<em>The exposure of sea bed or undersea surface is called sea-level regression.</em>
<u>Explanation:</u>
Sea-level regression occurs when sea level drops down due to several climatic changes. This triggers extinction of several species. There had been several mass extinctions in the past due to <em>sea-level regression.
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<em>Chances of survival of shallow</em> water species become feeble when the sea level falls. In the case of mass extinctions regression can be seen as a symptom and not a cause.
Marine transgression is the opposite <em>phenomena of regression</em> where sea level rises and covers the land which was previously above the sea level.
Lipid - <span>any of a class of organic compounds that are fatty acids or their derivatives and are insoluble in water but soluble in organic solvents. They include many natural oils, waxes, and steroids.
Its plays the role of storing energy or forming cell membranes alone.</span>
