Energy

Animals use the chemical energy in food to sustain form and function • All organisms require chemical energy for growth, repair, physiological processes, regulation, and reproduction

Bioenergetics • Bioenergetics, the flow of energy through an animal, limits behavior, growth, and reproduction • It determines how much food an animal needs • Studying bioenergetics tells us much about an animal’s adaptations

Energy Sources and Allocation • Animals harvest chemical energy from food • Energy-containing molecules from food are usually used to make ATP, which powers cellular work • After the needs of staying alive are met, remaining food molecules can be used in biosynthesis

Quantifying Energy Use • Metabolic rate is the amount of energy an animal uses in a unit of time • One way to measure it is to determine the amount of oxygen consumed or carbon dioxide produced

Bioenergetic Strategies • An animal’s metabolic rate is closely related to its bioenergetic strategy • Birds and mammals are mainly endothermic: Their bodies are warmed mostly by heat generated by metabolism • Endotherms typically have higher metabolic rates • Amphibians and reptiles other than birds are ectothermic: They gain their heat mostly from external sources • Ectotherms generally have lower metabolic rates

Influences on Metabolic Rate • Metabolic rates are affected by many factors besides whether an animal is an endotherm or ectotherm • Two of these factors are size and activity

Size and Metabolic Rate • Metabolic rate per gram is inversely related to body size among similar animals • Researchers continue to search for the causes of this relationship

Activity and Metabolic Rate • The basal metabolic rate (BMR) is the metabolic rate of an endotherm at rest • The standard metabolic rate (SMR) is the metabolic rate of an ectotherm at rest • Activity greatly affects metabolic rate • In general, maximum metabolic rate is inversely related to the duration of the activity

Energy Budgets • Different species use energy and materials in food in different ways, depending on their environment • Use of energy is partitioned to BMR (or SMR), activity, homeostasis, growth, and reproduction