18-3 Energy Transfer

1. 18-3 Energy Transfer Energy • Why do organisms need energy? • Maintain HOMEOSTASIS, growth, reproduction, etc. • How does energy affect an ecosystem? • Determines how many and what kind of organisms live in an ecosystem.

2. Energy Flow: • The sun is the ultimate source of energy • The PRODUCERSuse this energy to make “food” energy for themselves and for the CONSUMERS

3. Trophic Levels • The organism’s position in the sequence of energy transfers. • A.K.A. Trophic Level is a group of organisms whose feeding source is the same number of steps from the Sun.

4. Common Trophic Levels: • First = Producers (Autotrophs) • LARGEST • Second = Herbivores (Heterotrophs, Consumers) • Third and above = All other consumers (Heterotrophs, Omnivores, Carnivores, Decomposers) • SMALLEST

5. Omnivores (Humans) • Eat Plants & Animals • Detritivores (Scavengers) • Feed On Dead Plant & Animal Remains (buzzards) • Decomposers • Fungi & Bacteria

6. Consumers Heterotrophs eat other organisms to obtain energy. (e.g. animals) • Herbivores • Eat Only Plants • Carnivores • Eat Only Other Animals

7. Energy Gain by Trophic Levels: • At each trophic level, the energy stored in an organism is about 1/10 that of the level below it  (10%).

9. Implications on the ecosystem: • Because energy diminishes at each successive trophic level, few ecosystems can contain more than 4 or 5 trophic levels. • Organisms at higher levels (large carnivores) tend to be fewer in number than those at lower levels (producers).

10. Food Chain • A single pathway of feeding (and energy transfer) relationships among organisms in an ecosystem.

11. Ex) Food chain

12. Food Web • A diagram of the interrelated food chains in an ecosystem. • More accurate description of the ecosystem.

13. Can you now answer these questions? • Contrast between producers and consumers. • Explain the important role of decomposers in an ecosystem. • Contrast a food chain with a food web. • Explain why an ecosystem usually contains only a few trophic levels.

14. Energy flows through an ecosystem and nutrients cycle in an ecosystem. Ecosystem Recycling (18.4)

15. Water Cycle Steps: • EVAPORATION from lakes, rivers, and oceans.  • TRANSPIRATION from plants and trees. • CONDENSATION – Cloud Formation • PRECIPITATION – Rain, Snow, Sleet, Hail. • RUN OFF, or RETURNED back into the Cycle. • GROUNDWATER- water in soil or in underground formations of porous rock.

16. The Water Cycle

17. The Carbon Cycle • Cellular Respiration • Photosynthesis • Combustion • Death and decomposition

18. Human Influences • Atmospheric CO2 has risen more than 30% in the past 150 years. • Burning of fossil fuels- coal, oil, and natural gas • Burning down the tropical rain forest

19. The Nitrogen Cycle Nitrogen Fixation: the process of converting atmospheric nitrogen (N2) into nitrate, its useable form.

20. Key Terms Nitrogen-fixing bacteria: turn nitrogen gas into nitrates. Located in soil and the roots of some plants. Ammonification: bacteria decompose dead matter and release the nitrogen they contain as ammonia Denitrification: bacteria break down nitrates and return nitrogen to the atmosphere So… How do plants and animals get nitrogen?

21. Phosphorous Cycle • obtained by plants from water and soil, and animals from the food they eat • used to form bones, teeth, and molecules such as DNA and RNA • Source: erosion of rocks into the soil or water, decomposition of organisms, and fertilizers