Ecology Web Practice
Multiple Choice
Identify the choice that best completes the statement or answers the question.
____
1. Cougars are predators that often eat weakened or diseased animals. This is a description of the ____ of
cougars.
a. habitat
b. community
c. niche
d. none of these
Figure 2-1
____
2. Referring to Figure 2-1, suppose 10, 000 units of energy are available at the level of the grasses. What is the
total number of energy units lost by the time energy reaches the coyote?
a. 90 units
c. 9900 units
990
units
b.
d. 9990 units
____
3. Referring to Figure 2-1, the coyotes would be considered ____.
a. herbivores
c. second-level consumers
third-level
consumers
b.
d. decomposers
Figure 2-2
____
4. The group of animals in Figure 2-2 is an example of what?
a. community
c. population
b. ecosystem
d. biosphere
Figure 2-3
____
____
____
____
5. In the energy pyramid shown in Figure 2-3, which level has the smallest number of organisms?
a. fox
c. grasshoppers
b. birds
d. grass
6. Which of the following is the ultimate source of energy for the pyramid in Figure 2-3?
a. grass
c. sunlight
b. heat
d. water
7. Organisms with overlapping niches probably have which type of relationship?
a. commensal
c. mutualistic
b. competitive
d. parasitic
8. What is “soil type” to an earthworm?
a. abiotic factor
c. biotic factor
biome
b.
d. carbon source
Figure 2-5
____
____
9. The graph in Figure 2-5 is probably showing which of the following?
a. amount of biomass at three trophic levels in a particular community
b. number of food chains that can be drawn from the same food web
c. number of species present in a community at each of three trophic levels
d. number of abiotic factors affecting three species in the same community
10. Which of the following would be the easiest way to diagram predatory and parasitic relationships between
several species?
a. biomass pyramid
b. food chain
c. food web
d. numbers pyramid
Completion
Complete each statement.
11. The range of temperatures in which an insect is able to live and reproduce is one element of that organism’s
____________________, a description of its ecological requirements.
12. Mosquito larvae are eaten by some fish species when they are present in the same body of water. For the
mosquito these fish are a ____________________ factor.
Short Answer
13. Compare and contrast a food web and a food chain.
Figure 2-6
14. Use the diagram in Figure 2-6 to complete Table 2-1. Classify each member of the food web as autotroph or
heterotroph, and identify the heterotrophs as herbivores, carnivores, or omnivores.
Table 2-1
Autotrophs
Heterotrophs
Herbivore, carnivore,
or omnivore
15. When a grouse (a type of bird) eats berries, the berry seeds are eliminated as waste materials and may be
dropped in another part of the forest where they may sprout and eventually grow into new berry plants.
How would you classify the relationship between the berry plant and the grouse? Explain your reasoning.
16. Explain why graphs of the amount of energy at each trophic level in a community forms a pyramid.
Problem
A scientist wrote the following summary of her observations:
Milkweed is a plant commonly found throughout fields and pastures and along roadsides in eastern and
central North America. It gets its name from the milky white sap that oozes when the plant is broken or cut.
Milkweed plants bloom in June and July. When fertilized, the flowers form large seedpods that open in the
fall. The following observations were taken from a scientist's field study of milkweed plants from spring
through fall.
In the summer, the sugary nectar secreted by the milkweed's flowers attracts many bees, butterflies,
moths, and a variety of smaller insects that carry away pollen when they depart. Milkweed nectar seems to
be the major source of nutrition for several species of small moths, flies, mosquitoes, and ants. Monarch
butterflies, which visit in large numbers, lay their eggs on milkweed plants, and the hatching caterpillars
feed on the leaves. As fall approaches, milkweed bugs begin to attack the developing seeds, and milkweed
beetles eat the foliage.
Aphids, which suck milkweed sap, are found throughout the year. Crab spiders do not feed on the plant
itself, but rather on most of the insects that visit the plant. In the two to three weeks while the milkweed
plants are in bloom, successful adult female crab spiders may increase ten times in mass before laying their
eggs on the inner surface of leaves. Some species of flies and wasps, which feed on crab spider eggs, visit
the plants periodically. Harvestmen, also known as "daddy longlegs," recover the remains left by predators.
17. Based on the scientist's observations, formulate two possible hypotheses about the effects of crab spiders on
the survival of the milkweed plant.
