BIO203 Midterm II Review - Plant Evolution

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Questions and Answers

What role does the guard cell play in regulating transpiration?

They transport nutrients through the plant.

They absorb carbon dioxide from the atmosphere.

They regulate the opening and closing of stomata. (correct)

They store water for the plant.

How does temperature affect stomatal transpiration?

Higher temperatures increase vapor pressure difference (vpd), enhancing transpiration. (correct)

Higher temperatures decrease the rate of transpiration.

Lower temperatures increase the stomatal opening.

Temperature has no effect on the transpiration process.

What is the primary function of vacuoles in plant cells?

To store nutrients and maintain turgor pressure. (correct)

To facilitate gas exchange.

To provide structural support and rigidity.

To conduct photosynthesis.

What type of transpiration is primarily facilitated by the leaf cuticle?

Cuticular transpiration. Signup and view all the answers

What does osmosis in plant cells for turgor pressure primarily depend on?

The concentration of solutes in the vacuole. Signup and view all the answers

Which of the following factors can cause stomata to remain open?

Presence of sulfur dioxide (SO2). Signup and view all the answers

What is the primary purpose of the Calvin Cycle in photosynthesis?

To capture atmospheric CO2 and convert it into organic molecules. Signup and view all the answers

What is the net output of the Calvin Cycle for every three molecules of CO2?

1 G3P and require 9 ATP and 6 NADPH. Signup and view all the answers

What is the primary function of sunken stomata in plants?

To minimize water loss in arid environments Signup and view all the answers

How does osmotic potential (𝛹s) affect water potential in plant cells?

Higher solute concentration decreases 𝛹s, making it more negative Signup and view all the answers

What role does turgor pressure (𝛹p) play in plant cells?

It provides mechanical support and drives cell expansion Signup and view all the answers

What is a characteristic of negative pressure potential (𝛹p) in plants?

It typically occurs in the xylem during transpiration Signup and view all the answers

What is the primary function of the vacuole in plant cells?

Storage of nutrients and waste products Signup and view all the answers

How does cuticular transpiration differ from other types of transpiration?

It involves water loss through the cuticle and leaf surface Signup and view all the answers

What effect does increasing solute concentration in a plant's environment have on water potential?

It decreases the osmotic potential and makes the water potential more negative Signup and view all the answers

In what condition would you expect water-stressed plants to have a water potential range of -1 MPa to -1.5 MPa?

Under conditions of low soil moisture availability Signup and view all the answers

What is the primary role of turgor pressure in plant cells?

Supports the structural integrity of the plant Signup and view all the answers

How does auxin contribute to cell wall expansion?

By activating wall-loosening enzymes called expansins Signup and view all the answers

What is the main function of vacuoles in plant cells?

To store water and maintain osmotic balance Signup and view all the answers

Which type of transpiration accounts for the majority of water loss in plants?

Stomatal transpiration Signup and view all the answers

What effect does high humidity have on cuticular transpiration?

It lowers the gradient for water loss Signup and view all the answers

How does temperature influence cuticular transpiration?

Higher temperatures can increase water evaporation Signup and view all the answers

What role do lenticels play in transpiration?

Involved in gas exchange and minor water loss Signup and view all the answers

Which condition is most likely to cause stomata to close?

Drought conditions Signup and view all the answers

What is the main mechanism that causes guard cells to open stomatal pores?

Activation of proton pumps in guard cell membranes Signup and view all the answers

What happens to guard cells when potassium ions exit during stomatal closure?

Water exits guard cells, reducing turgor pressure Signup and view all the answers

What is one of the primary roles of the cuticle on plant surfaces?

Reduces water loss while allowing gas exchange Signup and view all the answers

What factor can influence the rate of lenticular transpiration?

Size and number of lenticels Signup and view all the answers

Which ions are primarily stored in vacuoles to facilitate osmotic adjustment?

Potassium and chloride Signup and view all the answers

What is the formula used to calculate the water content of a plant cell?

Fresh weight - Dry weight Signup and view all the answers

Study Notes

BIO203 Midterm II Review - Study Notes

Chapters Studied: Weeks 5-9, focusing on plant evolution, water relations, and growth/development.

LECTURE 5 – Plant Evolution

Plants' role: Essential to Earth's ecosystems, producing oxygen and supporting terrestrial food chains.
Evolutionary Origin: Land plants (embryophytes) evolved from green algae (charophytes).
Key Milestones:
- Cambrian: First embryophytes.
- Ordovician: Development of xylem and phloem.
- Silurian: Emergence of vascular plants.
- Devonian: Rise of seed plants (gymnosperms, early trees).
- Carboniferous: High oxygen levels, abundant plant evolution (cuticles, roots, etc.).
- Permian: Dry conditions, gymnosperm diversification.
- Triassic: Dominance of gymnosperms.
- Jurassic: Gymnosperms dominant, angiosperm emergence.
- Cretaceous: Rise of angiosperms.
- Neogene/Paleogene: Angiosperms become the major group with diversification.

The Transition to Land

Challenges: Obtaining nutrients, structural support in non-aquatic environments, and reproduction without water.
Adaptations:
- Gametangia: Structures to protect gametes.
- Stomata: Minimize water loss.
- Cuticle: Prevent water loss.
- Alternation of generations: Life cycle alternating between haploid (gametophyte) and diploid (sporophyte) stages.

Groups of Plants

Bryophytes (non-vascular): Liverworts, mosses, and hornworts. Have flagellated sperm that require water for fertilization. Dominated by a gametophyte stage. Small in size.
Vascular Plants (Tracheophytes):
- Non-seeded vascular plants (lycophytes, ferns): Dominant sporophyte stage, reproduction involving spores; still dependent on water for fertilization.
- Seeded vascular plants (gymnosperms): Reproduce using seeds, not enclosed in fruits; wind-pollinated.
- Angiosperms: Reproduce using flowers and seeds enclosed in fruit; use specialized pollinators

LECTURE 6 – Plant Water Relations

Water's importance: Cells are mostly water (80-95%), crucial for transport, maintaining shape, supporting growth, and cooling.
Water potential (Ψ): A measure of water potential energy, affecting water movement (high to low).
Water potential components: Osmotic potential (solute concentration), pressure potential (hydrostatic pressure).
Water movement: Water loss through transpiration (evaporation from leaves), affecting water potential gradients.
Plant adaptations: Structures like stomata, cuticles, and specific leaf structures (e.g. sunken stomata, thick cuticles, narrow leaves) influence water loss and gain.

LECTURE 6 (continued) – Plant Water Relation and Stomata

Stomata: Pores on leaves controlling water loss and gas exchange.
Guard cells: Control stomatal opening/closing.
Stomatal mechanisms: Responses to light, CO2 levels, water availability, and environmental cues, influencing water loss.

PHOTOSYNTHESIS

The Calvin Cycle:
- Steps: Carbon fixation, Reduction, Regeneration
- Key enzyme: Rubisco (Ribulose-1,5-biphosphate carboxylase/oxygenase)
- Purpose: Convert atmospheric CO2 into sugar, using ATP and NADPH from light-dependent reactions within chloroplasts

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Description

Prepare for the BIO203 Midterm II with a focused review of plant evolution, water relations, and growth and development from weeks 5 to 9. This quiz covers critical milestones in the evolutionary history of plants, their ecological roles, and significant physiological adaptations.