Solution for: CBT AC Reading Test 4: American Black Bear

American Black Bear

{A} Not all black bears are black - their fur can range in color from pure white to a cinnamon color to very dark brown or black. Most populations have a mixture of these colors, including the pure white form which is found in some individuals in the island archipelago in southern British Columbia (Kermodi Island). This white-black bear, which is called spirit bears, revered by Native Americans, is caused by inheriting a recessive gene for coat color from both the mother and the father who could, themselves, both be black. A genetic reason results in the light grey coat color called the "blue" or glacier bear in southeastern Alaska. Regardless of these genetic variants, most of the bears in any region are black in color. Some bears have a white patch on their chests. They have a short, inconspicuous tail, longish ears, a relatively straight profile from nose to forehead, and small, dark eyes.

{B} Black bears have relatively short claws which enable them to climb trees. Unlike cats, the claws are non-retractable. Other than color, how do black bears differ from grizzly bears? Black bears have longer and less rounded ears and a more straight profile from forehead to nose compared to grizzly bears. Grizzlies have larger shoulder humps and a more dished-in facial profile and much longer front claws that are evident in the tracks. Black bears and grizzly bears can both have a wide variety of colors and sizes, but most commonly in areas where both species occur, black bears are smaller and darker than grizzly bears. Size: Black bears in some areas where food is scarce are much smaller than in other areas where food is abundant. Typically, adults are approximately 3 feet tall at the shoulder, and their length from nose to tail is about 75 inches. All bears, including black bears, are sexually dimorphic -- meaning adult males are much larger than adult females. A large male black bear can exceed 600 lbs in weight while females seldom exceed 200 lbs.

{C} American black bears are omnivorous, meaning they will eat a variety of things, including both plants and meat. Their diet includes roots, berries, meat, fish, insects, larvae, grass and other succulent plants. They are able to kill adult deer and other hoofed wildlife but most commonly are only able to kill deer, elk, moose and other hoofed animals when these are very young. They are able to kill livestock, especially sheep. Bears are very attracted to human garbage, livestock food or pet food, or other human-associated foods including fruit trees. Bears using these human-associated foods can quickly become habituated to them and this commonly results in the bears being killed as nuisances. This is true for bee hives as well as bears are very attracted to honey.

{D} Black bears can live up to 30 years in the wild but most die before they are in their early 20s. Because of their versatile diet, black bears can live in a variety of habitat types. They inhabit both coniferous and deciduous forests as well as open alpine habitats. They typically do not occur on the Great Plains or other wide-open areas except along river courses where there is riparian vegetation and trees. They can live just about anywhere they can find food, but largely occur where there are trees. The American black bear's range covers most of the North American continent. They are found in Alaska, much of Canada and the United States, and extend as far south as northern Mexico.

{E} Black bears are typically solitary creatures except for family (a female with cubs) groups and during mating season, which peaks in May and June. Following fertilization, the embryo doesn't implant in the uterus until fall at the time of den entrance. This process of delayed implantation occurs in all bear species and allows the female bear's body to physiologically "assess" her condition before implantation occurs and the period of gestation leading to the birth of cubs really begins. Delayed implantation allows the female to not waste fat reserves and energy in sustaining a pregnancy that would have little chance of success because her condition is too poor. Females give birth to cubs every other year if food sources are sufficiently plentiful. In years when food supplies are scarce a female may skip an additional year or two between litters. The cubs are born in the mother's winter den, and will den with her again the following winter. The following spring when the cubs are 1.5 years old, the cubs and female will separate and the female will breed again. A black bear litter can be 1-5 cubs but most commonly litters are 2 cubs.

{F} Conservation efforts for black bears have been effective and in most areas, black bears are increasing and can sustain managed sport hunting. In areas with human populations, this can cause conflicts because bears are very attracted to human foods and refuse as well as to livestock and livestock foods. Since bears are large and strong animals, many people fear them and resent the damage they can cause. The key to successful coexistence between humans and bears is to recognize that it is no longer possible for either species to occupy all habitats but that where co-occupancy is possible and desirable, humans must be responsible for the welfare of the bear population. Wild areas with little human footprint will remain the most important habitat for bears but peaceful co-existence can occur in the urban-wildland interface as long as humans take the necessary steps to assure that the relationship remains a positive one.

