Ch 5

1. Ch 5 How Ecosystems work

2. Energy in Ecosystems • What is the source of energy for most ecosystems? • The sun! • What kingdom of organisms use this energy first ON LAND? • Plants • What kingdom of organisms use this energy first IN WATER? • Protists: Algae • Phytoplankton: small, mostly microscopic, photosynthesizing algae that drift in the lighted part of aquatic ecosystems • Phyto = plant or plant-like • Plankton = remainder of above definition

3. Energy Flow in Ecosystems • What is the process plants and phytoplankton use to produce their own food, using energy from the sun? • Photosynthesis • What “food” does photosynthesis produce? • Glucose, a simple sugar, C6H12O6 • What gas do plants use for photosynthesis? • Carbon dioxide (CO2)

4. Energy Flow in Ecosystems • What else do autotrophs need for photosynthesis? • water • What gas is released as a waste product of photosynthesis? • Oxygen (O2) • So, putting it all together, photosynthesis • CO2 + H2O  O2 + C6H12O6 • Balancing the reaction, we get • 6CO2 + 6H2O  6O2 + C6H12O6 • What powers this reaction? • The sun!

5. Energy Flow in Ecosystems • What do we call organisms that make their own food? • Autotrophs • Another term? • Producers • These make up the base of the food chain for all other organisms in an ecosystem

6. Energy Flow in Ecosystems • What types of organisms are most of the producers on land? • Plants • What types of organisms are most of the producers in water? • Phytoplankton

7. Energy Flow in Ecosystems • Why do we say the sun powers most (not all) of the ecosystems on earth? • Deep ocean vent communities have autotrophic archaebacteria that use energy from hydrogen sulfide.

8. Energy Flow in Ecosystems • So… producers form the basis of energy of all ecosytems • Energy is transferred through ____________ • Eating/consumption • What types of organisms do the consuming? • Consumers! – duh!, or heterotrophs • What had to come first?The autotrophs or heterotrophs? • Autotrophs, because heterotrophs had to have something to eat!

9. Energy Flow in Ecosystems • What process do consumers use to break down the sugars in plants and release the stored sun energy from them? • Cellular respiration • 6O2 + C6H12O6  6CO2 + 6H2O • The exact opposite of photosynthesis

10. Energy Flow in Ecosystems • Every time a consumer consumes, it gets only 10% of the original energy of the organism it consumed • So, _________ % is lost with each step along the way • Producers get 100% of the sun’s energy • The organisms that eat producers, ____, get only 10% of that sun’s energy • Herbivores, 1st level consumers, primary consumers • What do we call human herbivores? • Vegetarians

11. Energy Flow in Ecosystems • Organisms that eat the primary consumers are called • Secondary consumers • Another ___ % of the sun’s energy is lost in the transaction • So, secondary consumers only get ____ % of the original sun’s energy • 1 %  (that’s us, when we eat beef, chicken or pork)

12. Energy Flow in Ecosystems • Some secondary consumers can also be primary consumers. How? • They eat plants and animals; i.e. steak and salad • Organisms that eat both plants and animals are called • Omnivores

13. Energy Flow in Ecosystems • At the top of the food chain are organisms that consume only other consumers • These are called • Carnivores • Top carnivores are usually few and far between in an ecosystem because there isn’t enough of the sun’s energy left to go around at that level • Third level, or _______ consumers, get only ___% • .1%   of the sun’s energy that went to the producers in the ecosystem • Most ecosystems cannot support more than 4 or 5 trophic levels • Organisms that feed on organisms at the top level are usually small and need small amounts of energy, like • Decomposers, or parasites like fleas

14. Energy Flow in Ecosystems • So…, the more producers in an ecosystem, the more of the sun’s energy can be absorbed • And the more ___ can be supported by the producer level • consumers • All food chains start with ___ • producers

15. Energy Pyramid What’s missing in this picture?

16. Energy Flow in Ecosystems Each level of consumerism is called a TROPHIC LEVEL

17. Food chain vs. food web • Food chains show one path of energy from the sun to the last consumer (decomposer) • Food webs show the many interconnected paths of energy through an ecosystem • The arrows represent ____________________ • Energy transfer from one organism to the next