chapter 10 section 2 biodiversity at risk. objectives define and give examples of endangered and...
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Chapter 10
Section 2
Biodiversity at Risk
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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.
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Biodiversity at Risk• Mass extinction- extinction of many
species in a relatively short period of time
• Earth has experienced several mass extinctions, each probably caused by a global change in climate
• It takes millions of years for biodiversity to rebound after a mass extinction
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Species prone to Extinctions
• Small populations in limited areas can easily become extinct
• Species that are especially at risk of extinction are those that migrate, those that need large or special habitats, and those that are exploited by humans
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Species prone to Extinction
• Endangered species - species that has been identified to be in danger of extinction throughout all or a significant part of its range, and that is thus under protection by regulations or conservation measures
• Threatened species - species that has been identified to be likely to become endangered in the foreseeable future
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How do humans cause extinctions?
• In the past 2 centuries, human population growth has accelerated and so has the rate of extinctions
• Major causes of extinction today:
–Destruction of habitats
–Introduction of nonnative species
–Pollution
–Overharvesting of species
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PA Endangered Species• Black tern
• Peregrine falcon
• Northern flying squirrel
• Least shrew
• Sedge wren
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Habitat Destruction & Fragmentation
• As human populations grow, we use more land to build homes and harvest resources- destroying habitats and other species
• It is estimated that habitat loss causes almost 75% of the extinctions now occurring
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Habitat Destruction & Fragmentation
• EXAMPLE: cougars, including the Florida Panther, require expansive ranges of forest and large amount of prey
• Today, much of the cougars’ habitat has been destroyed or broken up by roads, canals, and fences
• In 2001, fewer than 80 Florida panthers made up the only remaining wild cougar population east of the Mississippi River
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Invasive Exotic Species
• Exotic species - species that is not native to a particular region
• Exotic species can threaten native species that have no natural defenses against them
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Harvesting, Hunting, & Poaching
• Excessive hunting can also lead to extinction as seen in the 1800s and 1900s when 2 billion passenger pigeons were hunted to extinction
• Thousands of rare species worldwide are harvested and sold for use as pets, houseplants, wood, food, or herbal medicine
• Poaching - illegal harvesting of fish, game, or other species
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Pollution• Pesticides, cleaning agents, drugs, and
other chemicals used by humans are making their way into food webs around the globe
• EXAMPLE: The bald eagle was endangered because of a pesticide known as DDT. Although DDT is now illegal to use in the United States, it is still manufactured here and used around the world
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Areas of Critical Biodiversity
• Endemic species - species native to a particular place and that is found only there
• Ecologists often use the numbers of endemic species of plants as an indicator of overall biodiversity because plants form the basis of ecosystems on land
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Tropical Rain Forests• Biologist estimate that over half of the
world’s species live in these forests even though they cover only 7% of the Earth’s land surface
• Most of the species have never been identified
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Coral Reefs & Coastal Ecosystems
• Reefs provide millions of people with food, tourism revenue, coastal protection, and sources of new chemicals
• Nearly 60% of Earth’s coral reefs are threatened by human activities, such as pollution, development along waterways, and overfishing
• Similar threats affect coastal ecosystems, such as swamps, marshes, shores, and kelp beds
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Islands• When an island rises from the sea, it is
colonized by a limited number of species from the mainland. These colonizing species may then evolve into several new species. How did the organisms get to the islands?
• Thus, islands often hold a very distinct but limited set of species.
• Many island species, such as the Hawaiian honeycreeper, are endangered because of invasive exotic species
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Biodiversity Hotspots• The most threatened areas of high species
diversity on Earth have been labeled biodiversity hotspots and include mostly tropical rainforests, coastal areas, and islands
• Most of these hotspots have lost at least 70% of their original natural vegetation
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Biodiversity in the United States
• Unique ecosystems: Florida Everglades, California coastal region, Hawaii, Midwestern prairies, and the forests of the Pacific Northwest
• USA: high numbers of species of freshwater fishes, mussels, snails, and crayfish, pine trees and sunflowers
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Biodiversity in the United States
• EXAMPLE: California Floristic Province, a biodiversity hotspot, is home to 3,488 native plant species (2,124 are endemic and 565 are threatened or endangered)
• Threats to this area: use of land for agriculture and housing, dam construction, overuse of water, destructive recreation, and mining- All of which stem from local human population growth
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REVIEW!!!• 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.