Your answer is <span>3.
Iron</span>
Answer:
Some organs are both a source and sink. Leaves are sinks when growing and sources when photosynthesizing. Rhizomes are sinks when growing but become sources in the spring when they provide energy for new growth.
Albinism is a recessive trait characterized by an absence of pigment melanin responsible for skin and hair color. Actually, albinism is caused by a defect in gene for enzyme which synthesizes melanin. The central dogma of molecular biology explains that the sequence of DNA specifies the sequence of mRNA, which, further, specifies codes for the sequence of proteins. Since a gene is a segment of DNA, altered gene will cause altered mRNA which will cause altered protein. Thus, <span>defect in gene for enzyme which synthesizes melanin will cause the absence of melanin and consequently, albinism.</span>
Answer:
Main sequence stars fuse hydrogen atoms to form helium atoms in their cores. About 90 percent of the stars in the universe, including the sun, are main sequence stars. These stars can range from about a tenth of the mass of the sun to up to 200 times as massive.
Stars start their lives as clouds of dust and gas. Gravity draws these clouds together. A small protostar forms, powered by the collapsing material. Protostars often form in densely packed clouds of gas and can be challenging to detect.
"Nature doesn't form stars in isolation," Mark Morris, of the University of California at Los Angeles (UCLS), said in a statement. "It forms them in clusters, out of natal clouds that collapse under their own gravity."
Smaller bodies — with less than 0.08 the sun's mass — cannot reach the stage of nuclear fusion at their core. Instead, they become brown dwarfs, stars that never ignite. But if the body has sufficient mass, the collapsing gas and dust burns hotter, eventually reaching temperatures sufficient to fuse hydrogen into helium. The star turns on and becomes a main sequence star, powered by hydrogen fusion. Fusion produces an outward pressure that balances with the inward pressure caused by gravity, stabilizing the star.
How long a main sequence star lives depends on how massive it is. A higher-mass star may have more material, but it burns through it faster due to higher core temperatures caused by greater gravitational forces. While the sun will spend about 10 billion years on the main sequence, a star 10 times as massive will stick around for only 20 million years. A red dwarf, which is half as massive as the sun, can last 80 to 100 billion years, which is far longer than the universe's age of 13.8 billion years. (This long lifetime is one reason red dwarfs are considered to be good sources for planets hosting life, because they are stable for such a long time.)
Explanation:
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<span>Strip mining is used where coal seams are located very near the surface and can be removed in massive layers, or strips. </span>
