Vertebrates and Invertebrates: Key Concepts

Vertebrates

Evolutionary Advances from Invertebrates to Vertebrates

• Evolution in vertebrates shows a trend towards increased complexity and specialization.

• Such advances enhance the survival of organisms.- Example: Evolution of digestive systems, segmentation.

Evolution of Digestive Systems

• Gastrovascular Cavity:

  • Food enters and exits through the same opening.

  • Lacks specialized areas for processing nutrients.

• Alimentary Canal:

  • Possesses two openings: one for food intake and the other for waste.

  • Can be simple or complex in structure.

  • More complex systems allow for greater specialization in nutrition processing, matching varied diets.

Evolution of Segmentation

• Segmentation can occur externally or internally in vertebrates.

• Williston’s Law states:- Over time, the number of segments tends to decrease.

  • Remaining segments become more specialized in function.

Shared Traits Between Vertebrates and Invertebrates

• Characteristics that all vertebrates share, which may vary in invertebrate phyla:- Tissue Layers: Triploblastic (three layers: ectoderm, mesoderm, endoderm).

  • Symmetry: Bilateral symmetry is common.

  • Body Cavity: Coelomate structure, which allows for more complex body systems.

  • Body Systems: Presence of specialized systems (circulatory, digestive).

Key Characteristics of Vertebrates

• Every vertebrate possesses:- Segmentation: Evidence of segmented bodies.

  • Digestive System: Complete systems with mouth and anus.

  • Circulatory System: Closed circulatory systems with a heart.

Evolutionary Progression in Vertebrates

• Major groups of vertebrates and evolutionary developments:- Lampreys: Defined by having vertebrae.

  • Sharks: Presence of jaws, teeth, paired fins.

  • Ray-finned Fishes: Lobe fins, development of bony skeletons, swim bladders/lungs.

  • Amphibians: Transition to terrestrial realms (limbs with digits).

  • Birds: Adaptation for flight; amniotic eggs.

  • Reptiles: Evolved more efficient egg structures for land.

  • Mammals: Advanced adaptations including hair and mammary glands.

Nervous System in Vertebrates

• All vertebrates possess:- Central nervous system: Brain and spinal cord.

  • Sensory organs vary significantly;

  • Examples include eyes (sight), ears (hearing), nose (smell).

  • Some species have additional sensory capabilities such as:

  • Electroreception: Sensing electric fields.

  • Magnetoreception: Detecting magnetic fields.

Circulatory and Respiratory Systems

• Circulatory System:

  • Varies by the number of heart chambers and circulatory loops.

  • Understand advantages and disadvantages of each design.

• Respiratory System:

  • Structures involved in gas exchange with the environment (e.g., gills, lungs).

Digestive System Characteristics

• Vertebrates generally have a two-ended tube gut:- Accessory organs (liver, pancreas) vary across species.

  • Solutions for enhancing

  • surface area/volume ratios are crucial for efficient digestion.

Excretory and Support Systems

• Excretory Systems: Universally have certain functions, but specific structures may vary between species.

• Support Systems:- Muscles attach to a structured skeleton, which has unique adaptations to different lifestyles.

Anatomical Orientation Terminology

• Terms to describe position:- Caudal: Towards the tail.

  • Dorsal: Back side.

  • Cranial: Head end.

  • Ventral: Belly side.

  • Proximal/Distal: Referencing closeness or distance from the center of the body.

  • Lateral/Medial: Towards the side or middle.