Which characteristic is found in the whale but not in it's food source, the phytoplankton

Whales don't eat phytoplankton. They eat zooplankton. Phytoplankton are photosynthetic micro-organisms. They are eaten by small fish, such as herrings and other small animals known as zooplankton. The zooplankton are small animals such as krill or the larvae of fish, molluscs and crustaceans or other marine animals. Baleen whales may eat a lot of small fish and zooplankton, but their baleen plates are too coarse to trap the microscopic phytoplankon.

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