Biodiversity is life Biodiversity is our lifeachs.amherst.k12.va.us/sites/default/files/Chapter 10...
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Transcript of Biodiversity is life Biodiversity is our lifeachs.amherst.k12.va.us/sites/default/files/Chapter 10...
Chapter 10 Section 2
Biodiversity at Risk 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 at Risk
Key Terms:
Endangered species Threatened species
Exotic species Poaching
Endemic species
Major Extinction Events
• Mass extinction – extinction of many species in a relatively short period of time.
• The rate of extinction is estimated to have increased by a multiple of 50 since 1800.
• Between 1800 and 2100 up to 25% of all species on Earth may become extinct.
• Sixth extinction?
• Endangered species are those likely to become extinct if protective measures are not taken immediately.
• Threatened species are declining in population and likely to become endangered if not protected.
Major human causes of extinction:
• Habitat destruction and fragmentation
• Introduction of non-native species
• Pollution
• Over-harvesting of species
(Human population growth affects rate of extinctions.)
Habitat destruction and fragmentation
It is estimated that habitat loss causes about 75% of current extinctions.
Habitat destruction and fragmentation
• Example: Florida Panther, which is the most endangered species in North America. Habitat loss is the major reason.
Introduction of non-native species
• Invasive exotic species are not native to a particular region.
• Can threaten native species that have no natural defenses.
• Example: invasive fire ants threaten livestock, people, and native species in southeastern United States.
Pollution: Pesticides, cleaning agents,
pharmaceuticals, other chemicals used by humans
Example: Bald eagle and DDT
Over-harvesting of species
• Poaching – harvesting wildlife illegally.
• Thousands of species are harvested and sold as pets, houseplants, wood, food, and herbal medicine.
• Many countries have laws to regulate hunting, fishing, harvesting, and trade of wildlife.
Example: Bison numbers went from 60 million before North America was settled by Europeans to only 300 in 1906. Many killed for their tongues (considered a delicacy) and bodies were left to rot. Current population is 200,000 +.
Areas of Critical Biodiversity
• Endemic species – species native to and found only within a limited area.
• Number of endemic species of plants are an indicator of overall biodiversity because plants form the basis of terrestrial ecosystems.
Areas of Critical Biodiversity
Tropical Rain Forests
• Less than 7% of Earth’s land surface; 50% or more of biodiversity
• Threats: clearing for farming, cattle grazing, logging
Areas of Critical Biodiversity
Coral Reefs and Coastal Ecosystems
• Provide food, tourism revenue, coastal protection, sources of new chemicals
• Nearly 60% of coral reefs are threatened
• Threats: development along waterways, overfishing, pollution.
Example: Great Barrier Reef near Australia is the largest and maybe oldest reef (2000 km/1,250 miles long and 3,400 individual reefs).
Areas of Critical Biodiversity
Islands • Colonized by a limited number of species
from mainland;
• Colonizing species evolve into several new species
Hawaiian Islands have 28 species of endemic birds (honeycreepers) endangered because of invasive exotic species. Threats: cattle and feral pigs that destroy habitat, rats that eat eggs and young birds, and introduced birds that have out-competed the honeycreeper for habitat.
Biodiversity hotspots
• Biodiversity hotspots – most threatened areas of high species diversity.
• High number of endemic species threatened by human activities.
• International conservationists have identified 25 biodiversity hotspots.
Biodiversity hotspots
• Most have lost at least 70% of their original vegetation.
• Most are tropical rain forests, coastal areas, or islands.
Biodiversity hotspots Example: Island of Madagascar
• Only 18% of original forests remain
• 80% of 10,000 flower plant species are endemic
• 91% of 300 reptile species are endemic
• All 33 species of lemur are found only in Madagascar
Examples of U.S. biodiversity hotspots:
• Florida Everglades
• California coastal region
• Hawaii
• Midwestern prairies
• Forests of the Pacific Northwest
The U.S. has an unusually high number of species of freshwater fishes, mussels, snails, crayfish, pine trees, and sunflowers.