have never before been
explored
Hydrothermal vents along the floor
provide energy for bacteria that use
this energy like plants use the
energy of the sun.
They form the base of a giant food
web thousands of feet below the
surface.
Now scientists believe there could
be as many as a million species just
in on the ocean floor.
UNEVEN SPECIES DISTRIBUTION
BUGS RULE THE PLANET!
LATITUDINAL GRADIENT
Species richness gradually increases as one
approaches the equator
HYPOTHESIS: LATITUDINAL GRADIENT
The variable climates of
polar and temperate
latitudes favor organisms
that can survive a wide
range of conditions.
Such generalist species
have expansive niches;
they can do many things
well enough to survive, and
they spread over large
areas.
HYPOTHESIS LATITUDINAL GRADIENT
In tropical latitudes,
abundant solar energy, heat,
and humidity induce greater
plant growth, which supports
more organisms.
The stable climates of
equatorial regions favor
specialist species, which
have restricted niches but do
certain things very well.
Together these factors are
thought to promote greater
species richness in the
tropics.
Where Is Declining Biological
Diversity the Greatest Problem?
THREATENED SPECIES
Top Six Hot Spots
1 Hawaii
2 San Francisco Bay
area
3 Southern
Appalachians
4 Death Valley
5 Southern California
6 Florida Panhandle
Concentration of rare species
Low
Moderate
High
EXTINCTION OF SPECIES
PANDA SAYS: SEE YA LATER
– STUDY HARD