Herpetology Exam 2 Review

Multiple Choice Questions on Reptiles and Amphibians

  • Strategies for Excretion of Nitrogenous Waste
    • Most reptiles, especially terrestrial species, excrete nitrogenous waste primarily in the form of uric acid.
  • Heat Loss Components
    • Among the components of heat loss affecting temperature regulation, metabolic heat production has the smallest effect, particularly in most reptiles, except for very large species.

Short Answer Section

  • Characteristics of Larval Salamanders

    • One characteristic of larval salamanders is that they do not gradually develop limbs; instead, limbs develop quite quickly.

  • Temperature Regulation in Various Groups

    • Identified groups that do not conform to specific temperature regulation traits were mentioned, with check-ins answering A for the multiple-choice questions.

  • Skin Components Preventing Water Loss

    • The stratum corneum is one component; however, the mesos layers (lipid-filled cells between skin layers) play a significant role as the primary barrier to prevent water loss.

  • Reptiles Gaining Heat

    • Fangalothermy is defined as gaining heat from the substrate or soil, which involves absorbing heat from another surface.

Relationship Between Egg Size, Clutch Size, and Development Type

  • Species that undergo metamorphosis typically lay large clutches of small eggs, given that much of their development occurs outside the egg.
  • Conversely, species that exhibit direct development tend to produce smaller clutches of larger eggs.

Parental Care Behavior in Group Differences

  • The group exhibiting the most parental care is noted for protecting their eggs and young, often remaining with them for extended periods.

Overview of Circulatory Systems

  • Amphibian Circulatory System:

    • Two main circuits: pulmonary circuit (to lungs) and systemic circuit (to body).
    • Homocutaneous is blood that circulates to both skin and lungs.
    • The heart structure includes:
    • Atrial septum divides atria, but there exists only one ventricle with no separation into right and left.
    • Blood flow:
    • Deoxygenated blood returns to the right atrium; oxygenated blood returns to the left atrium from the lungs.
    • The ventricle contains an anatomical division (trabeculae) that minimizes mixing of oxygenated and deoxygenated blood.
    • A spiral valve prioritizes blood flow from the right ventricle to the lungs versus systemic flow.

  • Reptilian Heart Structure:

    • Variants in heart structures exist:
    • Turtles and squamates have a single ventricle that is partially subdivided, allowing for differentiated flow of oxygenated and deoxygenated blood.
    • Cavum venosum receives deoxygenated blood; cavum arteriosum receives oxygenated blood.
    • The ventricle contracts to create a functional wall that directs blood flow appropriately.
    • Oxygen poor and oxygenated blood flows separately via respective aortas, with provisions for adjusting circulatory flow based on activity.

  • Crocodilian Heart Structure:

    • Crocodilians possess two distinct atria and a complete ventricular septum, which completely separates the right and left ventricle.
    • Blood flow dynamics change under different physiological conditions:
    • Higher pressure during normal respiration favors systemic circulation.
    • Under underwater conditions, deoxygenated blood can be redirected via the left aorta (despite it originating from the right ventricle) to prolong time without oxygen.

Heat Gain and Loss in Reptiles and Amphibians

  • Heat Gain and Loss Equation:
    • Components:
    • Radiative heat absorption from solar radiation:
      • Factors involved include intensity of solar radiation, surface area of the animal, and the absorptivity of the animal’s surface.
    • View factor: proportion of the animal exposed to sunlight affecting solar gain.
    • Metabolic heat production in reptiles is often negligible.
    • Infrared Radiation:
    • Emission and absorption depend on the temperature difference between the animal and environment, along with the area exposed to the radiative surfaces.
    • Convection:
    • Movement of air/water around the animal increases heat transfer; the speed and nature of the medium play a role, influenced by the shape and posture of the animal.
    • Heat gained through condensation and lost via evaporation can vary based on skin permeability and environmental humidity and air movement rates.
    • Physical Contact Conductive Heat Transfer:
    • Direct contact with a cooler surface allows for effective heat loss or gain, a mechanism also referenced as figmotherapy.

Sex Determination Mechanisms

  • Genotypic Sex Determination:
    • Activation of specific genes on sex-determining chromosomes post-fertilization leading to gonadal development, producing hormones defining sex.
  • Temperature-Dependent Sex Determination:
    • External temperatures trigger enzymes and hormones affecting gene expression regarding sexual development instead of direct genetic inheritance.

Summary

  • These notes encapsulate definitions, relationships between traits and physiological adaptations of reptiles and amphibians, their circulatory system functions, and mechanisms for thermal regulation, including both heat gain and loss dynamics. They conclude with the understanding of various sex determination systems in these organisms.