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Content Benchmark L.12.C.4
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Life Science
Heredity
Structure of Life
Organisms and Their Environment
  L.12.C.1
  L.12.C.2
  L.12.C.3
  L.12.C.4
Diversity of Life
Content Areas
Nature of Science (NOS)
Life Science
Earth Science
Physical Science

Students know the unique geologic, hydrologic, climatic, and biological characteristics of Nevada’s bioregions. E/S

When one views the biodiversity in Nevada it is surprising to note that only ten states are richer in their biodiversity. Nevada lists 3,872 species in the state, of which, plants are the most common with 2,875 species. In addition Nevada ranks sixth in terms of endemic species (native species not found elsewhere) with 309 species found only in Nevada. The chart below shows the taxa where these endemic species are distributed.

Figure 1. Endemic species in Nevada by major taxa.
http://dcnr.nv.gov/nrp01/figure3-1.gif

To learn more on Nevada’s biodiversity go to
http://heritage.nv.gov/reports/scor2006.pdf
and, http://www.natureserve.org/Reports/stateofunions.pdf

At the same time Nevada has 25 species that are on the Federal List of Endangered. Of these are 17 fish which include a number of pupfish in Ash Meadows.

To find the names of endangered species in Nevada go to
http://heritage.nv.gov/endanged.htm

The names of additional threatened species in Nevada are found at http://www.fws.gov/nevada/protected_species/nevada_species_list.html

A map of threatened and endangered species is located at
http://ecos.fws.gov/tess_public/StateListing.do?state=all


The question then becomes, why does Nevada have so much biodiversity relative to the other 50 states? Size alone is not the answer considering Texas the second largest state in area is second in biodiversity, while the largest state, Alaska ranks 49 in biodiversity. Of more importance is the geographical diversity in the state. Nevada lies in a geological region known as Basin and Range (see map below) which is vast system of valleys and mountain ranges. This area extends east-west from the Colorado Plateau to the Sierra Nevada, while stretching south from the borders of Nevada, Washington and Idaho to the northern parts of Mexico.

Figure 2. Extent of the Basin and Range topography in North America.
http://en.wikipedia.org/wiki/Basin_and_Range

The Basin and Range topography has resulted from the extension or pulling apart of the earth’s crust in this area of North America. This stretching occurred as the North American and Pacific Plates have moved apart over of the last 20 million years. As a result Nevada has hundreds of active extension faults which results in earthquake activity in most parts of Nevada. This stretching and pulling has also produced some of the thinnest crust on the earth.

This pulling continues today and the direction of this pulling can be seen in the map below.

Figure 3. Direction of tectonic plate separate between the Pacific and North American Plates. http://www.seismo.unr.edu/ftp/pub/louie
/class/100/plate-tectonics.html

To learn more about plate tectonics, go to
http://www.ucmp.berkeley.edu/geology/tectonics.html

The formation of this geological feature has left Nevada with 314 named mountain ranges and 232 hydrographic basins. Twenty-five of these mountain ranges have peaks over 10,000 feet, while elevations of the larger valleys range from 500 to 6,800 ft above sea level. As can be seen in the map below these mountains and valleys tend to run in a north south direction. (Note in Spanish “Nevada” means “snowcapped”.)

Figure 4. Topography of Nevada
http://geology.com/state-map/nevada.shtml

The photo of the Kingston Range from Emigrant Pass illustrates this system of mountains and valleys.

In addition, climate changes over the past 10,000 years have produced many freshwater lakes that have developed and disappeared along with other ecosystems such as mountain coniferous forests and riparian zones. These changes have provided the raw materials for evolution and natural selection. As ecosystems developed, disappeared or became isolated selective pressures were place upon organisms to adapt or become extinct. Nevada biodiversity can therefore be seen as a direct interaction between geological and biological evolution.

The geological action that created the basin and range topography also formed a number of mountain peaks which are isolated by broad valleys which surround them. An example of this “sky island” ecosystem can be seen in the Spring Mountains which is typically 20-30°F cooler than the valleys below. In this sky island biologists have identified nearly 40 endemic species of plants and animals including the Palmer chipmunk, the prairie falcon, spotted bat and blue mountain butterfly. This is the highest number of endemic species of any mountain range in the Great Basin. Ash Meadows (see below) is another example of this oasis of species in Armargosa Valley. Ash Meadows contained numerous artesian springs that sustained isolated populations of endemic fish. However, due to extensive ground water pumping many of the artesian springs have stopped flowing, resulting in the extinction or near extinction of their endemic populations.

