Plankton are most commonly found in the _______.

• A. photic zone of aquatic biomes
• B. littoral zone of rivers
• C. intertidal zone of oceans
• D. benthic zone of lakes

Answer: (A)

Verified step by step guidance

1. Understand the term 'plankton': Plankton are small organisms that drift in water. They are typically divided into phytoplankton (plant-like organisms) and zooplankton (animal-like organisms). Phytoplankton, in particular, require sunlight for photosynthesis.
2. Review the concept of the 'photic zone': The photic zone is the upper layer of a body of water where sunlight penetrates, allowing photosynthesis to occur. This is where phytoplankton thrive due to the availability of light.
3. Analyze the other options: The littoral zone of rivers refers to the shallow areas near the shore, which may not always have the conditions suitable for plankton. The intertidal zone of oceans is the area between high and low tide, which is more suited for organisms adapted to changing water levels. The benthic zone of lakes is the bottom layer, which receives little to no sunlight, making it unsuitable for photosynthetic plankton.
4. Match the characteristics of plankton with the correct zone: Since plankton, especially phytoplankton, require sunlight, they are most commonly found in the photic zone of aquatic biomes.
5. Conclude that the photic zone is the correct answer because it provides the necessary light conditions for plankton to thrive, particularly for photosynthetic organisms like phytoplankton.