Topic 4.2 Energy Flow

1. Topic 4.2 Energy Flow

2. QOD • Why did the hippy girl say that all humans should be vegetarians?

3. Energy in Ecosystems • Initial source of energy is the sun (in most ecosystems) = photosynthesis • Deep ocean trenches rely on chemosynthesis

4. Energy in Food Chains • Chemical energy in carbon compounds flow through food chains by means of feeding • Food chains show direct flow of energy from one feeding level to the next • Each feeding level is called a trophic level • Arrows drawn in food webs represent the direction of energy transfer • Most of the energy consumed is lost

5. Food Chain • 10% if ingested food is converted to new organic molecules • 3-5 organisms in each food chain

6. Food Webs • Collection of food chains • Many organisms feed on a variety of things • Complex feeding interactions

7. Trophic Levels • A feeding level in a food chain or food web • Represent organism’s position in the food chain/web • Trophic levels include the following: • Producers (autotrophs) • Primary consumers (herbivores) • Secondary consumers (omnivores or carnivores) • Tertiary consumers (omnivores or carnivores)

8. What eats what • Herbivores – eat only plants • Omnivores – eat both plants and meat • Carnivores – eat meat

9. Pyramid of energy

10. Biomass • The total mass of a group of organisms • Biomass decreases at each trophic level • Reasons for this trend • Most of the energy in food that is digested and absorbed by organisms in a trophic level is released by them in respiration for use in cell activities. So only chemical energy is available at the next level • Organisms in trophic levels are not usually entirely consumed • Not all parts of food ingested by organisms are digested and absorbed • Biomass diminishes due to loss of CO2, H20, and other waste products(urea)

11. Respiration & Energy Release • Energy released by respiration is used in living organisms and converted to heat • Living organisms need energy for the following • Synthesizing large molecules like DNA, RNA and proteins • Pumping molecules or ions across membranes by active transport • Moving things inside the cell, or muscles ATP supplies energy for these activities

12. ATP production • ATP produced by cellular respiration • Carbon compounds are oxidized • This is exothermic and energy is released, this is used in endothermic reactions to make ATP • Cell respiration transfers chemical energy from glucose to ATP

13. 2nd law of Thermodynamics Energy transformations are never 100% efficient Not all is transferred to ATP the rest becomes heat.

14. Heat Energy in Ecosystems • Living organisms cannot convert heat to other forms of energy • Perform various energy conversions • Light energy to chemical energy in photosynthesis • Chemical energy to kinetic energy in muscle contractions • Chemical energy to electrical energy in nerve cells • Chemical energy to heat energy in heat-generating adipose tissue

15. Heat losses from Ecosystems • Heat passes from hotter to cooler bodies • Heat produced in living things is all eventually lost to the abiotic environment • Heat may remain for a while but will ultimately be lost