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Q42 (IAS/2021) Environment & Ecology › Ecology & Ecosystem Basics › Marine productivity Official Key

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?

Result
Your answer: —  ·  Correct: B
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.

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Q. Consider the following kinds of organisms : 1. Copepods 2. Cyanobacteria 3. Diatoms 4. Foraminifera Which of the above are primary produc…
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Origin: Books + Current Affairs Fairness: Low / Borderline fairness Books / CA: 2.5/10 · 7.5/10
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This 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.

How this question is built

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?
Origin: Web / Current Affairs Fairness: CA heavy Web-answerable

Web source
Presence: 5/5
"phytoplankton represent the primary producers of organic matter and zooplankton are the link between the phytoplankton and higher trophic levels."
Why this source?
  • 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.
Web source
Presence: 4/5
"These chains involve small metazoans and predominate in the northern open waters (Atkinson et al., 2012) with multiple trophic levels (copepods, chaetognaths, amphipods, myctophids, fish and birds) in contrast with the classical short chain of diatoms –"
Why this source?
  • 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.

Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 3: MAJOR BIOMES > Food Chains in Marine Biomes > p. 33
Strength: 5/5
“Te food chains in the ocean water are much more complex than that of the terrestrial biomes as there is no efective barrier in the oceans and seas which can restrict fauna and fora to certain fxed localities. Te phytoplanktons are the primary producers in the photic zone (up to a depth of 200 m from the sea surface). Te primary producers (planktons) provide directly or indirectly, food to all the plant and animal communities of the oceans. Zooplanktons are the heterotrophic primary consumer animals and form trophic level two of the food chain because these feed on phytoplanktons. Phytoplanktons manufacture food through the process of photosynthesis because of the availability of sunlight during daytime.”
Why relevant

States that phytoplanktons are the primary producers in the photic zone and that zooplanktons are heterotrophic primary consumers feeding on phytoplankton.

How to extend

A student can check whether copepods are classified as zooplankton; if so, they would be consumers rather than producers.

Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 30: Climatic Regions > Geographical advantage > p. 465
Strength: 4/5
“• Phytoplankton, algae and other plants (primary producers) are able to photosynthesise to produce organic material from inorganic nutrients. And the organic material forms the building block for all animals higher up in the marine food chain.• Almost all biomass in the ocean is derived from the phytoplankton and to a lesser extent the benthic algae (found on the bottom of a sea or lake; algae are insignificant players in the marine ecosystem compared to the phytoplankton as they only inhabit a narrow zone around the coast). Hence phytoplankton are called the grass of the sea.• There is a fundamental problem that phytoplankton in the open ocean face.”
Why relevant

Explicitly defines phytoplankton (and benthic algae) as the main primary producers — 'grass of the sea' — forming the base of marine food chains.

How to extend

Combine this rule with identification of copepods’ trophic category (zooplankton vs phytoplankton) to infer their role.

Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 2: Functions of an Ecosystem > i) Grazing food chain > p. 12
Strength: 5/5
“The consumers which start the food chain, utilizing the plant or plant part as their food, constitute the grazing food chain. This food chain begins from green plants at the base and the primary consumer is herbivore. For example, In terestrial ecosystem, grass is eaten up. by caterpillar, which is eaten by lizard and lizard is eaten by snake. In Aquatic ecosystem phytoplanktons (primary producers) is eaten by zoo planktons which is eaten by fishes and fishes are eaten by pelicans.”
Why relevant

Gives a concrete aquatic grazing food chain example: phytoplanktons (producers) → zooplanktons (primary consumers) → fishes.

How to extend

Map copepods onto the 'zooplankton' slot in this example to test if they are primary consumers rather than producers.

Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 14: Marine Organisms > 14.3. ZOOPLANKTON > p. 209
Strength: 4/5
“• Zooplankton play vital role in food web of the lcod chain, nutrient recycling, and in transfer of organic matter from primary producers to serondary consumers like fishes. • They are more abundant within mangrove waterways than in adjacent coastal waters, and a large proportion of the juvenile fish of mangrove habitat are zooplanktivorous. • The zooplanckton determine the quantum of fish stock.”
Why relevant

Describes zooplankton roles in transferring matter from primary producers to higher consumers and their importance for fish stocks.

How to extend

If copepods are members of zooplankton, this supports treating them as consumers that feed on phytoplankton.

Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 14: Marine Organisms > The food web > p. 208
Strength: 4/5
“rti7 ;It r Phytoplanktons are the foundation of the aquatic food web, the primary producers; they feed everything from microscopic animal-like zooplankton to whales. Small fish and invertebrates graze on the phytoplanktons, and then those smaller animals are eaten by bigger ones.”
Why relevant

Reiterates that phytoplanktons are the foundation (primary producers) feeding zooplankton and higher animals.

How to extend

A student can use this general pattern plus a taxonomic lookup of copepods to judge whether they fit as producers or consumers.

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Statement analysis

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Statement analysis

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