Transcript BIODIVERSITY_x

BIODIVERSITY
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Introduction
 The
species and resources on our planet are limited,
but the human population is growing unchecked
 surge in human population will drastically affect
biodiversity
 rapid deforestation of Borneo has had devastating
effects on species like the orangutan
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Figure 57.1
(a) Rapid deforestation of Borneo
1900
2010
300 km
Borneo
Samboja
(b) Orangutans are one casualty of deforestation
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What Is Biodiversity?
 Biodiversity
 Describes
the evolutionary relationships among all
forms of life


branches represent all of the lineages of organisms living today
tips represent all of the species
 When
biodiversity increases, branches and tips are
added to the tree
 When
extinctions occur, tips and perhaps branches are
removed
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Measuring and Analyzing Biodiversity
 Biologists
recognize and analyze biodiversity at the
genetic, species, and ecosystem level.
 Genetic diversity
 The
total genetic information contained within all individuals
of a species
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Measuring and Analyzing Biodiversity
 Species
diversity
 The
variety of life-forms on Earth
 Measured as the number and relative frequency
of species in a particular region
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Measuring and Analyzing Biodiversity

Recent efforts to document species diversity have used a new
technique called bar coding

well-characterized gene sequence to identify distinct species
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Figure 57.2
Dogs: 43
Bears: 19
Seals: 36
Approximate
number of
species in
each group
Skunks: 13
Red panda
Raccoons: 15
Badgers: 10
Weasels: 38
Otters: 8
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Measuring and Analyzing Biodiversity
 Ecosystem
diversity
 variety
of biotic communities in a region, along with abiotic
components such as soil, water, and nutrients
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How Many Species Are Living Today?
 1.5
million species have been
cataloged to date
 tiny
2
fraction of the number actually present
general approaches--estimate the total number of species:
1.
Surveys of species-rich groups at small sites

2.
Taxon-specific surveys
Surveys of all the species present in a particular region

All-taxa surveys
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Taxon-Specific Surveys
 Example:
Researchers estimated the number of insect
species living in the canopy of a single tropical tree
 recovered
1000 species of beetles, many previously
undiscovered
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All-Taxa Surveys
 Census
of Marine Life
 massive
international effort to record the global diversity of
life in the oceans
 2700 scientists
 30 million records (600 potentially new species)
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5 mm
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Where Is Biodiversity Highest?
 tropical
rain forests are particularly species
rich
 7%
of Earth’s land area
 at least 50% of all
species present
 Some
regions of the world have a high
proportion
of endemic species
 Species
that are found in a particular area and
nowhere else
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(a) Biodiversity distribution in terms of species richness of birds
959
720
480
240
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Number of
breeding bird
species per
cell in grid
(b) Biodiversity distribution in terms of endemic species of birds
89
66
45
22
1
Number of
endemic bird
species per
cell in grid
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Mapping Biodiversity Hotspots
 Biodiversity
hotspots
 at
least 1500 endemic plant species
 at least 70% of the traditional or primary
vegetation has been lost
 most urgent need of conservation action
 efforts to preserve habitat would have the highest
return on investment
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Amazon
Borneo
Galápagos
Arctic tundra
Boreal forest
Montane grassland
Temperate forest
New Guinea
Congo River
basin
Madagascar
Temperate grassland
Mediterranean forest
Subtropical desert
Tropical wet forest
Tropical coniferous or dry forest
Tropical grassland
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Threats to Biodiversity
 Although
extinction is natural, rates of extinction are
increasing
 Species are vanishing faster than at virtually any other
time in Earth’s history
 Modern
rates of extinction are 100 to 1000 times greater than
the average, or “background,” rate
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Threats to Biodiversity
 The
International Union for the Conservation
of Nature (IUCN)--red list of species that are
threatened with extinction
3
categories:
1.
2.
3.
Vulnerable
Endangered
Critically Endangered
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Birds
13% threatened
Threatened
Mammals
25% threatened
Amphibians
41% threatened
Critically endangered
Endangered
Vulnerable
Near threatened
Least concern
Data deficient
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Threats to Biodiversity
endangered species: species whose numbers have
decreased so drastically that it is almost certain to go
extinct without effective conservation efforts
 majority of biologists agree that the sixth mass
extinction in the history of multicellular life is now
occurring
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Habitat Destruction
 Humans
cause habitat destruction in many
ways
 Logging
and burning forests
 Grazing livestock
 Filling in wetlands
 Building housing developments
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Habitat Destruction
 On
a global scale, one of the most important
types of habitat destruction is deforestation
 As
many as 3 million hectares (ha) were
deforested each year in the Amazon in the 1990s
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Habitat Destruction
 The
total area of wet tropical forest dropped by
2.4% during 2000–2005
 If this rate of tropical deforestation continues
 Over
28% of the wet tropical forest that exists
today
will be gone in your lifetime
 Including almost half of the Brazilian Amazon
 Forest
loss in South America and Africa is
particularly important because it is occurring in
biodiversity hotspots
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Figure 57.8
1985
2000
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Habitat Degradation
 Habitat
fragmentation
 One
of the most pervasive forms of habitat degradation
 breakup of large, contiguous areas of natural habitat into
small, isolated pieces
 Concerns:
1. reduce
habitats to a size that is too small to support some
species
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Habitat Fragmentation
2.
Fragmentation reduces the ability of individuals to
disperse from one habitat to another


3.
Small, isolated populations may be more vulnerable to catastrophes
Can suffer from inbreeding depression and loss of alleles due to
genetic drift
Fragmentation creates large amounts of “edge” habitat

suffer a rapid loss of species diversity and a startling drop in
biomass
 When
habitats are fragmented, the quality and quantity
of habitat decline drastically
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Habitat Fragmentation
A
long-term experiment in a tropical wet forest
is documenting the decline in habitat quality
caused by fragmentation
 Plots of different sizes were shown to have
A
rapid loss of species diversity, especially from
the smaller fragments
 A startling drop in biomass, or the total amount of
fixed carbon, in the study plots located near the
edges of logged fragments
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Habitat Fragmentation
 This
experiment demonstrates that when
habitats are fragmented, the quality and
quantity of habitat decline drastically
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Overexploitation
 Overexploitation
 Any
unsustainable removal of wildlife from the
natural environment of use by humans
 The dominant threat for marine species

Two-thirds of harvestable marine species are depleted
 Overhunting
has also emerged recently as a
dire threat to many mammal populations in
Africa and elsewhere
 capture of animals for the pet trade can
include a wide range of species
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Bushmeat trade
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Invasive Species
 exotic
species
 nonnative
species that is introduced into a
new area
 If it grows to a large population size and disrupts
native species, is is considered an invasive
species
 Global
trade and travel have vastly increased
the
rate of exchange of plants, animals, fungi, and
microorganisms
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Exotic reptiles in Florida
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