Chapter 37: Communities and Ecosystems
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Chapter 37: Communities and Ecosystems
Guided Reading Activities
Big idea: Community structure
Answer the following questions as you read modules 37.1–37.13:
1. What is the relationship among an organism, a population, and a community?
2. When populations of different species compete for limited resources, we call this
_____________________.
3. Which of the following type of interspecific interaction benefits both organisms?
a. Mutualism
b. Parasitism
c. Predation
d. Herbivory
4. Interspecific competition occurs when the ____________ of two species ____________.
5. True or false: Interspecific competition increases the carrying capacity for competing species
within an area. If false, make it a correct statement.
6. How does mutualism differ from competition?
7. List three types of defenses that prey species have gained through evolution by natural
selection.
A group of organisms of the same species makes up a population. All of the populations in a
given area make up a community.
False, interspecific competition reduces the carrying capacity.
Mutualism is different from competition because mutualism benefits both organisms.
Three types of defenses are (1) mechanical defenses, (2) chemical defenses, and
(3) camouflage.
interspecific competition
niches overlap
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Chapter 37: Communities and Ecosystems
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8. Consider two populations of organisms: gazelles and cheetahs. Briefly explain how this
predator-prey relationship can actually drive adaptations in both species.
9. When two species undergo a series of reciprocal evolutionary adaptations, we call it
____________.
10. Briefly describe how Passiflora and Heliconius have driven evolutionary adaptations in each
other.
11. Would you expect a fungal pathogen to have more or less of a negative effect on a population
of genetically modified corn plants where there was very little genetic diversity? Briefly explain
your answer.
12. Every food chain must begin with a ____________.
a. collection of primary consumers
b. quaternary consumer
c. group of producers
d. group of decomposers
13. What feature is characteristic of all organisms in trophic levels above the producers?
14. What would happen to an ecosystem if all the decomposers were removed?
15. How is an elf owl linked to a brittlebush in this desert food web? Be sure to list all the ways.
Refer to Figure on page 745 of your textbook.
16. What is the relationship between a food chain and a food web?
17. Could an organism like the red-tailed hawk be both a quaternary consumer and a tertiary con-
sumer? Briefly explain your answer either way.
All organisms above producers are heterotrophs.
Organic matter from dead organisms would not be broken down; thus, organic matter would
quickly build up in an ecosystem and soils would be deficient in certain inorganic material.
Grasshoppers can eat brittlebush, and the owl can eat the grasshoppers. The brittlebush can
be eaten by harvester ants, which can be eaten by a praying mantis, which in turn can be eaten
by the elf owl.
A food web is a series of interconnected food chains and is more representative of the actual
complexity of energy transfer in an ecosystem.
Natural selection weeds out the organisms that are unable to compete well in this relationship.
It selects for organisms in both populations that have traits best suited for predation or avoid-
ing predation.
Passiflora produces a toxin that protects it from most insects, but Heliconius has enzymes that
break down the toxin. Some Passiflora plants have developed yellow spots on their leaves that
resemble Heliconius eggs. In this case, a female butterfly will not leave eggs.
You would expect the fungal pathogen to have more of a negative effect. With reduced genetic
diversity, the plants will have less variability in their traits to resist the fungus.
Yes, because the red-tailed hawk can eat organisms at the secondary level or tertiary level.
If the owl consumed a kangaroo rat, then it would be considered a tertiary consumer; if the
hawk ate a diamondback snake, then it would be a quaternary consumer.
coevolution
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Chapter 37: Communities and Ecosystems
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18. Is it possible for two biological communities to have the same species richness but have very
different species abundance? Briefly explain your answer.
19. Crops that are grown in ____________ plots would consist of large tracts of land planted with
the same plant.
20. Removal of a keystone species from a community will
a. have an effect only if the species removed is a predator.
b. likely reduce species richness.
c. have no effect at all.
d. most likely increase species richness.
21. How many years did it take for the number of species to drop to just a couple in Robert
Paine’s experiment on Pisaster? Refer to Figure 37.11B on page 747 of your textbook.
22. Complete the following table, which compares primary succession with secondary succession.
Primary succession Secondary succession
Description Primary succession occurs when
ecological succession happens in a
relatively lifeless area with poor soil.
This type of ecological succession
occurs when an event has removed
the current biological community
from an area but has left the soil
relatively intact.
Example A fresh lava flow A fire burns down a forest
23. A wildfire swept through parts of Yosemite National Park in the summer of 2013. This type
of event would be considered a(n) __________________.
24. A grocery store goes out of business. The building and parking lot sit vacant for over 15 years.
Over time, you notice the parking lot becoming more and more overgrown with vegetation.
What kind of succession is this?
Yes, you can have two forests with the same types of tree species, but each one can have differ-
ent amounts of each of those different tree species.
This would be considered primary succession.
It took just three years.
monoculture
secondary succession
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Chapter 37: Communities and Ecosystems
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25. A(n) _____________ is a non-native species that was introduced accidentally or intentionally
to an ecosystem.
26. You are staying at a campsite that has a lake for boating. A large sign out front asks that, as
soon your boat leaves the water, you drain the bilge water on land and wash the outside of the
boat with a 5% beach solution. What are the campsite owners concerned about?
