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