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Ecosystem of Change
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Printed: August 20, 2015
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C HAPTER
Chapter 1. Ecosystem of Change
1
Ecosystem of Change
Lesson 24.3: True or False
Name___________________ Class______________ Date________
Write true if the statement is true or false if the statement is false.
1.
2.
3.
4.
5.
6.
7.
_______ No ecosystem is completely unchanging.
_______ All ecological change is either primary or secondary succession.
_______ Wind and water help weather rock and form soil in primary succession.
_______ Plants can grow in an area only after soil has formed.
_______ Trees usually colonize an area before small plants such as grasses.
_______ Ecological succession always ends at a final, stable state.
_______ Most ecosystems have climax communities.
Lesson 24.3: Critical Reading
Name___________________ Class______________ Date________
Read this passage based on the text and answer the questions that follow.
The towering trees in an old forest have been growing there for hundreds of years. It may seem as though the forest
has been there forever. But no ecosystem is truly static. The numbers and types of species in most ecosystems
change to some degree through time. This is called ecological succession.
Two important cases of ecological succession are primary succession and secondary succession. Primary succession
occurs in an area that has never before been colonized by living things. Generally, the area starts out as nothing but
bare rock. This type of environment could come about when a landslide uncovers bare rock, a glacier retreats and
leaves behind bare rock, or lava flows from a volcano and hardens into bare rock. Secondary succession occurs in
a formerly inhabited area that was disturbed. Secondary succession could result from a fire, flood, or human action
such as farming. For example, a forest fire might kill all the trees and other plants in a forest, leaving behind only
charred wood and soil.
Does a changing ecosystem ever stop changing? Does its community of organisms ever reach some final, stable
state? Scientists used to think that ecological succession always ended at a stable state, called a climax community.
Now their thinking has changed. Theoretically, a climax community is possible, but continued change is probably
more likely for real-world ecosystems. Most ecosystems are disturbed too often to ever develop a climax community.
Questions
1. Define ecological succession.
2. Contrast primary and secondary succession.
3. Why is a climax community unlikely for most ecosystems?
1
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Lesson 24.3: Multiple Choice
Name___________________ Class______________ Date________
Circle the letter of the correct choice.
1. Which events would most likely produce conditions where primary succession would occur?
a.
b.
c.
d.
plowing by a farmer
retreating of a glacier
flooding by a river
burning of a forest
2. In primary succession, the first few species to colonize the area
a.
b.
c.
d.
can live on rock.
weather rock.
help form soil.
all of the above
3. During primary succession, the first plants to live in the area
a.
b.
c.
d.
must be able to grow in thin, poor soil.
use up all the organic matter in the soil.
prevent trees from moving into the area.
are usually tall plants such as shrubs.
4. Which statement about secondary succession is false?
a.
b.
c.
d.
It is faster than primary succession.
The soil is already in place.
Pioneer species include plants.
none of the above
5. Which statement applies to most ecosystems?
a.
b.
c.
d.
They rarely change.
They reach a final, stable community.
They change continuously.
They are rarely disturbed.
6. Adding organic matter to soil
a.
b.
c.
d.
improves soil quality.
helps soil hold water.
may allow shrubs and trees to grow.
all of the above
7. Pioneer species
a.
b.
c.
d.
are the same in primary and secondary succession.
always include plants such as grasses.
are always the first species to colonize a disturbed area.
all of the above
Lesson 24.3: Matching
Name___________________ Class______________ Date________
2
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Chapter 1. Ecosystem of Change
Match each definition with the correct term.
Definitions
1.
2.
3.
4.
5.
6.
7.
_______ type of succession that occurs in a formerly inhabited area
_______ theoretical, final stable state of an ecosystem
_______ first species to colonize a disturbed area
_______ type of succession that occurs in an area that has never before been colonized
_______ possible cause of primary succession
_______ any change over time in the numbers and types of species in an ecosystem
_______ possible cause of secondary succession
Terms
a.
b.
c.
d.
e.
f.
g.
secondary succession
forest fire
ecological succession
climax community
pioneer species
primary succession
landslide
Lesson 24.3: Fill in the Blank
Name___________________ Class______________ Date________
Fill in the blank with the appropriate term.
1.
2.
3.
4.
5.
6.
7.
_____ succession occurs where there is nothing but bare rock.
_____ succession occurs where there is nothing but bare soil.
Bacteria and lichen are pioneer species in _____ succession.
Fireweed and grasses are pioneer species in _____ succession.
_____ succession would occur on lava rock from a volcano.
_____ succession would occur on sediments left behind by a flood.
Most ecosystems are disturbed too often to ever develop a(n) _____ community.
Lesson 24.3: Critical Writing
Name___________________ Class______________ Date________
Thoroughly answer the question below. Use appropriate academic vocabulary and clear and complete sentences.
Assume that lava poured out of a volcano over a large area. When the lava cooled, it hardened to form rock. Explain
how ecological succession will occur in this area.
3