1. Introduction to ENERGY FLOW
ECOSYSTEMS
and
FOOD CHAINS
Introduction to ENERGY FLOW
(Revised August 4, 2003)

2. What is an ecosystem? Habitat – place where an organism lives.
Population – group of organisms from the same species.
Community – group of organisms from several species.
Ecosystem – a community and all of the physical aspects of a habitat.

3. Ecosystem
Community
Population
Organism

4. Ecology
The scientific study of interactions between organisms and their environments.

5. Biotic Factors All living organisms that inhabit an environment.
Ex: animals, plants, protists…

7. Abiotic Factors All nonliving factors in the environment.
Ex: air currents, temperature, moisture, light, and soil

8. the ultimate energy source is the SUN!!!
sun eclipse with palm
(picture sun eclipse with palm)
the ultimate energy source
(photo from Astronomy Picture of the Day)

9. Energy Flow How does the sun’s energy enter the biological world?
PHOTOSYNTHESIS
Energy Flow
How does the sun’s energy enter the biological world?
Organisms called autotrophs can use the sun’s energy to make their own food through photosynthesis. (Point out that auto means “self” and troph means “feeding” - self-feeding, makes own food. Also troph will carry over to trophic levels, feeding levels)
What is photosynthesis?
Photosynthesis is the process by which autotrophs convert the sun‘s energy into organic material.
(Photo from Nature Planet)

10. Energy Flow
The sun’s energy flows into organisms that can change the sunlight into food then into organisms that eat them.
This flow is:
Energy Flow
The sun’s energy flows into organisms that can change the sunlight into food then into organisms that eat them.
This flow is:
(diagram of food chain: sun-plant-mouse-snake)
sunlight
producer
consumer 1
consumer 2

11. PRODUCERS
Producers make their own food. They can also be called autotrophs.
Ex. Plants, algae and some bacteria
PRODUCERS
What are producers?
Producers are autotrophs that trap solar energy into organic molecules during photosynthesis.
Ex. Plants, algae and some bacteria
sunlight
producer
consumer 1
consumer 2

12. CONSUMERS Consumers eat something
else. They also are called heterotrophs.
Examples: deer, rabbits, cows, mice, lions, humans, hawks, snakes
CONSUMERS
What are consumers?
Consumers are heterotrophs that eat other organisms to obtain energy. (“Hetero” means others, “troph” means eating.)
Examples: deer, rabbits, cows, mice, lions, humans, hawks, snakes
sunlight
producer
consumer 1
consumer 2

13. HERBIVORES Herbivores eat plants. They can be called primary consumers
Ex. Cows, caterpillars, bunnies
HERBIVORES
What are herbivores?
Herbivores are consumers that eat plants. (Mention that “vore” means eating.)
Primary Consumers
Ex. Cows, caterpillars, bunnies
sunlight
producer
consumer 1
Or primary consumer
consumer 2
Or secondary consumer

14. CARNIVORES Carnivores eat meat and can be called secondary consumers.
Ex. tigers, wolves, snakes, hawks
CARNIVORES
What are carnivores?
Carnivores are consumers that eat other animals.
Secondary Consumers
Ex. tigers, wolves, snakes, hawks
sunlight
producer
consumer 1
consumer 2

15. TOP CARNIVORES
A “top” carnivore is a tertiary consumer. They are at the top of the food chain.
sunlight
producer
consumer 1
consumer 2
consumer 3
Ex. whale eating a sea lion or hawk eating a snake.
TOP CARNIVORES
What is a “top” carnivore?
“Top” carnivores eat secondary consumers; usually nothing feeds on them.
Ex. whale eating a sea lion or hawk eating a snake.

16. OMNIVORES Omnivores eat meat and plants.
They are considered secondary consumers.
Ex. bears and humans
OMNIVORES
What are omnivores?
Omnivores are consumers that eat both plants & animals
Secondary Consumers
Ex. bears and humans

17. Where do all the dead things go?
They are eaten. YUMMMM!
They decay. SMELLY!
decomposer
detritivore
Where do all the dead things go?
They are eaten. YUMMMM!
They decay. SMELLY!
What’s the difference? Is it just a matter of taste?
Decomposer: breaks down organic matter (bacteria & fungi)
Detritivore: feed on the remains of dead plants and animals and other dead matter (detritus)
What’s the difference? Is it just a matter of taste?

18. Detritivore vs Decomposers
DETRIVORES:
feed on the remains of dead plants and animals and other dead matter (detritus)
Crabs, mites, earthworms, snails
Detritivore vs Decomposers
DETRIVORES:
feed on the remains of dead plants and animals and other dead matter (detritus)
Keywords: eat, consume
Crabs, mites, earthworms, snails

19. Detritivore vs Decomposers
break down dead organic matter
Bacteria & fungi
Detritivore vs Decomposers
DECOMPOSERS:
break down dead organic matter
Keywords: decay, break down
Bacteria & fungi
Do these two have anything in common? Mushrooms are a decomposers feeding off dead organic material and crabs are detrivores feeding off dead plants & animals. Both use dead organisms for food.

20. “RECYCLERS”
They break down and release nutrients from dead matter back into the environment

21. Detritivores and Decomposers
Why would they be called the environmental “recyclers”?
sunlight
producer
consumer 1
consumer 2
consumer 3
decomposer
Detritivores and Decomposers
Why would they be called the environmental “recyclers”?
They rid our environment of excrement, dead bodies and leaf litter, actually returning elements back to the soil or atmosphere (return nutrients to the physical environment).

22. Food Chains & Food Webs
Organisms in ecosystems transfer energy from organism to organism in a graphic organizer known as trophic levels.
producer
consumer 1
consumer 2
consumer 3
Food Chains & Food Webs
Organisms in ecosystems transfer energy from organisms to organism in feeding relationships called trophic level.
How does a food chain describe this path of energy? (arrows)
It shows the energy passing from one organism to the next as it is eaten. Make sure to talk about the direction of the arrows pointing INTO the animal that eats it. 1 2 3 4

23. The Path of Energy
ARROWS on a food chain describe this path of energy.
Notice that the arrows point from the organism being eaten to the organism that is eating it.
producer
consumer 1
consumer 2
consumer 3

24. Food Chains & Food Webs
Energy is “lost” at each trophic level as a result of the activities of the organisms such as metabolism.
Only 10% of the energy is actually passed on to the next level.
Food Chains & Food Webs
What important energy transfer is not shown in a food chain?
the sun, the ultimate energy source
Why is it that some energy is lost from one level to the next level?
Some energy is lost as heat energy or in metabolism (daily life activities).
How much energy is actually passed on to the next level?
The rule of thumb is 10% (although it is an average across levels and chains.) No trophic level can contain more energy than the level below.
producer
consumer 1
consumer 2
consumer 3

25. Food Chains & Food Webs
What vital “recycler” is not shown in this food chain?
Food Chains & Food Webs
What vital “recycler” is not shown in this food chain?
Decomposers
Upon which organism(s) would it feed?
All organisms.
producer
consumer 1
consumer 2
consumer 3

26. Food Chains & Food Webs
If all of the snakes in this chain died, what would happen to the hawk?
To the decomposers?
decomposer
Food Chains & Food Webs
If all of the snakes in this chain died, what would happen to the hawk?
It would die or have to find a new food supply, exist on mice in this chain.
To the decomposers?
They would not be severely affected as they have a multiple food source.
consumer 3
consumer 1
consumer 2
producer