They drop on the ground and the wind blows them or birds pick them up and drop them or bees
The muscle pulling on a bone often works like a type of simple machine called a lever. Most of the bones of the limbs (arms & legs) act as levers for the body. I hope that this is the answer that you were looking for and it has helped you.
Carbon dioxide (chemical formula CO2) is a colorless and odorless gas that is vital to life on Earth. This naturally occurring chemical compound is made up of a carbon atom contently double bonded to two oxygen atoms. Carbon dioxide exists in Earth's atmosphere as a trace gas at a concentration of about 0.04 percent (400 ppm) by volume.Natural sources include volcanoes, hot springs and geysers, and it is freed from carbonate rocks by dissolution in water and acids. Because carbon dioxide is soluble in water, it occurs naturally in groundwater, rivers and lakes, in ice caps and glaciers and also in seawater. It is present in deposits of petroleum and natural gas.
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Because migration and and other seasonal movements can affect the possibility of finding a mate, stresses, that could affect offspring survival(can vary with season), and also availability of thing that are available for the offspring.