Download Extinction & the Biodiversity Crisis

1 - Armstrong, D
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3 - Bailey, Ariella
4 - Bailey, Jasmine
5 - Belitz, M
6 - Brand, E
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8 - Carlson, I
9 - Chapin, N
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13- Cusimano, J
14- Davis, C
1516- Diaz, A
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1) Which of the following statements
about ecosystems is true?
A) Energy is recycled through the trophic structure.
B) Chemicals are recycled between the biotic and
abiotic sectors, whereas energy makes a one-way
trip through the food web and is dissipated as heat
along the way.
C) There is a continuous process by which energy is
recycled and chemical elements leave the
ecosystem through runoff.
D) A food web shows that all trophic levels may feed
off each other.
2) Why are big, predatory animals rare? Most
big, predatory animals are tertiary consumers,
which implies that
A) typically, they are highly territorial.
B) it’s hard for an ecosystem to support many of them
because so much energy is lost at each level of energy
exchange.
C) by overexploitation, humans have caused many
predatory species to become endangered.
D) it takes a long time for big, predatory animals to evolve.
E) it’s hard for a big animal to consume vegetation.
EXTINCTION
&
THE BIODIVERSITY CRISIS
Biodiversity:
All the variety of life, at every level of organization...
Genetic diversity
Species diversity
Ecosystem diversity
• According to the U.S. Endangered Species Act:
– A threatened species is “likely to become
endangered in the foreseeable future”
– An endangered species is “in danger of becoming
extinct throughout all or a significant portion of its
range”
Extinction:
The death of the last surviving
individual of a species, population,
or gene, locally or globally.
The Biodiversity Synthesis Report
KEY FINDINGS:
• Decline in biodiversity due to human activities more rapid
in past 50 yrs than at any time in human history
• Over last 100 yrs, human-caused species extinctions have
multiplied ~ 1,000 times
The most accurate estimates of current
extinction rates probably come from studies of
A) Birds and mammals, because they are
relatively well-known and visible taxa
B) Marine invertebrates, because of their
relatively long and complete fossil history
C) Insects, because they comprise the vast
majority of extant multicellular organisms
D) Vascular plants, because they do not move
around.
12 % of birds, 23% of mammals, and 32% of
amphibians are threatened with extinction
Current estimates of loss of all species range
between 10-50% over next 20-50 years.
This current rapid decline in biodiversity
is known as the “Biodiversity Crisis”
What makes a species vulnerable
to extinction?
• Vulnerability to introduced exotics
• Overexploitation
• Rarity
• Habitat loss / Fragmentation
Introduced Exotics
• Species that humans have moved
from native locations to new
geographic regions.
• In absence of native competitors,
predators, and parasites, introduced
species may spread rapidly and
disrupt native community.
Brown tree snake on Guam has caused
extinction of 12 spp birds, 6 spp lizards
Kudzu introduced to control erosion
now chokes out native plants
Overexploitation
• Human harvesting of wild plants or animals at rates
exceeding ability of populations of those species to rebound
• Large organisms with low reproductive rates are
especially vulnerable
Rarity
• Rare species are the most vulnerable to
extinction, though common species can also
become extinct.
Three ways a species can be rare...
1.
Cave Salamander
2.
3.
Maned Wolf
4.
Proboscis Monkey
5.
Hawaiian Hawk
6.
Dwarf Naupaka
The Problem with Rarity
• A small population is prone to positive-feedback loops
that draw it down an extinction vortex
• The key factor driving the extinction vortex is loss of
the genetic variation necessary to enable evolutionary
responses to environmental change
Fig. 56-10
Small
population
Inbreeding
Genetic
drift
Lower
reproduction
Higher
mortality
Reduction in
individual
fitness and
population
adaptability
Smaller
population
Loss of
genetic
variability
The most serious threat to biodiversity is
A) Competition from introduced species
B) Environmental toxins
C) Habitat destruction
D) Overharvesting
E) Disruptions of community dynamics
Habitat Loss
Estimates of current
rates of extinction
worldwide are based
primarily on speciesarea relationships
and rates of tropical
deforestation.
Habitat Fragmentation
• The fragmentation of habitats into patches
that are too small to support populations is a
major cause of extinction...
Problems due to fragmentation:
• edge effects
• small area
• isolation
Fig. 56-14
(a) Natural edges
(b) Edges created by human activity
Edge Effects
Problems due to fragmentation:
• edge effects
• small area
• isolation
Smaller fragments have:
• fewer habitat types
• fewer species
• smaller populations
• higher extinction rates
Area-sensitive species with large home ranges
are especially vulnerable to small area effects...
Jaguar
Spider Monkey
White-plumed Antbird
Problems due to fragmentation:
• edge effects
• small area
• isolation
Isolation
Rates of extinction are much higher on
oceanic islands than on the mainland
The more isolated an island is from the mainland,
the lower the chances of “rescue effect”.
Habitat fragments are habitat “islands”...
Bogor Botanical Garden, Java
A possible solution to fragmentation?
Habitat (movement) corridors are
A) The routes taken by migratory animals
B) Strips or clumps of habitat that connect small isolated
habitats to larger, continuous habitats
C) Connections within a landscape that includes several
different ecosystems
D) The areas forming the boundary or edge between two
ecosystems
E) Buffer zones for human traffic that promote the longterm viability of protected areas
Habitat (Movement) Corridors:
-strips or clumps of habitat that connect small
isolated habitats to larger, continuous habitats
Habitat (Movement)
Corridors:
Can even be man-made
to maintain natural
migratory routes
Advantages of Habitat Corridors
- increased species richness
- “rescue effect”
- maintain genetic variation
- altitudinal migration
Three-wattled Bellbird - altitudinal migrant
Biodiversity ‘Hot Spot’:
A relatively small ecosystem with
a high concentration of species,
many of which are endemics.
Terrestrial biodiversity
hot spots
Marine biodiversity
hot spots
Equator
Hotspots of biodiversity are also
hotspots of extinction…
Video Topics
Population Ecology: life history strategies
parental care / fecundity
Community Ecology: biodiversity
mutualisms, competition, predation
Ecosystem Ecology: primary producers (plants)
primary, secondary, tertiary consumers
water cycle
Conservation Biology: hot spot, endemic species, rarity,
habitat fragmentation, extinction