1. FOOD CHAINS
& WEBS
Introduction to ENERGY FLOW

2. the ultimate energy source

3. 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:
sunlight
producer
consumer 1
consumer 2

4. PRODUCERS What are producers?
Autotrophs that trap solar energy into organic molecules during photosynthesis; can produce their own food
Ex. Plants, algae and some bacteria
sunlight
producer
consumer 1
consumer 2 ``

5. CONSUMERS What are consumers?
Heterotrophs that eat other organisms to obtain energy
Examples: deer, rabbits, cows, mice, lions, humans, hawks, snakes
sunlight
producer
consumer 1
consumer 2

6. HERBIVORES What are herbivores? Organisms that eat plants
Primary Consumers
Ex. Cows, caterpillars, bunnies
sunlight
producer
consumer 1
consumer 2

7. CARNIVORES What are carnivores?
Organisms that eat meat (other animals/consumers)
Secondary Consumers
Ex. tigers, wolves, snakes, hawks
sunlight
producer
consumer 1
consumer 2

8. TOP CARNIVORES What is a top-level carnivore?
Top-level carnivores eat secondary consumers; usually nothing feeds on them
consumer 3
Ex. killer whale eating a sea lion or hawk eating a snake.
sunlight
producer
consumer 1
consumer 2

9. OMNIVORES What are omnivores?
Consumers that eat both plants and animals
Primary and Secondary Consumers
Ex. bears and humans

10. Where do all the dead things go?
They are eaten. YUMMMM!
They decay. SMELLY!
detritivore
decomposer

11. Detritivore vs Decomposers
Decomposers breakdown (decay) organic matter and feed on it
Detritivores eat the remains of dead plants and animals
Crabs, mites, earthworms, snails
Bacteria & fungi

12. Detritivore vs Decomposers
What is a scavenger?
A scavengers is a type of detritivore that feeds on carrion (dead animal remains).
Ex. vultures, sharks, maggots, hyenas
Detritivores and Decomposers
When is a detritivore called a scavenger?
Detritivores are scavengers when they feed mainly on carrion (dead animals).
Ex. vultures, sharks, maggots, hyenas
Planetware.com, photo by Jim Steinhart

13. Detritivore vs Decomposers
Why would they be called the environmental “recyclers”?
They decompose excrement, dead bodies and leaf litter, returning nutrients
to the physical environment.
sunlight
producer
consumer 1
consumer 2
decomposer
consumer 3

14. Food Chain
The series of steps in which organisms transfer energy by eating and being eaten
sunlight
producer
consumer 1
consumer 2

15. Food Chains & Food Webs
The steps in the transfer of energy from organism to organism in feeding relationships are called Trophic Levels.
producer
consumer 1
consumer 2
consumer 3

16. Food Chains & Food Webs
Name the number of the trophic levels in the food chain below.
How do the trophic level numbers correspond with the “eating terms”?
producer
consumer 1
consumer 2
consumer 3 1
Trophic
Level 2 4 3

17. Food Chains & Food Webs
What important energy transfer is not shown in a food chain?
Why is it that some energy is lost from one level to the next level?
How much energy is actually passed on to the next level? (rule of thumb)
producer
consumer 1
consumer 2
consumer 3

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

19. Food Chains & Food Webs
If all of the snakes in this chain died, what would happen to the hawk?
To the decomposers?
decomposer
producer
consumer 1
consumer 3
consumer 2

20. Food Chains & Food Webs
Most organisms feed on more than one trophic level and feed on several different species at each trophic level. This is a food web.
Food Chains & Food Webs
Most organisms feed on more than one trophic level and feed on several different species at each trophic level.

21. Ecological Pyramids
Introduction to ENERGY FLOW

22. Ecological Pyramids
Grass (10,000 kcal)
Grasshopper (1,000 kcal)
Frog (100 kcal)
Snake (10 kcal)
Hawk
(1 kcal) 1 2 3 4 5
Instead of representing trophic levels in a food web, an ecological pyramid can be used.
Ecological Pyramids
Instead of representing trophic levels in a food web, an ecological pyramid can be used.

