1. Energy Flow in Ecosystems

2. What are we learning today?
Benchmark
Objectives
SC.912.L.17.9 – Use a food web to identify and distinguish producers, consumers, and decomposers. Explain the pathway of energy transfer through trophic levels and the reduction of available energy at successive trophic levels. AA
Describe the structure of a food chain.
Explain how food chains and food webs are related.
Describe the energy pathways through the different trophic levels of a food web or energy pyramid.
Benchmark Clarifications
Students will describe the energy pathways through the different trophic levels of a food web or energy pyramid.
Students will analyze the movement of matter through different biogeochemical cycles.
Content Limits
Items referring to organisms in food webs are limited to the impact of changes in matter or energy in trophic levels.
Items addressing food webs will require application of the knowledge of roles of organisms in a food web to describe energy pathways rather than the identification of producers, consumers (primary, secondary, tertiary), and decomposers.
Items will not require knowledge of specific organisms or their feeding habits.
Items assessing biogeochemical cycles are limited to the water cycle and the carbon cycle.
Items referring to the biogeochemical cycles may address but will not assess photosynthesis and cellular respiration in isolation.

3. What is the essential question?
The energy pyramid shown depicts the feeding patterns a team of ecologists observed in several populations in a desert. Explain the pathway of energy transfer through trophic levels and the reduction of available energy at successive trophic levels.

4. What is a food chain?
3rd Consumer
Tertiary Consumer – Carnivores which eat other carnivores.
Energy Flow
The order that animals feed on other plants and animals is called a food chain.
Secondary Consumer – Carnivores that eat herbivores.
2nd Consumer
Energy Flow
Primary Consumer – Herbivores that eat plants.
“I do” – Help students understand that a food chain usually begins with a green plant or algae (producer) which is eaten by an animal (consumer). The arrow means 'is eaten by', and shows the flow of energy along the food chain. Explain the connection between food chains and food webs. Introduce the different trophic levels.
“We do” – The food chain image is linked to a website where students can be guided to build a sample food chain.
1st Consumer
Energy Flow
Producer – Plants, algae, or bacteria that produce their own food by photosynthesis.
Producer

5. What are trophic levels?
Greek (trophē) referring to food or feeding
Position that an organism occupies in a food chain
Can be represented by numbers, starting at level 1 with producers. 4 3 2 1

6. Can You Guess The Order of the Trophic levels?
Energy Flow
Energy Flow
Trophic Level 2
Trophic Level 4
Fourth trophic level - Golden eagles eat foxes at the third trophic level, so they are tertiary consumers.
Third trophic level - Foxes eat rabbits at the second trophic level, so they are secondary consumers.
Second trophic level - Rabbits eat plants at the first trophic level, so they are primary consumers.
First trophic level - The plants, algae and phytoplankton, are primary producers. They take nutrients from the soil or the water, and manufacture their own food by photosynthesis, using energy from the sun.
Energy Flow
Trophic Level 1
Trophic Level 3

7. What is a food web? Herbivore - a plant eater
Carnivore – eats other animals
Omnivore - Eats both plant and animal matter
Detritivore - Obtains its nutrients from decaying organic matter.
A food web shows how animals and plants are connected in many ways.
“I do” – Help students understand that a food chain usually begins with a green plant or algae (producer) which is eaten by an animal (consumer). The arrow means 'is eaten by', and shows the flow of energy along the food chain. Explain the connection between food chains and food webs. Introduce the different trophic levels.
“We do” – The food chain image is linked to a website where students can be guided to build a sample food chain.

8. Show Your Understanding
Your job is to build a food web.
Click the picture
Move each arrow from the predator and put it directly on its prey.
Make sure the arrow overlaps the food image, and if you are right; the arrow will lock into place.
You can move the pictures around at any time to make sure the food web is easier to read.
When you have connected all the arrows, you have created a food web.
“We do” – The food web image is linked to a website where students can be guided to build a sample food web.
Click me!!!

9. Energy Flow Through Ecosystems
The first law of thermodynamics states that energy cannot be created or destroyed; it can only be changed from one form to another.
Light energy is absorbed by plants where it is converted to stored chemical energy.
Heat Loss
Energy Flow
Heat Loss
Energy Flow
Heat Loss
Energy Flow

10. Energy Flow Through Ecosystems
The second law of thermodynamics states that whenever energy is transformed, there is a loss of energy through the release of heat
When one animal feeds off another, there is a loss of heat (energy) in the process
This occurs when energy is transferred between trophic levels through biotic interactions
Additional loss of energy occurs during respiration and movement
About 90% of energy is lost each time one moves up a trophic level 1 2 3

11. Energy Flow in an Ecosystem
The flow of energy through an ecosystem starts with the plants and ends as heat loss
Without a constant input of energy, living things cannot function.
Sunlight is the main source of energy for life on Earth.
Energy flows in one direction from the sun to autotrophs (producers) and then to various heterotrophs (consumers).
The flow of energy through an ecosystem is one of the most important factors that determine the system’s capacity to sustain life.

12. Ecological Pyramids Pyramid of Energy 100% Primary Producers
90% Heat loss
0.1% Tertiary Consumers
1% Secondary Consumers
10% Primary Consumers (herbivores)
100% Primary Producers
Energy Decreases
10% energy transferred
90% Heat Loss
10% energy transferred
90% Heat Loss
10% energy transferred
Parasites and decomposers feed at each level
Pyramid of Biomass
Represent the amount of living organic matter at each trophic level.
Pyramid of Numbers
Shows the relative number of individual organisms at each trophic level.
Pyramid of Energy
Shows the relative amount of energy available at each trophic level

13. In Review: Interdependence…
Where Abiotic Meets Biotic!
Nutrients cycle through ecosystems, but energy flows and eventually leaves. Energy must be continually supplied to the ecosystem by the Sun.

14. What is the essential question?
The energy pyramid shown depicts the feeding patterns a team of ecologists observed in several populations in a desert. What explanation can you offer to best describe the difference in the amount of available energy in the trophic levels of the desert ecosystem?