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This is Scientific American's 60-Second Science. I'm Karen Hopkin. This will just take a minute.

Life requires balance. We balance work and family. We eat a balanced breakfast, sometimes. And we balance our electrolytes. That salt-water synergy is not just key to our health, but to our very existence. Because the appearance of molecules¹ that maintain our fluid balance coincide with the evolution of multicellular life. The findings appear in the journal Physiological² Genomics.

When it comes to osmolarity, single cells keep it simple. They adjust their fluid intake³ by importing or exporting salts across their membranes⁴. But once a creature is multicellular, things are more complex. Many cells don't have direct access to the environment, so a complex system of hormones⁵ and sodium⁶ channels and pumps has to manage the movement of salts, cell by cell, to keep the whole body hydrated.

To trace the evolution of this regulatory system, scientists searched the genomes of organisms that represent the major branches of life's tree. And they found that two proteins—a sodium channel and part of a sodium pump—arose slightly before the first multicellular animals. Which strongly implies that the ability to regulate electrolytes is a big reason we're here. As any scientists worth their salt will tell you.

Thanks for the minute. For Scientific American's 60-Second Science, I'm Karen Hopkin.

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1 molecules
分子( molecule的名词复数 )
参考例句：
The structure of molecules can be seen under an electron microscope. 分子的结构可在电子显微镜下观察到。 Inside the reactor the large molecules are cracked into smaller molecules. 在反应堆里，大分子裂变为小分子。

2 physiological
adj.生理学的，生理学上的
参考例句：
He bought a physiological book.他买了一本生理学方面的书。 Every individual has a physiological requirement for each nutrient.每个人对每种营养成分都有一种生理上的需要。

3 intake
n.吸入，纳入；进气口，入口
参考例句：
Reduce your salt intake.减少盐的摄入量。 There was a horrified intake of breath from every child.所有的孩子都害怕地倒抽了一口凉气。

4 membranes
n.（动物或植物体内的）薄膜( membrane的名词复数 )；隔膜；（可起防水、防风等作用的）膜状物
参考例句：
The waste material is placed in cells with permeable membranes. 废液置于有渗透膜的槽中。来自辞典例句 The sarcoplasmic reticulum is a system of intracellular membranes. 肌浆网属于细胞内膜系统。来自辞典例句

5 hormones
n. 荷尔蒙，激素名词hormone的复数形式
参考例句：
This hormone interacts closely with other hormones in the body. 这种荷尔蒙与体內其他荷尔蒙紧密地相互作用。 The adrenals produce a large per cent of a man's sex hormones. 肾上腺分泌人体的大部分性激素。

6 sodium
n.（化）钠
参考例句：
Out over the town the sodium lights were lit.在外面，全城的钠光灯都亮了。 Common salt is a compound of sodium and chlorine.食盐是钠和氯的复合物。