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Packera Franciscana
''Packera franciscana'' (syn. ''Senecio franciscanus'') is a rare species of flowering plant in the aster family known by the common name San Francisco Peaks groundsel, or San Francisco Peaks ragwort. It is endemic to Arizona in the United States, where it is known only from the San Francisco Peaks in Coconino County. It is threatened by recreational activities in its habitat. It is a federally listed threatened species of the United States. Description ''Packera franciscana'' is a small rhizomatous perennial herb growing just a few centimeters tall. The purple or purple-tinged stems have woolly or cobwebby fibers. The basal leaves have lyre-shaped to somewhat oval blades measuring up to 2 centimeters long by 5 wide. They have ruffled edges and purple undersides.''Packera franciscana''. Center f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Edward Lee Greene
Edward Lee Greene (August 20, 1843–November 10, 1915) was an American botanist known for his numerous publications including the two-part ''Landmarks of Botanical History'' and the describing of over 4,400 species of plants in the American West. Early life Edward Lee Greene was born on August 20, 1843 in Hopkinton, Rhode Island. In 1859 Greene moved to Wisconsin and began studying at Albion Academy, a very reputable institution with a religious emphasis. There Greene met Thure Kumlien, a Swedish Naturalist with an interest in botany. Greene accompanied Kumlein on field trips, further developing Greene's interest in botany. In August 1862, Greene joined his father and brothers in joining the 13th Wisconsin Volunteer Infantry Regiment of the Union Army. Though he never rose above the rank of private in his three years of service, Greene was able to advance his botanical studies, collecting specimens as he marched through Tennessee, Kentucky and Alabama. Following his release ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sexual Reproduction
Sexual reproduction is a type of reproduction that involves a complex life cycle in which a gamete ( haploid reproductive cells, such as a sperm or egg cell) with a single set of chromosomes combines with another gamete to produce a zygote that develops into an organism composed of cells with two sets of chromosomes ( diploid). This is typical in animals, though the number of chromosome sets and how that number changes in sexual reproduction varies, especially among plants, fungi, and other eukaryotes. Sexual reproduction is the most common life cycle in multicellular eukaryotes, such as animals, fungi and plants. Sexual reproduction also occurs in some unicellular eukaryotes. Sexual reproduction does not occur in prokaryotes, unicellular organisms without cell nuclei, such bacteria and archaea. However, some process in bacteria may be considered analogous to sexual reproduction in that they incorporate new genetic information, including bacterial conjugation, transformatio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cloning
Cloning is the process of producing individual organisms with identical or virtually identical DNA, either by natural or artificial means. In nature, some organisms produce clones through asexual reproduction. In the field of biotechnology, cloning is the process of creating cloned organisms (copies) of Cell (biology), cells and of DNA fragments (molecular cloning). Etymology Coined by Herbert J. Webber, the term clone derives from the Ancient Greek word (), ''twig'', which is the process whereby a new plant is created from a twig. In botany, the term ''lusus'' was used. In horticulture, the spelling ''clon'' was used until the early twentieth century; the final ''e'' came into use to indicate the vowel is a "long o" instead of a "short o". Since the term entered the popular lexicon in a more general context, the spelling ''clone'' has been used exclusively. Natural cloning Cloning is a natural form of reproduction that has allowed life forms to spread for hundreds of millio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adventitiousness
Important structures in plant development are buds, shoots, roots, leaves, and flowers; plants produce these tissues and structures throughout their life from meristems located at the tips of organs, or between mature tissues. Thus, a living plant always has embryonic tissues. By contrast, an animal embryo will very early produce all of the body parts that it will ever have in its life. When the animal is born (or hatches from its egg), it has all its body parts and from that point will only grow larger and more mature. However, both plants and animals pass through a phylotypic stage that evolved independently and that causes a developmental constraint limiting morphological diversification. According to plant physiologist A. Carl Leopold, the properties of organization seen in a plant are emergent properties which are more than the sum of the individual parts. "The assembly of these tissues and functions into an integrated multicellular organism yields not only the characteristi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fellfield
A fellfield or fell field comprises the environment of a slope, usually alpine or tundra, where the dynamics of frost (freeze and thaw cycles) and of wind give rise to characteristic plant forms in scree interstices. Soil dynamics The freeze-thaw cycles tend to push plants out of the soil. In addition, the high porosity of the soil makes a fellfield a difficult place for plants to grow. Fellfields often have typical patterns of rocks: lines of rocks that have been pushed out of the soil, and slid into a low region. Botany In botany the term "fellfield" describes an ecoregion, ecosystem, habitat, or plant community. The term frequently used is alpine fellfield. Fellfield is usually applied to an alpine tundra region of high altitude mountains, or high latitude islands, and the alpine plants there. Flora Fellfields are typically populated by cushion plants: perennials that grow close to the ground. Cushion plants are well-adapted to the dryness and short growing season of a fellfie ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Elevation
