The Six Kingdoms. When Linnaeus developed his system of classification, there were only two kingdoms, Plants and Animals. But the use of the microscope led to the discovery of new organisms and the identification of differences in cells.A two-kingdom system was no longer useful.Today the system of classification includes six kingdoms.he Six Kingdoms. When Linnaeus developed his system of classification, there were only two kingdoms, Plants and Animals. But the use of the microscope led to the discovery of new organisms and the identification of differences in cells.
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1 Price to Compare. 2  The Price to Compare (PTC) is the average cost per kilowatt-hour (kWh) for supply, based on your rate classification. The PTC is a tool for you to use in comparing Delmarvaâs Standard Offer Service (SOS) electric supply rates with offers from competing certified electric suppliers.