Ecosystems

1. Ecosystems 18.3 Energy Transfer

2. Sun: ultimate source of energy • Photosynthetic organisms convert solar energy into energy-rich organic compounds. • They then use the organic compounds as fuel for their metabolic processes and some is stored. • The energy moves through the ecosystem as one organism consumes another for food. • The flow of energy is one way: Sun photosynthetic organisms other organisms

3. The Autotroph • Usually a photosynthetic organism • 6CO2 + 6H2O C6H12O6 + 6O2 • Also referred to as producers because they make food that is used by the entire community. • Example: Algae which are phytoplankton and plants. • Some autotrophs are chemosynthetic - use inorganic compounds as an energy source (sulfur compounds, ammonia) • Chemosynthetic producers can be found in deep sea communities and other extreme environments.

4. The Autotroph • Biomass - the organic material added by producers in an ecosystem. • Gross Primary Productivity (GPP) =Total amount of light energy converted to chemical energy in organic material • Net Primary Productivity (NPP) = GPP minus the energy used by organisms for cellular respiration (GPP – CR) • C6H12O6 + 6O2 6CO2+ 6H20 + energy

5. The Heterotroph • An organism that cannot make its own food. • Obtains energy and nutrients by consuming other organisms. • Also referred to as the consumers of an ecosystem. • Herbivores, Carnivores and Omnivores or…. • Lions and Tigers and Bears, oh my!

6. The Heterotroph • Detritivores- obtain energy from dead and decaying organisms. • Scavengers - vultures and hyena • Decomposers - bacteria and fungi

7. Food Chains • The pathway for the transfer of energy within an ecosystem from one trophic level to the next. • Trophic level - the position in the sequence of energy transfers. • Each organism provides food for the next higher level.

8. Example of a Food Chain • Meadow Ecosystem • Sunflower (producer) • Caterpillar eats sunflower leaves (consumer) • Blackbird eats the caterpillar (consumer) • Fox eats the blackbird (consumer) • Bacteria and fungi consume the remains of any dead organisms (decomposers)

9. Food Chain Only some of the energy and matter is transferred each time one organism consumes another. At every step in the food chain, part of the energy is lost to metabolism and as heat to the environment. Because of this energy loss, food chains generally support no more than 4 links.

10. Trophic Levels Each step in the transfer of energy and matter in an ecosystem. 1. Producers: the autotrophs, the source of organic molecules. 2. Primary consumers: feed directly on producers. Herbivores are primary consumers that eat plants.

11. Trophic Levels 3. Secondary consumers: feed directly on primary consumers. Carnivores only eat meat. 4. Tertiary consumers: feed on secondary consumers.

12. Transfer of Energy Decomposer Tertiary Consumer Secondary Consumer Primary Consumer Producer

13. Food Web Most organisms in an ecosystem eat more than one kind of food.

14. Types of Consumers • Omnivore: eat both producers and other consumers. • May be primary, secondary or tertiary because they feed on all levels • Scavenger: a consumer that feeds on the tissues of dead animals. • vultures, crows, ants, etc.

15. Types of Consumers • Decomposers: bacteria or fungi that feed on wastes and dead organic matter from all trophic levels. • Break down complex organic compounds into simpler nutrients. • Nutrients are returned to soil or water where producers reuse them. • Recycling nutrients is critically to all trophic levels.

16. Energy Flow • The transfer of energy from one trophic level to the next is not very efficient. • Only a fraction of the energy (about 10-20%) moves from one trophic level to the next. • Known as the10% Rule

17. 3 Reasons for Energy Loss • 1. Much of the energy consumed is used for metabolism and life processes. • 2. Many of the organisms are not consumed by the organisms at the next trophic level. • 3. Some of the energy at each trophic level is in materials that consumers at the next level are not likely to eat. • Ex: wood, bones, teeth, beaks, and shells

18. Ecological Pyramid • Shows the relationships between trophic levels in an ecosystem • Producers and Consumers • Energy Flow • Biomass - the massof organic material in a trophic level • Numbers

19. Ecological Pyramid • In most ecological pyramids, fewer organisms occupy each higher trophic level • Meadow covered by grasses and plants • Meadow has many primary consumers such as mice and insects • Less secondary consumers such as snakes, robins etc. • Even less amount of tertiary consumers such as hawks and tigers

20. Ecological Pyramid Energy Flow

21. A Few Facts • The number of organisms at each trophic level is proportional to the amount of biomass and energy available at the level below it. • Resources at lowest level determine how much life the environment can support. • What is the primary resource? • The more biomass and energy the producers supply, the more the environment can handle.

22. Harmful Substances May Move Through a Food Web • The pesticide DDT was used to kill insects that damaged crops. • Went into the soil and ran off into rivers and lakes. • Contaminated planktonic organisms. • Transferred to fish and then to bigger fish in even higher concentrations. • biological magnification: buildup of a pollutant in organisms at higher trophic levels of food chains. • Bald eagles ate the large contaminated fish.

23. Harmful Substances May Move Through a Food Web DDT was now in bird tissues at levels ten million times the original concentration of DDT in the water. Interfered with the formation of eggs shells making them soft. Eggs broke easily and embryos inside did not survive. Eagle population declined. DDT banned in the United States.

24. The End