ENV 101 Exam 3 V3 | ENV 101
Environmental Science | StraighterLine |
Q&A with Rationale (StraighterLine
ENV101 Exam 3)
1. Which of the following is considered the primary cause of the current global decline in
biodiversity?
A. Introduction of invasive species
B. Habitat destruction and fragmentation
C. Overexploitation of resources
D. Global climate change
Answer: B
Rationale: Habitat loss remains the single greatest threat to biodiversity worldwide due to
human activities like agriculture and urban development. When natural areas are broken
into smaller patches, species often lose the resources necessary for survival and
reproduction. This fragmentation disrupts ecological processes and reduces the resilience
of remaining populations.
2. In the context of ecosystem management, what defines a ‘keystone species’?
A. A species that is the most abundant in an ecosystem
B. A species that is first to colonize a barren habitat
,C. A species that is at the bottom of the food chain
D. A species that has a disproportionately large effect on its environment relative to its
biomass
Answer: D
Rationale: Keystone species play a critical role in maintaining the structure of an
ecological community. Their removal can lead to a drastic shift in the ecosystem or even
total collapse. For example, sea otters are keystone species because they control sea urchin
populations, preventing the destruction of kelp forests.
3. Which U.S. law provides for the protection and recovery of imperiled species and the
ecosystems upon which they depend?
A. The Endangered Species Act
B. The National Environmental Policy Act
C. The Clean Water Act
D. The Lacey Act
Answer: A
Rationale: The Endangered Species Act (ESA) was enacted in 1973 to protect species at
risk of extinction. It prohibits the ‘taking’ of listed species and requires federal agencies to
ensure their actions do not jeopardize species survival. The law is a cornerstone of
American conservation policy and has been instrumental in the recovery of the bald eagle.
, 4. What process occurs when excess nutrients, such as nitrogen and phosphorus, enter a body
of water, leading to excessive algal growth?
A. Salinization
B. Bioaccumulation
C. Eutrophication
D. Biomagnification
Answer: C
Rationale: Eutrophication is often triggered by agricultural runoff or sewage discharge
into water bodies. The resulting algal blooms block sunlight and eventually die, leading to
decomposition that consumes dissolved oxygen. This lack of oxygen creates ‘dead zones’
where most aquatic life cannot survive.
5. Which of the following is an example of a point source of water pollution?
A. Acid rain falling over a large forest area
B. Runoff from a large agricultural field after a rainstorm
C. A pipe discharging waste from a factory into a river
D. Oil and grease runoff from city streets
Answer: C
Rationale: Point source pollution originates from a single, identifiable location such as a
pipe, ditch, or smokestack. Because the source is localized, it is generally easier to monitor
Environmental Science | StraighterLine |
Q&A with Rationale (StraighterLine
ENV101 Exam 3)
1. Which of the following is considered the primary cause of the current global decline in
biodiversity?
A. Introduction of invasive species
B. Habitat destruction and fragmentation
C. Overexploitation of resources
D. Global climate change
Answer: B
Rationale: Habitat loss remains the single greatest threat to biodiversity worldwide due to
human activities like agriculture and urban development. When natural areas are broken
into smaller patches, species often lose the resources necessary for survival and
reproduction. This fragmentation disrupts ecological processes and reduces the resilience
of remaining populations.
2. In the context of ecosystem management, what defines a ‘keystone species’?
A. A species that is the most abundant in an ecosystem
B. A species that is first to colonize a barren habitat
,C. A species that is at the bottom of the food chain
D. A species that has a disproportionately large effect on its environment relative to its
biomass
Answer: D
Rationale: Keystone species play a critical role in maintaining the structure of an
ecological community. Their removal can lead to a drastic shift in the ecosystem or even
total collapse. For example, sea otters are keystone species because they control sea urchin
populations, preventing the destruction of kelp forests.
3. Which U.S. law provides for the protection and recovery of imperiled species and the
ecosystems upon which they depend?
A. The Endangered Species Act
B. The National Environmental Policy Act
C. The Clean Water Act
D. The Lacey Act
Answer: A
Rationale: The Endangered Species Act (ESA) was enacted in 1973 to protect species at
risk of extinction. It prohibits the ‘taking’ of listed species and requires federal agencies to
ensure their actions do not jeopardize species survival. The law is a cornerstone of
American conservation policy and has been instrumental in the recovery of the bald eagle.
, 4. What process occurs when excess nutrients, such as nitrogen and phosphorus, enter a body
of water, leading to excessive algal growth?
A. Salinization
B. Bioaccumulation
C. Eutrophication
D. Biomagnification
Answer: C
Rationale: Eutrophication is often triggered by agricultural runoff or sewage discharge
into water bodies. The resulting algal blooms block sunlight and eventually die, leading to
decomposition that consumes dissolved oxygen. This lack of oxygen creates ‘dead zones’
where most aquatic life cannot survive.
5. Which of the following is an example of a point source of water pollution?
A. Acid rain falling over a large forest area
B. Runoff from a large agricultural field after a rainstorm
C. A pipe discharging waste from a factory into a river
D. Oil and grease runoff from city streets
Answer: C
Rationale: Point source pollution originates from a single, identifiable location such as a
pipe, ditch, or smokestack. Because the source is localized, it is generally easier to monitor