18. How would you describe the symbiotic relationship between the milkweed plant and aphids?
19. From the scientist's data, infer which abiotic factor affects milkweed. Explain how the data support your
inference.
20. Based on the scientist's observations, what is one food chain that begins with a milkweed plant?
21. What would you call a patch of milkweed plants plus all the organisms that visit or live on the plants?
Essay
22. What are the possible outcomes of the extinction of a species in a biological community? Use the structure
of a food web to explain what might happen in the event of an extinction.
Ecology Web Practice
Answer Section
MULTIPLE CHOICE
1. ANS: C
The role the cougar plays in the ecosystem, and the relationships it has with other animals, is part of its
niche.
Feedback
A
B
C
D
You're on the right track.
What's the definition of a community?
That's correct!
Look at page 38 for a clue.
PTS: 1
NAT: LS_5e
2. ANS: D
DIF: Bloom's Level C
STA: III.5.1
TOP: 2-3
REF: 38
9000 units are lost between the grass and the mouse, 900 between the mouse and the cat, and 90 between
the cat and the coyote.
Feedback
A
B
C
D
How much energy is transferred between the grass and the mouse?
Review the pyramid model on page 44.
You're on the right track.
That's correct!
PTS: 1
NAT: LS_5f
3. ANS: B
DIF: Bloom's Level E
STA: III.5.2
TOP: 2-6
REF: 42–44
The mouse is a herbivore, or first-level consumer. The cat is a second-level consumer and the coyote is a
third-level consumer.
Feedback
A
B
C
D
A herbivore is a first-level consumer.
That's correct!
You're on the right track.
What are examples of decomposers?
PTS: 1
NAT: LS_4b
4. ANS: C
DIF: Bloom's Level B
STA: III.5.2
TOP: 2-4
A group of animals of the same species is a population.
Feedback
A
Review the definition of a community.
REF: 41–43
B
C
D
An ecosystem includes abiotic factors.
That's correct!
How big is the biosphere?
PTS: 1
STA: III.5.2
5. ANS: A
DIF: Bloom's Level A
TOP: 2-2
REF: 36–37
The fox-containing trophic level, at the top, will have both the smallest biomass and the smallest number of
individuals.
Feedback
A
B
C
D
That's correct!
You're on the right track.
Where are the grasshoppers on the diagram?
Try counting the blades of grass.
PTS: 1
NAT: LS_5f
6. ANS: C
DIF: Bloom's Level A
STA: III.5.1
TOP: 2-6
REF: 44
The Sun provides the ultimate source of energy for all food chains based on photosynthetic producers.
Feedback
A
B
C
D
Where does the grass get its energy?
You're on the right track.
That's correct!
Water is a nutrient.
PTS: 1
NAT: LS_5b
7. ANS: B
DIF: Bloom's Level D
STA: III.5.2
TOP: 2-5
REF: 41 | 44
Competition is most intense when organisms are competing for the same resources, and organisms with
similar niches rely on the same resources by definition.
Feedback
A
B
C
D
Do commensal organisms eat the same things?
That's correct!
Check the definition of mutualism.
Did you consider all the factors?
PTS: 1
NAT: LS_4c
8. ANS: A
DIF: Bloom's Level E
STA: III.5.1
TOP: 2-3
Soil type is a physical characteristic that impacts the earthworm.
Feedback
A
B
C
That's correct!
A biome is a group of ecosystems.
You're on the right track.
REF: 38–40
D
Check the carbon-cycle reservoirs on page 47.
PTS: 1
NAT: LS_5e
9. ANS: A
DIF: Bloom's Level E
STA: III.5.1
TOP: 2-1
REF: 35–36 | 47
The amount of biomass decreases as trophic level increases.
Feedback
A
B
C
D
That's correct!
What would level = 2 and y = 3 represent?
You're on the right track.
It's not very likely that three species would be affected by such small numbers of abiotic
factors.
PTS: 1
NAT: LS_5f
10. ANS: C
DIF: Bloom's Level D
STA: III.5.2
TOP: 2-4
REF: 44
A food web is the only one of these four methods that would allow a detailed and accurate representation of
several different types of relationships.
Feedback
A
B
C
D
How would you show the difference between predation and parasitism?
You're on the right track.
That's correct!
Review the numbers pyramid on page 44.
PTS: 1
NAT: LS_4b
DIF: Bloom's Level F
STA: III.5.2
TOP: 2-6
REF: 38 | 40 | 43–45
COMPLETION
11. ANS:
niche
A niche is a description of a species’ complete ecological requirements.