Big idea: Ecosystem structure and dynamics
Answer the following questions as you read modules 37.14–37.23:
1. Which of the following converts inorganic components of the ecosystem into organic
substances?
a. Producers
b. Decomposers
c. Consumers
d. None of the above
2. What is meant by the following phrase: All organisms “borrow” chemical elements from the
earth?
3. The two processes that help to sustain and drive ecosystems are ____________ and
______________.
4. Net primary productivity is explained by which of the following?
a. The fact that you have to account for the energy expended by the plant to move water to
the leaves
b. The fact that plants perform photosynthesis only during the day
c. The amount of biomass removed for the plants’ own cellular respiration
d. How much energy the plant loses due to the inefficiency of photosynthesis
invasive species
energy flow
chemical cycling
They are concerned with the transfer of aquatic organisms to another body of water. Those
transferred aquatic organisms could be considered invasive in another area.
This phrase refers to the fact that the elements in organic matter are eventually returned to the
soil because when an organism dies, decomposers in the soil break down its organic matter.
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5. True or false: Even though the open ocean has a low net primary productivity, it still
accounts for the majority of Earth’s total net primary productivity because of its sheer size.
If false, make it a correct statement.
6. Ecosystems vary in their energy efficiency, but as a general rule, ____________% of the
energy available at one level is transferred to the next trophic level.
7. Why do ecosystems tend to have very few tertiary and quaternary predators while having an
abundance of different producers and primary consumers?
8. Humans can learn something about our own sustainability from the fact that available energy
decreases as you go up in trophic levels. What is a simple solution (that would require no new
technology) for how humans could feed more of our species?
9. A quote by a scientist reads: “Three hundred trout are needed to support one man for a year.
The trout, in turn, must consume 90,000 frogs that must consume 27 milliongrasshoppers that
live off 1,000 tons of grass.”What is this quote trying to make us aware of?
10. True or false: Certain elements are continuously cycled between biotic and abiotic portions of
an ecosystem. If false, make it a correct statement.
11. List four components of the biogeochemical cycles that replenish the abiotic reservoir. Refer
to Figure 37.18 on page 753 of your textbook.
a. ____________________________
b. __________________________
c. _____________________________________________________________
d. _______________________________________
12. List the sources of carbon in the abiotic reservoirs.
13. Briefly explain the roles of cellular respiration and photosynthesis in the carbon cycle.
14. Would clear cutting massive expanses of forests affect the carbon cycle? If so, what aspect of
the carbon cycle would be altered? Refer to Figure 37.19 on page 753 of your textbook.
The quote is trying to make us aware of the idea that less energy is available at successive
trophic levels.
True
Nutrients available to consumers
Consumers feed on producers
Release of chemicals into the environment by producers and consumers
Breakdown of organic matter by decomposers
It exists as CO
2
in the atmosphere and in fossil fuels and sedimentary rocks. It is also dissolved
in water as various carbon compounds that include CO
2
.
They are chemical opposites of each other: photosynthesis removes carbon from the abiotic
reservoir and incorporates it into organic matter, and cellular respiration removes carbon from
the biotic reservoir and returns it to the abiotic reservoir.
10
True
Only a fraction of the energy in biomass is available to consumers in subsequent trophic levels.
For example, it takes a lot of mice to maintain a population of owls. As such, the population
of tertiary and quaternary consumers is limited.
We could eat at a lower trophic level (vegetarianism) and have more energy available to us.
Yes, because the ability to remove carbon from the abiotic reservoir would be hindered now
that the trees are gone and they are no longer performing photosynthesis.
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15. List three uses for phosphorous in organisms.
16. The ____________ of ____________ releases __________________ ions to the soil.
17. In general, what would a human need to eat in order to get phosphorous?
18. True or false: Plants cannot absorb atmospheric nitrogen gas. As such, plants require
bacteria to convert atmospheric nitrogen to a form they can readily uptake. If false, make it a
correct statement.
19. Nitrogen is made available to plants by the action of soil ____________ in a process called
______________.
20. What is the natural increase in a lake’s primary productivity over time called?
21. List three sources of phosphate pollution.
22. Which of the following explains why nitrate-heavy fertilizers are problematic?
a. Bacteria convert it to N
2
.
b. It is easily washed out by rain or irrigation.
c. Bacteria convert it to NH
3
.
d. It combines with oxygen in the soil, which increases the soil acidity.
23. The goal of developing and managing Earth’s natural resources so that current and future
generations can benefit from them is known as ____________.
CONNECTING THE BIG IDEAS
Use your knowledge of the information contained within this chapter’s “Big Ideas” to answer this
question.
You are discussing conservation with your neighbor. He tells you that saving biodiversity in polar
regions is pointless because most biodiversity is found in the tropics. What would your response be?
Do you agree or disagree?
Its uses include: a component of teeth and bones, a component of nucleic acids, and a compo-
nent of phospholipids.
True
This is known as eutrophication.
They are found in pesticides, fertilizers, and runoff from livestock feedlots.
Humans need to eat plants.
weathering
rock
bacteria
sustainability
nitrogen fixation
inorganic phosphate
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