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1st Midterm Exam
Fall, 2001
Multiple choice questions.
Correct answers marked in bold.
1. Which is the most ancient division of plants to use pollination as a means of reproduction?
A. angiosperms
B. gymnosperms
C. bryophytes
D. pteridophytes
2. Which of the following is not true of a gametophyte?
A. generated by fertilization
B. grows in cell number by mitosis
C. composed of haploid cells
D. generates gametes by mitosis
3. Why do H2O molecules exhibit cohesion?
A. evaporation
B. ionic bonds
C. covalent bonds
D. hydrogen bonds
4. Which of the following has the properties of a meristem?
A. pollen tube
B. endodermis
C. ovule
D. pericycle
5. Endodermal cells are found in the root. What feature of an endodermal cell limits the flow of ground water from the cortex to the vascular tissue?
A. at maturity, the living part of the cell (protoplast) is dead
B. specialization of its cell wall
C. electric potential across its cell membrane
D. plasmodesmata
6. In a tree, which of the following phenomena is primarily responsible for generating the force that draws water upwards against gravity?
A. electric potential
B. osmosis
C. evaporation
D. active transport of water across cell membranes
7. Geneticists isolate a mutant strain in which the apical meristems produce abnormally large quantities of auxin. Based on your knowledge of plant growth and assuming that everything else is normal, what would you expect this mutant to look like?
A. unusually short shoots with few sidebranches
B. unusually short shoots with excess sidebranches
C. overly long shoots with few sidebranches
D. overly long shoots with excess sidebranches
8. As a tree grows, the trunk sheds the original epidermis and replaces it with bark. Bark contains which kind(s) of tissue?
A. phloem and xylem
B. ground tissue and phloem
C. ground tissue and xylem
D. ground tissue only
9. During pollination, a pollen tube elongates without any significant increase in diameter. Given what you know about the growth of plant cells, what would you predict to be the orientation of cellulose microfibrils in the cell wall of the pollen tube?
A. random
B. aligned along the length of the tube
C. aligned around the circumference of the tube
D. criss-crossed diagonally
10. An H2O molecule enters a leaf as part of the xylem sap. From the time it enters the leaf, what is the minimum number of cell membranes this H2O molecule would have to cross before it could evaporate into the atmosphere?
A. zero
B. one
C. two
D. four
Questions 12-15 are short-answer essay questions. Answers are shown in italics.
12. Vascular tissue
A. [4 pts]
Describe the anatomy of the cells that compose functional xylem tissue.
The living part [protoplast] of the xylem cell dies, leaving behind its cell wall to serve as an empty tube. These cell walls have perforations to facilitate water flow across the wall.
B. [3 pts]
What general class of nutrients are dissolved in the 'xylem sap' that flows through xylem vessels?
Minerals.
C. [6 pts]
Describe the anatomy of the cells that compose functional phloem tissue.
Phloem is composed of sieve tubes and companion cells.
The sieve tube lacks a nucleus or ribosomes, and is connected to neighboring cells by plasmodesmata.
The companion cell has a nucleus, and provides the sieve tube with gene products through the plasmodesmata that join them. However, the companion cells are not directly involved in transporting sap and do not have plasmodesmata joining them to one another.
D. [3 pts]
What is the most important difference in the chemical composition of 'phloem sap' and xylem sap?
Phloem sap carries organic nutrients, typically in the form ofsimple sugars.
E. [4 pts]
Where does phloem sap flow from, and where does it flow to? Be specific.
Phloem sap flows away from a source of organic nutrients. This could be a leaf that is actively generating sugar by photosynthesis, or it could be an organ such as a tuber where such nutrients are stored.
Phloem sap flows to other parts of the plant where organic nutrients are needed or will be stored.
13. Reproduction of flowering plants
For all of the following questions, assume that the flower is complete.
NOTE: any one of the listed answers was accepted as correct.
A. [4 pts]
Name the floral organ(s) in which meiosis takes place.
1. stamen/anther
2. carpel/ovary/ovule
B. [3 pts]
Name the floral organ(s) in which fertilization takes place.
carpel/ovary/ovule/embryo sac
C. [5 pts]
Angiosperms undergo 'double fertilization'. What does this mean?
The mature pollen grain generates two sperm cells. If pollination is successful, both sperm are delivered to the embryo sac where they each fertilize a different cell [egg cell & central cell with polar nuclei]
D. [5 pts]
What structures are produced as a result of double fertilization?
1. zygote/embryo (which becomes the sporophyte)
2. endosperm
E. [3 pts]
Following fertilization, what part of the flower gives rise to the seed? Be specific.
ovule
14. Plant cell physiology
A. [4 pts]
What does it mean when we say that a plant cell is 'turgid'?
A turgid cell has absorbed so much water that it is pressing outward against its cell wall.
B. [5 pts]
If you know that a plant cell is turgid, what does this tell you about the osmotic pressure across that cell's membrane?
In a turgid cell, osmotic pressure is drawing water into the cell from its surroundings. Put another way, the inside of the cell is hyperosmotic compared to the extracellular fluid.
C. [3 pts]
What is the primary difference between the active and passive transport of ions across a cell membrane?
Active transport requires the energy released by hydrolysis of ATP. Passive transport does not.
D. [8 pts]
According to the 'Acid Growth Hypothesis', how does the binding of auxin to its receptor lead to the activation of the enzyme expansin?
1. Binding of auxin to its receptor results in increased activity of the proton pump.
2. Increased activity of the proton pump lowers the pH outside of the cell membrane, i.e. in the cell wall. [Lowering the pH is the same as "acidification", or an increase the concentration of H+ ions.]
3. This lower pH activates expansin.
15. Growth
A. [12 pts]
Name the parts of a primary meristem and the differentiated tissue that each part will produce.
1. protoderm, which produces epidermis
2. ground meristem, which produces ground tissue
3. procambium, which produces vascular tissue
B. [3 pts]
Woody plants contain both primary xylem and secondary xylem. How does the plant produce its primary xylem?
Primary xylem is produced during primary growth by cell divisions of the apical meristem and/procambium.
C. [3 pts]
How does a woody plant produce its secondary xylem?
Secondary xylem is produced during secondary growth by cell divisions of the vascular cambium, one of the two lateral meristems. But only those cells that come to lie inside the vascular cambium will differentiate into xylem.
D. [2 pts]
What becomes of primary and secondary xylem as the tree ages?
With age, both primary and secondary xylem cease to function as vascular tissue, and instead serve as the heartwood which provides mechanical support to the tree trunk.
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