1. Energy Flow Through an Ecosystem
Food Chains, Food Webs, Energy Pyramids
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Begins with the SUN
Photosynthesis
6CO2 + 6H2O + sunlight & chlorophyll 6C6H12O6 + 6O2
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Photosynthesis
Chemical reaction where green plants use water & carbon dioxide to store the sun’s energy in glucose
ENERGY is stored in glucose
Glucose is stored as starch in plants
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Organisms that can make glucose during photosynthesis are called PRODUCERS.
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5. Producers use most of the energy they make for themselves.
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The energy that is not used by producers can be passed on to organisms that cannot make their own energy.
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7. Organisms that cannot make their own energy are called CONSUMERS.
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8. Consumers that eat producers to get energy:
Are first order (1st) or primary consumers
Are herbivores (plant-eaters)
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Most of the energy the primary consumer gets from the producer is used by the consumer.
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10. Some of the energy moves into the atmosphere as heat.
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Some energy in the primary consumer is STORED & not lost to the atmosphere or used by the consumer itself. This energy is available for another consumer (predator).
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12. A Consumer that Eats Another Consumer for Energy:
Is called a secondary or 2nd order consumer
May be a carnivore or a omnivore
May be a predator
May be a scavenger
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Most of the energy the secondary consumer gets from the primary consumer is used by the secondary consumer.
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Some of the energy is lost as heat, but some energy is stored and can passed on to another consumer.
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15. A consumer that eats a consumer that already ate a consumer:
Is called a 3rd order or tertiary consumer
May be a carnivore or a omnivore
May be a predator
May be a scavenger
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16. Consumers that eat producers & other consumers
Are called omnivores
Omnivores eat plants and animals
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Consumers that hunt & kill other consumers are called predators. The animals that are hunted & killed are called prey.
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18. Consumers that eat other dead consumers are called scavengers
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19. ENERGY FLOW IN ECOSYSTEM
How does energy flow in an ecosystem?
What is an energy pyramid?
What is a trophic level?

20. ENERGY ENTERS ECOSYTEM
All energy in ecosystem comes from the sun
First law of Thermodynamics: Energy cannot be created or destroyed (but it can be transformed into stored energy & heat)

21. ENERGY LEAVES ECOSYSTEM
Second law of thermodynamics: Energy is lost as energy is transformed
In ecosystem, when energy is transformed, some energy is lost as HEAT

22. ENERGY PATHS 3 ways to illustrate energy flow
1. Food Chain: Single path
3 ways to illustrate energy flow
3. Food Pyramid
2. Food Web: many paths

23. FOOD CHAINS
A food chain shows the path of energy from one organism to the next
energy flows from producers to consumers
arrows point to who is eating (plant is eaten by herbivore)
Usually decomposers are left out

24. FOOD WEBS
A food web shows all feeding relationships in an ecosystem (made of many food chains)

25. FOOD WEBS Typically, food webs go like this:
remember: decomposers receive energy from all other organisms in an ecosystem
CONSUMER (CARNIVORE)
CONSUMER (OMNIVORE)
CONSUMER (HERBIVORE)
DECOMPOSER
PRODUCER

26. FOOD CHAINS AND WEBS
Practice! Draw a food chain that includes the following organisms:
grasshopper
mouse
grass
owl
CONSUMER (CARNIVORE)
CONSUMER (CARNIVORE)
CONSUMER (HERBIVORE)
Now label the organisms as producers, consumers (which type?), or decomposers
PRODUCER

27. FOOD CHAINS/WEBS & ENERGY PYRAMIDS
Food chains/webs can be written as a pyramid:
Producers form the base of the pyramid
Consumers form the upper layers

28. ENERGY PYRAMIDS The energy pyramid shows energy flow in an ecosystem:
Top Consumer
Energy stored by
Secondary Consumers
Primary Consumers
ENERGY STORED
BY PRODUCERS
A level of the energy pyramid is called a TROPHIC LEVEL
Each trophic level represents the energy for those organisms

29. TROPHIC LEVELS Energy is lost with each trophic
~90% is released to the environment as heat
~10% of the energy is used
Only about 10% of the energy from one level is passed on to the next level

30. QUICK REVIEW
Practice! If 100% of the energy is available at the first trophic level, what percentages of the energy are available at the second and third trophic levels? 1%
10%
100%

31. QUICK REVIEW! energy pyramid organism Producers 10%
All organisms in an ecosystem need _______ from food to live. An energy ________ shows how much food energy is passed from one ________ to another through food chains. __________ have the largest spot at the base of the pyramid. Altogether, only about _____ of the food energy at each level gets passed up to the next level.
pyramid
organism
Producers
10%