1. Fifth lecture

2. Energy Flow Energy flows through ecosystems, while matter cycles within them. Resources critical to human survival and welfare, ranging from the food we eat to the oxygen we breathe, are products of ecosystem processes.

3. Energy Flow Energy in ecosystems follows the rules of thermodynamics –Ecosystems are open systems where energy is transformed, and is ultimately released as heat from organisms. –Heat lost from organisms is disordered, unusable energy and therefore has increased entropy of the system. –Energy transfers between organisms are not completely efficient –Without energy input (sun) ecosystems collapse

4. Photosynthesis Is the process that captures light energy and transforms into the chemical energy of carbohydrates –Energy stored in chemical bonds Occurs in: –Plants –Algae –Certain Bacteria

5. –1. Pigments capture energy from sunlight –Water is split, O 2 released –2. Using energy to make ATP and NADPH –3. Using ATP and NADPH to power the synthesis of carbohydrates from CO 2 Light-dependent reactions Light-independent reactions The Calvin cycle 6 CO 2 carbon dioxide + 12 H 2 O water + Light energy C 6 H 12 O 6 glucose + 6 O 2 oxygen + 6 H 2 O water

6. Building New Molecules Light-dependent reactions provide the raw material –Conversion of light energy into immediate source of chemical energy ATP NADPH Light independent reactions: –Energy stored during light reactions used to drive the Calvin Cycle (C 3 photosynthesis) –assembles the new molecules –It takes place in the stroma of the chloroplast

7. Chemiosmosis in a chloroplast Thylakoid space Photosystem IIATP synthase Electron transport system Photon H2OH2O ½O2½O2 e–e– H+H+ 2 H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ ADPATP Membrane is impermeable to protons

9. Primary productivity Gross Primary Productivity (GPP): –total amount of photosynthetic energy captured in a given period of time. Net Primary Productivity (NPP): –the amount of plant biomass (energy) after cell respiration has occurred in plant tissues. NPP = GPP – Plant respiration plant growth/ total photosynthesis/ unit area/ unit area/unit time unit time

10. Secondary Productivity Secondary productivity: the rate at which consumers convert the chemical energy of the food they eat into their own new biomass

11. The Laws of Thermodynamics A set of universal laws governing all energy changes in the universe The First Law thermodynamics: “Energy cannot be created or destroyed it can only change forms”. –During each conversion, some energy is lost into the environment as heat energy.

12. The second Law of Thermodynamics : “as energy changes form it becomes more disorganized. i.e., ENTROPY increases”

13. Biomass The total mass of the organic matter at each trophic level is called biomass. Biomass is just another term for potential energy (energy that is to be eaten and used). The transfer of energy from one level to another is very inefficient (10% Law).

14. Ecological Pyramid An ecological pyramid shows the relationship between consumers and producers at different trophic levels in an ecosystem. It shows the relative amounts of energy or matter contained at each trophic level. It shows which level has the most energy and the highest number of organisms.

15. Pyramid of number Fairly large animals

16. Pyramid of energy

17. Pyramid of biomass Found in larger numbers, but still contain 90% less energy Inverted pyramid

18. Exceptions to the rule? Carnivorous plants capture and digest animal prey They are able to grow without animal prey. ~600 sp. of carnivorous plants have been described