SPECIFICITY AND EXTINCTION
NUMBERS OF SPECIES:
There are about 1.5 million species which are known to exist on earth. The number of as yet undescribed species is probably greater than the number already known to exist. Why are there so many different species? Although there are widespread generalist species which are found throughout the world, most species only exist in certain parts of the world and often depend on food sources and environmental conditions which are specific to that part of the world.
For example, in comparing the wildlife of the Northeastern United States and central South America, there are different species of deer.
There are wild pigs (peccaries) which are found in Paraguay which do not exist in the Northeast, including the endangered tagua (the second image) which can only be found in the central South American region known as the Chaco.
North America possesses hoofed animals which are not found in South America such as bison.
Rodents such as beaver are native to North America while capybaras are native to South America.
While there are a handful of species of warbler in central South America, the majority of species are native to North America (and winter in Northern Latin America).
While there are a handful of species of flycatcher in the Northeast U.S., more than one hundred are native to central South America.
While the ruby-throated hummingbird is the only species of hummingbird found east of the Mississippi River, the small country of Paraguay is home to more than a dozen species of hummingbird.
The woodpeckers of North America
differ from those of South America.
The birds found in aquatic environments in central South America are different from those one would find in the Northeastern U.S.
No matter what groups of organisms were considered, those of central South America would be distinct from those of the Northeast U.S.
Because biomes vary across the world or across the country, one finds many organisms occurring only in certain areas. Within the United States, for example, there is great variation in the native species of birds.
1) the east coast: great black-backed gull, surf & white-winged scoters, black-bellied plover, purple sandpiper, Louisiana heron, white ibis, glossy ibis, tufted duck, whistling swan, red-necked grebe,
2) the Northeast: chestnut-sided warbler, golden-winged warbler, alder flycatcher, magnolia warbler, black-throated green warbler, blackburnian warbler, black-throated blue warbler
3) grasslands: greater prairie chicken, gray partridge, lark bunting, chestnut-collared, McCown's, & Smith's longspurs,
4) Fla:brown noddy, black noddy, magnificent frigatebird, swallow-tailed kite (Georgia also), wood stork, great white heron, limpkin, short-tailed hawk, everglade kite, spotted-breasted oriole, gray kingbird, blue-gray tanager, black-whiskered vireo, mangrove cuckoo, red-whiskered bulbul, smooth billed ani
5) Texas:whooping crane (50 individuals), least grebe, green kingfisher, white tailed hawk, black-capped vireo, jacana, scaled quail, chachalaca, pauraque, white-winged dove, cave swallow, golden-fronted woodpecker, black-headed oriole, kiskadee flycatcher, yellow green vireo, black-crested titmouse, buff-bellied hummingbird
6) New England: common eider, mourning warbler, spruce grouse, hawk owl, boreal owl, bay-breasted warbler, yellow throated flycatcher, gray-cheeked thrush, boreal chickadee, blackpoll warbler
About one quarter of the earth’s mammals and reptiles, 21% of amphibians, 30% of fish, and 12% of the earth’s birds are in danger of extinction. The loss of habitat is the greatest threat to 85% of the earth’s most threatened birds. About 1/3 of parrot species are endangered by habitat loss and collecting for pets or plumage.
Many populations now exist in such small
numbers that they are in danger of extinction.
Some occur in
I) MANY ENDANGERED SPECIES ARE FOUND ONLY IN CERTAIN PARTS OF THE WORLD
The maps above depicted the limited distribution of many species globally.
