Chapter 2, Problem 24A

Summary Introduction

To explain:

Why food webs are better models for explaining energy flow than food chains.

Introduction : Organisms interact with each other in different ways within an ecosystem. They differ in how they derive their energy and so they are classified as autotrophs or heterotrophs based on how they obtain their food in an ecosystem. Food chains and food webs help us in studying the flow of energy from one organism to another.

Answer to Problem 24A

Food webs are better models for explaining energy flow than food chains because they are more complex and show energy flow in more communities or ecosystems.

Explanation of Solution

Food chain- Ecologists use food chain to show the flow of energy through an ecosystem. In a food chain, the first trophic level is that of autotroph, followed by heterotrophs. For example, in a grassland type of food chain, grasses are autotrophs. The grasshopper forms second trophic level as it is dependent on grass for food. This is followed by a fox or a mouse as a carnivore.

Food web- Feeding relationships are more complex than a single food chain because most organisms feed on more than one species. So a food web is a most preferred model to study the flow of energy. A food web is a model consisting of many interconnecting food chains and pathways showing flow of energy through a group of organisms. Food web is far more complex than a food chain. Example: