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The Passenger Pigeon: The Passenger Pigeon: Gone ForeverGone ForeverOnce the most
numerous bird on earth.
In 1858, Passenger Pigeon hunting became a big business.
By 1900 they became extinct from over-harvest and habitat loss.
I. Endangered and Threatened I. Endangered and Threatened Species: Ecological Smoke AlarmsSpecies: Ecological Smoke Alarms
A. Endangered species: so few individual survivors that it could soon become extinct.
B. Threatened species: still abundant in its natural range but is likely to become endangered in the near future.
II. Species ExtinctionII. Species ExtinctionA. Species can become extinct:
1. Locally: A species is no longer found in an area it once inhabited but is still found elsewhere in the world.
2. Ecologically: Occurs when so few members of a species are left they no longer play its ecological role.
3. Globally (biologically): Species is no longer found on the earth.
3. Globally (biologically): continued.
Some species have become permanently extinct because of human activities.
II. Species ExtinctionII. Species Extinction
Some species have characteristics that make them vulnerable to ecological and biological extinction.
II. Species ExtinctionII. Species Extinction
1. The International Union for the Conservation of Nature and Natural Resources (IUCN) publishes an annual Red List, listing the world’s threatened species.
2. The IUCN takes the following into account:Population Size & Reduction of it
# of Mature Individuals
Geographic Range of Population
Quality of Habitat
Probability of Extinction
B. Scientists use measurements and models to estimate extinction rates.
II. Species ExtinctionII. Species ExtinctionC. Causes: Conservation biologists summarize
the most important causes of premature extinction as “HIPPO”:
1. Habitat destruction, degradation, and fragmentation
2. Invasive Species
3. Population growth
4. Pollution
5. Overharvest
H. Habitat loss…Biggest threat to biodiversityWhen area to live is gone, organisms
die
Why would the habitats go away?
Ex. deforestation
Habitat FragmentationSeparation of wilderness areas from
other wilderness areasFragmented areas are like islands; the
smaller the fragment, the less biodiversity it will support
Habitat destruction, degradation, and fragmentation
Reduction in ranges of four wildlife species, mostly due to habitat loss and overharvest.
Biotic and Abiotic Issues of Fragmentation
Biotic:-some organisms need
large areas to gather food
Ex. Lions
Ex. Zebra
-no migratory routes to re-establish populations lost due to natural disasters
Abiotic:-climate can change
-can cause EDGE EFFECT
(different conditions along the boundaries of an ecosystem)
I. Introduction of Exotic (invasive) SpeciesNew orgs introduced into an
ecosystem; do not have any natural predators and is little competition with other orgs, so native species are at risk
Exotics may take over niches of native species and eventually replace the native species completely
Invasive SpeciesMany nonnative species provide us with food, medicine, and other benefits but a few can wipe out native species, disrupt ecosystems, and cause large economic losses.
Kudzu vine was introduced in the Kudzu vine was introduced in the southeastern U.S. to control erosion. It has southeastern U.S. to control erosion. It has taken over native species habitats.taken over native species habitats.
Invasive SpeciesPrevention is the best way to reduce threats from invasive species, because once they arrive it is almost impossible to slow their spread.
PopulationPopulation
Human populations put pressure on species◦Direct use, habitat conversion, pollution
Large numbers of humans use resources wild species need◦ Even if each person uses small amounts of resources
A small group of people can overuse resources◦ People with highly consumptive resources have a
disproportionate effect on the environmentDifferent levels of consumption and numbers of
people drive tensions between countries
O. OverexploitationO. OverexploitationSome protected species are killed for their
valuable parts or are sold live to collectors.
Killing predators and pests that bother us or cause economic losses threatens some species with premature extinction.
Legal and illegal trade in wildlife species used as pets or for decorative purposes threatens some species with extinction.
Overexploitation
Rhinoceros are often killed for their horns and sold illegally on the black market for decorative and medicinal purposes.