Question map
Consider the following kinds of organisms : 1. Copepods 2. Cyanobacteria 3. Diatoms 4. Foraminifera Which of the above are primary producers in the food chains of oceans?
Explanation
The correct answer is Option 2 (2 and 3) because primary producers are autotrophic organisms that synthesize organic compounds via photosynthesis, forming the base of the marine food web.
- Cyanobacteria (2): Also known as blue-green algae, these are prokaryotic photosynthetic bacteria (e.g., Prochlorococcus) responsible for a significant portion of the ocean's oxygen and carbon fixation.
- Diatoms (3): These are single-celled eukaryotic algae and a major group of phytoplankton. They are the most dominant primary producers in nutrient-rich marine environments.
- Copepods (1): These are small crustaceans and belong to the category of zooplankton. They are primary consumers (herbivores) that feed on phytoplankton, not producers.
- Foraminifera (4): These are single-celled amoeboid protists with shells. They are generally heterotrophic consumers or decomposers, though some harbor symbiotic algae, they are not classified as primary producers themselves.
Therefore, only Cyanobacteria and Diatoms function as the fundamental producers in oceanic food chains.
PROVENANCE & STUDY PATTERN
Full viewThis is a classic 'Classification' question disguised as technical biology. You don't need a PhD in Marine Biology; you just need to distinguish the 'Grass of the Sea' (Phytoplankton) from the 'Cows of the Sea' (Zooplankton). If you skipped the examples list in the 'Aquatic Ecosystem' chapter of Shankar/NCERT, you lost 2 easy marks.
This question can be broken into the following sub-statements. Tap a statement sentence to jump into its detailed analysis.
- Statement 1: Are copepods primary producers in the food chains of oceans?
- Statement 2: Are cyanobacteria primary producers in the food chains of oceans?
- Statement 3: Are diatoms primary producers in the food chains of oceans?
- Statement 4: Are foraminifera primary producers in the food chains of oceans?
- Defines which organisms are primary producers in ocean food chains (phytoplankton).
- Distinguishes zooplankton as the link between phytoplankton (producers) and higher trophic levels, implying producers are not zooplankton.
- Lists copepods among the small metazoans occupying multiple trophic levels in microbial food chains (i.e., as consumers).
- Places copepods in chains contrasted with the 'classical short chain of diatoms' (diatoms being producers), supporting that copepods are not primary producers.
States that phytoplanktons are the primary producers in the photic zone and that zooplanktons are heterotrophic primary consumers feeding on phytoplankton.
A student can check whether copepods are classified as zooplankton; if so, they would be consumers rather than producers.
Explicitly defines phytoplankton (and benthic algae) as the main primary producers — 'grass of the sea' — forming the base of marine food chains.
Combine this rule with identification of copepods’ trophic category (zooplankton vs phytoplankton) to infer their role.
Gives a concrete aquatic grazing food chain example: phytoplanktons (producers) → zooplanktons (primary consumers) → fishes.
Map copepods onto the 'zooplankton' slot in this example to test if they are primary consumers rather than producers.
Describes zooplankton roles in transferring matter from primary producers to higher consumers and their importance for fish stocks.
If copepods are members of zooplankton, this supports treating them as consumers that feed on phytoplankton.
Reiterates that phytoplanktons are the foundation (primary producers) feeding zooplankton and higher animals.
A student can use this general pattern plus a taxonomic lookup of copepods to judge whether they fit as producers or consumers.
- Explicitly lists cyanobacteria among common kinds of phytoplankton.
- Defines phytoplankton as microscopic plant organisms that photosynthesize (i.e., act as primary producers).
- States phytoplankton are the foundation of the aquatic food web and identifies them as primary producers.
- Describes phytoplankton as feeding organisms across trophic levels, linking primary production to ocean food chains.
- Specifies phytoplanktons are primary producers in the photic zone of the ocean.
- Notes primary producers (planktons) provide food directly or indirectly to all marine plant and animal communities.
- Explicitly identifies diatoms as a major group responsible for primary production in the ocean.
- Quantifies their importance (≈20% of photosynthetically fixed CO2), showing a primary-producer role.
- States many diatoms are part of phytoplankton size-classes (nano- and microphytoplankton), linking them to primary producers.
- States that phytoplankton represent the primary producers of organic matter in ocean food chains and food webs.
