Food Chains & Energy Flow

1. Food Chains & Energy Flow

2. Food Chains • Food chain: sequence of organisms, showing how energy and nutrients move from one to another

4. Food Chains • Which are more numerous in an ecosystem: producers or consumers? • Producers are always more numerous than consumers, why?

5. Energy Loss • Of the energy that an organism consumes, only a small fraction (ecological efficiency of about 10%) is transferred to the next trophic level

7. Where does that energy go? • Most of the energy is lost as heat That’s hot.

8. House Analogy • Just like how much of the energy used to heat a house is wasted, much of the energy used by organisms is wasted

9. Efficiency Example • Cars are only about 25% efficient • Only 25% of the total energy in gasoline is used to make cars move • What happens to the other 75%???

10. Energy Efficiency • Why is it more energy efficient to eat grains directly, rather than the meat of grain-eating animals? 15 lbs. of feed 1 lb. of beef

11. Energy Efficiency • Why is it more energy efficient to eat grains directly, rather than the meat of grain-eating animals? 6 lbs. of feed 1 lb. of pork

12. Energy Efficiency • Why is it more energy efficient to eat grains directly, rather than the meat of grain-eating animals? 5 lbs. of feed 1 lb. of chicken

13. Energy Efficiency • Why is it more energy efficient to eat grains directly, rather than the meat of grain-eating animals? 2 lbs. of feed 1 lb. of fish

14. Summary Question • Why do food chains rarely have more than 4 or 5 trophic levels?