Early Vertebrates

Early Vertebrates

  • Description of Lampreys and Hagfishes as early vertebrates.
  • Also referred to as cyclostomes; focus on remembrance of term 'early vertebrates.'
  • Potential discussion on jawed organisms such as sharks.

Echinoderms Overview

  • Groups of echinoderms include:
    • Star-shaped organisms (e.g., sea stars, brittle stars)
    • Round organisms (e.g., sand dollars, sea urchins)
  • Emphasis on differentiation from other marine life (e.g., sea cucumbers, sea sponges).
  • Importance of diversity of life and evolutionary history reflected in shared and unique characteristics.
  • Relationships between traits, benefits, and evolutionary advantages discussed.

Questions for Discussion

  • Inquiry: What traits do echinoderms share?
  • Consideration of how echinoderm traits match their environments.
  • Types of mobility in echinoderms discussed.
  • Example: Sea stars have mouths underneath to match their environment.

Chordates

  • Definition and characteristics of chordates:
    • Notochord
    • Dorsal nerve cord
    • Pharyngeal clefts or slits
    • Post-anal tail

Characteristics and Functions

  • Benefits of these characteristics:
    • Tails aid in mobility, nerve cords aid development of brains and spinal cords.
    • Pharyngeal clefts contribute to parts of the ear in some organisms.
    • Notochord leads to development of a jointed skeleton.

Early Chordates

  • Distinction between lancelets and tunicates as early chordates.

Vertebrates

  • Introduction to vertebrates, with focus on hagfishes and lampreys.
  • Character table linking notochord, vertebrae, and their evolutionary connections discussed.

Functions of Vertebrae

  • Function of the vertebral column:
    • Protects the spinal cord, allowing mobility.
    • Replacement of the notochord during evolution.
  • Vertebrates allow the development of a larger skull supported by stronger internal skeletons.

Characteristics of Early Vertebrates

  • Early vertebrates exhibit cartilaginous vertebral columns.
  • Comparison of cartilaginous and bony vertebrae highlighted.

The Development of Jaws

  • Evolution of jaws and their advantages:
    • Enhances ability to grip, slice, and tear food.
  • Description of the derivation of jaws from skeletal structures supporting gills.
  • Benefits of jaws allow for more complex predatory behaviors.

Brain Development

  • Jaws enhance space for processing sensory information in the forebrain, associated with smell and vision.
  • Connection to decision-making capabilities in higher vertebrates.

Lateral Line System

  • Description of the lateral line system in fish:
    • Allows fish to sense water movements, aiding in predation and evasion.
    • Critical for swimming synchronously in schools.

Evolutionary Changes in Fish

  • Reference to early jawed fishes and their evolution post-Cambrian explosion.
  • Development of streamlined bodies and fins in sharks and bony fishes.

Lungs and Breathing in Fish

  • Discussion of swim bladders in bony fishes as precursors to lungs.
    • Swim bladders assist in buoyancy control.
  • Transition to land through modification of lung structures from existing genetic variations.

Lungfish and Terrestrial Transition

  • Description of lungfish and their adaptations for surviving on land:
    • Development of appendages from lobes, adapting to dry conditions.

Evolutionary Concepts

  • Reinforcement of understanding that evolutionary changes build upon existing structures (natural selection operates on existing genetic variations).

Study Guide Tips

  • Utilization of character tables and phylogenetic relationships to study traits, benefits, and clades.
  • Prepare for exam questions on the benefits of specific traits and their relation to various groups.
  • Focus on the diversity of both invertebrates and vertebrates for a comprehensive understanding of animal life.