{G} The American black bear is not currently a species of conservation concern and even the formerly listed black bear of Florida and Louisiana is now increasing. Habitats in western Texas from which black bears were extirpated are now being re-colonized.

Brunel: 'The Practical Prophet

{A} In the frontispiece of his book on Brunel, Peter Hay quotes from Nicholson's British Encyclopaedia of 1909 as follows: 'Engineers are extremely necessary for these purposes; wherefore it is requisite that, besides being ingenious, they should be brave in proportion.' His father, Sir Marc Isambard Brunel (1769-1849), was himself a famous engineer, of French parents. He eventually settled in Britain and married the Sophia Kingdom, an English woman whom he had known in France in earlier days. Their only son Isambard was born on 9 April 1806. He was sent to France at the age of 14 to study mathematics and science and was only 16 when he returned to England to work with his father. Sir Marc was then building his famous tunnel under the River Thames. Isambard was recuperating near Bristol from injuries received in a tunnel cave-in when he became involved with his own first major project.

-- The Suspension Bridge on the Avon Gorge

{B} The span of Brunel's bridge was over 700ft, longer than any existing when it was designed, and the height above water about 245ft. The technical challenges of this engineering project were immense, and Brunel dealt with them with his usual thoroughness and ingenuity. But it is also interesting to look at how Brunel handled the other side of the engineering business: selling his ideas. Two design competitions were held, and the great bridge designer Thomas Telford was the committee's expert. Brunel presented four designs. He went beyond technicalities to include arguments based on, among other things, the grace of his tower design. Unfortunately, he only got so far as to put up the end piers in his lifetime. The Clifton Suspension Bridge was completed in his honour by his engineering friends in 1864 and is still in use. 

The Great Western Railway 

C While Brunel was still in Bristol, and with the Avon Bridge project stopped or going slowly, he became aware that the civic authorities saw the need for a railway link to London. Railway location was controversial since private landowners and towns had to be dealt with. Mainly, the landed gentry did not want a messy, noisy railway anywhere near them. The Duke of Wellington (of Waterloo fame) was certainly against it. Again Brunel showed great skill in presenting his arguments to the various committees and individuals. Brunel built his railway with a broad gauge (7ft) instead of the standard 4ft 8 in, which had been used for lines already installed. There is no doubt that the broad gauge gave superior ride and stability, but it was fighting a standard. In this, he was also up against his professional rival (but a personal friend) Robert Stephenson and Robert's father, George Stephenson. After much argument, the government settled the matter in 1846 by requiring any new lines to be standard gauge.

Atmospheric railway: 

{D} Brunel's ready acceptance of new ideas overpowered good engineering judgment (at least in hindsight) when he advocated the installation of an 'atmospheric railway in South Devon. It had the great attraction of doing away with the locomotive and potentially could deal with steeper gradients. The system consisted of a 15in-diameter pipe, laid between the rail lines, with a slit cut along the top. A piston fitted into the pipe and was connected to the driving railcar above by an arm. The pipe ahead of the piston was then evacuated of air by pumps stationed about two miles apart along the line. The atmospheric pressure then drove the train. Since this connecting arm had to run along the slit, it had to be opened through a flap as the train progressed, but closed airtight behind it. Materials were not up to it, and this arrangement was troublesome and expensive to keep in repair. After a year of frustration, the system was abandoned. Brunel admitted his failure and took responsibility. He also took no fee for his work, setting a good professional example,

Brunel's ships: 

{E} The idea of using steam to power ships to cross the ocean appealed to Brunel. When his GWR company directors complained about the great length of their railway (it was only about 100 miles) Isambard jokingly suggested that they could even make it longer - why not go all the way to New York, and call the link the Great Western. The "Great Western" was the first steamship to engage in transatlantic service, Brunel formed the Great Western Steamship Company, and construction started on the ship in Bristol in 1836. Built of wood and 236ft long, the Great Western was launched in 1837, and powered by sail and paddlewheels. The first trip to New York took just 15 days, and 14 days to return. This was a great success; a one way trip under sail would take more than a month. The Great Western was the first steamship to engage in transatlantic service and made 74 crossings to New York.

