REM's are associated with dreaming. we spend the longest time in the REM stage. REM sleep is marked by a return to fast, irregular EEG patterns similar to those of stage 1. the brain is so active during REM it looks like the person may be awake
The concentration of a liquid refers to how diluted or saturated the liquid is. This orange juice is so diluted it tastes like water.
Answer:
Because natural selection selects for it. Thus it persists.
Explanation:
You have to understand heterozygote advantage. Basically, it's where heterozygotes have an advantage over homozygotes. In the case of sickle cell disease, heterozygotes have an advantage, and natural selection favors whatever is advantageous. Thus, because heterozygotes each have one recessive sickle-cell allele, as natural selection favors the heterozygotes, the recessive sickle-cell allele persists and remains in the gene pool.
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