1. What is biodiversity and how is it
measured?
• What is Biodiversity?
– The variation that exists in the natural
world at all levels of biological organization
– All organisms in a defined area, all of their
variations and all of their interactions with
each other and with the physical
environment
2. Levels of Biodiversity
1. Genetic diversity: the gene pool within
a population
2. Species diversity: the number and
types of species in an area
3. Higher taxonomic diversity
4. Community Diversity
5. Ecosystem diversity (Habitat diversity)
3. Species diversity
has two components:
1. Species richness: how many different
species are present in a habitat
2. Relative abundance: total number of
individuals of each species present
4. Species Richness and Abundance of a
Swamp Forest on Maryland’s Eastern
Shore
4%
6%
8%
14%
17%
18%
33%
7. American Beech
6. Loblolly Pine
5. American Holly
4. Oaks
3. Sweet Gum
2. Black Gum
1. Red Maple
2003
5. Species diversity has
two components:
1. Species richness: how
many different species
are present in a habitat
2. Relative abundance:
total number of
individuals of each
species present
3. Which area is more
diverse?
6. Defining Biodiversity:
• Old growth forest in the Shenandoah
Mountains of Virginia
– 50,000 trees represented by 10 species.
• Managed forest, recently clear cut
– 45,000 trees are maple and birch
– Only 1/10th
of the forest is represented by
the remaining 8 species
7. Importance of Taxonomy
Naming Species
1. Naming things upon which we depend for
food and medicine means survival.
2. Important to measuring biodiversity
3. Conservation
18. Kingdom Animalia Animalia
Phylum Arthropoda Chordata
(Vertebrates)
Class Malacostraca Mammals
Order Decapoda Primates
Family PORTUNIDAE
swimming crabs
Hominids
Genus Callinectes Homo
Species Callinectes sapidus
The Blue Crab
Homo sapiens
21. What you need to know about
Classification
• The order of classification
• Binomial nomenclature (genus,
species)
• The three Domains
• The five Kingdoms
• The ecological role of each kingdom
• The scientific name of the Blue Crab
22. Rich in Species, Poor in
Knowledge
E.O. Wilson estimated 1.75 million
species are living on the planet.
Scientists generally disagree with the
exact number but, agree with Wilson
that 1.4 M represents probably a mere
1/10th
of the total diversity.
Why do we know so little?
Other estimates:
4-112 million (7 million)
23. Number of
Living
Species of All
Kinds of
Organisms
Currently
Known
Insects
54%
Other Animals 20%
Bacteria 4%
Fungi 5%
Algae 2%
Plants 18%
Protozoa 2%
24. What do we know?
• Estimates of the # of species
• More species are located in the tropical
regions of the world
– 2/3rd
– 3/4th
of all species live in tropical rain
forests which cover only 7% of the earth’s
surface
26. Why do we know so little?
1. Not all species have been discovered
– #’s are biased toward animal species
– Know more about species in developed Nations
– Not all species are named as a result of unclear
species concepts in taxonomy
2. On-going extinction: species loss in tropical
forest is estimated at 6000/year,
27. • Tropical rain forests are more species rich than northern
regions of the world
• What are some factors that might account for this?
28. Some factors that affect the
biodiversity of an area
1. Historical Events
– Time
2. Habitat conditions
3. Habitat structure
4. Climate stability
5. Competition
– Predators
– Keystone species
6. Disturbance
29. 1. Historical Events
• Each part of the world
has a unique history
• Effect of the recent
Ice Age in the
northern hemisphere
– Ireland has no snakes
• Time: Older Areas
have more species
than younger areas
31. 2. Habitat
Conditions
• Areas with extreme
climate or conditions
harbor fewer species
• Soldiers Delight Natural
Environment Area (NEA)
is comprised of 1,900
acres of serpentine
barren. The area has
over 39 rare, threatened,
or endangered plant
species as well as rare
insects, rocks and
minerals.
• Delaware River and
Pollution
32. 3. Habitat Structure
• Terrain that is simple, uniform, and
without much physical variation tends to
have fewer species than a complicated
terrain with wet and dry spots
• Ecologists call these microhabitats
• A piece of property with a patch of forest,
a small wetland, and a field with harbor a
greater diversity than the same sized
property that is covered with only forest.
33. 3. Habitat Structure:
The Forest Community
stratification
• The canopy
• The shrub layer
• The understory
• The herbaceous layer
– most conspicuous in the spring
• The forest floor
35. 5. Competition Among Species
• Predators can enhance an area by
reducing the population size of prey
species
• Other species have a chance to get
established
• Keystone Species have a large effect on
the other species of a community
– Oysters of the Chesapeake Bay
– Vital as water filters, provide habitat, income
for watermen
36. 6. The Nature of Disturbance
1. Damage communities
2. Remove organisms
3. Alter resource availability
Fire
Flooding
Storms and Hurricanes
Tornados
Ice Storms
37. 6. Disturbance
1. Create opportunities for the
colonization of new species
2. Disturbance is a natural part of the life
of a community: most communities
are always in recovery from
disturbance
3. Humans as agents of disturbance
38. Hurricane Katrina
• Cypress trees play a crucial
role in the swamp forests
that cover hundreds of
thousands of acres of
coastal Louisiana. These
swamps prevent floods by
collecting storm waters and
clean water by filtering out
pollution. They also provide
habitat for a wide variety of
animals, such as migratory
songbirds (the ivory-billed
woodpecker, until recently
believed extinct, once thrived
in the swamps).