- Explains phytoplankton provide food for a wide range of sea creatures, showing their base role in marine food chains.
States that phytoplanktons are the primary producers in the photic zone and provide food to all marine communities.
A student could check whether diatoms are a major group within phytoplankton (using a standard biology source) to infer their likely role as primary producers.
Explicitly calls phytoplankton and algae primary producers and notes most ocean biomass is derived from phytoplankton.
Use the general rule that members of phytoplankton/algal groups are autotrophs; verify if diatoms are classified among phytoplankton/algae.
Gives a food-chain example in aquatic ecosystems where phytoplankton (primary producers) are eaten by zooplankton and so on.
A student can place any organism identified as phytoplankton into this food-chain role; confirm whether diatoms occupy that trophic position.
Describes phytoplankton as the foundation of the aquatic food web feeding organisms up to whales, highlighting their central producer role.
Treating diatoms as a subset of phytoplankton (if supported by outside taxonomy) would imply they function as these foundational producers.
Defines the photic zone as the layer with enough light for primary producers and notes lack of primary producers below it.
A student can check where diatoms live (e.g., in sunlit surface waters) to see if they occupy the photic-zone producer niche described here.
- Explicitly names phytoplankton as the organisms that "represent the primary producers of organic matter" in ocean food chains.
- Shows primary producers are the base of pelagic food webs, implying producers are photosynthetic planktonic organisms rather than other groups.
- Identifies diatoms as "one of the major primary producers in the ocean," highlighting photosynthetic microalgae as key producers.
- Reinforces that primary producers in the ocean are photosynthetic algae (e.g., diatoms), not non-photosynthetic protozoans.
- Defines primary producers (algae) as small, solitary photosynthetic cells (microalgae) in marine waters.
- Emphasizes that primary producers are photosynthetic algae, supporting the view that producers are algal/phytoplankton groups rather than other taxa.
Gives the definitional rule: primary producers are 'green plants (and certain bacteria and algae)' that synthesise carbohydrates by photosynthesis.
A student could check whether foraminifera perform photosynthesis themselves or are classified as algae/bacteria to judge if they meet this definition.
States that phytoplankton are the primary producers in the photic zone and that primary producers manufacture food by photosynthesis.
Compare foraminifera's typical feeding mode and habitat (photic vs aphotic) to see if they function like phytoplankton producers.
Notes the photic zone constraint: 'There are not enough primary producers below the photic zone', and that deep primary production can be by chemosynthetic bacteria.
Determine whether foraminifera live in photic depths or deep zones and whether any known production mechanism (photosynthesis/chemosynthesis) applies to them.
Emphasises that 'almost all biomass in the ocean is derived from phytoplankton' and distinguishes phytoplankton/algae as the 'grass of the sea' (primary producers).
Use this pattern to assess if foraminifera are commonly listed among phytoplankton/algae or instead grouped with consumers.
Describes trophic roles in aquatic systems: phytoplankton are primary producers and zooplankton are primary consumers that feed on them.
Check whether foraminifera are described in sources as consumers (e.g., feeding on phytoplankton) or as producers to infer their trophic role.
- [THE VERDICT]: Sitter. Source: Shankar IAS Chapter 14 (Marine Organisms) explicitly lists Cyanobacteria and Diatoms as common kinds of phytoplankton (producers).
- [THE CONCEPTUAL TRIGGER]: Functions of an Ecosystem > Energy Flow > Trophic Levels. The fundamental split between Autotrophs (Self-feeders) and Heterotrophs (Other-feeders).
- [THE HORIZONTAL EXPANSION]: Memorize the 'Big 5' Marine Producers: Diatoms, Cyanobacteria (Blue-green algae), Dinoflagellates, Coccolithophores, and Green Algae. Memorize the 'Big 3' Zooplankton (Consumers): Copepods, Krill, and Foraminifera (Protozoans).
- [THE STRATEGIC METACOGNITION]: When reading Ecology chapters, never stop at definitions. The exam asks for *examples*, not definitions. Create a T-chart for every ecosystem (Marine, Terrestrial, Freshwater): Who makes the food? Who eats it?
Phytoplankton are the autotrophic base that fix solar energy and form the first trophic level in oceanic food chains.
