Trophic level

NCERT numbers the steps of a food chain like this:

• First level: producers, the green plants.
• Second level: herbivores, the primary consumers.
• Third level: small carnivores, the secondary consumers.
• Fourth level: larger carnivores, the tertiary consumers.

Green plants capture about 1% of the sunlight that falls on their leaves. After that, an average of 10% of the food eaten at one level reaches the next. Much of the rest is lost as heat. This is why food chains generally have only three or four steps.

A small example

Start with 10,000 kJ at the producers. With 10% passed on each time, herbivores get 1,000 kJ. Secondary consumers get 100 kJ. The fourth level gets just 10 kJ.

Where marks go

CBSE's 2026-27 Science sample paper tests this three times. The board's Science marking scheme for 2026-27 gives these answers:

• Question 7: a fish eats insect larvae, which eat algae. The fish is a secondary consumer.
• Question 9: the assertion says 1% of energy passes between levels. It is false, and the reason, 10%, is true.
• Question 14: 10 kJ at the fourth level means 10,000 kJ at the producers.

Question 9 mixes the 1% and the 10%. Keep them apart: 1% is sunlight into plants, and 10% is from one level to the next. More on the assertion-reason format.

About the author

Deepti Sardana

Founder Member & Academic Lead

An IIT alumna (M.Sc., M.Phil.) with over 25 years in teaching, child psychology and learning assessment. As Academic Lead at EduBrahma, she leads the method TRUtesting uses to find where and why a child loses marks.

Deepti Sardana on LinkedIn