Biology · Ecosystems · NEET
| Carried out by | Producers (autotrophs) like green plants | Consumers (heterotrophs) like animals |
| Process used | Photosynthesis | Eating food and building body tissue (no photosynthesis) |
| Definition (NCERT) | Rate of production of organic matter by plants | Rate of formation of new organic matter by consumers |
| Sub-types | GPP and NPP (GPP − R = NPP) | No standard GPP/NPP split |
| Amount of energy | Higher (captures solar energy directly) | Lower (only ~10% passed on) |
| Units | g m⁻² yr⁻¹ or (kcal m⁻²) yr⁻¹ | g m⁻² yr⁻¹ or (kcal m⁻²) yr⁻¹ |
Primary productivity is carried out by producers (autotrophs) like green plants and algae. They make organic matter from CO2 and water using sunlight. Secondary productivity is carried out by consumers (heterotrophs) like animals. They do NOT make food from sunlight. They take in food, and the rate at which they form new organic matter (body mass) is secondary productivity. This is a very common NEET trap, so remember: producers = primary, consumers = secondary.
No. This is the biggest mistake students make. Photosynthesis happens ONLY in producers, so photosynthesis is part of PRIMARY productivity (it makes GPP). Secondary productivity does not use photosynthesis at all. Consumers eat food and convert part of it into their own body tissue. So if a question links photosynthesis to secondary productivity, that statement is wrong.
No. GPP (gross primary productivity) and NPP (net primary productivity) are both parts of PRIMARY productivity, done by plants. GPP is the total organic matter made in photosynthesis, and NPP is what is left after respiration (GPP minus R equals NPP). Secondary productivity is a separate idea for consumers only: it is the rate of formation of new organic matter by consumers. Do not mix these up in NEET.
Because energy is lost at every step. Producers capture solar energy and store it as NPP. When consumers eat producers, only about 10 percent of that energy is passed on and stored as new consumer body mass (the 10 percent law). The rest is lost in respiration, heat, and undigested waste. So secondary productivity is always much smaller than primary productivity in the same ecosystem.
NCERT (Chapter Ecosystem) says: primary productivity is the amount of biomass or organic matter produced per unit area over a time period by plants during photosynthesis. Secondary productivity is defined as the rate of formation of new organic matter by consumers. Memorise these two lines word for word, because NEET asks them directly in match-the-column and statement questions.
Given below are two statements: Statement I: The primary source of energy in an ecosystem is solar energy. Statement II: The rate of production of organic matter during photosynthesis in an ecosystem is called net primary productivity (NPP). In the light of the above statements, choose the most appropriate answer:
Match List I with List II: List I: A. Productivity, B. Net primary productivity, C. Gross primary productivity, D. Secondary productivity List II: I. Gross primary productivity minus respiration losses, II. Rate of formation of new organic matter by consumers, III. Rate of biomass production, IV. Rate of production of organic matter during photosynthesis Choose the correct answer:
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Primary productivity is organic matter made by producers (plants) using photosynthesis. Secondary productivity is new organic matter formed by consumers (animals) from the food they eat. Producers vs consumers is the key difference.
Yes. Because only about 10 percent of energy passes to the next trophic level (10 percent law), the organic matter built by consumers is always much less than that made by producers in the same ecosystem.
The clear GPP and NPP split is used for primary productivity (plants). For consumers, NCERT simply defines secondary productivity as the rate of formation of new organic matter by consumers, without a separate GPP/NPP division.
Same as primary productivity, because both are rates: g m-2 yr-1 or (kcal m-2) yr-1. The per-year (time) part is what makes it a productivity and not just biomass.
For NEET, secondary productivity is defined for consumers. Decomposers break down dead matter and are usually discussed under decomposition, not secondary productivity. Stick to the NCERT wording: consumers form new organic matter.
