ENERGY FLOW WITHIN AN ECOSYSTEM
AND
ECOLOGICAL PYRAMIDS
ENERGY FLOW WITHIN AN ECOSYSTEM
Food represents:
•
•
building materials for body parts
energy for life functions
1st Law of Thermodynamics:
•
energy cannot be created or destroyed, just changed
from one form to another
o
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ex. food (chemical energy) is used to transmit
messages (electrical energy) from the brain to body
ENERGY FLOW WITHIN AN ECOSYSTEM
2nd Law of Thermodynamics:
•
energy transfers are never 100% efficient; there is
always a loss of energy in the form of heat
HEAT LOSS
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ENERGY FLOW WITHIN AN ECOSYSTEM
Energy Flow:
• producers only capture 1% of available solar energy
1%
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ENERGY FLOW WITHIN AN ECOSYSTEM
Energy Flow:
• Most of the energy that enters a trophic level is
used by the organism to stay alive
•
Only 10 % of the energy consumed is retained in the
body tissues and is available for the next trophic
level (Ten Percent Rule)
10%
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10%
90 % of the energy is lost to waste, movement,
warmth and metabolism (bodily functions)
ENERGY FLOW WITHIN AN ECOSYSTEM
solar energy
(10,000,000 kJ)
1%
10%
producer
(100,000 kJ)
1o consumer
2o consumer
(10,000 kJ)
90% lost
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10%
90% lost
10%
3o consumer
(1,000 kJ)
90% lost
10%
4o consumer
(100 kJ)
(10 kJ)
90% lost
ENERGY FLOW WITHIN AN ECOSYSTEM
Note:
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food chains rarely have more than 4-5
trophic levels (why?)
energy is not recyclable, it must
constantly be added to support an
ecosystem
added by the Sun
Sun powers all food chains
ECOLOGICAL PYRAMIDS
food chains:
only indicate the number of trophic levels (energy
transfers), not how much energy is available
example:
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•
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therefore, ecologists prefer to use ecological
pyramids (3 kinds) to estimate populations and
energy flow through an ecosystem
ECOLOGICAL PYRAMIDS
1. Pyramid of Numbers:
• A pyramid of numbers shows the actual
number of organisms at each trophic level in
an ecosystem
• The concept is that the number of actual
organisms decreases at each trophic level
• Most times the graph looks like a true
pyramid, but sometimes a small number ends
up on the bottom
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PYRAMID OF NUMBERS:
snake
frog
cricket
grass
snake
frog
cricket
tree
ECOLOGICAL PYRAMIDS
2. Pyramid of Biomass:
• A pyramid of biomass shows the actual mass
(kg) of all the organisms at each trophic level
in an ecosystem
•
The concept is that the amount of biomass
(kg) available decreases at each trophic level
•
the graph looks like a true pyramid all of the
time
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PYRAMID OF BIOMASS:
snake
frog
cricket
grass
ECOLOGICAL PYRAMIDS
3. Pyramid of Energy:
• A pyramid of energy shows the actual amount
of energy (kJ) available at each trophic level
in an ecosystem
•
The concept is that the amount of energy
(kJ) available decreases at each trophic level
•
the graph looks like a true pyramid all of the
time
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PYRAMID OF BIOMASS:
snake
frog
cricket
grass
PYRAMID OF NUMBERS
Pyramid of numbers:
•
the area of each rectangle represents the # of organisms at
each trophic level
owls
30 consumer
9
20 consumer
moles
10 consumer
grasshoppers
producer
blades of grass
advantage:
• simple & cheap
• just count representative #’s of organisms
disadvantage:
• not very accurate
• can result in inverted pyramids
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105
78 624
842 424
HOMEWORK
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Energy Flow Worksheet
Pyramid Worksheet