During the Pleistocene many barriers to fish dispersal and recolonization already existed in the western United States. The Rocky Mountain Range was formed before the Miocene and the Sierras elevated in the Pliocene, both formidable North-South barriers (Smith 1981). Along with these significant geographic barriers, the western U.S. has historically had much smaller and more climatically unpredictable basins compared to the east. These basins held lower populations of fish which increased the probabilities of extinction and the lack of stability often interrupted speciation (Smith 1981). Despite these factors, there is still some diversity that arose out of these basins largely due to the lacustrine environment that was in place during …show more content…
2; Echelle 2008). The three species diverged from one another in the last one million years, with C. diabolis falling out most recently some 0.5 MYA. The speciation is believed to be allopatric, but there is still some uncertainty regarding C. diabolis (Duvernell & Turner 1998). The reason for this uncertainty is that the cavern that C. diabolis currently inhabits, Devil’s Hole, only opened to the surface around 60,000 years ago (Martin et al. 2016). It is possible that there was some degree of sympatric speciation happening before a colonization event occurred or, because mtDNA was used to determine divergence times, C. nevadensis could have been polymorphic for mtDNA before the cavern opened and was subsequently colonized (Echelle 2008). So how did the allopatric speciation of the Death Valley pupfish occur? Was it the result of dispersal or vicariance? When we examine figure 2 closely, we see that although the Pleistocene lakes in the Death Valley region were extensive, they still might not have connected all of the waterways. In addition, this map shows a summary of the lakes, that is to say that all of them did not exist at the same time (Knott et al. 2008). Limited connectivity of waterways as well as the late colonization and subsequent speciation of C. diabolis are potentially evidence against the hypothesis for speciation through vicariance. On the other hand, pupfish are notoriously very poor dispersers.
My hike was carried out in the form of a mountain bike ride with our school’s racing team. It took place northeast of the Utah State Capitol Building along the Bonneville Shoreline Trail. This path, however, begins near the University of Utah and ends just shy of the Idaho border. As the name suggests, this footpath was created by Lake Bonneville, a saltwater lake that was at it’s peak 8,500 years ago. The massive lake was nearly completely drained by an enormous natural dam buckling under the immense pressure, causing an enormous flood(O’Connor, 2011). Today, all that remains is the Great Salt Lake. A water mass that is now almost 12 times smaller that Lake Bonneville. The lake has many tributaries flowing into it, resulting in a small incline of salt as time passes. Brine shrimp are barely able to process the high levels of salt in the water making
The skeletal characteristics of these hominines suggest that their mode of locomotion was likely a cross between occasional bipedalism and obligate bipedalism. From the reading we have learned that obligate bipedalism is bipedal locomotion that is practiced all of the time while occasional bipedalism is bipedalism that is practiced on occasion. The ratio of arm length to leg length (longer arms) suggests that they did spend time climbing trees, however the cranial and post cranial traits of these fossils suggest that they spent much of their time on the ground and likely ambulating bipedally combined with a variation of upright walking and knuckle walking. This is evidenced by two factors: the fact the foramen magnum of the skull is centrally located, and the ratio of arm to leg length. In creatures with bipedal ambulation, the foramen magnum is located in the center of the base of the skull to keep the head aligned over the center of gravity of the creature. If the fossils were walking primarily with their knuckles, the
Introduction: The Bull trout (Salvelinus confluentus) in the family Salmonidae and are a char native to Washington, Oregon, Idaho, Nevada, Montana and western Canada. Compared to other salmonids, bull trout have more specific habitat requirements that appear to influence their distribution and abundance (USFWS, 2015). Bull trout were historically regarded as pests due to their voracious predatory behavior. It was thought that bull trout depleted populations of “more desirable” game fish by feeding on them when they were very small thus supposedly depleting the numbers. In fact at one point there was a bounty placed on bull trout tails in Canada to encourage fisherman to rid the waters of this “Bully,” which effectively eliminated them from certain watersheds (Donald, D. B., and D. J. Alger. 1993). At one time in the early 1900’s the Bull Trout thrived in the waterways of the Northwest. The Upper Snake Recovery Unit for the Bull trout occurs within central Idaho, northern Nevada, and eastern Oregon. Major drainages include: the Salmon River, Malheur River,
“The main lesson of biogeography is that only evolution can explain the diversity of life on continents and islands.” (Coyne 109).In convergent evolution 3 of the six components discussed in chapter 1 are working together. These 3 components are common ancestry, speciation, and natural selection. If evolution did exist, ancestors of species today that lived in the same place, when dug up, should be fossils that resemble organisms today.
These drainage basins that formed 6,000 years ago are the origin of the Great Lakes we are familiar with today. These glacial lakes are thought to much larger than the current bodies of water surrounding Michigan. The evidence of these lakes can be found, for example, around Saginaw bay where there are eroded bluffs and plains located far away from the current Lake.
