The inhabited history of the Las Vegas Valley stretches to 23,000 b.c. , when much of the area was covered by a prehistoric lake. During this period, the indigenous people lived in caves, hunting the mammals that gathered at the shoreline. The landscape of the valley changed dramatically over the next 200 centuries. The glaciers feeding the lake melted away and the lake evaporated. Fossils tell an obscure story of man's slow and sporadic development. Around 3000 b.c. , native Archaic Indians began to develop a lasting hunting and gathering culture. By this time, the valley was in much the same geographic state as it exists in today, with one exceptionthe presence of artesian springs that bubbled to the surface in several areas. These springs fed a network of streams draining through the Las Vegas Wash to the Colorado River. The areas surrounding the springs were desert oases: sprawling collections of grasses, trees, and wildlife. Many springs lay in areas that would eventually become the center of the modern Las Vegas metropolis. For about 4000 years, the Archaics thrived in a culture that included many signs of early civilization. Signs of even more advancement appeared halfway through the first millennium a.d. , when the Anasazi Indians inhabited the valley. Far more progressive than the Archaics, the Anasazi utilized such formal agricultural techniques as irrigation to assist their harvest. This permitted the Anasazi to achieve a benchmark of advanced societythe ability to live in permanent shelters year-round without need to follow wildlife. Mysteriously, the Anasazi vanished from the valley around a.d.
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QUESTION: How long did the Anasazi inhabit the Las Vegas Valley?

The dermis is the inner layer of skin. The dermis has blood vessels and nerve endings. The nerve endings explain why your skin is sensitive. You can sense pain, pressure, and temperature. You cut your finger and it starts to bleed. What has happened? If your skin bleeds, it means you have cut the dermis layer and damaged blood vessels. The cut really hurts. It hurts because of the nerve endings in this skin layer. The dermis also contains hair follicles and two types of glands. Hair follicles are structures where hairs originate. Each hair grows out of a follicle. Hair passes up through the epidermis. It then extends above the skin surface. Oil glands produce an oily substance. The oil is secreted into hair follicles.
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QUESTION: What is the relationship of hair to the dermis?

His famous series of sixteen great designs for the Apocalypse is dated 1498, as is his engraving of St. Michael Fighting the Dragon. He made the first seven scenes of the Great Passion in the same year, and a little later, a series of eleven on the Holy Family and saints. The Seven Sorrows Polyptych, commissioned by Frederick III of Saxony in 1496, was executed by Durer and his assistants c. Around 1503-1505 he produced the first seventeen of a set illustrating the Life of the Virgin, which he did not finish for some years. Neither these, nor the Great Passion, were published as sets until several years later, but prints were sold individually in considerable numbers. During the same period Durer trained himself in the difficult art of using the burin to make engravings. It is possible he had begun learning this skill during his early training with his father, as it was also an essential skill of the goldsmith. In 1496 he executed the Prodigal Son, which the Italian Renaissance art historian Giorgio Vasari singled out for praise some decades later, noting its Germanic quality. He was soon producing some spectacular and original images, notably Nemesis (1502), The Sea Monster (1498), and Saint Eustace (c. 1501), with a highly detailed landscape background and animals. His landscapes of this period, such as Pond in the Woods and Willow Mill, are quite different from his earlier watercolours. There is a much greater emphasis on capturing atmosphere, rather than depicting topography. He made a number of Madonnas, single religious figures, and small scenes with comic peasant figures. Prints are highly portable and these works made Durer famous throughout the main artistic centres of Europe within a very few years.
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QUESTION: Which of his works place greater emphasis on capturing atmosphere rather than depicting topography?

Sometimes traits can vary from parent to offspring. These changes are due to mutations. Mutations are a random change. Mutations are natural. Some mutations are harmful. In this case, the organism may not live to reproduce. The trait will not be passed onto offspring. Others variations in traits have no effect on survival. Can some mutations be good for a living thing? Other mutations can have great benefits. Imagine being the first moth that can blend into its background. It would have a better chance of survival. A living thing that survives is likely to have offspring. If it does, it may pass the new trait on to its offspring. Thats good news for the offspring. The offspring may be more likely to survive. Mutations are one way living things adapt to new conditions.
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QUESTION:
What would make offspring more likely to survive?