S25 DFF Midterm 2 Study Guide v2

Biological Interests Organization (BIO) Class Study Guide for Exam 2

Tips for Exam Preparation

• Utilize learning objectives for structured study.

• Focus on identifying areas of discomfort in understanding.

Transport in Plants

Movement of Xylem Sap

• Speed of Movement: Xylem sap can travel up to 15 meters/hour.

• Height Examples:

  • Redwood trees: 110 meters

  • Douglas fir: 100 meters

  • Sitka spruce: 90 meters

• Forces Behind Movement:

  • Root Pressure: Creates pressure in roots, aiding upward water movement.

  • Transpiration Pull: Driven by water loss from leaves.

Transpiration Pull

• Leaves are crucial for water loss through transpiration.

• Water Loss in Maple Trees: Up to 200 liters/hour on sunny days.

• Properties of Water:

  • Cohesion: Water molecules stick together through hydrogen bonding.

  • Adhesion: Water molecules attach to other substances.

• Xylem Structure: Made up of hollow cells (tracheids and vessel elements) with hydrophobic lignin walls.

• Transpiration-Cohesion-Tension Theory: Explains upward water movement in plants due to transpiration in leaves.

Movement of Phloem Sap

• Direction of Movement: From sources (e.g., leaves) to sinks (e.g., roots, fruits).

• Phloem Loading:

  • Propelled by hydrostatic pressure from high sucrose concentration in the phloem.

• Mechanism: Water from xylem enters phloem, creating pressure that pushes sap away from the source.

Regulation of Stomata Opening and Closing

• Guard Cells: Regulate stomatal pores for gas exchange, responsive to water uptake.

• Mechanism:

  • Water uptake decreases water potential (y), leading to guard cell turgidity and pore opening.

  • Potassium ions (K+) play a key role; proton pumps facilitated by ATP help regulate ion balance.

Factors Influencing Stomatal Behavior

• Stomatal Opening: Activated by blue light triggering proton pumps in guard cells, increasing sugar concentration and lowering water potential.

• Stomatal Closing: In darkness, potassium ions exit, leading to flaccidity and closure. Water stress or abscisic acid can also trigger closure.

Study Questions

• What creates the "push" and "pull" forces for sap movement?

• How does sucrose concentration affect Ψp?

• Explain how a maple leaf contributes to negative pressure for water movement.

Plant Nutrition

Overview

• Autotrophs: Plants produce their own food via photosynthesis and respiration.

Key Elements

• Carbon, Hydrogen, Oxygen: Sourced from environment. Photosynthesis converts CO2 and H2O into carbohydrates.

• Mineral Elements: Require various minerals for growth, often termed mineral nutrients.

  • Characteristic deficiency symptoms guide soil improvements.

Plant Cell Wall

• Composed mainly of carbohydrates; provides structural support.

Parasitism in Plants

• Some plants extract nutrients through parasitic relationships; may be photosynthetic or non-photosynthetic.

Nitrogen Sources and Cycle

• Nitrogen (N): Most limiting mineral for growth; cannot be utilized directly from atmosphere (N2). Requires nitrogen-fixing bacteria to convert N2 into usable forms.

• Nitrogen Cycle Steps:

  • Conversion of N2 to ammonium (NH4+) facilitated by beneficial bacteria.

Plant Development and Hormones

Dynamic Growth

• Plants exhibit indeterminate growth, continually responding to environmental stimuli.

Germination Process

• Factors: Water, light, mechanical break, temperature (stratification) activate dormant embryos.

• Water Imbibition: Starts germination; activates gibberellin (GA).

Gibberellin Action

• • Stimulates aleurone cells to produce a-amylase for starch digestion, fueling seedling growth.

Plant Hormones Overview

• Types:

  • Auxin: Regulates growth and phototropism.

  • Cytokinin: Promotes branching; counteracts auxin.

  • Abscisic Acid (ABA): Induces stomatal closure and seed dormancy.

  • Ethylene: Involved in fruit ripening.

External Cues: Light

• Essential for photosynthesis, triggers flowering via critical daylength response. Photoreceptors like phytochrome mediate responses to light changes.

Flowers and Control of Flowering

Floral Components

• Structure includes sepals, petals, stamen, and pistil. Each plays a specific role in reproduction and attraction of pollinators.

Pollination Process

• Involves pollen recognition at stigma and germination leading to fertilization.

Endosperm Function

• Provides nutrients for the developing embryo; GA facilitates processes necessary for germination.

Homeostasis

Definition and Importance

• Homeostasis: Maintaining internal stability (e.g., constant temp, pH levels) is vital for survival.

Parameters to Regulate

• Includes temperature, pH, blood glucose, and ion concentrations.

• Thermoregulation: Heat conservation/dissipation through blood vessel adjustments (vasoconstriction and vasodilation).

Q10 Temperature Coefficient

• Indicates physiological sensitivity to temperature changes.

  • Q10 = 3 means the rate triples with a 10°C rise.

Types of Temperature Regulators

• Homeotherms: Maintain a consistent body temperature (e.g., mammals).

• Poikilotherms: Body temperature varies with the environment.

Muscles

Definition and Role

• Muscles are specialized tissues that convert ATP to mechanical energy.

Types of Muscles

• Skeletal Muscle: Voluntary, striated; responsible for body movement.

• Cardiac Muscle: Involuntary, striated; pumps blood in the heart.

• Smooth Muscle: Involuntary; controls hollow organ functions like digestion.

Skeletal Muscle Structure

• Comprised of muscle fibers and myofibrils, organized into contractile units (sarcomeres).

Muscle Contraction Mechanism

• Neuromuscular Junction: Site of nerve impulse transmission, triggering contraction.

• Calcium Ions: Vital in excitation-contraction coupling.

Neurons

Function Overview

• Neurons process sensory input, integrate information, and execute motor outputs.

Structures of Neurons

• Includes cell body, dendrites, axons, and axon terminals.

Action Potentials

• Rapid electrical changes essential for nerve impulse transmission.

• Saltatory Conduction: Increases impulse speed via myelinated axons.

Sensory Systems

Overview

• Sensory systems detect and interpret various stimuli for environmental interaction.

Types of Sensory Modalities

• Include visual, auditory, olfactory, gustatory, tactile, and temperature sensations.

Transduction in Receptor Cells

• Mechanisms convert stimuli into electrical signals processed by the nervous system.

Types of Receptor Proteins

• Ionotropic: Function as ion channels.

• Metabotropic: Involved in secondary messenger systems.

Specific Sensory Systems

• Include olfactory, auditory, and visual systems with specialized receptors for detection.