Vertebrate Evolution and Diversity

Overview of Vertebrates

  • Vertebrates include three main groups: amphibians, reptiles, and turtles. Each has distinct characteristics and coursework.
  • The upcoming test will cover plants, protostomes, and specific vertebrate traits.
  • Time provided for the test will allow for thorough completion.

The Evolution of Vertebrates

  • Transition from extinct vertebrates to modern lineages.
    • Discussed hagfishes and lampreys as examples of living vertebrates with rudimentary features (e.g., neural crest).

Chondrichthyes (Cartilaginous Fish)

  • This group includes sharks, rays, and skates.
  • Characterized by:
    • Cartilaginous skeleton rather than bone, an evolutionary loss from earlier fish.
    • Streamlined body shape for efficient movement in water.
    • Unique buoyancy mechanism involving high-density lipids in their livers (shark livers used historically for oil).

Elasmobranchs (Subgroup of Chondrichthyes)

  • Includes sharks and rays, distinguished by:
    • Their teeth develop in whorls, enabling continuous replacement as older teeth fall out.
    • Presence of a spiral valve in the digestive system, enhancing nutrient absorption by increasing digestion time in the intestines.

Sensory Adaptations in Sharks

  • Lateral Line System:
    • A line of electroreceptors along the sides of sharks.
    • Detects electrical impulses from nearby movement, aiding in navigation and hunting.
    • This system helps compensate for their limited visual capabilities underwater.

Bony Fish (Osteichthyes)

  • Major transition from cartilaginous structures to bony skeletons.
    • Swim bladders evolved for buoyancy control; some species developed lungs.
  • Osteichthyes is the most successful vertebrate group, containing over 36,000 species.

Ray-finned vs. Lobe-finned Fish

  • Ray-finned Fish (Actinopterygii):
    • Constitute 99% of fish diversity and include most modern species.
  • Lobe-finned Fish (Sarcopterygii):
    • Much rarer, with fewer than 100 known species.

Unique Examples in Michigan

  • Sturgeon:
    • Long-lived species found in Michigan (over 100 years, 100+ pounds).
    • Notable population in Black Lake:
    • Strict fishing regulations in a lottery system for anglers.
    • Emphasizes sustainability with limits on catches and visible identifiers (flags) for caught fish during ice fishing.