1. Energy & Living Systems Agricultural Biology Mrs. Sperling

2. Almost all energy in living systems comes from the sun Plants, algae, and certain bacteria absorb sunlight Photosynthesis:The process of converting light energy (from the sun) to chemical energy (sugar)

3. Autotrophs vs. Heterotrophs Autotrophs:Organisms that use energy from sunlight Most are photosynthetic Heterotrophs:Organisms that get their energy from food (rather than directly from sunlight) Humans and other animals Get energy from cellular respiration

4. Cellular Respiration A metabolic process similar to burning fuel This process releases much of the energy in food to make ATP ATP: the main energy source of cells

5. How do we get energy from eating food? 1) Food is eaten. 2) Digestion begins. 3) Chemical energy is released gradually by enzyme-assisted reactions. 4) Some energy is released as heat. 5) The remaining energy is stored in ATP molecules. 6) ATP delivers energy within the cell (to power chemical reactions).

6. Energy Flow in an Ecosystem