Lecture Notes on Transport in Biology

Overview

• Focus on plant transport systems with a segment on fish circulatory system.
• Includes questions and answers covering the entire B3.2 module.

Fish Circulatory System

• Double Circulation in Animals (Humans):
  • Blood is pumped twice: systemic and pulmonary circulation.
  • High pressure from the heart pushing oxygenated blood through arteries.
  • Oxygen and nutrients exchanged in capillaries.
  • Deoxygenated blood returns to the heart via veins.
• Single Circulation in Fish:
  • Two chambers in the heart.
  • Blood flows from heart to gills (like lungs in fish), then to body.
  • Blood pressure decreases after passing through gills.
  • Limitations: Significant loss of blood pressure due to single pass through heart.

Plant Transport Systems

• Structure:

  • Roots: Absorb minerals and water.
  • Stem: Supports the plant.
  • Leaves and Flowers: Photosynthesis and reproduction.

• Types of Plants:

  • Monocots and Dicots (IB focus is on dicots).

Xylem

• Transports water from roots to leaves.
• Mechanism:
  • Transpiration from leaves creates negative pressure (suction).
  • Water drawn up through xylem due to transpiration pull.
  • In absence of leaves/transpiration, root pressure occurs via active transport of ions.

Phloem

• Transports organic nutrients (e.g., sucrose) around the plant.
• Composed of living cells: Companion and sieve tube cells.
• Mechanism:
  • Source-to-sink transport via translocation.
  • Active transport moves nutrients to companion cells, then passively to sieve tubes.
  • High sucrose concentration draws water via osmosis, creating pressure that moves sap.

Summary of Key Differences: Xylem vs Phloem

• Xylem:

  • Dead tissue, unidirectional flow, transports water and minerals.
  • Movement from roots to leaves.

• Phloem:

  • Living tissue, bidirectional flow, transports organic molecules.
  • Movement from source (where produced) to sink (where needed).

Key Terminology

• Transpiration: Loss of water from leaves.
• Translocation: Movement of organic molecules in phloem.
• Osmosis: Movement of water across membranes due to concentration differences.

Exam Practice Questions

• Heart and Blood Vessels:

  • Identify vessels carrying deoxygenated blood (e.g., pulmonary artery, vena cava).
  • Sequence of blood flow in the heart.
  • Heart valve positions during various phases.

• Plant Vascular Systems:

  • Process of translocation and its details.
  • Comparison of xylem and phloem.

Conclusion

• Comprehensive understanding of transport systems in plants and fish is essential.
• Practice with sample questions to solidify concepts.

This chapter is extensive, and understanding the circulatory systems in both plants and animals is crucial for mastering the content.