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Tornadoes are large, destructive columns of spinning air that stretch from a thunderstorm to the ground. They can have wind speeds over 300 miles per hour (mph), grow over a mile wide, and travel over 50 miles before dissolving. Tornadoes are incredibly dangerous and should be avoided at all costs. Tornadoes, also known as twisters, need a few ingredients in order to form. They require warm, moist winds in the lower atmosphere; cold, dry winds in the upper atmosphere; and a thunderstorm’s updraft, or an upward current of air. A tornado forms when the warm, moist winds meet the cold, dry winds. This causes the warm and cold air to spin around each other in an invisible horizontal tube. The updraft then tilts the horizontal spinning winds vertical, causing the winds to spin more violently and form a funnel cloud. Once this funnel cloud grows longer and touches the Earth’s surface, it becomes a tornado.

Tropical cyclones start as tropical storms that form in warm ocean waters near the Earth's equator. The Earth's equator is an invisible line that wraps around the center of the Earth. It divides the Earth into two halves: the Northern and Southern hemispheres. The warm air and water at the equator rise into the atmosphere, cool off, and then sink back down. As this cycle repeats itself over and over again, the storm begins to grow and the winds around the storm begin to move faster. Once wind speeds reach 74 miles per hour, the tropical storm becomes a tropical cyclone. Depending on where a tropical cyclone is in the world, it is called either a hurricane, a typhoon, or a cyclone. If a tropical cyclone moves over the northwestern Pacific Ocean, it is called a typhoon; if that storm was to move over the northeastern Pacific or the Atlantic Ocean, it is called a hurricane; and if that storm moves over the South Pacific or the Indian Ocean, it is called a cyclone.

Lizards are part of a group of animals known as reptiles. They are most closely related to snakes. In fact, some lizards, called sheltopusiks, look like snakes because they have no legs! Many lizards today resemble the ancient reptiles of the dinosaur era. Their ancestors appeared on Earth over 200 million years ago. In general, lizards have a small head, short neck, and long body and tail. Unlike snakes, most lizards have moveable eyelids. There are currently over 4,675 lizard species, including iguanas, chameleons, geckos, Gila monsters, monitors, and skinks.

Most lizards have eyelids, just like we do, that clean and protect their eyes when they blink. But some lizards, like geckos, can’t blink! Instead, they have a clear membrane that shields their eyes from dirt or bright sun and use their tongue to clean their eyes. Many lizards, such as iguanas, can see in color. Their colorful body parts allow them to communicate with each other and help them tell which are male and which are female.5Lizards have dry, scaly skin that does not grow with their bodies. Instead, most lizards shed, or molt, their old skin in large flakes to make way for the new skin growth underneath. The exception to this is with the alligator lizard, which may shed its skin in one piece, like a snake. The scales on lizards vary, depending on their habitat. Skinks have smooth scales so mud won’t cling to them; some lizard species have bony plates, called osteoderms, under their scales for added protection against rough terrain.

Industrial Revolution, in modern history, the process of change from an agrarian and handicraft economy to one dominated by industry and machine manufacturing. This process began in Britain in the 18th century and from there spread to other parts of the world. Although used earlier by French writers, the term Industrial Revolution was first popularized by the English economic historian Arnold Toynbee (1852–83) to describe Britain’s economic development from 1760 to 1840. Since Toynbee’s time the term has been more broadly applied.

The main features involved in the Industrial Revolution were technological, socioeconomic, and cultural. The technological changes included the following: (1) the use of new basic materials, chiefly iron and steel, (2) the use of new energy sources, including both fuels and motive power, such as coal, the steam engine, electricity, petroleum, and the internal-combustion engine, (3) the invention of new machines, such as the spinning jenny and the power loom that permitted increased production with a smaller expenditure of human energy, (4) a new organization of work known as the factory system, which entailed increased division of labour and specialization of function, (5) important developments in transportation and communication, including the steam locomotive, steamship, automobile, airplane, telegraph, and radio, and (6) the increasing application of science to industry. These technological changes made possible a tremendously increased use of natural resources and the mass production of manufactured goods.

