Consider the following kinds of organisms: Which of the above are primary producers in the food chains of oceans?

Answer: (b) 2 and 3

Cyanobacteria and diatoms are photosynthetic phytoplankton.

Statement by statement

1. ✗ NO — consumer Copepods are tiny crustaceans (zooplankton) that eat phytoplankton.

2. ✓ YES Cyanobacteria (e.g. Prochlorococcus, Trichodesmium) photosynthesise.

3. ✓ YES Diatoms, algae with glass (silica) shells, produce a large share of ocean oxygen.

4. ✗ NO — consumer Foraminifera are protists that feed on other organisms (some host algae, but they are not producers).

The idea

Plankton means anything that drifts. Divide it into two. Phytoplankton are the plant-like drifters that make food from sunlight; they are the producers. Zooplankton are the animal-like drifters that eat them.

Producers: diatoms, cyanobacteria, dinoflagellates → Consumers: copepods, krill, foraminifera, larvae of fish and crabs

The trap

All four are tiny plankton, so they feel alike. Split them into phyto (make food) and zoo (eat it).

Also know

Diatoms have glassy shells of silica. Copepods are tiny crustaceans and may be the most numerous animals on Earth. The limy shells of foraminifera pile up on the sea floor and are used to read past climates.