This document defines key terms related to food chains and cycles of life. It explains that a cycle of life includes birth, growth, reproduction, and death for living things. Photosynthesis is defined as the process by which plants use sunlight, water and carbon dioxide to produce food. Food chains represent the transfer of nutrients between organisms, with plants as producers, herbivores as primary consumers, and carnivores as secondary consumers or predators of prey. The environment and adaptations help animals survive, and animals have evolved variations over years through the process described by Charles Darwin's theory of evolution.