Every cell in the body is enclosed by a cell (Plasma) membrane. The cell membrane separates the material outside the cell, extracellular, from the material inside the cell, intracellular. It maintains the integrity of a cell and controls passage of materials into and out of the cell. All materials within a cell must have access to the cell membrane (the cell's boundary) for the needed exchange. The cell membrane is a double layer of phospholipid molecules. Proteins in the cell membrane provide structural support, form channels for passage of materials, act as receptor sites, function as carrier molecules, and provide identification markers.

The cytoplasm is the gel-like fluid inside the cell. It is the medium for chemical reaction. It provides a platform upon which other organelles can operate within the cell. All of the functions for cell expansion, growth and replication are carried out in the cytoplasm of a cell. Within the cytoplasm, materials move by diffusion, a physical process that can work only for short distances.

An ecosystem is a geographic area where plants, animals, and other organisms, as well as weather and landscape, work together to form a bubble of life. Ecosystems contain biotic or living, parts, as well as abiotic factors, or nonliving parts. Biotic factors include plants, animals, and other organisms. Abiotic factors include rocks, temperature, and humidity. Every factor in an ecosystem depends on every other factor, either directly or indirectly. A change in the temperature of an ecosystem will often affect what plants will grow there, for instance. Animals that depend on plants for food and shelter will have to adapt to the changes, move to another ecosystem, or perish.

Ecosystems can be very large or very small. Tide pools, the ponds left by the ocean as the tide goes out, are complete, tiny ecosystems. Tide pools contain seaweed, a kind of algae, which uses photosynthesis to create food. Herbivores such as abalone eat the seaweed. Carnivores such as sea stars eat other animals in the tide pool, such as clams or mussels. Tide pools depend on the changing level of ocean water. Some organisms, such as seaweed, thrive in an aquatic environment, when the tide is in and the pool is full. Other organisms, such as hermit crabs, cannot live underwater and depend on the shallow pools left by low tides. In this way, the biotic parts of the ecosystem depend on abiotic factors.The whole surface of Earth is a series of connected ecosystems. Ecosystems are often connected in a larger biome. Biomes are large sections of land, sea, or atmosphere. Forests, ponds, reefs, and tundra are all types of biomes, for example. They're organized very generally, based on the types of plants and animals that live in them. Within each forest, each pond, each reef, or each section of tundra, you'll find many different ecosystems.

Mountain, landform that rises prominently above its surroundings, generally exhibiting steep slopes, a relatively confined summit area, and considerable local relief. Mountains generally are understood to be larger than hills, but the term has no standardized geological meaning. Very rarely do mountains occur individually. In most cases, they are found in elongated ranges or chains. When an array of such ranges is linked together, it constitutes a mountain belt.

A mountain belt is many tens to hundreds of kilometres wide and hundreds to thousands of kilometres long. It stands above the surrounding surface, which may be a coastal plain, as along the western Andes in northern Chile, or a high plateau, as within and along the Plateau of Tibet in southwest China. Mountain ranges or chains extend tens to hundreds of kilometres in length. Individual mountains are connected by ridges and separated by valleys. Within many mountain belts are plateaus, which stand high but contain little relief. Thus, for example, the Andes constitute a mountain belt that borders the entire west coast of South America; within it are both individual ranges, such as the Cordillera Blanca in which lies Peru’s highest peak, Huascarán, and the high plateau, the Altiplano, in southern Peru and western Bolivia.

Of the 100-plus annual shark attacks worldwide, a third to a half are attributed to great white sharks. Most of these, however, are not fatal. Research finds that great whites, which are naturally curious, often "sample bite" then release their human target. It's not a terribly comforting distinction, but it does indicate that humans are not actually on the great white's menu. Fatal attacks, experts say, are typically cases of mistaken identity: Swimmers and surfers can look a lot like their favorite prey—seals—when seen from below.

Scholars generally agree that the earliest form of writing appeared almost 5,500 years ago in Mesopotamia (present-day Iraq). Early pictorial signs were gradually substituted by a complex system of characters representing the sounds of Sumerian (the language of Sumer in Southern Mesopotamia) and other languages. From 2900 BC, these began to be impressed in wet clay with a reed stylus, making wedge-shaped marks which are now known as cuneiform.

