Food Chains and Food Webs notes with answers
1. Energy flows from where into the biological world? From the sun
2. How does the sun’s energy enter the biological world? Organisms called autotrophs can use the
sun’s energy to make their own food through photosynthesis.
3. What is photosynthesis? Photosynthesis is the process by which autotrophs convert the sun‘s
energy into organic material.
4. How does energy flow from plants to other organisms? The sun’s energy flows into organisms that
can change the sunlight into food then into organisms that eat them.
Vocabulary – use the following word bank to answer the questions below.
consumers
decomposers
carnivores
producers
detritivore
“top” carnivore
herbivores
omnivores
5. Organisms which gain energy by eating other organisms: Consumers
6. Organisms which are able to create their own energy: Producers
7. Consumers that eat both plants & animals: omnivores
8. Consumers that eat only plants: herbivores
9. Organisms which break down organic matter (bacteria & fungi): decomposers
10. Consumers that eat other animals: Carnivores
11. Organisms that eat secondary consumers; usually nothing feeds on them: top carnivore
12. Organisms that feed on the remains of dead plants and animals and other dead matter: detritivore
13. Why would decomposers and detritivores be called the environmental “recyclers”? They rid our
environment of excrement, dead bodies and leaf litter, actually returning elements back to the soil
or atmosphere (return nutrients to the physical environment).
Label this food chain with the appropriate term
Decomposers
Producer
Primary consumer
secondary consumer
tertiary consumer
14. What is a trophic level? Feeding level
15. How does a food chain indicate the path of energy? arrows
16. How do the tropic level numbers correspond with the “eating terms”? The first trophic level is the
plants/producers which first produce the food using the sun’s energy. The second trophic level is
the herbivore that eats the plants. The third trophic level is the primary consumer/carnivore which
the first to eat meat. The fourth trophic level is the secondary consumer/carnivore which is the
second meat eater in the chain and continuing through succeeding trophic levels and consumers, etc
17. Why is it that some energy is lost from one level to the next level? Some energy is lost as heat
energy or in metabolism (daily life activities). Use it, lose it, save it.
18. How much energy is actually passed on to the next level? 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.
19. If all of the snakes in this chain died, what would happen to the hawk? It would die or have to find a
new food supply, exist on mice in this chain.
20. If all the snakes in this chain died, what would happen to the decomposers? They would not be
severely affected as they have a multiple food source.
21. What is a food web? A network of feeding interactions. Each organism has more than one food
source and more than one role.
Ecological Pyramids notes with answers
A. The Pyramid of Energy
1. What does an ecological pyramid of energy show? the relative amount of energy available at each
trophic level of a food chain or food web.
2. Why is the transfer of energy and matter in a food chain only about 10% efficient? The other 90% is
used to perform life processes.
3. Where is the most energy located in this type of pyramid? At the bottom level
4. Where is the least amount of energy located? At the top level
B. The Pyramid of Biomass
1. What is biomass? The total amount of living tissue within a given trophic level.
2. What does a biomass pyramid represent? The relative amount of living organic matter available at
each trophic level
3. Using the biomass pyramid, where is the majority of the biomass located? The second level
4. Using the biomass pyramid, where is the least amount of biomass located? The bottom level
5. Explain why the largest section is not at the bottom? Whatever organisms are at the bottom level are
very small and have little biomass.
C. The Pyramid of Numbers
1. What does a pyramid of numbers represent? The relative number of individual organisms at each
trophic level.
2. Using the numbers pyramid, where is the majority of the numbers located? The second level
3. Using the numbers pyramid, where is the least amount of numbers located? The bottom level
4. Explain why the largest section is not at the bottom? The organisms at the bottom level(producers)
must be very large in sixe because there is not very many of them and they are able to support the
large numbers in the first level consumers.
5. Pyramids Ecosystem A: Label the pyramids as Biomass, Numbers or Energy
Follows the normal pattern of
having many more
phytoplankton at TL1
Numbers
The phytoplankton reproduce
at 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.
Follows the normal pattern
of having much more
energy available at TL1
Energy
Biomass
6. Pyramids of Ecosystem B: Label the pyramids as Biomass, Numbers or Energy
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.
Numbers
Follows the normal pattern
of having much more mass
at TL1 from the huge trees.
Biomass
Follows the normal
pattern of having much
more energy available
at TL1
Energy
The diagrams below represent the amount of biomass and the number of organisms in the same
ecosystem. Use them the pyramids to answer questions 7 and 8.
3rd Level Consumers
2nd Level Consumers
1st Level Consumers
Producers
Pyramid of Biomass
Pyramid of Numbers
7. What can you conclude about the ecosystem from the pyramid of numbers shown?
A.
There are more first-level consumers than producers.
B.
There are more third-level consumers than second-level consumers.
C.
There are more producers than first-level consumers.
D.
There are more second-level consumers than first-level consumers.
8. What can you conclude about the producers in the ecosystem based on the two pyramids shown?
A.
B.
C.
D.
The producers in the ecosystem are probably very small organism.
There are no producers in the ecosystem.
The producers in the ecosystem are probably large organisms.
Decomposers in the ecosystem outnumber the producers in the ecosystem.