Transport in Animals

Transport systems distribute nutrients, gases, and waste products within animals.

Introduction

• Transport Systems: Function to circulate essential substances throughout an animal's body, similar to city transport networks.
• Open Circulatory Systems:
  • Definition: A system where haemolymph flows into body cavities, directly bathing the organs.
  • Examples: Seen in arthropods and mollusks.
  • Structure & Function:
    • Lacks capillary beds; organs are directly bathed by haemolymph.
    • Requires less energy but is less efficient than closed systems.

• Closed Circulatory Systems:
  • Definition: A system in which blood is contained within vessels, allowing for efficient circulation.
  • Examples: Common in vertebrates such as mammals and birds.
  • Structure & Function:
    • Comprises the heart, arteries, veins, and capillaries.
    • Facilitates efficient exchange of nutrients and gases.

Gas Exchange & Respiratory Structures

In Mammals

• Lungs and Alveoli:
  • Structure: Lung lobes contain alveoli, which maximise surface area for gas diffusion.
  • Function: Enable the exchange of oxygen and carbon dioxide.

• Ventilation Mechanism:

  • Involves the diaphragm and intercostal muscles, controlling respiratory pressure changes.
  • Breathing involves the intake of air into the lungs through negative pressure.

• Gas Transport:

  • Oxygen binds to haemoglobin once in the bloodstream.
  • Carbon dioxide is transported from the blood to alveoli for expulsion.

In Fish

• Gills:
  • Structure: Composed of arches, filaments, and lamellae.

• Counter-Current Exchange:
  • Mechanism where blood and water flow in opposite directions to sustain an oxygen gradient.

In Insects

• Tracheal System:
  • Structure: Includes spiracles, tracheae, and tracheoles.
  • Adaptations are aimed at minimising water loss while maximising oxygen intake.

Adaptations to Environment

• Species develop circulatory adaptations to address specific environmental challenges.
• Example: Elevated red blood cell count at high altitudes.

Summary Table of Respiratory Strategies

Feature	Mammals	Fish	Insects
Respiratory Organs	Lungs, Alveoli	Gills, Lamellae	Tracheae, Spiracles
Gas Exchange Medium	Air	Water	Air
Main Transport System	Blood circulation	Counter-current	Direct diffusion

Questions with Solutions

1. Explain the fundamental differences between open and closed circulatory systems.

   Solution: In open circulatory systems, haemolymph flows directly into body cavities, bathing organs without being confined to vessels. This is common in arthropods and mollusks. Closed circulatory systems contain blood within vessels (arteries, veins, capillaries), allowing more efficient and directed transport of substances. Closed systems are found in vertebrates and provide better control of blood distribution.

2. What makes the closed circulatory system as efficient as a high-speed railway network?

   Solution: The closed circulatory system is efficient like a railway network because blood remains contained within vessels, allowing for:

   • Directed flow to specific tissues through specialised pathways
   • Maintenance of different pressures in different parts of the system
   • Efficient oxygen delivery through capillaries that reach individual cells
   • Coordinated regulation through the heart's pumping action (similar to a central station)

3. How does natural selection modify these systems based on environmental factors?

   Solution: Natural selection modifies circulatory systems based on:

   • Oxygen availability (e.g., fish in oxygen-poor environments develop more efficient gills)
   • Altitude adaptation (increased red blood cell production at high altitudes)
   • Temperature regulation needs (varying blood vessel distribution in cold vs warm environments)
   • Activity levels (highly active animals develop more sophisticated closed systems)
   • Size considerations (larger animals require more sophisticated circulation)