Biology and Physiology of Amniotes and Turtles

Breathing Mechanics

  • Exhalation and Inhalation
    • Exhale and then take a deep breath.
    • Diaphragm: Located just below the rib cage, it's a vital muscle for breathing.
    • Action of the Diaphragm: When the diaphragm contracts, it flattens and moves down, increasing the volume in the thoracic cavity, leading to negative pressure within the chest.
    • Air Rushes In: Air enters the lungs because atmospheric pressure is greater outside the chest cavity when the diaphragm contracts, creating a suction effect.

Lung Anatomy and Function

  • Model of Lungs: Diagram or visualization where the diaphragm is represented (e.g., with a lab glove), helps illustrate how lung inflation occurs.
  • Breathing Cycle:
    • Contract: Diaphragm tightens, lungs inflate.
    • Relax: Diaphragm returns to its relaxed state, lungs deflate.
    • This process repeats, allowing continuous respiration.

Amniote Characteristics

  • Diaphragm in Amniotes:
    • Not all amniotes have diaphragms, but all possess rib structures and intercostal muscles that aid respiration.
    • Efficiency: Diaphragms improve oxygen intake efficiency compared to organisms without them.
Circulatory System Evolution

  • Amphibians:

    • Possess a three-chambered heart: mixing of oxygen-rich and oxygen-poor blood occurs in a common ventricle.
    • Circulation includes a homocutaneous circuit and a systemic circuit.

  • Reptiles (excluding birds):

    • Improved circulatory system with three chambers and an incomplete septum, which reduces blood mixing.
    • Display a better-guided blood flow to their respective circuits.

  • Mammals and Birds:

    • Four-chambered heart design leads to complete separation of oxygenated and deoxygenated blood, optimizing circulatory efficiency.
Temperature Regulation in Amniotes

  • Ectotherms:

    • Examples: Lizards, turtles, snakes, crocodiles.
    • Characterized by behavioral thermoregulation: they rely on environmental heat sources, often seen basking in the sun.
    • Have low metabolic rates, generating little internal heat.

  • Endotherms:

    • Examples: Birds and mammals.
    • Characterized by physiological thermoregulation: possess mechanisms to generate and maintain their body temperature independently of environmental temperature.
    • Require insulation: Feathers, Fat, and Fur.

Turtles: Unique Reptiles

  • Distinct Features:

    • Turtles are reptiles with scaly skin, and unique characteristics like a low profile stance and leathery eggs.
    • Special Skeleton: Their shells are part of their skeleton, with the carapace (top part of the shell) having fused vertebral column and ribs.
    • The outer part of their shells is covered in keratin.

  • Feeding:

    • Turtles do not have teeth but possess a beak made of keratin, suitable for their dietary needs (herbivorous/carnivorous).
    • They are oviparous: lay eggs on land, even if they are aquatic. Sea turtles return to shore to lay eggs.

  • Feeding Behavior: Evidence of opportunistic feeding behaviors, such as stealing fish from fishermen's lines.