GENERAL BIOLOGY 2 EXAM 3 ULTIMATE
STUDY PACKAGE CHALLENGING Q AND AS
WITH DETAILED RATIONALES COVERS
PLANT ANATOMY PHYSIOLOGY AND
ANIMAL EVOLUTION)
1. A botanist isolates a mutant strain of Arabidopsis
thaliana that exhibits abnormally high rates of
transpiration even under drought conditions and
elevated atmospheric \(CO_{2}\). Upon closer cellular
inspection, the guard cells are found to have a defective
plasma membrane \(\text{H}^{+}\)-ATPase that
continuously pumps protons out of the cell regardless of
environmental signals. What is the immediate proximal
cause of this open-stoma phenotype?
A. Continuous hyperpolarization of the guard cell membrane
causes a passive efflux of potassium ions (\(\text{K}^{+}\)),
driving water out.
B. Continuous hyperpolarization of the guard cell membrane
facilitates an influx of potassium ions (\(\text{K}^{+}\)) through
voltage-gated channels, driving osmotic water influx.
C. Accumulation of intracellular protons lowers the internal pH,
activating aquaporins to pump water into the guard cells against
its concentration gradient.
D. The extracellular proton gradient directly drives the active co-
,transport of water molecules into the vacuole through sucrose
symporters.
CORRECT ANSWER: B
RATiONAlE: The plasma membrane \(\text{H}^{+}\)-
ATPase pumps protons out of the guard cell, creating a negative
membrane potential (hyperpolarization). This electrical gradient
drives the influx of potassium ions (\(\text{K}^{+}\)) through
inward-rectifying voltage-gated channels. Water follows down
its osmotic gradient into the guard cells, increasing turgor
pressure and forcing the stomata to remain open.
2. You are examining a cross-section of a plant stem
under a microscope and observe the following structural
configuration: a central pith surrounded by isolated
discrete vascular bundles arranged in a distinct
concentric ring, with a clear separation between xylem
facing inward and phloem facing outward. Which plant
group and developmental stage does this specimen
represent?
A. A monocotyledonous stem undergoing advanced secondary
growth.
B. A eudicotyledonous stem exhibiting primary vegetative tissue
organization.
C. A gymnosperm trunk exhibiting mature tertiary wood
formation.
D. A lycophyte shoot illustrating a protostelic vascular
configuration.
CORRECT ANSWER: B
RATiONAlE: Eudicot stems organize their primary vascular
,bundles in a characteristic ring surrounding a central pith.
Monocots show scattered vascular bundles throughout the
ground tissue and typically do not undergo traditional
secondary growth. Gymnosperms form continuous rings of
vascular cambium rather than isolated primary bundles
separated by clear ground tissue zones.
3. During the evolutionary transition from bryophytes to
seedless vascular plants (pteridophytes), a massive shift
in generational dominance occurred. Which of the
following statements accurately characterizes the life-
cycle comparison between a true moss (Bryophyta) and
a typical fern (Polypodiopsida)?
A. The functional moss sporophyte is independent and
photosynthetic, while the fern sporophyte relies entirely on the
gametophyte for nutrition.
B. The moss gametophyte is the dominant, independent
generation, whereas the fern sporophyte is the dominant
generation and becomes independent of the gametophyte.
C. Both groups feature a dominant sporophyte phase, but only
ferns utilize flagellated sperm requiring an aquatic medium for
fertilization.
D. Ferns lack an alteration of generations entirely, utilizing a
diplontic life cycle similar to multicellular animals.
CORRECT ANSWER: B
RATiONAlE: Bryophytes (mosses) are unique among land
plants because the haploid gametophyte is the dominant,
macroscopic, photosynthetic stage of the life cycle, and the
sporophyte remains attached and nutritionally dependent. In
seedless vascular plants like ferns, the diploid sporophyte is
, much larger, independent at maturity, and represents the
dominant generation.
4. A physiological experiment blocks the symplastic
transport pathway in the root cortex of a corn plant
using a specific metabolic inhibitor that induces rapid
closure of all plasmodesmata. Which process would
remain largely unaffected during the initial stages of
root mineral absorption?
A. The bulk movement of water and dissolved nitrates through the
extracellular matrix of the root cortex prior to reaching the
endodermis.
B. The selective migration of sodium ions from cell to cell via
cytoplasmic streams down a concentration gradient.
C. The systemic translocation of heavy metal ions through the
internal cytoplasmic network of the pericycle into the phloem
stream.
D. The active uptake of sucrose from companion cells into sieve-
tube elements via symplastic connections.
CORRECT ANSWER: A
RATiONAlE: The apoplastic pathway consists of the
continuum of cell walls and extracellular spaces. Water and
solutes can move freely through the apoplast of the root cortex
without crossing a plasma membrane or passing through
plasmodesmata until they encounter the impermeable Casparian
strip at the endodermis.
