BISC-132: Recorded Lecture 3-5 Notes

Invertebrates: Arthropods

• Subphylum Hexapoda
  • Meaning: Hexa = six; Poda = foot (six-footed insects)
  • Largest subphylum in Arthropoda.
  • Examples: Ants, beetles, cockroaches, butterflies, crickets, flies.
  • Characteristics:
    • Three tagmata: Head, thorax, abdomen.
    • Wings: Significant for success and diverse lifestyles.
    • Mouthparts: Modifiable for diverse feeding strategies (e.g., nectar, blood, etc.).
    • Metamorphosis:
      • Complete: e.g., butterflies (larva → pupa → adult)
      • Incomplete: e.g., grasshoppers (nymph stages)

Transition to Deuterostomes

• Protostomes: Mouth forms first.
• Deuterostomes: Anus forms first.
• Remaining focuses: Chordates and Echinodermata.

Phylum Echinodermata

• Examples: Sea stars, brittle stars, sea urchins, sea cucumbers.
• Characteristics:
  • All marine, no freshwater or terrestrial species.
  • Coelomates: Independently evolved coelom.
  • Symmetry:
    • Larvae: Bilateral symmetry.
    • Adults: Pentaradial symmetry (e.g., sea stars).
  • Anatomy:
    • Organ systems radiate from a central ring.
    • Endoskeleton: Made of calcium carbonate.
  • Water Vascular System:
    • Unique to echinoderms.
    • Uses hydraulic pressure for movement.
    • Functions also as a circulatory system.

Phylum Chordata

• Five Key Features:
  1. Notochord: Flexible rod for support.
  2. Dorsal Hollow Nerve Cord: Forms spinal cord and brain.
  3. Pharyngeal Slits: Used in filter feeding.
  4. Endostyle: Mucus-producing, aids in filter feeding.
  5. Post-Anal Tail: Tail extending beyond the anus.
• Chordates are coelomates with a closed circulatory system.

Non-Vertebrate Chordates

• Subphylum Cephalocordata (Lancelets):
  • Fish-like, no bones or skull.
  • Filter feeders.
• Subphylum Urochordata (Tunicates):
  • Larvae have chordate features, lost in adults.
  • Sessile filter feeders.

Vertebrates (Subphylum Vertebrata/Craniata)

• Key Innovations:
  • Skull and vertebral column.
  • Fish: Paraphyletic group.

Simple Fish

• Hagfish: Scavengers with skull, no vertebrae.
• Lampreys:
  • Have skull and vertebrae.
  • Parasites or filter feeders; no jaws.

Jawed Vertebrates (Gnathostomata)

• Class Chondrichthyes (Cartilaginous Fishes):
  • Includes sharks, rays.
  • Cartilage skeleton, lightweight.
  • Paired fins.

Bony Fishes (Clade Osteichthyes)

• Characteristics:
  • Bone skeleton, heavier but stronger.
  • Swim Bladder: Regulates buoyancy.
  • Operculum: Protects gills, assists in breathing.
• Classes:
  • Actinopterygii (Ray-Finned Fishes):
    • Most bony fish, fins are webs of skin.
  • Sarcopterygii (Lobe-Finned Fishes):
    • Few members, robust fins with muscles and bones.
    • Precursors to limbs of land vertebrates.

Closing

• End of lecture 3-5 and exam content. Next topics include amphibians and beyond.