Zooplankton are tiny, often microscopic animals that drift in oceans, lakes, and rivers. They play a crucial role in aquatic ecosystems as they serve as a primary food source for larger animals like fish and whales. Zooplankton can be found in various forms, including tiny crustaceans and larval stages of larger animals, and they come in many shapes and sizes. These organisms feed on phytoplankton, which are microscopic plants that use sunlight to produce energy. By consuming phytoplankton, zooplankton help transfer energy through the food web, supporting the growth of larger marine life. Their presence is vital for maintaining the balance of aquatic environments.