1. Food Chain/Food Webs
Learning Target
#5, #6, #13

2. All food chains start with ENERGY from the sun

3. Feeding Relationships
A food chain shows a simple feeding relationship.
Sun →

4. Plants are producers. They turn energy from the sun into sugars that animals can use Through Photosynthesis

5. Because plants produce their own food, they are called ‘Producers’

6. Primary consumers eat plants. They are herbivores
Primary consumers eat plants. They are herbivores. Insects and other animals eat plants for energy.

7. Secondary consumers are animals that eat other animals for energy
Secondary consumers are animals that eat other animals for energy. They are called carnivores or omnivores

8. Decomposers are organisms that eat dead things for energy.

9. Food Chains are connected to Food Webs
Combined food chains make food webs.
Food webs start with the sun
Food webs contain producers, consumers, and decomposers.
Are you part of food webs?

10. Feeding Relationships
A food chain shows a simple feeding relationship.
Sun → grass →

11. Feeding Relationships
A food chain shows a simple feeding relationship.
Sun → grass → rabbit →

12. Feeding Relationships
A food chain shows a simple feeding relationship.
Sun → grass → rabbit → fox

13. The energy is then passed on to animals when they eat the plant.

14. Animals of all shapes…

16. …and sizes!

17. Because these animals are the first to take the food energy from the plants,
They are called primary consumers

18. Some of these primary consumers have predators
Some of these primary consumers have predators. Other animals that feed on them

19. Aphids are eaten by….

20. Ladybugs

21. Animals that eat primary consumers are called secondary consumers

22. So far this is a straightforward food chain Sun → leaf aphid → ladybug
But in reality it is more complicated than that

23. This bird eats ladybugs and aphids

24. This bird eats smaller birds, mice, and rabbits

25. Mice and rabbits have other predators

26. What do you think the frog eats?
What will eat the frog?
What do you think the frog eats?

27. Sometimes it’s not entirely clear who eats who!

28. We can show what goes on with the help of a Food Web

29. What would happen if a disease killed off many of the hawks?

30. There will be nothing to eat the snakes, so their numbers will increase.

31. Many of the frogs get eaten

32. No frogs.
More crickets

33. Most of the cattail gets eaten by the crickets

34. Now the crickets don’t have enough food so their numbers go down

35. ..and so on. Numbers of each species have an effect on the numbers of the other species in the web.

36. Use the food web worksheet to predict what might happen in the following situations:
A) There is very little rain and much of the Marsh Grass and Cattail die off.
B) Humans nearby bring cats into the area.
C) The frogs eats some poisoned slugs from a garden

37. Transfer of Energy
When a zebra eats the grass, it does not obtain all of the energy the grass has (much of it is not eaten)
When a lion eats a zebra, it does not get all of the energy from the zebra (much of it is lost as heat)

38. No organism EVER receives all of the energy from the organism they just ate
Only 10% of the energy from one trophic level is transferred to the next – this is called the 10% law

39. Key Points to Remember…
Energy moves from one organisms to another when it is eaten
Each step in this transfer of energy is known as a trophic level
The main trophic levels are producers, consumers, and decomposers

40. DDT affect on Food Webs
DDT: Used in the 40’s and 50’s as a pesticide .
Outlawed in 70’s: collects in fats of organisms and cannot be broken down.
Marine microorganisms greatly affected
collected in plankton and green algae
slows photosynthesis – not death
Mostly noted in birds eggs
thinning of eggshells
Brown Pelican: nests
only 1 chick survived

41. Food Web

42. Biomass
The total mass of the organic matter at each trophic level is called biomass
Biomass is just another term for potential energy – energy that is to be eaten and used.
The transfer of energy from one level to another is very inefficient (10% Law)

43. Biomass

44. Ecological Pyramid
An ecological pyramid shows the relationship between consumers and producers at different trophic levels in an ecosystem
Shows the relative amounts of energy or matter contained at each trophic level
The Pyramid shows which level has the most energy and the highest number of organisms

45. Ecological Pyramid

46. Ecological Pyramid

47. Ecological Pyramid Which level has the most energy?
Which level has the most organisms?
Which level has the least organisms?
Which level has the least energy?

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