New discoveries have pushed back the date for writing in Egypt close to that of Mesopotamia. Discoveries of large-scale incised ceremonial scenes at the rock art site of El-Khawy in Egypt date to around 3250 BC. They show features similar to early hieroglyphic forms. Some of these rock-carved signs are nearly half a metre in height. From 3200 BC onwards Egyptian hieroglyphs appeared on small ivory tablets used as labels for grave goods in the tomb of the pre-dynastic King Scorpion at Abydos and on ceremonial surfaces used for grinding cosmetics, such as the Narmer Palette. Writing in ink using reed brushes and pens is first found in Egypt. This ink writing came to be known in Greek as hieratic (‘priestly’ script), whilst the carved and painted letters we see on monuments are called hieroglyphs (‘sacred carvings’).

Nuclear family, also called elementary family, in sociology and anthropology, a group of people who are united by ties of partnership and parenthood and consisting of a pair of adults and their socially recognized children. Typically, but not always, the adults in a nuclear family are married. Although such couples are most often a man and a woman, the definition of the nuclear family has expanded with the advent of same-sex marriage. Children in a nuclear family may be the couple’s biological or adopted offspring. Thus defined, the nuclear family was once widely held to be the most basic and universal form of social organization. Anthropological research, however, has illuminated so much variability of this form that it is safer to assume that what is universal is a “nuclear family complex” in which the roles of husband, wife, mother, father, son, daughter, brother, and sister are embodied by people whose biological relationships do not necessarily conform to the Western definitions of these terms. In matrilineal societies, for example, a child may be the responsibility not of his biological genitor but of his mother’s brother, who fulfills the roles typical of Western fatherhood.

Anthropology, “the science of humanity,” which studies human beings in aspects ranging from the biology and evolutionary history of Homo sapiens to the features of society and culture that decisively distinguish humans from other animal species. Because of the diverse subject matter it encompasses, anthropology has become, especially since the middle of the 20th century, a collection of more specialized fields. Physical anthropology is the branch that concentrates on the biology and evolution of humanity. It is discussed in greater detail in the article human evolution. The branches that study the social and cultural constructions of human groups are variously recognized as belonging to cultural anthropology (or ethnology), social anthropology, linguistic anthropology, and psychological anthropology (see below). Archaeology (see below), as the method of investigation of prehistoric cultures, has been an integral part of anthropology since it became a self-conscious discipline in the latter half of the 19th century. (For a longer treatment of the history of archaeology, see archaeology.)

The dog evolved from the gray wolf into more than 400 distinct breeds. Human beings have played a major role in creating dogs that fulfill distinct societal needs. Through the most rudimentary form of genetic engineering, dogs were bred to accentuate instincts that were evident from their earliest encounters with humans. Although details about the evolution of dogs are uncertain, the first dogs were hunters with keen senses of sight and smell. Humans developed these instincts and created new breeds as need or desire arose.

Dogs are regarded differently in different parts of the world. Characteristics of loyalty, friendship, protectiveness, and affection have earned dogs an important position in Western society, and in the United States and Europe the care and feeding of dogs has become a multibillion-dollar business. Western civilization has given the relationship between human and dog great importance, but, in some of the developing nations and in many areas of Asia, dogs are not held in the same esteem. In some areas of the world, dogs are used as guards or beasts of burden or even for food, whereas in the United States and Europe dogs are protected and admired. In ancient Egypt during the days of the pharaohs, dogs were considered to be sacred.

Over the last decade, many of the big grocery companies have been accused of different unethical practices. They've thrown away a lot of food, underpaid their suppliers, and contributed to a lot of plastic waste in their packaging, all of which have had an impact on the environment. Supermarkets and grocers, on the other hand, are starting to take note. Some of the top UK supermarkets have signed up to an agreement vowing to alter packaging and reduce plastic waste in response to growing public anger over the vast volumes of plastic waste generated by plastic packaging. Without a doubt, we still have a long way to go in terms of decreasing food and plastic waste. However, perhaps the larger supermarkets will take inspiration from these little grocers and work towards a more sustainable future for all of us. 