(F) Having done so well with the Great Western, Brunel immediately got to work on an even bigger ship. Great Britain was made of iron and also built-in Bristol, 322ft in length. The initial design was for the ship to be driven by paddle wheels, but Brunel had seen one of the first propeller-driven ships to arrive in Britain, and he abandoned his plans for paddlewheel propulsion. The ship was launched in 1843 and was the first screw-driven iron ship to cross the Atlantic. Great Britain ran aground early in its career but was repaired, sold, and sailed for years to Australia, and other parts of the world, setting the standard for ocean travel. In the early 1970s, the old ship was rescued from the Falklands and is now under restoration in Bristol.

{G} Conventional wisdom in Brunel's day was that steamships could not carry enough coal to make long ocean voyages. But he correctly figured out that this was a case where size mattered. He set out to design the biggest ship ever, five times larger than any ship built up to that time. Big enough to carry fuel to get to Australia without refuelling, in addition, it would carry 4,000 passengers. The Great Eastern was 692ft long, with a displacement of about 32,000 tons. Construction began in 1854 on the Thames at Millwall. Brunel had chosen John Scott Russell to build the ship. He was a well-established engineer and naval architect, but the contract did not go well. Among other things, Scott Russell was very low in his estimates and money was soon a problem. Construction came to a standstill in 1856 and Brunel himself had to take over the work. But Brunel was nothing if not determined, and by September 1859, after a delayed and problem-ridden launch, the Great Eastern was ready for the maiden voyage. Brunel was too sick to go, but it was just as well, because only a few hours out there was an explosion in the engine room which would have destroyed a lesser ship. Brunel died within a week or so of the accident. The great ship never carried 4,000 passengers (among other things, the Suez Canal came along) and although it made several transatlantic crossings, it was not a financial success. Shortly after the Great Eastern began working life, the American entrepreneur Cyrus Field and his backers were looking for a ship big enough to carry 5,000 tons of telegraphic cable, which was to be laid on the ocean floor from Ireland to Newfoundland. Although Brunel did not have it in mind, the Great Eastern was an excellent vessel for this work. On July 27, 1866, it successfully completed the connection and a hundred years of transatlantic communication by cable began. The ship continued this career for several years, used for laying cables in many parts of the world.

Human Remain In GREEN SAHARA

{A} On October 13,2,000, a small team of paleontologists led by Paul Sereno of the University of Chicago clambered out of three battered Land Rovers, filled their water bottles, and scattered on foot across the toffee-colored sands of the Tenere desert in northern Niger. The Tenere , on the southern flank of the Sahara, easily ranks among the most desolate landscapes on Earth. The Tuareg , turbaned nomads who for centuries have ruled this barren realm, refer to it as a "desert within a desert"-a California-size ocean of sand and rock, where a single massive dune might stretch a hundred miles, and the combination of 120-degree heat and inexorable winds can wick the water from a human body in less than a day. The harsh conditions, combined with intermittent conflict between the Tuareg and the Niger government, have kept the region largely unexplored. 

{B} Mike Hettwer, a photographer accompanying the team, headed off by himself toward a trio of small dunes. He crested the first slope and stared in amazement. The dunes were spilling over with bones. He took a few shots with his digital camera and hurried back to the Land Rovers. "I found some bones:' Hettwer said, when the team had regrouped. "But they're not dinosaurs. They're human." 

