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Migration is when animals move on a regular cycle. For example, caribou in the Arctic go south in winter and return in summer when it's warmer. Many birds migrate, such as geese and storks. Migration is the travelling of long distances in search of new habitat.
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Answer:
Human embryonic stem cell (hESC) research is ethically and politically controversial because it involves the destruction of human embryos. In the United States, the question of when human life begins has been highly controversial and closely linked to debates over abortion.
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According to the Second law of thermodynamics, energy is never 100% efficient because some of the energy disperses as heat