Name _______________________
Energy and Food Webs Review Packet
Lesson Vocabulary
Write a definition for each vocabulary word in your own words!
Word
Definition
Autotroph
An organism that makes it’s own food
Herbivore
A consumer that eats only producers (plants)
Carnivore
A consumer that eats only consumers (meat)
Omnivore
A consumer that eats both producers and consumers
Decomposer
An organism that breaks down dead organic matter and
returns the nutrients to the ecosystem (atmosphere,
hydrosphere, or lithosphere)
Scavenger
A consumer that eats organisms that have already died
Food web
A map showing the transfer of energy through an
ecosystem
Trophic level
The level of an organism’s energy/food processing
(producer, primary consumer, secondary consumer, etc.)
Energy Flow Through Ecosystems
DIRECTIONS - Before you read the paragraph below, think of an organism for each of the
following descriptions:
A) A plant - _____any photosynthetic organism (that isn’t bacteria or protest) _
B) An organism that eats plants - _____any herbivore__________________
C) An organism that eats other organisms - _____any consumer (carnivore or omnivore) _
Next, use those organisms to complete the paragraph below and then answer the questions that
follow.
As the sun began to rise on a new day, (A) ___producer__________ stretched out its leaves to
capture the dancing rays. The energy from the sun helped the (A) _____producer________ to
produce its own food so that it could have energy to continue growing. Also early to rise was
a(n) (B) ____herbivore____________, which came along and nibbled at one of the leaves from
the (A) _______producer_____________. As the (B) ____herbivore____________ ate the leaf,
it also gained some energy and used it to scurry off in search for more food. Alas! On its way the
(B) _____herbivore__________ was snatched up quickly by a hungry (C)
____carnivore____________. With its breakfast finished, the (C) ______carnivore_________
found a cool shady spot in the dirt underneath a tree to take a nap.
Questions: Use the paragraph above to answer the following questions.
1.
A) Where did the energy start? ______the sun’s energy was captured by a plant through
photosynthesis______________________________
B) How did the energy move? __________as organisms ate each other, it was transferred from
one to the next__________________________
2.
A) In the ecosystem described, what are the living aspects? _____biotic factors are all
organisms (producers and consumers)________________________
______________________________________________________________________________
B) Non-living aspects? ______________the sun, the shady spot, and the dirt_______
3. Describe how a non-living factor impacted a living factor. ____the sun gave the plant energy,
the shade provided rest and prevented the carnivore from over-heating__
______________________________________________________________________________
4. Describe how a living factor impacted a non-living factor. ____________________________
__________the waste from the carnivore or the remains of the herbivore will return nutrients to
the soil (after it is decomposed) ________________
Reading – Annotate 5 times.
Trophic Levels
The feeding positions in a food chain or web are called trophic levels. The different trophic
levels are defined in Table 1.1. Examples are also given in the table.
Table 1.1: All food chains and webs have at least two or three trophic levels. Generally, there
are a maximum of four trophic levels.
Trophic Levels
Trophic Level
1st Trophic Level:
Producer
Where It Gets Food
Makes its own food
Example
Plants make food.
2nd Trophic Level:
Primary Consumer
Consumes producers
Mice eat plant seeds.
3rd Trophic Level:
Secondary
Consumer
Consumes primary consumers
Snakes eat mice.
4th Trophic Level:
Tertiary Consumer
Consumes secondary consumers
Hawks eat snakes.
Many consumers feed at more than one trophic level. Humans, for example, are primary
consumers when they eat plants such as vegetables. They are secondary consumers when they
eat cows. They are tertiary consumers when they eat salmon.
Trophic Levels and Energy
Energy is passed up a food chain or web from lower to higher trophic levels. However, only
about 10 percent of the energy at one level is available to the next level. This is represented by
the pyramid in Figure 1.8. What happens to the other 90 percent of energy? It is used for
metabolic processes such as cellular respiration or given off to the environment as heat. This
loss of energy explains why there are rarely more than four trophic levels in a food chain or
web. There’s not enough energy left to support any more trophic levels. This is why there are
there are fewer top-level consumers than primary consumers or producers.
Figure 1.8: This pyramid shows how energy and biomass decrease from lower to higher
trophic levels.
Ecological Pyramid
Secondary Consumers
Primary Consumers
Producers
Trophic Levels and Biomass
With less energy at higher trophic levels, there are usually fewer organisms as well. Organisms
tend to be larger in size at higher trophic levels, but their smaller numbers still result in less
biomass. Biomass is the total mass of organisms at a trophic level. The decrease in biomass
from lower to higher levels is also represented by Figure 1.8.
Review Questions
Recall
1.
Identify three different types of consumers. Name an example of each type.
Herbivore – deer, sea urchin
Omnivore – human, sea gull
Carnivore – lion, tuna
2.
Describe the role of decomposers in food webs.
Decomposers break down dead matter (plant and animal) and return the nutrients to the
ecosystem (hydrosphere, lithosphere, or atmosphere). Most decomposers are fungi and
bacteria.
Apply Concepts
3.
Draw a food chain that includes four trophic levels. Identify the trophic level of each
organism in the food chain.
Grass (producer)  antelope (primary consumer/herbivore)
consumer/carnivore)  vulture (scavenger)

lion
(secondary
Think Critically
4.
Explain how energy limits the number of trophic levels in a food chain or web.
According to the 10% rule, only 10% of the energy in each organism is passed on to the next.
Trophic levels are not unlimited because there is not usually enough energy in an ecosystem to
support more than 4-5 levels.