23. Ecological Pyramids Does this pyramid represent a food chain or web? 5
Grass (10,000 kcal)
Grasshopper (1,000 kcal)
Frog (100 kcal)
Snake (10 kcal)
Hawk
(1 kcal) 1 2 3 4 5
Ecological Pyramids
Does this pyramid represent a food chain or web?
A chain as there is only one eating path.
How could this pyramid be changed to represent a food web?
Different species of organisms could be added at each level to show more eating “opportunities for the organisms above it.
Broaden the discussion by asking “What organisms could you add at each trophic level for a web??

24. Ecological Pyramids What do the big numbers represent?
Grass (10,000 kcal)
Grasshopper (1,000 kcal)
Frog (100 kcal)
Snake (10 kcal)
Hawk
(1 kcal) 1 2 3 4 5
What do the big numbers represent?
What does the kcal mean?
Ecological Pyramids
What do the big numbers represent?
The trophic levels. Have them identify the type of organism at each level.
What does the kcal mean?
It stands for kilocalories, a measurement of energy.

25. Pyramid of Energy What happens to the energy as you go up?
Grass (10,000 kcal)
Grasshopper (1,000 kcal)
Frog (100 kcal)
Snake (10 kcal)
Hawk
(1 kcal) 1 2 3 4 5
How much energy is available for the next level? (What %)
Ecological Pyramids
What happens to the energy as you go up?
It gets less and less; lost in heat energy or used in metabolism.
What is the energy loss between levels?
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.

26. Pyramid of Energy
Pyramids of energy show the relative amount of energy available at each trophic level of a food chain or food web.
Grass (10,000 kcal)
Grasshopper (1,000 kcal)
Frog (100 kcal)
Snake (10 kcal)
Hawk
(1 kcal) 1 2 3 4 5

27. Pyramid of Energy

28. Pyramid of Energy

29. Ecological Pyramids
How is this pyramid different from the previous ones?
What could the multiple pictures of the species at each level represent?
Ecological Pyramids
How is this pyramid different from the previous ones?
It shows multiple pictures of each species at the different trophic levels.
What could the multiple pictures of the species at each level represent?
They could represent the total number of organisms of each species or their total biomass.

30. Pyramid of Biomass
Biomass-the total amount of living tissue within a given trophic level.
A pyramid of biomass illustrates the relative amount of living organic matter available at each trophic level

31. Pyramid of Biomass
What information would this pyramid include if it were a pyramid of biomass?
How do they get a number total for the biomass of a population?
Ecological Pyramids
What information would this pyramid include if it were a pyramid of biomass?
It would have the total biomass at each level or it would have a key for how much biomass was represented by each picture.
How do they get a number total for the biomass of a population?
The total mass of the organisms is determined by drying and weighing a sample number of organisms at each level and then calculating the total mass for the species at each level.

32. Pyramid of Biomass

33. Pyramid of Biomass

34. Pyramid of Numbers
A pyramid of numbers shows the relative number of individual organisms at each trophic level.

35. Pyramid of Numbers
What information would this pyramid include if it were a pyramid of numbers?
How do they get a number total for a population of organisms?
Ecological Pyramids
What information would this pyramid include if it were a pyramid of numbers?
It would have the total population at each level or it would have a key for how organisms were represented by each picture.
How do they get a number total for a population of organisms?
The population is determined by counting the organisms of a species in a sample portion at each level and then calculating an average for the total area.

36. Pyramid of Numbers

37. Pyramids of Aquatic Ecosystems
Numbers
Biomass
Energy
Pyramids of Aquatic Ecosystems
Numbers - Follows the normal pattern of having many more phytoplankton at TL1
Biomass - The phytoplankton reproduce a a rate only just slightly higher than the rate at which they are eaten. Since they are so small and weigh so little there is a very small biomass.
Energy - Follows the normal pattern of having much more energy available at TL1
Pyramid of biomass in aquatic ecosystems (ocean & fresh) and some terrestrial ecosystems such as the pyramid of numbers for the temperate forest. Because the trees are so large their numbers are small compared to the number of organisms at the higher trophic levels.
Phytoplankton are microscopic and weigh very little

38. Pyramids of Temperate Forests
Numbers
Biomass
Energy
Trees are huge but not as numerous as many smaller forest creatures.
Pyramids of Aquatic Ecosystems
Numbers - In the temperate forest, the trees are huge but smaller in number compared to the grasses in a prairie and so are fewer compared to the number of organisms at the higher trophic levels.
Biomass - Follows the normal pattern of having much more mass at TL1 from the huge trees.
Energy - Follows the normal pattern of having much more energy available at TL1