1. Notes 1 – Food Chains
SCI 10 Ecology

2. Food Chains Grass grasshopperrobinhawk
-Primary Consumer: eat producers
-Herbivore: only eat plants
-Heterotrophs: hetero = others, troph = food
Producer: makes its own food through photosynthesis which uses energy from the sun
-Autotroph: auto = self, troph = food
Secondary Consumer
Tertiary consumer
Energy transfer (90% lost at each step)

3. Other Definitions Omnivore: eats everything (plants and meat)
Ex. Human, brown bears
Carnivore: only eats meat
Ex. Lions
Scavengers: eat dead things
ex. Vultures, raccoons
Decomposers: consume dead material and recycle (return) nutrients to the soil
ex: worms, bacteria, fungi

4. Trophic Levels First trophic level = producers (plants)
Second trophic level = primary consumers (herbivores)
Third trophic level = secondary consumers (carnivores)
Fourth trophic level = tertiary consumers

5. In which trophic level do each of the following organisms belong?:
grass
crow
coyote
Maple tree
bacteria
snake
mouse
deer
porcupine
red squirrel
seeds
Producers
Primary consumers
Secondary consumers/
Decomposers

6. Energy What is the primary source of energy for all food chains?
The sun – without it we would not have food

7. Food Web: many food chains interlinked
Identify 3 food chains in the food web below
deer
snake
wolf
mouse
grass
rabbit
frog
shrubs
hawk
insect

8. Abiotic vs. biotic Abiotic factors: non-living
Ex: soil, water, a rock, sun
Biotic factors: living or was living
Ex: trees, birds, insects, bacteria

9. Complete the diagram using the following terms : primary consumer (herbivore) , secondary consumer (carnivore), tertiary consumer, decomposers, second trophic level, first trophic level, producer, fourth trophic level, third trophic level

10. Transfer of Energy
-Food energy ingested by a consumer is used for many processes
Only around ____ % is converted into body mass.
Why do we rarely see more than 4 links in a food chain?
Because energy decreases along the chain and so higher level consumers can’t be supported

11. Organisms are interconnected
Look at the following food chain :
Grass  deer  wolf
If the deer population increases, what would happen to:
The grass population?
The wolf population?

12. The grass population would decrease
The wolf population would increase because:
More food increases reproductive rates (more babies)
Eventually, the wolf population would start to decrease because food would run out

13. Definitions
Ecosystem: interactions among organisms and their environment
Biotic factors: components of an ecosystem that are, or use to be, living
i.e.:
Abiotic factors: components of an ecosystem that are non-living

14. p.14 – Copy the Pyramid Fig 1.8
The greatest amount of energy is in the _______________, that of the _______________.
A pyramid of numbers is used to represent the number of organisms at each trophic level
The ___________ are the organisms that are usually the most numerous

15. p.15
Look at this pyramid:
Which 2 organisms are most numerous?

16. p.16 – Copy Fig 1.11
___________ combines the number and size of organisms
It indicates how much living matter there is in a particular organism
A pyramid of biomass: shows the biomass at each trophic level
Which trophic level has the greatest biomass?
Which trophic level has the smallest biomass?

17. p.17 – Copy Fig 1.13
A pyramid of energy flow shows the total chemical energy at each trophic level
Total energy decreases from producers to consumers – how?
90% of the energy from your food is lost to: respiration, heat production, waste production
10% of the energy from your food is used to produce new tissues and grow

18. Calculate the Energy Transferred at Each Trophic Level
Look at the following food chain :
Grass  Rabbit  Snake  Wolf
Complete the table below
Grass receives 7400 kilojoules (kJ) or energy from the sun
Organism
Available energy (kJ)
Energy used (kJ)
Energy stored (kJ)

19. Notes 1 Questions
Which type of organism is at the beginning of all food chains?
Which organisms can eat all other organisms ?
In an ecosystem, the abiotic factors include…?
3 examples of decomposers are …?
What is the importance of decomposers in an ecosystem?
What is the principal source of energy for all ecosystems?