Prior to the last ice age, the entire region of the Great Plains is believed to have been an inland sea known as the Western Interior Seaway. As this seaway receded, large animals including mammoths and saber toothed tigers lived in the area. The majority of these animals became extinct to the region around 13,000 years ago during one of the ice ages.
The question of what caused the extinction of megafauna during the Late Pleistocene period is one that archaeologists have struggled to answer for decades, but why should it matter? Discovering with certainty the cause of megafaunal extinction would
The geologic timeline and events that occurred in the Northeast would have had a major impact in the creation and movement of wildlife, topography, and biodiversity throughout the region. When looking at the Northeast through the lens of a bioregional food shed the largest impact on the biological makeup of the Northeast would have occurred between the early 1700’s through modern day. In that span of time, “…the Northeast would show forests which had occupied 90% of the landscape in 1700 occupied less than 30% in 1900.” Forest ecology is arguably one of the important factors when looking at the long-term history and evolution of one’s bioregion. When European settlers made their most significant landfall with the intent on permanent colonization in the Northeastern territory of the United States they would have been stepping on to ground that was rich in biodiversity. The Northeast was a region plentiful with “great forests of American beeches, maples, birches, eastern hemlocks, and spruces from New England to northern Pennsylvania, and oaks, hickories, American chestnuts, and pines from Maryland through Ohio.” In terms of wildlife and game that would have provided food for the European settlement they would have had access to the harvest of “white-tailed deer, beaver, wild turkey, passenger
The author and his colleagues chose to focus on 375 million year old rocks in their search for fossils because amphibians that look dissimilar to fish were discovered in 365 million year old rocks, while fish without amphibian characteristics were discovered in 385 million year old rocks. Thus, it is possible that the evolutionary intermediary, or the “missing link” between fish and amphibians, would be discovered in 375 million year old rocks, between the two time periods. The rocks examined were sedimentary in composition, as the gradual and relatively gentle formation of sedimentary rock under conditions of mild pressure and low heat are conducive to the fossilization of animal remains. Sedimentary rock is also often formed in rivers and seas, where animals are likely to live. This site provides a resource that describes means by which fossils are formed and how the fossil record may be interpreted, and shows some examples of fossils demonstrating evolution through geological periods: http://www.fossilmuseum.net/fossilrecord.htm. In 2004, Shubin and his colleagues were looking for fossils on Ellesmere Island, in northern Canada. This location was chosen because of its lack of human development, as well as of obstructing natural formations and life forms such as trees, which
Even though Paleo is a very easy diet to keep by, the food prepared by its practitioners on a regular basis runs the risk of becoming boring and repetitive. With seemingly so few ingredients to put on the table, dieters can often benefit from a couple of easy tips to mix up their food and add something new to their daily meals.
Part A: Outline the purpose and methods of British propaganda using Source A and your own knowledge. (4 marks) British propaganda aimed to promote patriotic support for the war and justify Britain’s position in the war. Source A is a poster directed towards all classes of the British population. It aimed to create sympathy for Belgium and incite hatred for the enemy, Germany, in order to rally support for the war effort in Britain with the outbreak of war in August 1914. Such propaganda was universally accessible to stir widespread enthusiasm for Britain’s role in the war as Belgium’s ‘savior’ following their invasion by Germany, who violated Belgium’s neutrality according to the 1839 Treaty of London.
Throughout history, many changes occurred regarding the way humans got their food. These changes are usually caused by environmental changes and having to adapt to them. Adapting to new environments can cause long-term political, social, and economic effects on societies and regions. A lot of the changes regarding food production mainly happened during the Neolithic Revolution. Before the Neolithic Revolution, humans had to depend more on animals than plants as a food source.
Despite all of the progress that has made towards equal opportunity, discrimination is still a major problem in the United States of America. A relatively new phenomenon, titled genetic discrimination, occurs when individuals are discriminated against on account of their genetic information. On May 21st, 2008, the GINA Act was passed, making it illegal to refuse to provide employment or health insurance to individuals based on their genetic information in all U.S. states and territories. Title I prevents genetic discrimination in health coverage, while Title II prevents genetic discrimination in employment. Title I took effect on May 21st, 2009, and Title II took effect eighteen months later on November 21st, 2009. With the GINA Act, it is
1600-1849: Era of Abundance Americas being settles and Jamestown first settlement in history and abundance of wildlife (Shaw, 316)
The oldest rocks found in the Death Valley region were formed in the Precambrian time period no more than 1.8 billion years ago during the latter half of the Proterozoic Eon. The rocks are seen on the steep face of the Black Mountains above the current area of Badwater and were formed via deposits of mud and sand from an ancient volcanic mountain belt. Sometime between 1.8 and 1.7 billion years ago, the volcanic and sedimentary rocks were severely altered when chemical or structural changes occurred because of intense heat or pressure from the Earth's core. Because of this process, any fossilized information about the region was lost making it impossible to truly understand the origin of the region. There is some debate on whether basalt or schist was the original and dominate rock in the region before it was transformed into contorted gneiss, but again, there is no way to prove either theory.