Lecture Notes: The Evolution and Adaptation of Mollusks

Introduction to Mollusks

• Diversity: Over 150,000 species today.
• Origin: Appeared over half a billion years ago as small creatures with protective shells.

Survival and Evolution

• Adaptation: Mollusks adapted body parts in response to challenges.
• Basic Toolkit:
  • Foot: Used for mobility.
  • Radula: Rasping tongue used for eating.
  • Mantle: Secretes the shell, providing protection.

Defense Mechanisms

• Shell Modifications:
  • Example: Leafy horn mouth uses shell ridges to deter predators.
• Mobility:
  • Example: Abalone uses muscular foot to escape predators like sea stars.

Offensive Adaptations

• Predatory Mollusks:
  • Moon Snail: Uses a large foot to dig and capture prey.
  • Radula Types: Different mollusks have radulas adapted for specific diets.

Evolutionary Innovations

• Swimming:
  • Nautilus evolved jet propulsion and buoyancy.
• Speed vs. Defense:
  • Squid reduced shell size for speed.
  • Developed advanced jet propulsion and muscle structures.

Advanced Adaptations

• Intelligence and Camouflage:
  • Octopuses: Developed intelligence, camouflage, and flexible body designs.
  • Camouflage: Ability to change color and texture rapidly.

Conclusion

• Endurance through Adaptation: Mollusks' ability to change and adapt is a key to their survival over millions of years.
• Adaptability: Continues to be their greatest asset in the evolutionary arms race.