True Circulatory Systems: Blood Veins
545 Million Years Ago (after through-gut digestion: mouth/anus)
Circulatory fluid transport (veins)
Open and closed vascular systems: As animals increased in size and complexity during the Cambrian, specialized circulatory systems evolved. Open systems allowed fluid to bathe tissues directly, while closed systems developed vessels and true blood, enabling efficient long-distance transport of oxygen and nutrients.
Blood, a specialized fluid carrying nutrients and waste, evolved around 520 million years ago in multicellular organisms. It evolved to feed internal cells and carry away waste. As oxygen levels rose and multicellular life emerged, blood evolved to transport oxygen and nutrients to cells.
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About 545 million years ago, veins evolved. The digestive tract evolved more than 25 million years before this. Digestion breaks down food efficiently. Veins transport nutrients.
Subject: Animal Evolution.
By 545 million years ago, early animals evolved veins to better transport nutrients. More than 25 million years before this, the first eating with a mouth and gut evolved. Only later, as bodies grew larger and more complex, did evolution add circulatory vessels to move nutrients and oxygen efficiently. Digestion built the engine. Veins built the plumbing.
was first published on TST 2 years ago.
