<em>open lake </em>is a lake where water constantly flows out under almost all climatic circumstances. Because water does not remain in an open lake for any length of time, open lakes are usually fresh water: dissolved solids do not accumulate. Open lakes form in areas where precipitation is greater than evaporation. Because most of the world's water is found in areas of highly effective rainfall, most lakes are open lakes whose water eventually reaches the sea.
<em>closed lake </em>(see endorheic drainage), no water flows out, and water which is not evaporated will remain in a closed lake indefinitely. This means that closed lakes are usually saline, though this salinity varies greatly from around three parts per thousand for most of the Caspian Sea to as much as 400 parts per thousand for the Dead Sea. Only the less salty closed lakes are able to sustain life, and it is completely different from that in rivers or freshwater open lakes.
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Migration boosts the working-age population. Migrants arrive with skills and contribute to human capital development of receiving countries. Migrants also contribute to technological progress. Understanding these impacts is important if our societies are to usefully debate the role of migration
<span>There Are Four Main Arthropod Families.
Arthropods Account for 80 Percent of All Animal Species
Arthropods Are a Monophyletic Animal Group
The Exoskeleton of Arthropods Is Composed of Chitin</span>