Plant Form and Function, Sugar and Water Transport

Important Molecules for Plant Growth

Plants rely on specific molecules and tissues for growth, especially during secondary growth. These include:

• Primary and Secondary Growth: Meristems are regions of active cell division. Types: Apical meristems (primary growth), lateral meristems (secondary growth).

• Cambium: A type of lateral meristem responsible for secondary growth, producing vascular tissues such as xylem and phloem.

• Vascular/Cork: Vascular cambium produces xylem (water transport) and phloem (sugar transport); cork cambium produces protective outer layers.

SA: Volume Importance

The surface area to volume ratio is crucial for plant organs:

• Roots: Absorb water and minerals; their morphology maximizes surface area for absorption.

• Shoots: Support leaves and reproductive structures; maximize exposure to sunlight.

• Leaves: Large surface area for photosynthesis.

Simple/Compound Leaves

Leaves can be simple (single blade) or compound (divided into leaflets). This affects light capture and water loss.

• Examples: Maple (simple), rose (compound).

Tissue Systems in Plants

Plants have three main tissue systems:

• Dermal Tissue: Protective outer covering; includes epidermis and trichomes.

• Ground Tissue: Functions in photosynthesis, storage, and support.

• Vascular Tissue: Transports water, minerals, and sugars (xylem and phloem).

Water Potential and Transport

Water movement in plants is driven by water potential gradients.

• Water Potential (): The potential energy of water in a system; determines direction of water movement.

• Formula: where is solute potential and is pressure potential.

• Factors: Solute concentration, pressure, gravity.

Bulk Flow and Transpiration

Bulk flow moves water through xylem due to pressure differences.

• Transpiration: Evaporation of water from leaves creates negative pressure, pulling water upward.

• Tension-Cohesion Theory: Water molecules stick together (cohesion) and to walls (adhesion), enabling upward movement.

Active and Passive Transport

Plants use both passive and active transport mechanisms:

• Passive Transport: Movement along concentration gradients (osmosis, diffusion).

• Active Transport: Requires energy to move substances against gradients (e.g., loading sugars into phloem).

Phloem and Sugar Movement

Phloem transports sugars from sources (leaves) to sinks (roots, fruits).

• Companion Cells: Assist in loading/unloading sugars.

• Sieve Tube Elements: Specialized for transport.

Animal Form and Function

Controlling Animal Form and Function

Animal form and function are shaped by genetics, environment, and evolutionary pressures.

• Heritable Adaptations: Traits passed down genetically; subject to natural selection.

• Trade-offs: Adaptations may benefit one function at the expense of another.

Anatomical Organization

Animals are organized into tissues, organs, and organ systems.

• Tissue Types: Epithelial (coverings), connective (support), muscle (movement), nervous (control).

• Organs: Composed of multiple tissue types; perform specific functions.

• Organ Systems: Groups of organs working together (e.g., digestive, circulatory).

Metabolism and Body Size

Metabolic rate is influenced by body size and shape.

• Surface Area to Volume Ratio: Smaller animals have higher ratios, lose heat faster.

• Adaptations: Flattening, folding, branching increase surface area for exchange.

Homeostasis

Maintaining Internal Balance

Homeostasis is the maintenance of stable internal conditions.

• Set Point: The target value for a physiological variable.

• Feedback Mechanisms: Negative feedback reduces deviations; positive feedback amplifies changes.

Thermoregulation

Animals regulate body temperature through various mechanisms.

• Endotherms: Generate heat internally (e.g., mammals, birds).

• Ectotherms: Rely on external sources (e.g., reptiles, amphibians).

• Poikilotherms: Body temperature varies with environment.

Sensory Systems

Types of Sensory Receptors

Sensory receptors detect environmental stimuli and initiate responses.

• Photoreceptors: Detect light (e.g., rods and cones in eyes).

• Mechanoreceptors: Detect pressure, vibration, and touch.

• Chemoreceptors: Detect chemicals (taste, smell).

• Thermoreceptors: Detect temperature changes.

Action Potentials

Action potentials are electrical signals transmitted by neurons.

• Importance: Enable rapid communication within the nervous system.

• Process: Generated when membrane potential reaches threshold.

• Formula: (Ohm's Law, relating voltage, current, and resistance in neurons)

Plant Sensory Systems

Plants also respond to environmental stimuli using specialized proteins and hormones.

• Auxin: Plant hormone involved in growth and response to light.

• Amyloplasts: Organelles that detect gravity.

• Chromoproteins: Proteins involved in light detection.

Electroreception

Some animals detect electric fields for navigation and hunting.

• Electrocytes: Specialized cells that generate electric fields.

• Example: Amphibians and fish use electroreception for prey detection.

Table: Comparison of Thermoregulation Strategies

Additional info:

• Some details on plant and animal tissue types, homeostasis, and sensory systems were expanded for clarity and completeness.

• Equations and examples were added to support understanding of water potential and action potentials.