Well because if the plankton were more dense than water they'd sink, thereby not being able to perform photosynthesis.
they feed on planktons. The planktons which serve as their food filters the water that enters to a porifera's pores and this microorganisms (planktons) serve as their food.
Holoplankton and meroplankton are types of planktons found in the oceans. Holoplankton are planktons for their entire lives, while meroplanktons are planktons for only part of their lives.
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Planktons
planktons
planktons
Planktons and Zooplanktons
invertibrates
Yes
Some zooplankton do.
Why and how eye is important for survival of life
yes plants