CATS Biology and Physiology 2 — Questions and Answers
Question 1: What is the primary function of lenticels on a tree's bark?
- Gas exchange between inner tissues and atmosphere (Correct answer)
- Water absorption from rainfall
- Nutrient transport from roots to leaves
- Protection against insect boring
Correct answer: Gas exchange between inner tissues and atmosphere
Lenticels are porous openings in bark that allow oxygen and carbon dioxide to pass between the atmosphere and the living cells beneath.
Question 2: Which vascular tissue is responsible for transporting sugars produced by photosynthesis downward through the tree?
- Xylem
- Cambium
- Phloem (Correct answer)
- Pith
Correct answer: Phloem
Phloem conducts photosynthates (sugars) from leaves to roots and other non-photosynthetic tissues through sieve tube elements.
Question 3: In trees, what is the zone called where new xylem and phloem cells are produced?
- Heartwood
- Vascular cambium (Correct answer)
- Cork cambium
- Endodermis
Correct answer: Vascular cambium
The vascular cambium is the meristematic layer that divides to produce secondary xylem (wood) inward and secondary phloem outward.
Question 4: What happens to a tree's stomata during periods of drought stress?
- They open wider to increase CO2 uptake
- They close to reduce water loss (Correct answer)
- They produce more guard cells
- They convert to lenticels
Correct answer: They close to reduce water loss
Guard cells lose turgor pressure during drought, causing stomata to close and reducing transpiration, though this also limits photosynthesis.
Question 5: Which anatomical feature distinguishes hardwood (angiosperm) trees from softwood (gymnosperm) trees under a microscope?
- Presence of resin canals
- Presence of vessels (pores) (Correct answer)
- Presence of tracheids
- Absence of growth rings
Correct answer: Presence of vessels (pores)
Hardwoods contain vessels (large-diameter pores) for water conduction, while softwoods rely solely on tracheids for this function.
Question 6: What is the primary role of mycorrhizal fungi in association with tree roots?
- Fixing atmospheric nitrogen into soil
- Extending root surface area for water and nutrient absorption (Correct answer)
- Breaking down cellulose in dead wood
- Producing antifungal compounds to protect roots
Correct answer: Extending root surface area for water and nutrient absorption
Mycorrhizal hyphae dramatically increase the absorptive surface area of roots, improving uptake of phosphorus, water, and other minerals.
Question 7: What process describes water movement upward through xylem vessels driven by evaporation from leaves?
- Osmosis
- Transpiration-cohesion-tension (Correct answer)
- Root pressure alone
- Capillary action alone
Correct answer: Transpiration-cohesion-tension
The transpiration-cohesion-tension mechanism uses evaporative pull at leaves, water's cohesive properties, and negative pressure to move water from roots to canopy.
CATS Biology and Physiology 2
What is the primary function of lenticels on a tree's bark?