Phytoplankton are microscopic algae that live near the surface of the oceans.
The food chain shows some organisms in an ocean.
phytoplankton→zooplankton→herring→seal \text{phytoplankton} \rightarrow \text{zooplankton} \rightarrow \text{herring} \rightarrow \text{seal} phytoplankton→zooplankton→herring→sealExplain why phytoplankton are described as producers.
A volcanic eruption released ash into the air. The ash blocked some of the sunlight reaching the ocean for several months.
Explain how this could affect the population of herring.
State the source of the carbon atoms in the biomass of phytoplankton.
Most phytoplankton are found in the top 100 m of the ocean.
Suggest why.
44 exam-style questions on Edexcel GCSE Biology 6.1 Photosynthesis, covering 6.1.1 Photosynthetic organisms as producers, 6.1.2a Limiting factors on the rate of photosynthesis, 6.1.2b Interactions of limiting factors on photosynthesis, and 6.1.3 Inverse square law and light intensity. Each one has a worked solution and a mark scheme showing where the marks go.