3.4.7 Animal Adaptations For Their Environment

Key Adaptations of Mass Transport Systems:

1. Haemoglobin Affinity:

• Animals in different environments have haemoglobin with varying affinities for oxygen.
• High-altitude animals:
• Have haemoglobin with a higher oxygen affinity to load oxygen efficiently at low partial pressures.
• Active organisms:
• Have haemoglobin with a lower oxygen affinity, making it easier to unload oxygen to respiring tissues.

2. Circulatory System:

• Adapted to meet the metabolic demands of the organism:
• Large mammals have double circulatory systems to separate oxygenated and deoxygenated blood, maintaining high blood pressure and efficient oxygen delivery.
• Fish have a single circulatory system, which is sufficient for their lower metabolic rates.

3. Heart Rate and Cardiac Output:

• Endotherms (warm-blooded animals) have higher heart rates and larger cardiac outputs to meet the demands of maintaining body temperature.
• Ectotherms (cold-blooded animals) have slower heart rates as their metabolism is influenced by environmental temperatures.

4. Surface Area to Volume Ratio (SA
   ):

• Small animals:
• Have a high SA
  ratio and lose heat quickly. They compensate with high metabolic rates and efficient circulatory systems.
• Large animals:
• Have a low SA
  ratio, reducing heat loss, and are often adapted with slower metabolic rates.

Examples of Adaptations:

1. Polar Animals:

• E.g., seals, penguins.
• Large size and low SA
  ratio minimise heat loss.
• Myoglobin-rich muscles store oxygen for long dives.

2. Desert Animals:

• E.g., camels.
• Efficient water retention reduces plasma loss, maintaining blood volume.
• Can tolerate higher body temperatures to conserve water.

3. High-Altitude Animals:

• E.g., llamas, snow leopards.
• Haemoglobin with a high oxygen affinity ensures oxygen uptake in $pO₂$ low.
• Larger lung surface area to enhance gas exchange.

4. Diving Animals:

• E.g., whales, seals.
• Store oxygen in myoglobin in muscles rather than relying solely on haemoglobin.
• Lower heart rate during dives (bradycardia) conserves oxygen.

Summary of Key Adaptations:

Environment	Adaptation	Purpose
High Altitudes	High-affinity haemoglobin	Efficient oxygen uptake at low $pO₂$.
Aquatic/Diving Animals	Myoglobin storage, slow heart rate	Prolonged oxygen supply for underwater diving.
Cold Environments	Low SA ratio, fat insulation	Minimises heat loss.
Hot/Dry Environments	Water conservation, heat tolerance	Maintains blood volume and reduces water loss.

Key Terms:

• Myoglobin: A protein in muscles that stores oxygen.
• Bradycardia: Slowing of the heart rate during dives.
• SA
  Ratio: Surface area to volume ratio affecting heat and energy exchange.