Energy in a Community

1. Energy in a Community

2. Food Chain : who eats who? • Food Web : all the food chains in an ecosystem • Energy/biomass Pyramid : shows energy/mass of each trophic level

3. Trophic levels • Producer – plants, etc. • Primary consumer – eats producer • secondary consumer – eats primary consumer • Tertiary consumer – eats secondary consumer • Quaternary consumer – eats tertiary consumer • And so on

4. Energy/biomass Pyramid Trophic levels – where does an organism get its nourishment? makes own food? Feeds on plants? Feeds on animals?

5. Food Chains and the Food Web What trophic level is the lion at? It depends on which food chain you follow.

6. ENERGY AND NUTRIENT DIFFERENCES • There is a ONE-WAY FLOW of energy initiating from the sun • Energy is what allows an organism to move, grow, etc. • There is CYCLING of nutrients (the biogeochemical cycles) • nutrients are the chemicals necessary to move, grow, etc.

7. Autotrophs (producers) • are able to use the energy of the sun to make glucose. • Plants, algae, and a few other organisms like euglena • All have chloroplasts • Cool fact: euglena is one of only a few organisms that are both producers AND consumers! They have a flagellum to swim and an eyespot to move toward light for better photosynthesis. But they can also EAT other small microorganisms too!

8. photosynthesis 6 CO2 + 6 H2O  6 O2 + C6H12O6 ONLY when light hits the chloroplasts (green parts of cells) Endothermic reaction (net energy input) Only about 1% of all sunlight that hits the chloroplasts is captured by photosynthesis. The rest gets reflected back into space (albedo) Why do producers do photosynthesis? Who are they making sugar for? THEMSELVES! They need the food for their OWN respiration!

9. Cellular Respiration • ALL organisms undergo the process of cellular respiration (yes, even plants!) to produce energy the cell can use to grow, repair itself and conduct cellular reactions • 6 O2 + C6H12O6  6 CO2 + 6 H2O • Exothermic reaction Same reaction as COMBUSTION • Only difference between respiration and burning is that respiration goes through about 10 steps so the heat is given off GRADUALLY rather than all at once (SAME TOTAL AMOUNT OF HEAT) • “cold blooded” animals, plants, and other organisms that are not “warm” still give off heat! They just don’t respire as quickly as we do so they don’t produce nearly as much heat.

10. GPP Gross Primary Productivity (GPP): the rate at which producers in an ecosystem convert solar energy into chemical energy (glucose). Units= kJ/m2/yr GPP basically measures how much photosynthesis takes place Can also be measured in terms of biomass (increase in mass due to carbon) accumulated by producers. Units = gC/m2/yr In your groups, answer the following question: Where is GPP highest and lowest in the US? Why? http://www.earthobservatory.nasa.gov/IOTD/view.php?id=636

11. NPP Net Primary Productivity (NPP): the measure of GPP minus the energy these producers use via aerobic respiration Can also be measured via biomass. For respiration you just subtract off the mass lost as CO2 NPP is basically the amount of plant growth and respiration (metabolism) NPP = GPP – R (respiration) What patterns in productivity do you notice over time? How does this relate to climate? Biomes? http://www.earthobservatory.nasa.gov/GlobalMaps/view.php?d1=MOD17A2_M_PSN

12. What is the role of the oceans? • Phytoplankton and algae are responsible for a HUGE portion of the world’s productivity • Answer these questions with your group: • What patterns in productivity do you notice? • How does this relate to CO2 in the atmosphere? • http://www.earthobservatory.nasa.gov/GlobalMaps/view.php?d1=MY1DMM_CHLORA

13. Productivity • Climate affects productivity in terrestrial biomes • NPP can be negative! What does this mean? Where and when does this occur? • Most productivity in the oceans is at the POLES and a few other locations. • This has to do with nutrients concentration, ocean currents, upwellings, etc. More on this in our oceans unit. • Productivity varies with season. What is the implication for atmospheric carbon dioxide levels?

14. Cyclical red line is due to seasonal productivity variation

15. Heterotrophs • Must eat/consume another organism to attain energy so are also called consumers. • Herbivores = first order (primary) consumer • Carnivores/omnivores/insectivores = higher level consumer (secondary, tertiary, quaternary) • Also includes detritivores: • Decomposers • scavengers

16. Detritivores • Detritus is dead tissues and organisms (fallen leaves, feces, carrion, etc.) • Examples: dung beetles, hyenas, worms, etc. • Detritivores are heterotrophs that break down detritus into smaller particles

17. Decomposers • What are examples of decomposers? • What is the niche of the decomposer in the community? • Where do decomposers fit in the energy pyramid? Fungi, lichen, bacteria, etc. They break down dead organisms and return the nutrients to the ecosystem Off to the side! They feed on ALL trophic levels!

18. Decomposers Decomposers are able to break down dead organisms (using enzymes within their cells) and return the nutrients to the soil. So, where do you think most decomposers are found?

19. Scavengers • What is the niche of the scavenger in the community? • What are examples of scavengers in our community? They feed on carrion (animal carcasses) and help break down LARGE food particles (their feces can then be fed on by decomposers). Scavenging is NOT predation! It is eating already dead organisms! Crows, coyotes, etc. Note that MOST scavengers will often act as predators or eat a varied food source since very few organisms can survive by finding pre-killed meals.

20. 10% Rule Only a “rule of thumb” Approximately 10% of energy in one trophic level can be passed on to a higher level by consumption (eating) can be as low as 5% or up to 20% Global average: about 10% Known as “ecological efficiency”

21. Where does the rest of the energy go? 1ST LAW OF THERMODYNAMICS! (CONSERVATION OF ENERGY) The energy is: • stored internally as biomass (in chemical bonds in molecules of the cells) • Lost as heat (why? 2nd Law of thermodynamics!) • Lost as Work – moving, eating/chewing, digesting the food, incorporating the food into new cells, etc.  ultimately heat • Lost in waste mass (carbon dioxide, urine, feces, etc. have internal energy stored in their molecules)

22. Putting it all together…