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When do chromosomes line up in the center of the cell?

Mitosis is the process used by most of the body's cells in order to divide or reproduce. It consists of four, distinct subphases which are, in order, prophase, metaphase, anaphase and telephase. During each of these phases, as well as during its inactive, non-reproducing time, or interphase, the cell's chromosomes behave in a specific way to allow for proper reproduction and function throughout the body.As a cell moves from the inactive interphase into prophase, its chromosomes condense and become visible within the nucleus. However, at this time, the chromosomes are in constant moti..

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What is the structure of the human arm?

The bones of the arm are layered with large skeletal muscles, such as the biceps and triceps, that connect to the bone via tough, fibrous tendons. These muscles are connected to the central nervous system by a network of sensory and motor nerves that run from the muscle or skin to the spinal cord.\nParts of the arm, mainly the upper arm, are insulated with a layer of subcutaneous fat. Over this layer, the skin forms a protective outer layer of the arm and hand. At the ends of the fingers, the skin excretes small sheets of a protein called keratin from beds to form fingernails. The entire arm i..

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What are black dwarf stars?

Once a star becomes a white dwarf, it no longer has an internal source of heat and is only still shining due to residual heat. Just like food taken out of an oven, it slowly cools. It first becomes a red dwarf, then a brown dwarf and, eventually, a black dwarf.\nBlack dwarfs are entirely hypothetical unlike red, brown and white dwarfs. It would take a white dwarf longer to become a black dwarf than the universe has existed, so there are no black dwarfs in existence.

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How do water lilies reproduce?

On the first morning, the petals open and the flowers produce a fluid in the cup-like center, after which they are ready to receive pollen from other flowers. Insects covered in pollen are attracted by the sweet smell and fall in the liquid when they enter the flower. The liquid washes the pollen off their bodies and onto the female flower parts, which are called stigmas, causing fertilization. After three days, water lilies coil their stock so they go underwater, and the seeds mature during this time. The seeds are released underwater after several weeks.

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Why do animals become endangered?

According to the Endangered Species Act, a species can either be classified as endangered or threatened. An endangered species is one whose members are so few that the entire population suffers a high risk of extinction. A species is said to be threatened if it is likely to become endangered within the foreseeable future. The International Union for Conservation of Nature, keeps track of endangered species around the world.\nLoss of habitat is the main reason species become endangered. Habitat is not only where animals live, but also where they find food and raise their babies. Humans destroy ..

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What is the difference between a new moon and a full moon?

The moon goes through many phases in the course of a lunar month, which has 29.5 days in it, according to MoonPhases.info. The moon is said to be waxing when more of the sun's light falls upon it, leaving more and more of its surface visible. When waning, the moon travels further into the Earth's shadow, and visibility is decreased.

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When was Mendeleev's contribution to the atomic theory published?

Mendeleev, a Russian chemist and inventor, developed the Periodic Law and created the periodic table of elements that is used today. His research has given scientists a better understanding of the atom. Mendeleev was born in 1834 near Tobolsk, Russia and attended Saint Petersburg University. He died in 1907 in Saint Petersburg at age 72.

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What causes continental drift?

The concept of continental drift was presented by Alfred Wegener in the early 1900s. By noting the similarities of the shape of coasts along South America and Africa, Wegener theorized that at one point, the two continents had been attached. Finding fossils of the same lifeforms on both coasts confirmed this suspicion. Further work has indicated that a super-continent, called Pangaea, existed 200 to 240 million years ago.

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How is nobelium used?

Scientists named this new element after Alfred Nobel, the inventor of dynamite. Nobelium does not occur naturally. In the late 1950s, different groups of scientists in Sweden and the United States claimed the discovery of nobelium. However, in 1958, scientists at the University of Berkeley created this element through nuclear fission techniques that involved bombarding curium isotopes with carbon ions. There are 10 nobelium isotopes that include No-259, which has a half-life of approximately 58 minutes.

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How does oxidation occur?

When an element’s atoms lose electrons, it’s said to be oxidized. When an element’s atoms gain electrons, it’s called the oxidizing agent and is said to be reduced. When the atoms of an element gain electrons, it’s called reduction. Oxidation and reduction always occur simultaneously, so chemists describe this reaction with the terms oxidation-reduction or redox.\nOxygen is the oxidizing agent in most oxidation-reduction reactions. For example, rusted iron is caused by oxygen combining with iron to form iron oxide on its surface. The iron atoms give up electrons to the oxygen atoms. ..

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