Download Threatened species

Biodiversity
Section 2
Objectives
• Define and give examples of endangered and
threatened species.
• Describe several ways that species are being
threatened with extinction globally.
• Explain which types of threats are having the largest
impact on biodiversity.
• List areas of the world that have high levels of
biodiversity and many threats to species.
• Compare the amount of biodiversity in the United States
to that of the rest of the world.
Biodiversity
Section 2
Biodiversity at Risk
• mass extinction: extinction of many species in a
relatively short period of time
• Earth has experienced several
– probably caused by global changes in climate
– millions of years for biodiversity to rebound after a
mass extinction.
Biodiversity
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Current Extinctions
• in the midst of another mass extinction
• rate estimated to have increased by 50x since 1800
• @25 % of all species on Earth lost since 1800
• difference from past occurrences: humans primary
cause
Biodiversity
Species Prone to Extinction
• small populations in limited areas
• especially at risk
– those that migrate,
– those that need large or special habitats
– those that are exploited by humans
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Biodiversity
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• Endangered species: a species identified to be in
danger of extinction throughout all or a significant part of
its range, and under protection by regulations or
conservation measures
• Threatened species: a species identified as likely to
become endangered in the foreseeable future
Biodiversity
Section 2
How Do Humans Cause Extinctions?
• Large increase in human population considered to be
• major reason for current mass extinction
Biodiversity
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Habitat Destruction and Fragmentation
• Cause: use more land to build homes and harvest
resources
• Result: destroy and fragment the habitats of other
species
– estimated causes @ 75 % of extinctions
Biodiversity
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• Example:
– Florida Panther requires expansive ranges to obtain
prey
– habitat destroyed or broken up by roads, canals, and
fences
– Result- by 2001 <80 wild panthers east of Mississippi
river
Biodiversity
Section 2
Invasive Exotic Species
• Cause: species brought to regions where they never
lived before
• Result:
– threaten native species that have no natural defenses
against them
– out compete related native species, replace them
• Definition
• Exotic species: species not native to a particular region
Biodiversity
Section 2
Harvesting, Hunting, and Poaching
• Cause: Excessive hunting or harvesting for pets,
houseplants, wood, food, or herbal medicine
• Results: species eliminated, rare species endangered
• Examples:
– 2 billion passenger pigeons hunted to extinction
– thousands of rare species collected
• Definition
• Poaching: illegal harvesting of fish, game, other species.
Biodiversity
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Pollution
• Cause: pesticides, cleaning agents, drugs, other
chemicals get into food webs
• Results:
Short term- chemicals toxic or disrupt nutrient cycles
Long term- effects may not be clear
bald eagle endangered because of a pesticide DDT,
effects not noticed for @20 years
Biodiversity
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Areas of Critical Biodiversity
• Areas of the world that contain a great diversity of
species, have a large portion of endemic species
• Number of endemic plants used as indicator of overall
biodiversity because plants form the basis of ecosystems
• Definition
• Endemic species: species that is native to a particular
place and found only there
Biodiversity
Types:
Tropical Rain Forests
• Estimate- contain > ½ all species
• Only 7 percent of the Earth’s land surface
• Most of the species never described
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Biodiversity
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Coral Reefs and Coastal Ecosystem
• @60 % of coral reefs threatened by human activities
• Also affected coastal ecosystems: swamps, marshes,
shores, and kelp beds
– provide millions of people with food, tourism revenue,
coastal protection, and sources of new chemicals
– poorly studied, not as well protected by laws as
terrestrial areas
Biodiversity
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Islands
• Often hold a very distinct but limited set of species.
• Many island species endangered because of invasive
exotic species
– Example: Hawaiian honeycreeper
Biodiversity
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Biodiversity Hotspots
– most threatened areas of high species diversity
– high numbers of endemic species
– most have lost at least 70 % of their original
natural vegetation.
Biodiversity
Biodiversity Hotspots
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Biodiversity
Biodiversity in the United States
Wide variety of unique ecosystems
– Florida Everglades
– California coastal region
– Hawaii
– Midwestern prairies,
– temperate rain forest of Pacific Northwest
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Biodiversity
Types of diverse organisms
– freshwater fishes,
– mussels, snails, crayfish
– pine trees and sunflowers
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Biodiversity
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Example area: California Floristic Province
• home to 3,488 native plant species
• 2,124 are endemic
• 565 threatened or endangered.
• Threats: agriculture and housing, dam construction,
overuse of water, destructive recreation, and mining