Ecoregions of Nevada

The Basin and Range topography of Nevada is divided into four ecoregions. These include the Great Basin, Mojave Desert, Columbia Plateau and the Sierra Nevada.

Figure 6. Major Ecoregions of Nevada
http://dcnr.nv.gov/nrp01/bio01.htm

A more detailed map of Nevada ecoregions can be found at: http://www.fws.gov/nevada/habitats/documents/na_eco.pdf

Great Basin Ecoregion

Figure 6. Central Basin Topography
http://www.fws.gov/nevada/habitats/ecoregions_html.htm

The middle of the state is dominated by the Great Basin ecoregion. In fact over 68% of Nevada is covered by this ecoregion which also extents into Utah and parts of southern California. This area is also part of the larger Great Basin Desert. Compared with other ecoregions in the U.S. the Great Basin ranks fifth in total species richness. In the higher valleys sagebrush (The Nevada State Flower) dominates, while creosote bush can be found in the lower valleys. Salt flats are scattered throughout this region. In the lower mountain elevations single-leaf pinyon (One of Nevada’s state trees) and juniper are common. In the widely dispersed higher mountainous elevations conifers and woodlands occur. Most of the yearly precipitation falls in the winter. As such the Great Basin is often termed a “cold desert”.

The Great Basin makes up a landlocked drainage basin. The rivers in this ecoregion have no natural outlets to the ocean. It is bordered by the Rocky Mountains to the east and the Sierra Nevada to the west.

Figure 8. North American Basins
http://en.wikipedia.org/wiki /Image:Basin_New.png

For a map showing the major rivers of Nevada go to: http://geology.com/state-map/nevada.shtml

Mojave Ecoregion

The Mojave Desert (the smallest of the four major deserts found in the U.S.) is found in the southern part of the state.

Figure 9. Deserts of North America http://www.birdandhike.com/Veg/Veg_index.htm

In the Mojave Desert valleys are broader and mountain ranges are fewer as compared to the Great Basin. The area around Las Vegas illustrates the variety of life zones of the Mojave Desert. These life zones can be seen in Figure 15 below. In the Lower Sonoran life zone (below 4000 ft) creosote bush and White Bursage are the dominant plants with Mojave Yucca found at higher elevations. This area is also home to the endangered Desert Tortoise. The non-endemic red brome grass can be common, especially in high rainfall years. Temperatures range in excess of 110oF in the summer to 25oF in the winter.

As one moves up the slopes (from 4000 to 5000 ft) one enters the Upper Sonoran life zone. Here creosote bush, Joshua Tree (which is the indicator plant for this desert, as it is naturally found no place else in the world), various yucca and a mixture of shrub and cacti are found. One can find the Big Horned Sheep (The Nevada State Animal) in this zone.

To learn more about the creosote bush, go to
http://www.birdandhike.com/Veg/Species/Shrubs/Creosote/Larr-trid.htm

Figure 11. Joshua Tree
http://i1.trekearth.com/photos/8168/joshua_tree.jpg

To learn more about the Joshua Tree, go to
http://www.birdandhike.com/Veg/Species/Yucca/Y_brev/Y_brev.htm

As one moves out of the Mojave Desert into lower mountainous elevations (5500-7500 ft) pinyon pine and juniper can be found. Pines and firs are limited to higher elevations sometimes with sages and bunchgrasses. At lower elevations one can find Blackbrush and Rabbit Brush. Throughout this region numerous cacti such as Prickly Pear, Hedgehog Cactus and various varieties of cholla can be found. Generally less than 5 inches of precipitation falls during the summer monsoons and in winter. During the winter several feet of snow can sometimes occur at the highest elevations.

Figure 12. Pinyon Pine in the Sheep Range in southern Nevada
http://www.birdandhike.com/Veg/Species/Conifers/Pine_Pinyon1/Pine_Pinyon1.htm

To learn more about pinyon pine trees, go to http://www.birdandhike.com/Veg/Species/Conifers/Pine_Pinyon1/Pine_Pinyon1.htm

In the higher mountainous (over 7000 ft) areas within the Mojave Desert ponderosa pine become the dominate vegetation type. Other plants found in this area include sagebrush, Manzanita, shrub Live Oak and Quaking Aspens.