5. Evolutionary biologists utilize the concept of
"alternation of generations" to describe land plant life
cycles. If a mutation prevents meiosis from occurring in
STUDY PACKAGE CHALLENGING Q AND AS
WITH DETAILED RATIONALES COVERS
PLANT ANATOMY PHYSIOLOGY AND
ANIMAL EVOLUTION)
1. A botanist isolates a mutant strain of Arabidopsis
thaliana that exhibits abnormally high rates of
transpiration even under drought conditions and
elevated atmospheric \(CO_{2}\). Upon closer cellular
inspection, the guard cells are found to have a defective
plasma membrane \(\text{H}^{+}\)-ATPase that
continuously pumps protons out of the cell regardless of
environmental signals. What is the immediate proximal
cause of this open-stoma phenotype?
A. Continuous hyperpolarization of the guard cell membrane
causes a passive efflux of potassium ions (\(\text{K}^{+}\)),
driving water out.
B. Continuous hyperpolarization of the guard cell membrane
facilitates an influx of potassium ions (\(\text{K}^{+}\)) through
voltage-gated channels, driving osmotic water influx.
C. Accumulation of intracellular protons lowers the internal pH,
activating aquaporins to pump water into the guard cells against
its concentration gradient.
D. The extracellular proton gradient directly drives the active co-
,transport of water molecules into the vacuole through sucrose
symporters.
CORRECT ANSWER: B
RATiONAlE: The plasma membrane \(\text{H}^{+}\)-
ATPase pumps protons out of the guard cell, creating a negative
membrane potential (hyperpolarization). This electrical gradient
drives the influx of potassium ions (\(\text{K}^{+}\)) through
inward-rectifying voltage-gated channels. Water follows down
its osmotic gradient into the guard cells, increasing turgor
pressure and forcing the stomata to remain open.
2. You are examining a cross-section of a plant stem
under a microscope and observe the following structural
configuration: a central pith surrounded by isolated
discrete vascular bundles arranged in a distinct
concentric ring, with a clear separation between xylem
facing inward and phloem facing outward. Which plant
group and developmental stage does this specimen
represent?
A. A monocotyledonous stem undergoing advanced secondary
growth.
B. A eudicotyledonous stem exhibiting primary vegetative tissue
organization.
C. A gymnosperm trunk exhibiting mature tertiary wood
formation.
D. A lycophyte shoot illustrating a protostelic vascular
configuration.
CORRECT ANSWER: B
RATiONAlE: Eudicot stems organize their primary vascular
,bundles in a characteristic ring surrounding a central pith.
Monocots show scattered vascular bundles throughout the
ground tissue and typically do not undergo traditional
secondary growth. Gymnosperms form continuous rings of
vascular cambium rather than isolated primary bundles
separated by clear ground tissue zones.
3. During the evolutionary transition from bryophytes to
seedless vascular plants (pteridophytes), a massive shift
in generational dominance occurred. Which of the
following statements accurately characterizes the life-
cycle comparison between a true moss (Bryophyta) and
a typical fern (Polypodiopsida)?
A. The functional moss sporophyte is independent and
photosynthetic, while the fern sporophyte relies entirely on the
gametophyte for nutrition.
B. The moss gametophyte is the dominant, independent
generation, whereas the fern sporophyte is the dominant
generation and becomes independent of the gametophyte.
C. Both groups feature a dominant sporophyte phase, but only
ferns utilize flagellated sperm requiring an aquatic medium for
fertilization.
D. Ferns lack an alteration of generations entirely, utilizing a
diplontic life cycle similar to multicellular animals.
CORRECT ANSWER: B
RATiONAlE: Bryophytes (mosses) are unique among land
plants because the haploid gametophyte is the dominant,
macroscopic, photosynthetic stage of the life cycle, and the
sporophyte remains attached and nutritionally dependent. In
seedless vascular plants like ferns, the diploid sporophyte is
, much larger, independent at maturity, and represents the
dominant generation.
4. A physiological experiment blocks the symplastic
transport pathway in the root cortex of a corn plant
using a specific metabolic inhibitor that induces rapid
closure of all plasmodesmata. Which process would
remain largely unaffected during the initial stages of
root mineral absorption?
A. The bulk movement of water and dissolved nitrates through the
extracellular matrix of the root cortex prior to reaching the
endodermis.
B. The selective migration of sodium ions from cell to cell via
cytoplasmic streams down a concentration gradient.
C. The systemic translocation of heavy metal ions through the
internal cytoplasmic network of the pericycle into the phloem
stream.
D. The active uptake of sucrose from companion cells into sieve-
tube elements via symplastic connections.
CORRECT ANSWER: A
RATiONAlE: The apoplastic pathway consists of the
continuum of cell walls and extracellular spaces. Water and
solutes can move freely through the apoplast of the root cortex
without crossing a plasma membrane or passing through
plasmodesmata until they encounter the impermeable Casparian
strip at the endodermis.
5. Evolutionary biologists utilize the concept of
"alternation of generations" to describe land plant life
cycles. If a mutation prevents meiosis from occurring in
