WLHS/Biology/Ecology
Name___________________________
Date______________
How Do Ecosystems Work?
Use Chapter 3.3: Energy Flow in Ecosystems (pgs 73-78) to answer the following questions and fill in the
diagrams.
Part I: The Basics
1. Why do you think energy flow is the most important factor in an ecosystem?
2. What are producers? What are some examples?
3. What are consumers? What are some examples?
4. What are herbivores, carnivores, omnivores, and scavengers? Give examples of each.
5. What are decomposers and where do they fit in?
Part II: Food chains and webs
6. What is a trophic level?
7. Define food chain.
Fill in the food chain below. The first box has been done for you as an example.
Algae
Producers: an
organism that gets
their energy from
the sun
Trophic Level: 1
Cod
Leopard Seal
Killer Whale
Primary Consumer:
Secondary Consumer:
Tertiary Consumer:
Another Name:
Another Name:
Another Name:
Trophic Level:
Trophic Level:
Trophic Level:
Decomposer
WLHS/Biology/Ecology
8. What is a food web?
9. What do you think the arrows in food chains and food
webs show?
Crabeater seal
Killer Whale
Elephant Seal
10. Suppose that a disease has wiped out the squid
population in the food web to the right. Next to each
population draw an arrow pointing up if that population will
increase, or an arrow pointing down if the population will
decrease.
Adelie Penguin
Leopard Seal
Cod
Krill
Squid
Algae
Small Animals & Protists
Small animal & protists______ elephant seal_________
cod_____________
Krill ________________
killer whales______________________
Part III: Energy Pyramids
11. What is an ecological pyramid?
12. When energy transfers from one trophic level to another, energy is lost. What form is this energy in? What
happens to the amount of energy available to high trophic
levels?
13. How much energy actually gets passed on to the next
trophic level?
The pyramid to the right shows the number and kinds of
organisms in a small farm community. Use the diagram to
answer the questions below.
14. In this community, who are the producers? What are the
secondary consumers?
1 hawk
8 snakes
60 mice
1000 corn plants
15. Why do the number of organisms decrease as you
move up the pyramid? (be sure to use the word energy in
your answer)
16. If there were 100,000 calories present in corn plants, how many calories would make it to the
hawk? Remember, only 10% of the energy at a trophic level gets passed on to the next one.
WLHS/Biology/Ecology
Part IV. More practice with Food Chains and Ecosystems
Answer the following questions based upon the information below.
In an aquatic ecosystem, algae make their own food through photosynthesis, snails feed off the algae, sunfish eat
the snails. Bass, a larger fish, feed off of the sunfish.
17. Fill in the food chain below using the organisms list above.
Trophic Level:
1
2
3
4
18. According to the food chain in question 17, what are the:
a. producers ______________________
d. primary consumers _________________________
b. secondary consumers _____________
e. tertiary consumers __________________________
c. herbivores ______________________
f. carnivores _________________________________
19. If the sunfish ate algae as well as snails, what would they be called? _______________________________
20. What do the arrows in a food chain represent (what do they show)?
21. Place the organisms from the food chain into the energy
pyramid to the right.
22. What percentage of energy gets on to each trophic level?
23. If there are 650,000 calories in the producers, how many
calories are in the:
a. algae
________________________
b. bass
________________________
c. snails
________________________
d. sunfish
________________________
WLHS/Biology/Ecology
Part V. Food Web practice
Create a food web from the passage below and then answer the questions that follow. Make sure to use all
of the organisms in the passage below.
In a large forest, rabbits and field mice feed on grass, which makes its own food from photosynthesis. Rabbits also
feed on small shrubs located near their dens. The mouse is so busy feeding; it doesn’t sense the snake sneaking
up on it looking for a meal. Perhaps this was because of the crickets chirping nearby while feeding on the grass.
The crickets don’t chirp for long, though, because a frog has hopped onto the scene and made a dinner out of a
couple of them.
In the distance, up on the mountains, tall trees use the sun to make glucose. A couple of elk take advantage of this
and fill up on the tender leaves. As dusk approaches, a mountain lion sets out to find dinner. It takes off after the
elk but misses. Not willing to give up, it sneaks down the mountain and catches a rabbit to take back to her cubs.
A pair of owls sits high on a branch looking below for something to eat. One owl spots a field mouse and takes it
back to its nest while the owl brings back a frog for the feast. Overhead, another bird, a hawk is looking for food.
Being a true carnivore, it has many options for a meal. It chooses the rabbit first, but the lion beat him to it. Its
second chance is the field mouse, but since it was already a meal for the snake, the hawk secedes to eat the snake
instead. Perhaps tomorrow the hawk will set its sights on larger prey like the owl.
24. In the food web, who are the:
a. producers
___________________________________________
b. primary consumers
___________________________________________
c. secondary consumers ___________________________________________
d. tertiary consumers
___________________________________________
25. If a disease wipes out the rabbit population, predict what would happen to the shrub population and to the hawk
population. Provide reasons for your predictions.