Becky McCoy Lesson Title: Trophic Levels & 10% Rule Timing: 60 minutes Target Audience: 6 th grade General Science course (heterogeneous mixing) Objectives: Students Will Be Able To: Describe ecosystems by food webs and trophic levels. Model the 10% Rule graphically and by observing a physical model. The Teacher Will Be Able To: Assess student understanding. Provide students with a variety of ways to describe trophic levels and ecosystem.s Standards Assessed: New York State Middle Standards Key Idea 2: Interconnectedness: Common Themes Models are simplified representations of objects, structures, or systems used in analysis, explanation, interpretation, or design. Use models to study processes that cannot be studied directly (e.g., when the real process is too slow, too fast, or too dangerous for direct observation). Performance Standard 5.2: Compare the way a variety of living specimens carry out basic life functions and maintain dynamic equilibrium. All organisms require energy to survive. The amount of energy needed and the method for obtaining this energy vary among cells. Some cells use oxygen to release the energy stored in food. The methods for obtaining nutrients vary among organisms. Producers, such as green plants, use light energy to make their food. Consumers, such as animals, take in energy-rich foods. Herbivores obtain energy from plants. Carnivores obtain energy from animals. Omnivores obtain energy from both plants and animals. Decomposers, such as bacteria and fungi, obtain energy by consuming wastes and/or dead organisms.
Target Audience:6th grade General Science course (heterogeneous mixing)
Objectives:Students Will Be Able To:
Describe ecosystems by food webs and trophic levels. Model the 10% Rule graphically and by observing a physical model.
The Teacher Will Be Able To: Assess student understanding. Provide students with a variety of ways to describe trophic levels and ecosystem.s
Standards Assessed: New York State Middle StandardsKey Idea 2: Interconnectedness: Common Themes
Models are simplified representations of objects, structures, or systems used in analysis, explanation, interpretation, or design.
Use models to study processes that cannot be studied directly (e.g., when the real process is too slow, too fast, or too dangerous for direct observation).
Performance Standard 5.2: Compare the way a variety of living specimens carry out basic life functions and maintain dynamic equilibrium.
All organisms require energy to survive. The amount of energy needed and the method for obtaining this energy vary among cells. Some cells use oxygen to release the energy stored in food.
The methods for obtaining nutrients vary among organisms. Producers, such as green plants, use light energy to make their food. Consumers, such as animals, take in energy-rich foods.
Herbivores obtain energy from plants. Carnivores obtain energy from animals. Omnivores obtain energy from both plants and animals. Decomposers, such as bacteria and fungi, obtain energy by consuming wastes and/or dead organisms.
MATERIALS Dark green, light green, red, black, grey, and brown beads. Pipe cleaners.
SET UP Make the bead models as shown.
Becky McCoy
Lesson Plan
Aim: Describe ecosystems by their trophic levels.
Do Now: Science Fact & HW (5 minutes)Students should record the Science Fact of The Day (to be chosen at random) and the homework assignment in their lab notebooks.
Activity: Trophic Levels (35 minutes)Materials:
Computer and Projector “Populations and Ecosystems Resources” FOSS book or copy of page 19 Trophic Levels beaded model
Procedure:
REVIEWReview what has been discussed about food and energy with the following questions:
What is food? Energy, usually glucose. Where is food made? In producers. Where is food used in the food web? Every organism needs food (producers, consumers, decomposers). What is the point of consuming food? To get energy needed for movement, maintenance, growth and
reproduction, and producing waste.
“Let’s look at the ecosystem at Mono Lake. Here is a food web to help us get an idea of what types of organisms live there”
How does energy enter the Mono Lake ecosystem? Sunlight allows photosynthesis to occur. How else? Animals migrating in and out of the ecosystem.
Benthic Algae Planktonic Algae
Brine ShrimpBrine Flies
Heron
Coyote
Consumers
Producers
Decomposers are bacteria throughout the web
Becky McCoy
Do migratory birds bring energy in or do they take energy out? Birds are taking energy out when they leave?
Algae manufactures food. What happens to the food made by the algae? Some is used by the algae, some by the primary consumers, and the rest by the decomposers.
What happens to the energy in algae eaten by the brine shrimp? For shrimp growth/reproduction, movement, maintenance, and waste as well as the shrimp’s consumers, and the decomposers.
TROPHIC LEVELS“Trophic Levels are a way to describe the transfer of energy throughout the ecosystem. It sounds like a scary scientific word, but it is actually very similar to the food webs we have been using. The labels we used in our food webs (consumer, producer, decomposer) are actually the names of the trophic levels.”
Read p19 “Organizing the Ecosystem Based on Feeding Relationships” aloud from the books, on the screen, in groups, or individually.
Show students the simple trophic level chart on the bottom right corner of the page. It is very similar to the food web.
“The diagram on the top is the type of trophic level diagram we will be using. You can see it is shaped like a triangle with all the producers at the bottom.”
Ask students how much energy they think a gull will get if it eats 10g of brine shrimp. 1g.
“This is what we call the 10% Rule. In order to sustain 1g of gull life, the gull must eat 10g of shrimp. It’s exactly why the producer level on the chart is so big – the ecosystem needs many producers to support the primary consumers. There are also less secondary consumers than primary consumers and so on.”
On the board or overhead, define Trophic Levels and Biomass. Student should record these in their science notebook.
TROPHIC LEVEL BEAD MODELShow students the beaded model of trophic levels and explain the 10% Rule using the model.
Dark Green Benthic AlgaeBright Green Planktonic Algae
Red Brine ShrimpBlack Brine FliesGray Heron
Brown Coyote
On the board or overhead, define the 10% Rule.
Activity Summary:Have students repeat the 10% Rule in their own words and leave time for questions.
Homework:Students should write a paragraph about their knowledge of Trophic Levels.
Becky McCoy
Exit Strategy:Students show their homework assignment recorded in their notebook.
