Topic 4.2 Energy Flow

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Topic 4.2 Energy Flow
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QOD

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

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Energy in Ecosystems

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

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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

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Food Chain

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

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Food Webs

• Collection of food chains
• Many organisms feed on a variety of things
• Complex feeding interactions

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Trophic Levels

• A feeding level in a food chain or food web
• Represent organisms 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)

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What eats what

• Herbivores eat only plants
• Omnivores eat both plants and meat
• Carnivores eat meat

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Pyramid of energy
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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)

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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

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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

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2nd law of Thermodynamics

• Energy transformations are never 100 efficient
• Not all is transferred to ATP the rest becomes
  heat.

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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

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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