AP BIOLOGY

Detailed explanation-1: -Phytoplankton are the foundation of the aquatic food web, the primary producers, feeding everything from microscopic, animal-like zooplankton to multi-ton whales. Small fish and invertebrates also graze on the plant-like organisms, and then those smaller animals are eaten by bigger ones.

Detailed explanation-2: -As photoautotrophs, phytoplankton are generally present in the euphotic zone of the ocean, however, recently healthy phytoplankton cells were found to be also ubiquitous in the dark deep sea, i.e., at water depths between 2000 and 4000 m.

Detailed explanation-3: -Phytoplankton are the tiny, plant-like producers of the plankton community. They include bacteria and algae that form the base of aquatic food webs. Common phytoplankton include diatoms, dinoflagellates, cyanobacteria (blue-green algae), and green algae.

Detailed explanation-4: -Producers. Primary producers-including bacteria, phytoplankton, and algae-form the lowest trophic level, the base of the aquatic food web. Primary producers synthesize their own energy without needing to eat.

Detailed explanation-5: -In the euphotic or epipelagic zone (the first 500 feet below the sea surface) cyanobacteria and phytoplankters receive enough light for photosynthesis. These tiny organisms are the primary producers of the entire pelagic regions.