Astronomy is the study of everything in the universe beyond Earth's atmosphere. That includes objects we can see with our naked eyes, like the Sun , the Moon , the planets, and the stars . It also includes objects we can only see with telescopes or other instruments, like faraway galaxies and tiny particles. Since the 20th century there have been two main types of astronomy, observational and theoretical astronomy. Observational astronomy uses telescopes and cameras to observe or look at stars, galaxies and other astronomical objects. 

Bitcoin offers an efficient means of transferring money over the internet and is controlled by a decentralized network with a transparent set of rules, thus presenting an alternative to central bank-controlled fiat money.1 There has been a lot of talk about how to price Bitcoin, and we set out here to explore what the cryptocurrency's price might look like in the event it achieves further widespread adoption. First, however, it is useful to back up a step. Bitcoin and other digital currencies have been touted as alternatives to fiat money. 

Centuries of observation and scientific investigation have been centred on the nature and origin of the Moon. Early studies of the Moon’s motion and position allowed the prediction of tides and led to the development of calendars. The Moon was the first new world on which humans set foot; the information brought back from those expeditions, together with that collected by automated spacecraft and remote-sensing observations, has led to a knowledge of the Moon that surpasses that of any other cosmic body except Earth itself. Although many questions remain about its composition, structure, and history, it has become clear that the Moon holds keys to understanding the origin of Earth and the solar system. Moreover, given its nearness to Earth, its rich potential as a source of materials and energy, and its qualifications as a laboratory for planetary science and a place to learn how to live and work in space for extended times, the Moon remains a prime location for humankind’s first settlements beyond Earth orbit. 

Elephants are the largest land mammals on earth and have distinctly massive bodies, large ears, and long trunks. They use their trunks to pick up objects, trumpet warnings, greet other elephants, or suck up water for drinking or bathing, among other uses. Both male and female African elephants grow tusks and each individual can either be left- or right-tusked, and the one they use more is usually smaller because of wear and tear. Elephant tusks serve many purposes. These extended teeth can be used to protect the elephant's trunk, lift and move objects, gather food, and strip bark from trees. They can also be used for defense. During times of drought, elephants even use their tusks to dig holes to find water underground. 

Every cell in the body is enclosed by a cell (Plasma) membrane. The cell membrane separates the material outside the cell, extracellular, from the material inside the cell, intracellular. It maintains the integrity of a cell and controls passage of materials into and out of the cell. All materials within a cell must have access to the cell membrane (the cell's boundary) for the needed exchange. The cell membrane is a double layer of phospholipid molecules. Proteins in the cell membrane provide structural support, form channels for passage of materials, act as receptor sites, function as carrier molecules, and provide identification markers. 

Biology is the study of life. The word "biology" is derived from the Greek words "bios" (meaning life) and "logos" (meaning "study"). In general, biologists study the structure, function, growth, origin, evolution and distribution of living organisms. Biology is important because it helps us understand how living things work and how they function and interact on multiple levels, according to the Encyclopedia Britannica. Advances in biology have helped scientists do things such as develop better medicines and treatments for diseases, understand how a changing environment might affect plants and animals, produce enough food for a growing human population and predict how eating new food or sticking to an exercise regimen might affect our bodies.

 Although early conceptions of spaceflight usually depicted streamlined spacecraft, streamlining has no particular advantage in the vacuum of space. Actual vehicles are designed with a variety of shapes depending on the mission. The first spacecraft, the Soviet Union’s Sputnik 1, was launched on October 4, 1957; it weighed 83.6 kg (184 pounds). It was soon followed by other unmanned Soviet and U.S. spacecraft and, within four years (April 12, 1961), by the first manned spacecraft, Vostok 1, which carried the Soviet cosmonaut Yury Gagarin. Since then, numerous other manned and unmanned craft have been launched to increase scientific knowledge, augment national security, or provide important services in areas such as telecommunications and weather forecasting. 

Adrenaline is released mainly through the activation of nerves connected to the adrenal glands, which trigger the secretion of adrenaline and thus increase the levels of adrenaline in the blood. This process happens relatively quickly, within 2 to 3 minutes of the stressful event being encountered. When the stressful situation ends, the nerve impulses to the adrenal glands are lowered, meaning that the adrenal glands stop producing adrenaline.