Chapter 2, Problem 25A

Summary Introduction

To determine:

The error in the given sentence.

Introduction:

The position an organism occupies in a food web is its trophic level. A food chain is series of organism, where an organism eats upcoming organism, and it is also eaten by the other organism as well. A trophic level determines the position of an organism in the food chain from the starting.

Explanation of Solution

The trophic level starts from the autotrophs. Autotrophs are the plants that make their own food by the help of photosynthesis. If an organism eats a plant from the first trophic level, then only 10% of plant’s energy is passed on to the organism. The remaining energy is lost in the environment.

If there are three trophic levels, 1000 calories are produced by the autotrophs in the first trophic level. Now, if primary consumers (second trophic level) consume autotrophs, then only 10%, 100 calories are consumed by primary consumers. Further, secondary consumers (third trophic level) consume the primary consumers. Here also 10% energy, that is, 10 calories is passed on to the third trophic level.

During transfer of energy from first trophic level to second trophic level, around 900 calories are lost. When the energy is transferred from second trophic level to third trophic level, 90 calories are lost. So, the total energy lost is 990 calories.