1. Energy Flow In Ecosystems
Food Connections
Energy Flow In Ecosystems

2. What is the origin of all animals’ food?
PLANTS!
Whether herbivore or carnivore, all of our food comes from plants.

3. Where does the energy originate from?
The SUN!

4. The Sun The source of all energy
Light
Heat
Evaporation (for precipitation)
Photosynthesis
30% of the total energy is reflected by clouds or Earth’s surface
44% heats atmosphere, surfaces,
25% heats and evaporates water
1 % wind
0.023% for photosynthesis

5. Photosynthesis vs. Cellular Respiration
Do plants perform photosynthesis?
Do animals perform photosynthesis?
Do plants perform cellular respiration?
Do animals performs cellular respiration?
Therefore, plants can make their own food (photosynthesis) and use it (cellular respiration). Animals cannot make their own food, but they do use food. How do animals get their food?

6. Biotic Factors- Biological Niches
Producer
Consumer
Alternate Name
Autotroph
Heterotroph
Energy Source
Make (produce) their own food
From sunlight and basic nutrients (abiotic factors)
CANNOT make their own food
Must obtain it from autotrophs or other heterotrophs (biotic factors)
Example
Plants
Herbivores
Omnivores
Carnivores

7. Heterotrophs (Consumers)
Organisms that must consume (eat) other organisms to obtain energy and building materials
4 types of consumers depending on what they eat. (Herbivores, Carnivores, Omnivores, Scavenger/ Detrivores)

8. Omnivore Eat both plants and animals
Ex. Bears, robins, raccoons, blue jays, fox, humans

9. Parasites
Parasites are plants or animals that live on or in a host organism, and they get their nutrients from that host. Parasites that affect animals can live outside the body (ectoparasites) or inside the body (endoparasites).

10. Decomposers Organisms that feed on detritus
Detritus: Waste from biotic factors, including their dead remains
Return nutrients (abiotic factors) to the ecosystem
E.g.
Pseudomonas, bacteria in soil

11. Detritivores and Scavengers
Detritivores eat organic matter (dead organisms and their waste).
Scavengers are a type of carnivore that does not hunt animals. Instead, it eats the leftovers of dead or dying animals.
Which of the species below is a detritivore? Which is a scanveger?

12. Fill in the Classification of Organisms graphic organizer
Your Turn
Fill in the Classification of Organisms graphic organizer

13. Trophic Levels
Categorize living things (biotic factors) according to how they gain their energy.
How Scientists discuss and organize energy flow in ecosystems

14. 1st Trophic Level
Contains organisms that are able to make their own food from abiotic factors (e.g. soil nutrients, sunlight)
Organisms in the 1st trophic level are called producers or autotrophs
Examples:

15. 2nd Trophic Level Contains organisms that feed on producers
Rely DIRECTLY on producers for their source of energy.
Organisms in the 2nd trophic level are called herbivores/ primary consumers/ heterotrophs_
Examples:

16. 3rd Trophic Level
Contains organisms that rely on primary consumers as their main energy source
But, indirectly, are still dependent on producers
Organisms in the 3rd trophic level are called secondary consumers
Examples:

17. Trophic Levels In a food chain, food moves through trophic levels
Producers are plants. They are ALWAYS at the first trophic level, located at the bottom.

18. Trophic Levels
Producers are plants. They make their own food through photosynthesis
Primary consumers are herbivores. They eat plants. Give an example.
Secondary consumers are carnivores. They eat primary consumers. Give an example.
Tertiary consumers are carnivores. They eat secondary consumers. Give an example.
A carnivore that has no predators is called a “top carnivore”. Give an example.

19. Where do Omnivores Fit in?
Omnivores eat both plants and animals. For example, a bear. So what is its trophic level? Well let’s look at what it eats:
When the bear is eats berries, it is a primary consumer.
When the bear is eats rabbits, it is a secondary consumer.
When the bear is eats salmon, it is a tertiary consumer
However, if you have to choose one trophic level for the sake of simplicity, you must state the bear’s highest trophic level: “tertiary consumer”.
A bear is also a “top carnivore” because it has no predators (unless you consider humans!)

20. Decomposers Decomposers play an essential role in food chains.
Decomposers break down organic matter. They take nutrients from the organic matter and release them back into the ecosystem.
Fungi and many bacteria are decomposers. Instead of consuming food, they release chemicals called enzymes into the organic matter. These enzymes break down the organic matter and release nutrients. The decomposers can then absorb the nutrients.
Detritivores are classified as decomposers, but not all decomposers are classified as detritrvores since many fungi and bacteria cannot directly eat organic matter.

