Green plants get nourishment through a chemical process called photosynthesis, Which uses sunlight, carbon dioxide, and water to make simple sugars. Those simple sugars are then changed into starches, proteins, or fats, which give a plant all the energy it needs to perform life processes and to grow. Generally, sunlight (along with carbon dioxide) enters through the surface of a plant’s leaves. The sunlight and carbon dioxide travel to special food-making cells (palisade) deeper in the leaves. Each of these cells contain a green substance called chlorophyll.
Chlorophyll gives plants their green color and traps light energy, allowing food making to take place. Also located in the middle layer of leaves are special cells that make up a plant’s “transportation” systems. Tubelike bundles of cells called xylem tissue carry water and minerals throughout a plant, from its roots to its outermost leaves. Phloem cells, on the other hand, transport the plant’s food supply sugar dissolved in water—from its manufacturing site in leaves to all other cells.
In ancient times, just as today in third-world societies, dogs lived miserable lives with little or no human care, which led to the hard-times expressions, “it’s a dog’s life,” “sick as a dog,” and “dog-tired.” As for the proverb “Every dog has his day,” it was first recorded as an epilogue after the famed Greek playwright Euripides was killed by a pack of dogs in 405 BC.
The Australian actor Errol Flynn had an amazing prowess with the ladies, and of course the tabloids built this into a legend. During the Second World War, servicemen coined the phrase “in like Flynn” either to brag about their own conquests or to describe someone they envied. Flynn said he hated the expression, but his own boast that he had spent between twelve and fourteen thousand intimate nights ensured its survival.
The word fortnight is a unit of time that equals fourteen days. It comes from the Old English word feorwertyne niht, meaning “fourteen nights.” The term is used in Great Britain, where salaries and most social security benefits are paid on a fortnightly basis, but in the United States people use the term “two weeks.”
In many languages, there is no single word for a two-week period and the equivalent of “fourteen days” has to be used. In Spanish, Italian, French, and Portuguese, the terms quince días, quindicina, quinzaine, and quinzena—all meaning “fifteen days”—are used.
Guglielmo Marconi, of Bologna, Italy, was the first to prove that radio signals could be sent over long distances. Radio is the radiation and detection of signals spread through space as electromagnetic waves to convey information.
It was first called wireless telegraphy because it duplicated the effect of telegraphy without using wires. On December 21, 1901, Marconi successfully sent Morse code signals from Newfoundland to England.
Tropical coral reefs are ridgelike or moundlike structures composed of corals and other aquatic organisms. They border the shorelines of more than 100 countries. Although coral reefs comprise less than 0.5 percent of the ocean floor, it is estimated that more than 90 percent of marine species are directly or indirectly dependent on them—they are home to approximately 4,000 species of fish alone.
Reefs protect human populations along coastlines from wave and storm damage by serving as buffers between oceans and near-shore communities. The Great Barrier Reef, located in northeast Australia’s Coral Sea, measures 1,616 miles (2,000 kilometers) in length. It the largest living structure on Earth, and can be seen from the Moon.
High-definition television (HDTV) is a digital television broadcasting system with higher resolution than traditional television systems. The amount of detail shown in a television picture is limited by the number of lines that make it up and by the number of picture elements on each line.
The latter is mostly determined by the width of the electron beam. To obtain pictures closer to the quality of 35-millimeter photography, HDTV has more than twice the number of scan lines with a much smaller picture element. American and Japanese HDTVs have 525 scanning lines, and Europe has 625 scanning lines.
Once mail travels close to its destination, it is unloaded at another postal sorting office. A bar code–reading machine scans the letters again, separating them further for delivery to districts, neighborhoods, and streets.
The letters are sent to local post offices, where carriers are given the mail for their delivery areas. Routes may include homes, shops, and office buildings. Carriers who work in farm country, where people live very far apart, may have to travel many miles to deliver the mail each day.
Firstly, because is made of tungsten which has a very high melting point (34100C) whereas the temperature of the filament required to glow is only 2700oC. Secondly, oxygen is absent since the bulb is filled with an inert gas which does not help in burning.
Yes and no. Bones are hard connective tissue, made up of bone cells, fat cells, and blood vessels, as well as nonliving materials, including water and minerals. Some bones have a very hard, heavy outer layer made out of compact bone. Under this layer is a lighter layer called spongy bone, which is located inside the end, or head, of a long bone.
Spongy bone is tough and hard, but light, because it has lots of irregularly-shaped sheets and spikes of bone (called trabeculae) that make it porous (full of tiny holes). The soft, jelly-like inner core of bone is called the bone marrow. It is where red blood cells, certain white blood cells, and blood platelets are formed. The jawbone is the hardest bone in your body. Although bones are hard, they are not the hardest substance in the human body: the enamel on your teeth is harder.