Overview of Fish, Amniotes, and Evolution

May 4, 2025

Lecture Notes on Various Biological Concepts

Fish and Ventilation

  • Ray-finned Fish: To hover and ventilate gills effectively, uses operculum besides the swim bladder.

Tunicates and Pharyngeal Gill Slits

  • Blockage: Leads to difficulty in respiring and feeding.

Amniotes

  • Groups of Amniotes: Includes turtles.
  • Embryo Development: In water because amnion encases each embryo in water.
  • Success in Dry Environments: Due to shelled, amniotic egg.

Characteristics of Monotremes and Marsupials

  • Shared Trait: Both have some embryonic development outside the uterus.

Identifying Organisms

  • Hiking Observation: To distinguish between a snake or amphibian, check for presence of scales.
  • Chordates:
    • Most like earliest chordates in appearance are lancelets.
    • Fossil identification between reptile or mammal, examine teeth.

Vertebrate Evolution

  • First Structures: Earliest mineralized structures involved in feeding.
  • First Structures in Chordate Evolution: Paired fins.
  • Bipedalism Evolution Trait: Repositioning of foramen magnum.

Mammals and Birds

  • Feeding Habits: Eat more often than reptiles because of amniotic egg.

Amniotic Egg Structure

  • Closest to Embryo: The amnion.

Bird Respiratory System

  • Air Sacs: Despite not being thin/highly vascularized, they contribute to efficient respiration; not sites of gas exchange.

New Aquatic Chordate Species

  • Characteristics include external armor of bony plates, no paired lateral fins, suspension-feeding.
  • Likely characteristic: no jaws.

Geographic Distribution of Marsupials

  • Found in Australia and the Americas.

Common Ancestor of Tetrapods

  • Likely a sturdy-finned, shallow-water lobe-fin with appendages similar to terrestrial vertebrates.