Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
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 Section 2 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 Section 2 Biodiversity Section 2 • 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 Section 2 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 Section 2 • 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 Section 2 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 Section 2 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 Section 2 Biodiversity Section 2 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 Section 2 Islands • Often hold a very distinct but limited set of species. • Many island species endangered because of invasive exotic species – Example: Hawaiian honeycreeper Biodiversity Section 2 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 Section 2 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 Section 2 Biodiversity Types of diverse organisms – freshwater fishes, – mussels, snails, crayfish – pine trees and sunflowers Section 2 Biodiversity Section 2 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