Name _______________
Date _______________
Food Web Assignment
The flow of materials (and energy) in an ecosystem is the result of predator-prey
relationships. These relationships establish a long chain of events. They always
begin with a producer and end with consumers.
grass
grasshopper
frog
snake
eagle
1. For the food chain above, indicate the:
a) producer:
b) primary (1st) consumer:
c) secondary (2nd) consumer:
d) tertiary (3rd) consumer:
e) quarternary (4th) consumer:
f) herbivore:
g) first carnivore:
h) top carnivore:
2. Complete each of the following food chains with an appropriate animal:
a) in a woodlot:
leaves  worm  ________________
b) in a pond:
algae  insect  ________________
c) in a forest:
grass  rabbit  ________________
3. Consider a food chain that is common in Ontario:
sapling
deer
wolf
a) If the deer population increases, what will happen to:
i) the sapling population? (increase or decrease)
ii) the wolf population? (increase or decrease)
b) The changes in the sapling and wolf population will cause a change in the
number of deer. What happens to the deer population as a result?
(increase or decrease)
c) As a result of the change in (b) what will now happen to:
i) the sapling population? (increase or decrease)
ii) the wolf population? (increase or decrease)
4. The area of Ontario in which this food chain occurs contains other organisms
such as grass, mice, rabbits, hawks, frogs, snakes, and insects. We can
connect all these animals together in a food web as shown on the next page.
mouse
sapling
grass
snake
deer
wolf
rabbit
hawk
insect
frog
The food web represents a more realistic situation. In the above food chain;
a) What are the two foods that the deer eats?
b) What does the wolf feed on?
c) Why is it advantageous for the deer and the wolf to have more than one
food source?
d) Are there any omnivores in the above food web? If so, name them.
e) The above food web contains 16 food chains. Identify 4 of these chains:
i)
ii)
iii)
iv)
f) If the number of rabbits were to increase, what would happen to each of
the following populations:
i) grass (increase or decrease)
ii) hawks (increase or decrease)
g) Will the changes in (f) have any effect on the number of mice in the area?
EXPLAIN.
5. One important organism omitted from our food chain and food web is the
decomposer.
a) What is the role of a decomposer?
b) Why are decomposers important?
6. Consider the following food chain:
ENERGY
flower
caterpillar
bird
1000 kJ
100 kJ
10 kJ
900 kJ LOST
90 kJ LOST
At each level in this food chain, energy is lost. Approximately 90% of the energy
consumed by the caterpillar is used in its day-to-day metabolism, and only 10%
can be passed on to the bird who eats it.
Food chains rarely go beyond 5 trophic levels. Using energy, explain WHY.
SNC1D1 – Food Chains and Food Webs
Hawk
Mountain Lion
Snake
Fox
Owl
Beaver
Squirrel
Rabbit
Trees
Bird
Frog
Mouse
Grasshopper
Grasses
Figure 1: A typical food web for a terrestrial ecosystem.
1. Identify all the producers.
2. Construct a food chain that has four (4) trophic levels.
3. Identify three (3) herbivores.
4. Identify three (3) secondary consumers.
5. Identify all omnivores (if there are any).
6. Identify any organisms that occupy more than one possible trophic level.
7. Explain what might happen to the fox and the hawk populations if a disease
dramatically reduced the mouse population.
Energy Movement in Ecosystems
Draw a food web for the following ecosystems and identify:
 Producers (first trophic level)
 Primary consumers (second trophic level)
 Secondary consumers (third trophic level)
 Tertiary consumers (fourth trophic level)
A. In a pond, floating plants are found on the surface and phytoplankton (algae)
are found just below the surface. The floating plants serve as food for
muskrats, which are eaten by snapping turtles. The phytoplankton is food for
both tadpoles and minnows in the pond. Both the tadpoles and minnows are
eaten by the Kingfisher bird. Snapping turtles also eat the tadpoles.
B. In a forest ecosystem, land plants act as producers and provide food for
mice, bears, insects, and grouse (a bird). The mice, in turn, are eaten by
hawks and snakes. The insects are eaten by both grouse and spiders. The
grouse are eaten by foxes. Black bears in the area feed on plants and fish.
The fish eat crayfish in the streams, while the crayfish eat microscopic plants
in the water.