Fifth lecture. Energy Flow Energy flows through ecosystems, while matter cycles within them....
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Transcript of Fifth lecture. Energy Flow Energy flows through ecosystems, while matter cycles within them....
![Page 1: Fifth lecture. Energy Flow Energy flows through ecosystems, while matter cycles within them. Resources critical to human survival and welfare, ranging.](https://reader036.fdocuments.in/reader036/viewer/2022062518/56649f275503460f94c3f259/html5/thumbnails/1.jpg)
Fifth lecture
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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.
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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
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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
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– 1. Pigments capture energy from sunlight
– Water is split, O2 released
– 2. Using energy to make ATP and NADPH
– 3. Using ATP and NADPH to power the synthesis of carbohydrates from CO2
Light-dependent reactions
Light-independent reactions
The Calvin cycle
6 CO2
carbondioxide
+ 12 H2Owater
+ Light energy C6H12O6
glucose
+ 6 O2
oxygen
+ 6 H2Owater
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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 (C3 photosynthesis)
– assembles the new molecules– It takes place in the stroma of the chloroplast
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Chemiosmosis in a chloroplast
Thylakoidspace
Photosystem II ATP synthaseElectron transport system
Photon
H2O
½O2
e–
H+2
H+
H+
H+
H+
H+
H+
H+
ADP ATPMembrane is impermeable
to protons
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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 respirationplant growth/ total photosynthesis/ unit area/ unit area/unit timeunit time
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Secondary Productivity
• Secondary productivity: the rate at which consumers convert the chemical energy of the food they eat into their own new biomass
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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.
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The second Law of Thermodynamics:
“as energy changes form it becomes more disorganized. i.e., ENTROPY increases”
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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).
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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.
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Pyramid of number
Fairly large animals
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Pyramid of energy
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Pyramid of biomass
Found in larger numbers, but still contain 90% less energy
Inverted pyramid
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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