Well, when chromosomes cross over during prophase 1 of meiosis, the homologous pair of chromosomes exchange segments of DNA which happen to be the genes. So the significance of crossing-over during prophase 1 is that it adds genetic variation to sexually reproducing organisms.
Answer:
Most of the heavy metals on earth came from outer space from supernovas
This occurs when stars die
Explanation:
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Type in the origins of gold and take notes
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Overproduction of offspring, inherited variation, and the struggle to survive.
So: b, d, and e
