Flow of Energy
Energy in the ecosystem
• Energy comes into the living world as light
energy from the sun
• Plants capture this light energy and change it
to chemical energy (glucose) through the
process of photosynthesis.
Carbon dioxide +
CO2
+
Water
12H2O
Sunlight
Chlorophyll
Sunlight
Chlorophyll
Glucose + Oxygen + Water
C6H12O6 + 6O2
+
6H2O
Energy in the ecosystem
• Plants store glucose as starch, fats and
proteins (by adding Nitrogen from the soil)
• The energy which is now locked up in a food
molecule is passed from one organism to
another through a food chain/food web
Energy in the ecosystem
• At each link in the food chain, energy is
released by the process of respiration.
Glucose + Oxygen
C6H12O6 + 6O2
Enzymes
Carbon Dioxide + Water + Energy (ATP)
Enzymes
6CO2
+ 6H2O +
ATP
ATP
• ATP provides the energy for all the living
processes in the body
• It is used to create
– Mechanical energy when an organism moves
– Chemical energy when an organism makes new
cells or molecules
– Electrical energy when nerve cells fire
– Light energy like in a glow worm
– Energy of active transport
Energy in the ecosystem
• Eventually all energy changes to heat
• Energy flows in one direction
Sunlight
Photosynthesis
Food
Respiration
ATP
Light
Chemical
Mechanical
Electrical
Active transport
Heat
Energy flows
• There are two main ways energy flows through
an ecosystem
1. In the grazing food chain – herbivores eat plants
and carnivores eat the herbivores (what we have
already looked at)
2. In the organic detritus food chain – dead
material is broken down by bacteria and fungi
Energy flows
• Both systems are represented in food webs
and have levels known as trophic levels
• The energy available at each trophic level
equals the amount entering that trophic level
minus total loses to that level
Energy flow through an ecosystem
• Energy can be lost at each trophic level as
heat (due to metabolic activity) or as detritus
(this stays in the ecosystem for other
organisms to use)
• Only about 10% of energy is passed on to the
next trophic level
• Energy is in kilojoules per square metre per
year (kJ m-2 yr -1)
Energy flow in an ecosystem
Heat loss
Sunlight
Producer
Primary
consumer
Detritus
Secondary
consumer
Tertiary
consumer
Energy flow through the ecosystem
Energy from previous
trophic level
100
Energy lost
as heat
through
metabolic
activity
65
Trophic level
25
Energy passed on to
the next trophic level
10
Energy lost
to detritus
What can affect the energy flow?
• In silence think about this question for 1 min
and jot down any ideas you have
• Turn to the person next to you and discuss
your answer for 1 min
What can affect the energy flow?
• Block out light
– E.g. Road works
– E.g. Asteroid
• Remove a food source
– Can happen due to pollution, drought, over fishing
and the removal of an organism
Activity
• Construct an energy flow diagram for a bull
grazing in a paddock
Biozone
Pg 303-305