biodiversitysection 2 objectives define and give examples of endangered and 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.

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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.

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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

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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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• 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

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• Large increase in human population considered to be

• major reason for current mass extinction

How Do Humans Cause Extinctions?

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• Cause: use more land to build homes and harvest resources

• Result: destroy and fragment the habitats of other species

– estimated causes @ 75 % of extinctions

Habitat Destruction and Fragmentation

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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

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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

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• 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.

Harvesting, Hunting, and Poaching

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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

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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

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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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• @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

Coral Reefs and Coastal Ecosystem

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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

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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.

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Biodiversity Hotspots

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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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Types of diverse organisms

– freshwater fishes,

– mussels, snails, crayfish

– pine trees and sunflowers

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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