{C} In the spring of 2005 Sereno contacted Elena Garcea, an archaeologist at the University of Cassino, in Italy, inviting her to accompany him on a return to the site. Garcea had spent three decades working digs along the Nile in Sudan and in the mountains of the Libyan Desert, and was well acquainted with the ancient peoples of the Sahara. But she had never heard of Paul Sereno. His claim to have found so many skeletons in one place seemed far fetched, given that no other Neolithic cemetery contained more than a dozen or so. Some archaeologists would later be skeptical; one sniped that he was just a "moonlighting paleontologist." But Garcea was too intrigued to dismiss him as an interloper. She agreed to join him.

{D} Garcea explained that the Kiffian were a fishing-based culture and lived during the earliest wet period, between 8,000 and 10,000 years ago. She held a Kiffian sherd next to a Tenerian one. "What is so amazing is that the people who made these two pots lived more than a thousand years apart."

{E} Over the next three weeks, Sereno and Garcea-along with five American excavators, five Tuareg guides, and five soldiers from Nigeria's army, sent to protect the camp from bandits—made a detailed map of the site, which they dubbed Gobero, after the Tuareg name for the area. They exhumed eight burials and collected scores of artifacts from both cultures. In a dry lake bed adjacent to the dunes, they found dozens of fishhooks and harpoons carved from animal bone Apparently the Kiffian fishermen weren't just going after small fry: Scattered near the dunes were the remains of Nile perch, a beast of a fish that can weigh nearly 300 pounds, as well as crocodile and hippo bones.

{F} Sereno flew home with the most important skeletons and artifacts and immediately began planning for the next field season. In the meantime, he carefully removed one tooth from each of four skulls and sent them to a lab for radiocarbon dating. The results pegged the age of the tightly bundled burials at roughly 9,000 years old, the heart of the Kiffian era. The smaller "sleeping" skeletons turned out to be about 6,000 years old, well within the Tenerian period. At least now the scientists knew who was who.

{G} In the fall of 2006 they returned to Gobero, accompanied by a larger dig crew and six additional scientists. Garcea hoped to excavate some 80 burials, and the team began digging. As the skeletons began to emerge from the dunes, each presented a fresh riddle, especially the Tenerian. A male skeleton had been buried with a finger in his mouth.

{H} Even at the site, Arizona State University bio archaeologist Chris Stojanowski could begin to piece together some clues. Judging by the bones, the Kiffian appeared to be a peaceful, hard working people. “The lack of head and forearm injuries suggests they weren't doing much fighting," he told me. "And these guys were strong." He pointed to a long, narrow ridge running along a femur. "That's the muscle attachment," he said. "This individual had huge leg muscles, which means he was eating a lot of protein and had a strenuous lifestyle — both consistent with a fishing way of life.” For contrast, he showed me the femur of a Tenerian male. The ridge was barely perceptible. "This guy had a much less strenuous lifestyle," he said, "which you might expect of a herder."

{I} Stojanowski's assessment that the Tenerian were herders fits the prevailing view among scholars of life in the Sahara 6,000 years ago, when drier conditions favored herding over hunting. But if the Tenerian were herders, Sereno pointed out, where were the herds? Among the hundreds of animal bones that had turned up at the site, none belonged to goats or sheep, and only three came from a cow species. "It's not unusual for a herding culture not to slaughter their cattle, particularly in a cemetery, M Garcea responded, noting that even modern pastoralists, such as Niger's Wodaabe, are loath to butcher even one animal in their herd. Perhaps, Sereno reasoned, the Tenerian at Gobero were a transitional group that had not fully adopted herding and still relied heavily on hunting and fishing.

{J} Back in Arizona, Stojanowski continues to analyze the Gobero bones for clues to the Green Saharans' health and diet. Other scientists are trying to derive DNA from the teeth, which could reveal the genetic origins of the Kiffian and Tenerian- and possibly link them to descendants living today. Sereno and Garcea estimate a hundred burials remain to be excavated. But as the harsh Tenere winds continue to erode the dunes, time is running out. "Every archaeological site has a life cycle," Garcea said. "It begins when people begin to use the place, followed by disuse, then nature takes over, and finally it is gone. Gobero is at the end of its life.”