The elevation of a geographic location is its height above or below a fixed reference point, most commonly a reference geoid, a mathematical model of the Earth's sea level as an equipotential gravitational surface (see Geodetic datum § Vertical datum). The term ''elevation'' is mainly used when referring to points on the Earth's surface, while ''altitude'' or ''geopotential height'' is used for points above the surface, such as an aircraft in flight or a spacecraft in orbit, and '' depth'' is used for points below the surface. Elevation is not to be confused with the distance from the center of the Earth. Due to the equatorial bulge, the summits of Mount Everest and Chimborazo have, respectively, the largest elevation and the largest geocentric distance. Aviation In aviation the term elevation or aerodrome elevation is defined by the ICAO as the highest point of the landing area. It is often measured in feet and can be found in approach charts of the aerodrome. It is n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tree Line
The tree line is the edge of the habitat at which trees are capable of growing. It is found at high elevations and high latitudes. Beyond the tree line, trees cannot tolerate the environmental conditions (usually cold temperatures, extreme snowpack, or associated lack of available moisture). The tree line is sometimes distinguished from a lower timberline, which is the line below which trees form a forest with a closed Canopy (biology), canopy. At the tree line, tree growth is often sparse, stunted, and deformed by wind and cold. This is sometimes known as ''krummholz'' (German for "crooked wood"). The tree line often appears well-defined, but it can be a more gradual transition. Trees grow shorter and often at lower densities as they approach the tree line, above which they are unable to grow at all. Given a certain latitude, the tree line is approximately 300 to 1000 meters below the permanent snow line and roughly parallel to it. Causes Due to their vertical structure, tree ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scree
Scree is a collection of broken rock fragments at the base of a cliff or other steep rocky mass that has accumulated through periodic rockfall. Landforms associated with these materials are often called talus deposits. Talus deposits typically have a concave upwards form, where the maximum inclination corresponds to the angle of repose of the mean debris particle size. The exact definition of scree in the primary literature is somewhat relaxed, and it often overlaps with both ''talus'' and ''colluvium''. The term ''scree'' comes from the Old Norse term for landslide, ''skriða'', while the term ''talus'' is a French word meaning a slope or embankment. In high-altitude arctic and subarctic regions, scree slopes and talus deposits are typically adjacent to hills and river valleys. These steep slopes usually originate from late-Pleistocene periglacial processes. Notable scree sites in Eastern North America include the Ice Caves at White Rocks National Recreation Area in southern Ve ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Volcano
A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates are diverging or converging, and most are found underwater. For example, a mid-ocean ridge, such as the Mid-Atlantic Ridge, has volcanoes caused by divergent tectonic plates whereas the Pacific Ring of Fire has volcanoes caused by convergent tectonic plates. Volcanoes can also form where there is stretching and thinning of the crust's plates, such as in the East African Rift and the Wells Gray-Clearwater volcanic field and Rio Grande rift in North America. Volcanism away from plate boundaries has been postulated to arise from upwelling diapirs from the core–mantle boundary, deep in the Earth. This results in hotspot volcanism, of which the Hawaiian hotspot is an example. Volcanoes are usually not created where two tectonic plates slide ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alpine Tundra
Alpine tundra is a type of natural region or biome that does not contain trees because it is at high elevation, with an associated alpine climate, harsh climate. As the latitude of a location approaches the poles, the threshold elevation for alpine tundra gets lower until it reaches sea level, and alpine tundra merges with tundra#Arctic tundra, polar tundra. The high elevation causes an adverse climate, which is too cold and windy to support tree growth. Alpine tundra ecotone, transitions to sub-alpine forests below the tree line; stunted forests occurring at the forest-tundra ecotone are known as ''Krummholz''. With increasing elevation it ends at the snow line where snow and ice persist through summer. Alpine tundra occurs in mountains worldwide. The flora of the alpine tundra is characterized by dwarf shrubs close to the ground. The cold climate of the alpine tundra is caused by adiabatic cooling of air, and is similar to polar climate. Geography Alpine tundra occurs at hi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Summit (topography)
A summit is a point on a surface that is higher in elevation than all points immediately adjacent to it. The topographic terms acme, apex, peak (mountain peak), and zenith are synonymous. The term (mountain top) is generally used only for a mountain peak that is located at some distance from the nearest point of higher elevation. For example, a big, massive rock next to the main summit of a mountain is not considered a summit. Summits near a higher peak, with some prominence or isolation, but not reaching a certain cutoff value for the quantities, are often considered ''subsummits'' (or ''subpeaks'') of the higher peak, and are considered part of the same mountain. A pyramidal peak is an exaggerated form produced by ice erosion of a mountain top. Summit may also refer to the highest point along a line, trail, or route. The highest summit in the world is Mount Everest with a height of above sea level. The first official ascent was made by Tenzing Norgay and Sir Edmund Hillary ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mountain Pass
A mountain pass is a navigable route through a mountain range or over a ridge. Since many of the world's mountain ranges have presented formidable barriers to travel, passes have played a key role in trade, war, and both Human migration, human and animal migration throughout history. At lower elevations it may be called a hill pass. A mountain pass is typically formed between two volcanic peaks or created by erosion from water or wind. Overview Mountain passes make use of a gap (landform), gap, saddle (landform), saddle, col or notch (landform), notch. A topographic saddle is analogous to the mathematical concept of a saddle surface, with a saddle point marking the highest point between two valleys and the lowest point along a ridge. On a topographic map, passes are characterized by contour lines with an hourglass shape, which indicates a low spot between two higher points. In the high mountains, a difference of between the summit and the mountain is defined as a mountain pas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