High-yield concept for questions on energy flow, primary productivity and marine fisheries; links to topics like biomass distribution and global carbon cycling. Mastery helps answer questions on what supports higher trophic levels and why marine productivity concentrates in the upper layers.
- Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 3: MAJOR BIOMES > Food Chains in Marine Biomes > p. 33
- Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 30: Climatic Regions > Geographical advantage > p. 465
- Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 14: Marine Organisms > The food web > p. 208
Zooplankton feed on phytoplankton and occupy the second trophic level, transferring primary production to higher consumers.
Important for questions on trophic transfers, fish stock determinants, and impacts of pollutants on food webs; connects ecology to fisheries and conservation topics. Understanding this clarifies why animal plankton (not crustacean producers) are heterotrophs.
- Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 3: MAJOR BIOMES > Food Chains in Marine Biomes > p. 33
- Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 2: Functions of an Ecosystem > i) Grazing food chain > p. 12
- Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 14: Marine Organisms > 14.3. ZOOPLANKTON > p. 209
Photosynthetic primary producers are confined mainly to the photic zone where sunlight penetrates, limiting where autotrophic biomass can form.
Useful for questions on zonation in the ocean, deep-sea ecosystems versus surface productivity, and regional variations in productivity; connects physical oceanography (light penetration) with biological productivity and ecosystem services.
- Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 3: MAJOR BIOMES > Food Chains in Marine Biomes > p. 33
- Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 33: Ocean temperature and salinity > How Do Deep Water Marine Organisms Survive In Spite Of The Absence Of Sunlight? > p. 511
Phytoplankton form the base of oceanic food chains as the primary producers that convert sunlight to organic matter.
High-yield for environment and ecology questions: explains where marine productivity originates, underpins fisheries and carbon cycling topics, and links to questions on food webs and resource management.
- Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 3: MAJOR BIOMES > Food Chains in Marine Biomes > p. 33
- Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 14: Marine Organisms > The food web > p. 208
- Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 30: Climatic Regions > Geographical advantage > p. 465
Cyanobacteria are a constituent group of phytoplankton and thus contribute to marine primary production.
Useful for questions on biodiversity, primary production, and biogeochemical roles (oxygen production, nitrogen fixation); helps answer organism-level and ecosystem-level queries in GS papers.
- Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 14: Marine Organisms > 14.2 PHYTOPLANKTON > p. 207
Primary producers in oceans are concentrated in the photic zone where sunlight permits photosynthesis.
Explains spatial distribution of marine productivity and links to topics on deep-sea ecosystems, chemosynthesis, and limits to fisheries; commonly tested in physical geography and ecology contexts.
- Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 3: MAJOR BIOMES > Food Chains in Marine Biomes > p. 33
- Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 33: Ocean temperature and salinity > How Do Deep Water Marine Organisms Survive In Spite Of The Absence Of Sunlight? > p. 511
Phytoplankton are the autotrophic base of oceanic food chains, fixing solar energy into organic matter.
High-yield for ecology and GS papers because it explains the origin of marine biomass and underpins questions on fisheries, carbon cycling and marine productivity. Connects to topics on primary production, marine resources and food security; useful for questions that ask about drivers of oceanic food webs or causes of fishery collapses.
- Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 3: MAJOR BIOMES > Food Chains in Marine Biomes > p. 33
- Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 30: Climatic Regions > Geographical advantage > p. 465
- Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 14: Marine Organisms > The food web > p. 208
Dinoflagellates and Coccolithophores. These are the 'siblings' of Diatoms often mentioned in the same paragraph. Expect a question on 'Red Tides' (caused by Dinoflagellates) or 'Ocean Acidification impacts' (Coccolithophores have calcium carbonate shells).
Etymology Hack: 'Copepod' ends in 'pod' (meaning foot, like Tripod or Arthropod). Feet imply movement/animals. Animals are consumers, not producers. Eliminate Option 1. You are left with B or C. Between Cyanobacteria (Bacteria = usually decomposer, BUT 'Cyano' = Blue-Green = Photosynthesis) and Foraminifera (complex name, shell-building protozoa), Cyanobacteria is the classic textbook producer.
Link this to GS3 Environment (Climate Change): Diatoms and Cyanobacteria are the 'Biological Pump' of the ocean. They sequester carbon. If they die due to warming, the ocean stops absorbing CO2, accelerating climate change. This is a perfect intro point for a Mains answer on Blue Carbon.