The<em> cell membrane</em> controls the movement of substances in and out of cells and organelles. In this way, it is selectively permeable to ions and organic molecules.
Here is a link that can help you.
http://study.com/academy/lesson/what-is-an-organ-system-definition-pictures-quiz.html
An hypotheses plays an educated guess in the scientific inquiry.
Answer:
"Through the Tertiary period (from 65 Ma) the Earth's climate became cooler with frequent oscillations that increased in amplitude and led to a series of major ice ages in the Quaternary. Glacial advances and retreats over the Pleistocene resulted in global cycles of contraction, expansion and fragmentation of species ranges resulting in species extinctions, population bottlenecks and differentiation."
Explanation:
(Did offline will rewrite in my own words if you would like :)
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DNA replication is the process of copying a double-stranded DNA molecule. Both strands serve as templates for the reproduction of the opposite strand. The process is sometimes called "semi-conservative replication" because the daughter DNA from the original parent strand contains half of the original and half of the newly synthesized DNA.
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