22. Food Chain
Food chains show the feeding relationship between trophic levels.
It starts with producers and ends with the last consumer.
Arrows show the flow of energy (‘is eaten by’)
Show simple relationships

24. Food Webs
In reality, each organism has a variety of food sources and is therefore involved in multiple food chains
These food chains interlock to form a complex food web
Food Web: Representation of the complex feeding relationships in an ecosystem

28. Food Chain vs. Food Web
A food web is actually several food chains woven together
Look at the food web in the last slide. Identify the multiple food chains starting with the white spruce as the producer.

30. Ecological Pyramids
Show the relationships between the trophic levels in ecosystems (the amount of energy, numbers or biomass)

31. 4th Trophic Level
3rd Trophic Level
2nd Trophic Level
1st Trophic Level

32. 4th Trophic Level
3rd Trophic Level
2nd Trophic Level
1st Trophic Level

33. Energy and Trophic Levels
When a consumer eats another organism, does it absorb all of its energy?
Example: If a caterpillar eats 100 J of leaves, does it retain all of the 100 J?
If yes, if a bird eats the caterpillar, does it then retain all the 100 J from the leaves?
The answer to both is no.
In fact, the caterpillar would only retain 10 J of the leaves. And if the bird ate the caterpillar, it would only retain 1 J of the energy from the leaves.

34. What happens to energy?
When one organism consumes another organism, here is what happens to the energy:
60% of the energy cannot be used and is passed through waste
30% of the energy is used to for cellular respiration (keeps the body running)
10% of the energy is used to make new body tissues
Therefore, only 10% of the energy is retained in its body.

35. What happens to energy
This caterpillar ate 100 J of the leaf. However, only 10 J got stored as body tissue.
Therefore, when a bird eats the caterpillar, the bird will only get 1 J of energy that came from the leaf.
When a fox eats the bird, the fox will only get 0.1J of energy that originally came from the leaf.

36. Energy and Trophic Levels
Therefore, the caterpillars need to eat a lot of leaves to get enough energy in its body…. And then the birds would need to eat a lot of caterpillars to get enough energy in its body….. And then the foxes would need to eat a lot of birds to get enough energy in its body.

37. Energy Pyramid
Energy pyramids show the amount of available energy at each trophic level
The more trophic levels that exist in a food chain, the less energy there is left from the original amount at the bottom.

39. Think of it this way. The grain could feed one meat-eater; or it could feed 10 vegetarians.

40. 10% is transferred between trophic levels
Carnivore (20J)
Herbivore (200J)
Plants(2000J of sun’s energy)

41. Analogy Cut a pie into 10 equal slices
Only 1 piece is available to the next trophic level
Cut that slice into 10 smaller slices
Only 1 of those is available to the next trophic level

42. Ecological Pyramids
Are used to organize the information of matter transfers, and the most common are:
Type
Pyramid of numbers
Pyramid of Biomass
Pyramid of Energy
Based on…
Population of Organisms
Mass of Organisms
Stored energy in organisms
Drawing

43. Pyramid of Biomass: mass of all living organisms in an area
Predator, parasites
Insect herbivore
Grass

44. Pyramid of Biomass

45. Typical Upright Pyramid of Numbers

46. Typical Energy Pyramid Shape

47. To create your own Pyramid of Energy- start with 1,000,000J of energy

48. Group Work Complete the Ecological Pyramids practice questions
Complete Introduction to Food Chains and Food Webs
Homework: Food Webs Assignment

50. Energy Consumption
Which consumes more energy? An herbivore or a carnivore?
A carnivore.
When an herbivore consumes 1000 J of plants, that’s all in consumes.
However, when a carnivore that consumes 1000 J of prey, the prey had to consume J of plants. So the carnivore indirectly consumes 10x more energy!
Given this knowledge, can you explain what would happen if the number of secondary and tertiary consumers increased in an ecosystem? (e.g. if the number of foxes and lynx increased).

51. Niches
Ecosystems are kept balanced so that there aren’t too many primary consumers, and in turn fewer secondary consumers, and then even fewer tertiary consumers
To keep a balanced ecosystem, every species has its niche: food, predator, habitat, etc.
Niches reduce competition between species for the same territory and resources.
Top carnivores play an important role. For example, the lynx. If the lynx were to be extirpated in an ecosystem, there would be too many hares. If there are too many hares, they would eat too many plants, not leaving enough food for the rest of the ecosystem. The lynx’s presence ensures there is enough food for lower trophic levels.

52. What about humans?
Who consumes more food energy? A human omnivore, or a human vegetarian?
The omnivore. Vegetarians consume less energy and have a lower ecological footprint compared to non-vegetarian humans. Vegetarians only eat plants. Omnivores also eat animals, and these animals eat large quantities of plants (or other animals) in order to grow.

53. Think of it this way. The grain could feed one meat-eater; or it could feed 10 vegetarians.

54. Homework Read pp. 28-32 Answer Questions: p. 29 #1-4