Figure 13. Mary Jane trailhead, Kyle Canon, Mt. Charleston
http://www.birdandhike.com/Veg/HabType/YellowPine/YellowPine.htm

As move up mountains beyond 8000 ft conifers continue to change until one reaches the alpine tundra. If you were to climb some of the higher elevation trails in Mt Charleston you would see white fir and Bristlecone Pine (Nevada’s second state tree). In the alpine tundra sedges and bunchgrasses would be seen.

Figure 14. Alpine Life Zone on Mt. Charleston
http://www.birdandhike.com/Veg/Veg_index.htm

The idea of life zones was developed at the end of the 19th century by C. Hart Merriam, who was the first director of the U.S. Biological Survey. This scheme of life zones was developed in studies of the Grand Canyon and nearby San Francisco Mts. These life zones were developed to identify belts of vegetation and animals. They were expressed with increases in altitude. In addition annual totals in precipitation were considered.

To learn more about the concept of life zones, go to
http://www.cpluhna.nau.edu/Biota/merriam.htm and,
http://www.runet.edu/~swoodwar/CLASSES/GEOG235/lifezone/merriam.html

Figure 15. Life Zones of Mt. Charleston and the Las Vegas Valley.
http://www.birdandhike.com/Veg/Veg_index.htm

Columbia Plateau

Figure 16. The Columbia Plateau Ecoregion, Jarbidge Mts.
www.fws.gov/nevada/habitats/ecoregions_html.htm

In the northern part of Nevada the Great Basin Desert mixes in and joins the Columbia Plateau ecoregion. Geologically this region contains tablelands, intermountain basins, dissected lava plains and scattered mountains. With a cooler climate and volcanic soils a sagebrush steppe ecosystem prevails containing numerous perennial grasses. Near the Idaho border open prairie is evident with such large mammals as Mule Deer, Antelope and Elk being found here. Juniper woodlands and mountain mahogany tend to replace the salt desert scrub and pinyon woodlands of the Great Basin at lower elevations. At higher elevations Douglas-fir and aspen are common.

Sierra Nevada

Figure 17. Jeffrey Pines

The Sierra Nevada ecoregion is found near Carson City and Reno. Lake Tahoe lies on the border between Nevada and California. Vegetation is mainly mixed conifer consisting of white fire and lodgepole pine on western slopes and Jeffery pine and lodgepole pine on eastern slopes. In higher elevations red fir, mountain hemlock and western white pine are seen.

These higher elevations receive more precipitation and are the source of rivers like the Truckee and Walker. These rivers provide water to lower elevations in the Great Basin. There are many mountain lakes and meadow/riparian areas. At the highest elevations alpine conditions exist.

Other areas

Within these four major ecoregions several other micro-regions can be identified including riparian zones and wetlands. In each case these add to the biodiversity of Nevada. Riparian zones are quite diverse and include short or tall grasses, shrubs and trees including willow, cottonwood or aspen.

Figure 18. Riparian Habitat
http://dcnr.nv.gov/nrp01/bio08.htm

One of the unique micro-regions in Nevada is its numerous wetlands. These include thousands of springs that are found throughout Nevada. A number of these springs are “left-overs” from the last ice age. As the last North American Ice Age was in retreat 10,000 years ago, numerous isolated springs were created. Of particular interest is Ash Meadows in the Armargosa Valley of southern Nye County. Today Ash Meadows supports 24 species of plants and animals (including the pupfish) that are found nowhere else in the world. This area represents the highest concentration of indigenous species in the United States and second greatest in North America.

Figure 19. Ash Meadows
http://ndep.nv.gov/admin/ash.jpg

To learn more about Ash Meadows visit
http://www.fws.gov/desertcomplex/ashmeadows/

To learn more about the desert pupfish, go to http://sciences.unlv.edu/desertsurvivors/Pages/episode4.htm

Other useful information

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Content Benchmark L.12.C.4

Students know the unique geologic, hydrologic, climatic, and biological characteristics of Nevada’s bioregions. E/S

Common misconceptions associated with this benchmark:

1. Students mistakenly believe that there is little biodiversity in Nevada.

Biological surveys of United States have shown that Nevada shows more biodiversity than most states. In fact only ten states show more biodiversity than Nevada and it ranks sixth in terms of endemic species. At present 309 species are located in Nevada and nowhere else. Of particular interest is the desert pupfish located in southern Nevada.

