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BiologyMass Extinctions
The most recent mass extinction was about 65 million years ago, well before humans began...
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Scientists and ResearchBernardo Houssay
Dr. Bernardo Houssay was a pioneering researcher of the endocrine system, the system of glands...
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ChemistryThe Periodic Table of Elements II
This module traces the history of the periodic table of the elements. In the mid-1800s,...
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