Botany Practice Test — Medium Level

A free 10-question Botany practice test for Science Olympiad, written at regional and state level. Every question and answer choice is listed below — correct answers and scoring are revealed when you take the timed test.

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Easy (10 questions)

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1. A student observes a plant with small, leaf-like structures arranged along a stem and a low, carpet-like growth habit. The green structure that is most obvious is haploid, and the tall, stalk-like structures with capsules at the tip depend on it for nutrition. To which major plant group does this organism most likely belong?

A.A) Bryophytes (mosses and their relatives)
B.B) Seedless vascular plants (ferns and their relatives)
C.C) Gymnosperms (conifers and their relatives)
D.D) Angiosperms (flowering plants)

2. A student sets up an experiment to measure transpiration by placing identical potted bean plants on electronic balances and recording mass loss over 3 hours. Plant 1 has all leaves intact, Plant 2 has its leaves coated with a thin layer of petroleum jelly on both surfaces, and Plant 3 has only the upper (adaxial) surface of the leaves coated. All other conditions (light, temperature, humidity) are kept constant. Which result would best support the standard model of how transpiration occurs in leaves?

A.A) Plant 1 loses the most mass; Plant 2 loses very little; Plant 3 loses slightly less mass than Plant 1
B.B) Plant 1, Plant 2, and Plant 3 all lose mass at nearly the same rate
C.C) Plant 2 loses the most mass; Plant 3 loses an intermediate amount; Plant 1 loses the least mass
D.D) Plant 3 loses the most mass; Plant 1 and Plant 2 lose the same small amount of mass

3. A C₃ plant leaf fixes CO₂ at a rate of 1.8 × 10⁻⁶ mol CO₂·s⁻¹·m⁻² under constant light. Assuming all of this fixed CO₂ is used to make glucose via photosynthesis (6 CO₂ → 1 C₆H₁₂O₆), how many moles of glucose could theoretically be produced per square meter over 10 minutes? (You may find it helpful to recall that 10 minutes = 600 seconds.)

A.A) 3.0 × 10⁻⁵ mol C₆H₁₂O₆·m⁻²
B.B) 1.8 × 10⁻⁴ mol C₆H₁₂O₆·m⁻²
C.C) 1.08 × 10⁻³ mol C₆H₁₂O₆·m⁻²
D.D) 6.48 × 10⁻³ mol C₆H₁₂O₆·m⁻²

4. A botanist digs up an unknown flowering plant and makes the following observations: • Leaves have parallel veins • Roots form a dense, fibrous mat near the soil surface • Vascular bundles in the stem appear scattered in cross section Which classification best fits this plant?

A.A) Monocot angiosperm
B.B) Eudicot (dicot) angiosperm
C.C) Nonvascular bryophyte
D.D) Seedless vascular plant

5. A researcher grows three grass species in controlled growth chambers: a C₃ cool-season grass, a C₄ grass (corn), and a CAM succulent. Each species is tested under two conditions for 24 hours: (1) moderate temperature with adequate water and open stomata, and (2) hot, dry air where plants close stomata for most of the daylight period. Net photosynthetic rate is measured as mg CO₂ fixed per hour. Which pattern of results is most consistent with how C₃, C₄, and CAM pathways reduce photorespiration?

A.A) Under both conditions, the C₃ grass has the highest net photosynthesis; C₄ is intermediate; CAM is lowest
B.B) Under moderate conditions, C₃ and C₄ are similar and higher than CAM; under hot, dry conditions, C₄ is highest, CAM is moderate, and C₃ drops sharply
C.C) Under moderate conditions, CAM has the highest rate; under hot, dry conditions, CAM and C₃ are equal and higher than C₄
D.D) Under moderate conditions, C₄ is lowest because concentrating CO₂ is energetically costly; under hot, dry conditions, all three decline equally

6. A student performs a girdling experiment on a young tree by removing a complete 2-cm-wide ring of bark (including phloem) all the way around the stem, but leaving the xylem intact. Over the next several weeks, the following events occur: (A) Phloem transport from leaves to roots is interrupted at the girdle. (B) Sugars build up in tissues just above the girdle, causing swelling. (C) Roots starve and begin to die back due to lack of carbohydrate supply. (D) Reduced root function lowers water uptake, and the upper canopy eventually wilts. Which sequence best represents the correct order of these events after the girdle is made?

A.A) B → A → C → D
B.B) A → B → D → C
C.C) A → B → C → D
D.D) B → C → A → D

7. Which statement correctly matches a plant tissue system with its primary function?

A.A) Dermal tissue system – long-distance transport of water and sugars between roots and leaves
B.B) Vascular tissue system – protection and regulation of gas exchange at the plant surface
C.C) Ground tissue system – photosynthesis, storage, and support within leaves and stems
D.D) Meristematic tissue system – formation of protective cuticle over leaf surfaces

8. A student investigates plant hormones using a genetically dwarf pea variety that has very short internodes. She applies different hormones to separate groups of identical seedlings and measures stem height after 2 weeks. The average heights are: Control (no hormone): 4 cm; Treatment 1 (auxin applied to shoot tip): 5 cm; Treatment 2 (gibberellin applied to soil): 15 cm; Treatment 3 (cytokinin applied to leaves): 6 cm. Which conclusion is best supported by these data and current understanding of plant hormones?

A.A) Auxin is the primary hormone controlling stem elongation in dwarf peas, because Treatment 1 increased height the most
B.B) Gibberellins strongly promote internode elongation in this genotype, because Treatment 2 produced the tallest plants
C.C) Cytokinins are responsible for reversing dwarfism, because Treatment 3 plants were taller than all others
D.D) None of the hormones tested affect stem growth; the differences are likely due to experimental error

9. On a hot, dry afternoon, a plant experiences increasing water loss through its leaves. Which change at the cellular level in the leaf would most directly reduce further water loss while also limiting CO₂ uptake?

A.A) Increased turgor in guard cells, widening the stomatal pore
B.B) Decreased turgor in guard cells, causing stomata to close
C.C) Expansion of mesophyll cells to increase internal air space
D.D) Increased division of epidermal cells to thicken the leaf surface

10. An agronomist tests the effect of mycorrhizal fungi on phosphorus uptake in a eudicot crop with a taproot system. Four treatments are set up in replicated pots: (1) no fertilizer, no mycorrhizae; (2) no fertilizer, with mycorrhizae; (3) full-dose phosphorus fertilizer, no mycorrhizae; (4) half-dose phosphorus fertilizer, with mycorrhizae. After 6 weeks, she measures plant biomass and leaf phosphorus concentration. Which outcome would most strongly support the idea that mycorrhizae can reduce the need for phosphorus fertilizer?

A.A) Treatments 1–4 all have similar biomass and phosphorus levels, suggesting phosphorus is not limiting
B.B) Treatment 3 has the highest biomass and phosphorus; all others are much lower, suggesting only fertilizer is effective
C.C) Treatments 3 and 4 have similar high biomass and phosphorus, both clearly higher than Treatments 1 and 2
D.D) Treatment 2 has the highest biomass and phosphorus, much greater than any fertilized treatment