MANY OF THE ENDANGERED ORGANISMS FOUND IN THE
--Key Deer: FL
--Jaguarundi: one subspecies TX, the other AR
--Hawaiian Hoary Bat: HI
--Mariana Fruit Bat:
--6 species of Kangaroo
--Puerto Rican parrot,
Puerto Rican nightjar, Puerto Rican plain pigeon:
--Northern Spotted Owl: CA, OR, WA
--Atwaters Greater Prairie Chicken: TX
--Cactus ferrugineous Pygmy Owl: AZ
--Bluetail Skink, Sand
Skink, Atlantic Saltwater Marsh Snake:
Giant Garter Snake:
--Concho Water Snake: TX
--Yellow Blotched Map Turtle: MS
--Barton Springs Salamander: TX
--Red Hills Salamander:
--Shenandoah Salamander: VA
--Puerto Rican Crested
--Pygmy and Smoky Madtom: TN
--Pahrump Poolfish, Devils Hole and Ash Meadows Pupfish: NV
--Comanche Springs Pupfish: CA
--Chum Salmon: VA
--Coho Salmon: CA
--Pygmy Sculpin and
--Little Coloroado Spinedace: AZ
--Steelhead: OR, WA
--June Sucker: UT
--Warner Sucker: OR
--Greenback Trout: CO
6) INVERTEBRATES (Spiders and Clams as examples)
--Spruce-fir Moss Spider: NC, TN
--Brittons Beargrass, Amargosa Niterwort, White Birds in a Nest: FL
--Mohrs Barbaras Buttons: AL & GA
--a great diversity
of plants native to
--Macfarlanes : ID, OR
--Fassets Locoweed: WI
--Brady Pincushion Cactus:AZ
--Peebles Navajo Cactus
--Blowout Penstemon: NE
--Penland Beardtongue: CO
--Godfrey’s Butterwort: FL
LOSS OF HABITAT
The above land in
This region in
Although the following picture depicts forest of the
The previously mentioned maps and data demonstrated
that wildlife adapt to specific areas and that
many species are only found in certain habitats. Many habitats are being destroyed. Barely 1% of the original tall-grass prairie
remains in the
Between 1960 and 1990, 20% of all the earth’s
rainforests were cut. During this
Islands frequently carry species that occur
nowhere else in the world. For
example, of the 135 birds that occurred only in
About 140,000 square kilometers of tropical rainforest are cut/year. During the 1990s, the earth’s forest cover decreased by 4% and about half of the world’s forests have been lost since the dawn of agriculture. More than half the earth’s wild wetlands have been lost during the past century.
Due to population growth alone, the percentage of species in an average nation is expected to rise to about 7% by the year 2020 and 14% by 2050. Human population growth is a primary factor in an estimated 88% of the species whose condition is considered threatened (McKee, 2003).
which inhabit deep woods habitats are threatened when a habitat is fragmented,
not only because the physical area that they can inhabit is reduced, but
also because new species are introduced into the area which compete with
them. This is especially evident in the case of brown-headed cowbirds.
Many animals which inhabit deep woods habitats are threatened when a habitat is fragmented, not only because the physical area that they can inhabit is reduced, but also because new species are introduced into the area which compete with them. This is especially evident in the case of brown-headed cowbirds.
The brown headed cowbird parasitizes
other birds by laying its eggs in their nests. Other birds raise the cowbirds
as their own and the cowbird nestlings outcompete those of the other species.
This brood parasitism can decrease the populations of songbirds by half.
The brown headed cowbird originally inhabited western North America but
expanded its populations eastward when forests were cleared. They prefer
edge habitats so that the splitting of a large region of continuous forest
into smaller habitats drastically increases the effect of cowbirds on
Extinction is a natural process; it is estimated that over 99.9% of all the living things that have ever existed in earth's history are now extinct. Sometimes extinction occurs at a slow rate; there are other times known as mass extinctions.
Due to the human impact on the natural world, it is estimated that at least 100 species become extinct every day; at this rate, the mass extinction through which we are now living will soon (by the year 2000?) surpass the Cretaceous extinction and become the 2nd largest in earth's history.
Why aren’t you aware of the species which become extinct every day?
1) They are Rare:
at the list of endangered species in
2) Most people are unfamiliar with many groups of organisms, such as insects, freshwater mollusks, etc. Ninety-five percent of all animal species are invertebrates and therefore many species could go extinct from your area without your being aware of them ever existing.
Since most of
the species on earth do not even occur in the
CAN ANIMALS FROM THE
1) Some currently endangered species are very close to extinction because their numbers are so small (all of the following population estimates are from the mid-1990s):
--Schaus Swallowtail Butterfly: under 100
--Black Footed Ferret: 450
--Cooke’s Kokio: a Hawaiian tree that no longer occurs in the wild, fewer than 50 grafts still survive that have yet to produce seeds
--Flat Pocketbook Pearly Mussel: 9 small colonies
--Laysan Duck: 500
--Swamp Pink: 120 known sites
--Northeastern Beach Tiger Beetle: 45 groups
--Red Wolf: fewer than 300
--Macfarlanes Four-O’Clock: 10 patches
--Green Pitcher Plant: 26 known sites
--Hellers Blazing Star: 7 groups (most fewer than 50 plants)
--Na’u: 15 bushes
--Whooping Crane: 175
--Key Tree Cactus: under 200
--Boulder Darter (a small perch): 8 small groups
Wedge Mussel: 19 groups (some in
--Tenessee Purple Coneflower: 5 patches
There are a number of organisms on the Endangered
Species List that have not been seen in years/decades and may already
be extinct such as the turgid blossom, yellow blossom, little Mariana
fruit bat, Mariana mallard, scioto madtom. The Bachman’s warbler and Ivory billed woodpecker
are extinct from the
Some species that inhabited