Introduction

class="introduction"

class="summary" title="Sections Summary"

class="art-exercise" title="Art Connections"

class="multiple-choice" title="Multiple Choice"

class="free-response" title="Free Response"

The image shows a map of the world, colored by the levels of chlorophyll a on land and in the ocean.

The processes in all organisms—from bacteria to humans—require energy. To get this energy, many organisms access stored energy by eating, that is, by ingesting other organisms. But where does the stored energy in food originate? All of this energy can be traced back to photosynthesis.

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