To learn more on Nevada’s biodiversity, go to http://heritage.nv.gov/reports/scor2006.pdf and
(http://www.natureserve.org/Reports/stateofunions.pdf)

For a checklist of wildlife in Nevada visit http://heritage.nv.gov/spelists.htm

Images of Nevada’s wildlife can be found at http://heritage.nv.gov/images.htm#vascplants

2. Students incorrectly believe that Nevada shows very little variation in plant life and is mostly desert.

While a large percentage of Nevada can be classified as desert the diversity of plant life has been greatly increased because of Nevada’s location in the Basin and Range geographical region. This geologically diverse region of mountains and valleys has produced many ecoregions within Nevada. As a result of isolation and time 3,872 species (including 2,875 species of plants) are now found in Nevada.

The four major ecoregions are subdivided into smaller ecological regions as can be seen in the map below. Each of these major ecoregions should not be viewed as one region, but seen as “micro regions” which are often sub-divided from one another. This isolation is important in the evolution of species.
Refer to L.12.D.5 for a discussion on how isolation is important in the evolution of species.

For a detailed discussion of vegetation in the Great Basin, go to http://www.fs.fed.us/
pnw/lagrande/sagebrush/docs/Gr%20 Basin%20PDF%20Sept03/Ch03_Vegetation_Sept03.pdf

3. Students confuse the Great Basin Desert with the Basin and Range geographical region.

The Basin and Range geographical region is a broad area in the western part of the United States (Refer to Figure 2) of valleys and mountains ranges. This area has resulted from tectonic actions of the Pacific and North America Plates. Within this geographical area are several large deserts including the Great Basin Desert (Refer to Figure 9), sometimes called the Great Basin. The Great Basin is an inland drainage basin located in the northern region of the Basin and Range geographical region and centered in Nevada. This basin also extends into surrounding states of California, Oregon, Idaho and Utah.

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Content Benchmark L.12.C.4

Students know the unique geologic, hydrologic, climatic, and biological characteristics of Nevada’s bioregions. E/S

Sample Test Questions

1st Item Specification: Recognize the distinguishing characteristics of the Mojave Desert, alpine forest, and basin and range bioregions.

Depth of Knowledge Level 1

  1. Compared to most states in the US, the biodiversity in Nevada
    1. is the least diverse.
    2. is the most diverse.
    3. ranks in the top 10.
    4. ranks in the bottom 10.
  1. The area with highest concentration of endemic species in the United States is the
    1. wetlands in Ash Meadows.
    2. Florida Everglades.
    3. Great Plains.
    4. Mississippi River Delta.
  1. The most common type of endemic species in Nevada belongs to which taxa listed below?
    1. Fish
    2. Plants
    3. Reptiles
    4. Birds
  1. You would know that you are located in the Mojave Desert if you were surround by
    1. Joshua trees.
    2. Sagebrush.
    3. Creosote bush.
    4. Pinyon Pine trees.
  1. What is the state flower of Nevada?
    1. Joshua tree
    2. Sagebrush
    3. Barrel cactus
    4. Desert daisy

Depth of Knowledge Level 2

  1. Which reason best explains how the rain shadow of the Sierra Nevada Mountains effects the climate in Nevada.
    1. Descending air masses on the east side of the mountains generate greater rainfall.
    2. Descending air masses on the east side of the mountains have no effect on rainfall.
    3. Ascending air masses on the west side of the mountains pick up moisture.
    4. Ascending air masses on the west side of the mountains lose moisture.
  1. Which reason best explains why temperatures in Nevada are warmer than areas at the same latitude on the pacific coast of California.
    1. As air masses from the west descend into Nevada they begin to lose heat.
    2. As air masses from the west descend into Nevada they begin to gain heat.
    3. The Rocky Mountains block cool air from moving into Nevada.
    4. Warm air masses from the Rocky Mountains enter Nevada.
  1. Nevada has a very high biodiversity compared to other states. Which reason below best explains why this is the case.
    1. It is a large state in terms of area.
    2. It is surrounded by many mountains.
    3. It has numerous ecological ecosystems.
    4. It has few people to disturb plant and animal habitats.
  1. Use the diagram and information below to answer the next question. In the diagram below, an air mass starts at Location 1 and moves over several mountains and valleys eventually reaching Location 4. While moving over the highest mountains, rain occurs on the west side of the mountains.

Which statement below is true based upon the diagram and given information?

  1. Atmospheric humidity will be the greatest at Location 1.
  2. Highest temperatures will be recorded at Location 3.
  3. Location 3 will be cooler than Location 4.
  4. Location 1 will be cooler than Location 2.
  1. Use the diagram and information below to answer the next question. In the diagram below, an air mass starts at Location 1 and moves over several mountains and valleys eventually reaching Location 4. While moving over the highest mountains, rain occurs on the west side of the mountains.

Which statement below is true based upon the diagram and given information?

  1. Location 2 will be warmer than Location 1.
  2. Location 1 will be warmer than Location 4.
  3. Location 1 will have the driest climate.
  4. Location 3 will have the driest weather.

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Content Benchmark L.12.C.4

Students know the unique geologic, hydrologic, climatic, and biological characteristics of Nevada’s bioregions. E/S

Answers to Sample Test Questions

  1. C, DOK Level 1
  2. A, DOK Level 1
  3. C, DOK Level 1
  4. A, DOK Level 1
  5. B, DOK Level 1
  6. D, DOK Level 2
  7. B, DOK Level 2
  8. C, DOK Level 2
  9. B, DOK Level 2
  10. D, DOK Level 2

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Content Benchmark L.12.C.4

Students know the unique geologic, hydrologic, climatic, and biological characteristics of Nevada’s bioregions. E/S

Intervention Strategies and Resources

The following is a list of intervention strategies and resources that will facilitate student understanding of this benchmark.

1. Plate tectonics that shaped the SW region
The geography of Nevada is a major reason for the biodiversity of the state. The forces that caused those changes are still at work today.

To learn more about plate tectonics, go to
http://www.ucmp.berkeley.edu/geology/tectonics.html

2. Geology of the Basin and Range
The Basin and Range topography is the dominate topography of the State of Nevada. Its “Sky islands” mountains, and desolate valleys help to isolate species and provide the raw materials for evolution and speciation to occur.

To learn more about the geology of the Basin and Range one might investigate John McPhee’s book by the same name.

An example of such speciation is the Joshua Tree. To learn more about the Joshua Tree, go to http://www.birdandhike.com/Veg/Species/Yucca/Y_brev/Y_brev.htm

3. Vegetation Zones
Vegetation zones are used to group plants and animals found at given elevations and climate zones. It is useful to refer to these zones when discussing the endemic species of Nevada.

To learn more about the vegetation zones around Las Vegas, go to http://www.birdandhike.com/Veg/Veg_index.htm
http://www.cpluhna.nau.edu/Biota/merriam.htm and,
http://www.runet.edu/~swoodwar/CLASSES/GEOG235/lifezone/merriam.html

For a detailed discussion of vegetation in the Great Basin visit http://www.fs.fed.us/pnw
/lagrande/sagebrush /docs/Gr%20Basin%20PDF%20Sept03/Ch03_Vegetation_Sept03.pdf

Ash Meadows is one of the most diverse micro-regions in the Untied States. Nevada’s great biodiversity can be brought into almost any discussion of the various Taxa that are required to be taught. Providing “local” examples from our state’s diverse species is an excellent way to help students develop a sense of community.

Detailed information about Ash Meadows can be found at
http://www.fws.gov/desertcomplex/ashmeadows/

To learn more about the desert pupfish, go to
http://sciences.unlv.edu/desertsurvivors/Pages/episode4.htm

To further explore Nevada’s biodiversity visit http://heritage.nv.gov/reports/scor2006.pdf and
and, http://www.natureserve.org/Reports/stateofunions.pdf

For a checklist of wildlife in Nevada, go to http://heritage.nv.gov/spelists.htm

Images of Nevada’s wildlife can be accessed at
http://heritage.nv.gov/images.htm#vascplants

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