1. Sustaining Ecosystems
Food Chains and Food Webs

2. Terms Habitat – places where a species can live
Food Chain – a step by step sequence linking organisms that feed on each other
A food chain is made up of producers and consumers:
Producers – food sources such as plants
Consumers – animals and other living things that feed on the plants and on each other

3. Also in the food chain are:
Herbivore – animals that eat plants (ex. rabbits)
Carnivores – animals that feed on other animals (ex. wolf)
Omnivores – animals that eat both plants and animals (ex. humans)
Decomposers – are organisms that break down nutrients in decaying bodies and wastes of organisms and returns nutrients to abiotic parts of the ecosystem

4. Trophic Levels
To understand energy flows and how living things gain their energy we can categorize living things by their trophic level.
1st Trophic Level
Organisms that make their own food (also referred to as autotrophs)
Plants, algae and some types of bacteria

5. 2nd Trophic Level
Organisms that feed on the producers (they are called primary consumers)
They rely directly on autotrophs
3rd Trophic Level
Organisms that rely on primary consumers for their energy source of energy but are still dependent on the autotrophs in the first trophic level (secondary consumers)

6. Consumers at whatever trophic level, are sometimes called heterotrophs.
Heterotrophs cannot make their own food and must obtain their food and energy from autotrophs or other heterotrophs.

7. Energy and Food Webs TL = Trophic Level 1st TL 2nd TL 3rd TL
tree deer wolf
producer primary secondary
consumer consumer

8. A carnivore (tertiary consumer) eats another carnivore then that would be a 4th trophic level
The final carnivore in any food chain is called the top carnivore (they are not eaten by other animals at least while they are alive!)
Each individual organism in an ecosystem is involved in many food chains.
They interlock with each other to form a feeding relationship called a food web.

10. Pyramid of Energy
Measures the amount of energy available at each trophic level

11. Example of Food Chains Organism Diet Water Boatman Eats Tadpoles
Eats Algae
Perch
Eats Water Boatman
Algae
Produces own food

12. Which organism is the producer?
To create a food chain, we need to first find the producer.
Which organism is the producer?

13. Then find the organism that eats algae.
Which organism eats algae?

14. Draw an arrow FROM the algae TO the tadpole.
You can remember which way the arrow points by thinking that algae “goes into” the tadpole

15. Answer:
Algae  Tadpole  Water boatmen  Perch

16. Example 2: Organism Diet Frog Eats Grasshoppers Grass
Produces own food
Heron
Eats Frogs
Grasshopper
Eats Grass

17. Make the food chain

18. Answer:
Grass  Grasshopper  Frog  Heron

19. Examination of Food Chain
What would happen to the organisms if the Grasshopper was eliminated from the environment?

20. Nothing would eat the grass so the population of the grass would increase
The frog would have nothing to eat so its population would decrease. Perhaps even die!!!
If the frogs are decreasing then the heron population will decrease because they have nothing to eat.