2. The Energy of Life Energy is the ability to do work.

3. Biological work that requires energy l Growing l Moving l Reproducing l Maintaining and repairing damaged tissues

4. Forms of Energy l Energy exists in different forms: l Chemical l Radiant l Mechanical l Heat l Electrical l Nuclear

5. Potential Energy l Energy can exist as stored energy called potential energy.

6. Potential energy is stored in the drawn bow

7. Kinetic Energy l The energy of motion.

8. Potential energy is converted to kinetic energy as the arrow speeds toward its target

9. Thermodynamics l The study of energy and its transformation.

10. The First Law of Thermodynamics l Energy can not be created or destroyed, although it can be transformed from one form to another. l As far as we know, the energy present in the universe at its formation (18 billion years ago), equals the amount of energy present in the universe today.

11. True/false? l Organisms cannot create the energy that they require to live. l True

12. The Second Law of Thermodynamics l As each energy transformation occurs, some of the energy is changed to heat energy that can never again be used by any organism for biological work. l Heat still exists in the surrounding environment.

13. During energy transformation l Some usable energy (energy available to do work) is degraded into a less usable form, heat that disperses into the environment. l Energy flows: Solar Chemical Heat

14. Conclusion l The amount of usable energy available to do work in the universe decreases over time. l The total amount of energy in the universe is not decreasing with time.

15. Entropy l Less-usable energy is disorganized. l Entropy is the measure of this disorder. l Usable energy has low entropy. l Disorganized energy such as heat has high entropy. l Entropy is continuously increasing in the universe in all natural processes.

16. Entropy can be represented by beakers filled with marbles of two different colors

18. Highly organized system (Low entropy)

19. Disorganized system (with greater entropy)

20. It may be l that at some time, billions of years from now, all energy will exist as heat uniformly distributed throughout the universe. l If that happens, the universe will cease to operate because no work will be possible.