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DR. RAMESH
GRU4L3.2 Flow of Energy 10% rule
Objective!
The student will (TSW) evaluate the flow of energy within an ecosystem and calculate how energy is divided in a food pyramid using the
10% rule.
Why are we learning this?!
Ecology helps us understand the connections and relationships between living organisms and their physical
environment.
Energy Flow!
Tertiary
Secondary
Primary
Producers
Energy Flow!
Energy flow is the transfer of energy within an ecosystem.
(Energy comes from eating things.)
Energy Flow!
Energy Flow!
Energy that is not used by organisms is lost to the environment as heat.
Energy Flow!
Energy Pyramids!
Energy Pyramids!
Energy Pyramids show the amount of energy transferred as you move up the
food chain. Energy is measured in kcal (kilo calories)
or J (joules).
Energy Pyramids!
Energy Flow!
Tertiary
Secondary
Primary
Producers
Energy Flow!
0.1%
1%
10%
100%
10% Rule!
Only 10% of the energy in a food web is passed from one trophic level to the next.
As we move up the trophic levels, more energy is lost to the environment as heat.
10% Rule!
10% Rule!
How do we find out what the new amount of energy will be?
Move the decimal point one space to the
left as you go up the trophic levels.
Practice: 10% Rule!
What is 10% of 500?
500
Practice: 10% Rule!
What is 10% of 500?
500.
Practice: 10% Rule!
What is 10% of 500?
50.0
Practice: 10% Rule!
What is 10% of 500?
50
Practice: 10% Rule!
What is 10% of 10,000?
1,000
Practice: 10% Rule!
What is 10% of 25?
2.5
CHECK FOR UNDERSTANDING
• Voices at a Level Zero
• Raise your hand to answer the questions
Check For Understanding!
DEER OR FOX? Which trophic level has more energy?
Deer
Check For Understanding!
PLANTS OR SNAKES? Which trophic level has more energy?
Plants
Check For Understanding!
INSECTS OR RABBITS? Which trophic level has more energy?
Equal
Check For Understanding!
COUGAR OR PLANTS? Where is the least energy in this food web?
Cougar
DIRECTIONS
• Voices at a Level Zero
• Complete the ‘Guided Practice’
• Answer in complete sentences • Raise your hand if you have
questions
Check For Understanding!
PRODUCERS OR PRIMARY CONSUMERS?
Primary Consumers
Check For Understanding!
SECONDARY CONSUMERS OR PRODUCERS?
Secondary Consumers
Check For Understanding !
WHAT IS 10% OF 348.7?
34.87
Check For Understanding !
WHAT IS 10% OF 2,000?
200
Check For Understanding !
WHAT IS 10% OF 1?
0.1
DIRECTIONS
• Voices at a Level Zero
• Complete the ‘Independent Practice’
• Answer in complete sentences • Raise your hand if you have
questions
Grass: 1000kcal
Cows and Rabbits
Wolves
Example 1
So what if the grass received 1000 kcal from the sun? How much energy would cows and rabbits have? How much energy would wolves have?
Grass: 1000kcal
Cows and Rabbits: 100kcal
Wolves: 10kcal
Example 2
What percent of the grass’s energy moved on to the next trophic level? What percent was lost?
Grass: 3450kcal
Cows and Rabbits: 345kcal
Wolves: 34.5kcal
Example 2
Whatifthegrassnowreceived3450kcalofenergyfromthesun?Howmuchenergywouldbecarriedintoeachtrophiclevel?
DIRECTIONS
• Voices at a Level Zero
• Complete the ‘Exit Ticket’
• Answer in complete sentences
Exit Ticket!DIRECTIONS: Copy and answer the following questions.
1) If the producers have 3,450 kcal of energy, how much will be available to the whale?
2) If the whale ate all the krill, what would happen to the plankton population?