40. Optional Activity
Unit 3: Activity 31
Track Your Understanding
Answer Question #2 on pages 464-465
worth 5 points
41. Species Extinction:
Past and Present
• Extinction is a biological reality
• Extinction and evolution are intricately related
• Five mass extinctions in the earth’s history
– 99% of species that have ever existed are now
extinct
• Each mass extinction is followed by a rise in
biodiversity of a new set of species
42.
43. Humans Agents of Extinction
• Humans have played a role in the extinction of
species for thousands of years
• Some say we are facilitating the 6th
mass
extinction in the earth’s history
• Can scientists accurately measure extinction
rates?
44. Estimates of Extinction Rates
“the logic of loss”
• Estimating rates is difficult at best
• Most accurate estimates are for birds
and mammals
• Species-area relationships from Island
Biogeography
– # species is related to size of habitat
– Estimate habitat loss
– 90% habitat loss: 50% species loss
46. Conserving the
Biodiversity of the Commons
• Conserving the world’s biodiversity is
based on principles of biology
– Population biology
– Conservation biology
47. Principles of Population Biology
1. Small populations are more likely to
become extinct than large populations
2. To understand a population it is
important to consider factors such as
its age structure and sex ratio
3. Populations must be monitored to
determine the effects of a
conservation plan
48. Principles of Conservation Biology
1. A species that is
broadly
distributed across
its range is less
likely to become
extinct than a
species that is
restricted to a
small part of its
range
The range of the Eastern Fox Squirrel
49. • The Delmarva Fox
Squirrel
• Original range
included the entire
Delmarva peninsula
into southeastern PA.
• Remnant populations
exist at Blackwater,
Eastern Neck NWR
(Kent Co.), and
Assateague Island
50. Principles of Conservation Biology
2. Characteristics of habitats that favor
species preservation:
a. Large rather than small; Bigger is better
b. Close together rather than far apart
c. Whole rather than internally fragmented
d. Linked by corridors rather than isolated
e. Inaccessible rather than easily accessible
to people
52. • The main land of
South America is to
the Galapagos
Islands as
• An intact forest is to
the fragmented
parcels
53. Dooms species by confining them to
small, island-like parcels of habitat
surrounded by an ocean of human
impact. This often leads to:
– Inbreeding within small populations
– Roads, fences, houses, clear-cuts create
barriers to dispersal and reproduction
– More susceptible to environmental
fluctuations and catastrophes
When habitats become islands
55. Corridors are Important for
Connecting “Islands”
• Corridors function as pipelines that permit wildlife to
move between habitats
• Promote biodiversity
• But can also transmit disease, fire, predators, and
pests
• The effectiveness of habitat corridors depends on the
situation
58. Fragmentation of Habitat in Maryland
• Early tobacco farming
in the Mid-Atlantic
resulted in
fragmentation of the
land into a fine mosaic
of forest patches
interspersed with young
trees, herbs and
shrubs.
59. • Large scale agriculture
stripped extensive
areas of the landscape
leaving only small
patches of forest
• The most extensive
land clearance in the
region occurred in the
late 1800’s – early
1900’s
• 80% of the land around
the Chesapeake was
cleared of its forests.
• Wetlands were drained
for farm land.
60. • The pattern of
farm fields,
forests, and
marshes
surrounding
Blackwater
Wildlife Refuge
• Dorchester Co.
Eastern Shore
• Blackwater
Wildlife Refuge’s
Wildlife Drive is
circled
Notes de l'éditeur
Figure 55.4 Species density of North and Central American birds. Biogeographers often plot latitudinal trends in numbers of species on maps that illustrate how many species occupy different geographic areas. In this species-density map for breeding species of North and Central American birds, we can see that fewer than 100 species are found in arctic areas, whereas more than 600 species occupy some tropical regions.
Grasslands and chapparals are dependant on regular burning By mimicking natural disturbance when necessary, for example using prescribed fire in the sandplains.
Figure 53.22 Species richness and island size . This species-area graph illustrates that the number of amphibian and reptile species found on West Indian islands is closely related to island size. Large islands harbor more species because greater habitat diversity allows greater resource partitioning among the resident species, reducing the likelihood of competitive exclusion.
…We’d like to see the lowlands look more like this, with vegetated riparian areas, upland corridors, and large areas of restored forest.
