... Cramer in 1855 had already suggested that biological cells are separated from their environment by a membrane possessing special characteristics, and in 1900 Overton performed some simple but classical experiments which proposed that cell membranes were composed of lipids (1). By measuring the permeability of various compounds across the membrane of a frog muscle, Overton found some interesting results. He observed that lipophilic molecules (molecules attracted to fat solvents) could easily cross this cell membrane, however larger lipid insoluble molecules could not. He also observed that small polar molecules co ...

... When humans reach their sexual maturity at around the age of 14 or 15, koalas reach their sexual maturity at the age of two. The female produces one baby every other year. The koala almost never produces twins. In the female's pouch, there are two nipples. The female koala gives birth after a 20-35 day gestation period. When the joey (baby koala) is born, it is no longer than 2 cm and weighs no more than a 1/2 gram. The joey stays in its mother's pouch for 5-7 months. The term "joey² is used when you are talking about a baby marsupial. The mother gives "pap² to the joey, a liquid from the caecum (which ...

... do not leap as much. Therefore, their body weight has been reduced, allowing them to be more efficient with they water they can find. They also have wider feet than the kangaroos living in wetter climates. This allows the kangaroo to be able to have more traction in the higher elevations. The kangaroos that live in the coastal regions also have several special adaptations. They have wider feet to allow them to walk is shallow water. They can eat several different types of sea plants. They can do this because they have a higher tolerance to salt than normal kangaroos. Kangaroos that live in forests have ...

... throughout the body. When healthy, the nervous system reacts and responds to nerve impulses that allows us to maintain homeostasis. The nervous system can be broken down further into its three basic functions: sensory functions, integrative functions, and motor functions. In sensory functions, your body’s sensory receptors detect many different stimuli in and outside of your body. For example, your sensory receptors may detect a change in your blood temperature, or a change outside of your body such as a touch on the arm. Your body then goes through a process know as its integrative function. This is when you ...

... substances. In 1969 a Russian chemist, named Mendeleyev who a renowned teacher developed, the periodic law of the properties of the chemical elements (which states that elements show a regular pattern when they are arranged according to their atomic masses). Mendeleyev wrote a two-volume book called Principles of chemistry (1868-1870), which later became a classic. These books included an improved version of the periodic table. Sir Joseph Thomson, another important person in the development of the atomic theory, was born in 1906. Thomson won the Nobel Prize in physics (1906) for his work in the conducti ...

... miles (2284 kilometers) making it the smallest planet, and yet the furthest from the sun.Its mass only point four percent of Earth's, and radius only eighteen percent of Earth's it is quite a small planet.It has a density of one hundred ninety nine percent almost twice water. Plutos environment is one of a cold desolate place.The tempeture ranges from a frigid negative two hundred twenty three to negative two hundred thirty three degrees Celsius which converts to negative three hundred sixty nine and negative three hundred eighty nine degrees farenhiet.Its extremely frigid tempetures are due to its obvious distance ...

... changing world. Firstly, the developmental devices used in the essay are vital to it’s effectiveness. Without them, the author would not have been able to supply sufficient proof to his findings and convince the reader of the true severity of acid rain. Collins used noteworthy facts throughout the essay to prove is point about how severe acid rain truly is. The facts that he used added substance to the essay by validating his point of view. In the same way, the author used effective illustrations and examples to prove his point. These examples and illustrations simplified the readers understanding as to how ...

... are about 15,000 different kinds of distributed worldwide. They are especially suited for growth in harsh regions, where few plants can survive. They grow farther north and south than most plants, as well as higher on mountains. One unusual type grows completely submerged in the cold coastal waters of Antarctica. Some inhabit the Earth's driest deserts, where they grow almost entirely underground and obtain light and moisture through small openings in the ground. Few grow near cities because most cannot survive in industrial air pollution. There are notable exceptions, however: in England, for example, Lecanora c ...

... the abscess is formed. For starters, the collection of pus is the bodies white blood cells forming to protect the liver. However, it collects too much and that is how the abscess is formed. When you are diagnosed with amebic liver you are very likely to also have an intestinal infection from the disease as well. This is not true for all cases though. Most cases in which both occur are in places of high temperatures and poor sanitation. Africa, Latin America, Southeast Asia, and India have many health problems associated with the disease. The most common way to get this disease is from one person to ...

... belt was arbitrarily divided into twelve sections of 30 degrees each. these are the famous signs of the zodiac. The orgins of the names given to each sign extend into the most remote regions of antiquity. Terrestrial animal gods, whether real or imagined , were one day projected onto the constellations which, in the Chaldean imagination, they resembled. This celestial menagerie has furthermore given the zodiac its name, for in greek, it means "route of animals." The sun enters the first zodiacal sign, Aries , and then continues its path through the remaining eleven signs. The twelve signs of the zodiac ar ...