PTS: 1
NAT: LS_5e
12. ANS:
DIF: Bloom's Level B
STA: III.5.1
TOP: 2-3
REF: 38
biotic
Biotic factors are living things that affect an organism ecologically.
PTS: 1
NAT: LS_4c
SHORT ANSWER
DIF: Bloom's Level C
STA: III.5.1
TOP: 2-1
REF: 35
13. ANS:
Food chains and food webs are models that show how food and matter pass through organisms at different
trophic levels. A food chain shows only one organism at each trophic level. A food web can show many
different organisms at different trophic levels. Food webs are better representations of reality because many
organisms may consume the same organism, and one organism may consume many others.
PTS: 1
NAT: LS_4b
14. ANS:
DIF: Bloom's Level B
STA: III.5.2
TOP: 2-6
REF: 42–43
Table 2-1
Autotrophs
Heterotrophs
seeds
berries
grasses
grasshopper
elk
marmot
chipmunk
grouse
grizzly bear
goshawk
PTS: 1
NAT: LS_4b
15. ANS:
DIF: Bloom's Level D
STA: III.5.2
TOP: 2-4
Herbivore, carnivore,
or omnivore
herbivore
herbivore
herbivore
herbivore
omnivore
omnivore
carnivore
REF: 41–43
The relationship is one of mutualism as the grouse benefits by getting food energy from the berries and the
berry plant benefits by having its seeds dispersed; thus, its reproduction is aided.
PTS: 1
NAT: LS_4c
16. ANS:
DIF: Bloom's Level C
STA: III.5.1
TOP: 2-2
REF: 38–40
The graph is a pyramid because there is a loss of energy reaching each trophic level from the one below it.
That energy is lost as heat or in waste and is not available for the next trophic level to incorporate into its
own tissues. Because of this at each higher trophic level there is less and less energy, making the graph look
like a pyramid, wide at the bottom, narrow at the top.
PTS: 1
NAT: LS_5f
DIF: Bloom's Level D
STA: III.5.2
TOP: 2-6
REF: 44
PROBLEM
17. ANS:
Answers may vary. Because the crab spiders feed on insects that help pollinate the milkweed plant, they
threaten the reproductive success of those species. Because they feed on parasites, crab spiders increase the
chances of an individual plant's survival.
PTS:
1
DIF:
Bloom's Level E
REF: 38–40
NAT: IS_1a
18. ANS:
STA: III.5.1
TOP: 2-4
The aphids are parasites.
PTS: 1
NAT: LS_4c
19. ANS:
DIF: Bloom's Level B
STA: III.5.1
TOP: 2-2
REF: 39–40
The changing seasons affect the milkweed plant. The direct cause of this could be changes in temperature,
light, or precipitation. Evidence that supports this inference includes (a) blooming of the milkweed flowers
in June and July and (b) opening of the seedpods in the fall.
PTS: 1
STA: III.5.1
20. ANS:
DIF: Bloom's Level D
TOP: 2-1
REF: 35
Answers may vary. Milkweed-mosquito-crab spider-harvestman.
PTS: 1
NAT: LS_4b
21. ANS:
DIF: Bloom's Level C
STA: III.5.2
TOP: 2-6
REF: 43
A group of interacting populations is a community.
PTS: 1
NAT: LS_5f
DIF: Bloom's Level B
STA: III.5.1
TOP: 2-2
REF: 36
ESSAY
22. ANS:
The result of removing a species from a food web can vary. The species is probably eaten by something,
unless it is a top consumer. Because of this its disappearance will have some effect on the things that eat it.
Many organisms eat several different kinds of things, although some eat just one thing. If the missing
species is the only diet item of another species it may cause the extinction of that species, which will then
affect all the species it interacted with. If the missing species is one of many diet options for a species then
likely the species will just eat more of something else without suffering too much. This organism also eats
other organisms (unless it is an autotroph). Because of this, the organisms it eats will be affected. There will
also be a range of effects from a dramatic increase in numbers, to little or no effect at all. In addition, the
disappearing species probably competes with other species for food, which might allow them to increase in
numbers; these changes would also affect other parts of the food web.
PTS: 1
NAT: LS_4b
DIF: Bloom's Level F
STA: III.5.4
TOP: 2-6
REF: 43