Untitled Notes

20 Photo ID Questions:
- Understand diagnostic features for all 28+ species; features reviewed may differ from lecture images.
30 Multiple Choice Questions:
- Around 10 derived from guest lectures, specifically focusing on the Rio Caecilian invasion, along with other topics; remaining questions sourced from lecture material.
Priority Topics Include:
  - Four diseases
  - Atrazine study
  - Florida frog history
  - Gossner scale
  - Sexual dimorphism
  - Toxins
  - Foot types
  - Tadpoles
  - Different development types
  - Endemic versus invasive species

Class Amphibia ≡ Ectothermic (cold-blooded) tetrapod vertebrates; the origins of the name stem from Greek, where amphi means both and bios means life, indicating a life typically split between aquatic and terrestrial environments.

Ectothermic:
- Body temperature is regulated by the external environment; amphibians cannot produce internal heat, relying on behavioral thermoregulation.
Moist, Glandular Skin:
- Amphibians lack scales, feathers, or hair. Their skin is permeable, allowing for cutaneous respiration. Specialized glands secrete mucus (which maintains moisture) and toxins (for defense). Their skin does not provide waterproofing, making them susceptible to drying out (desiccation).
Double Life:
- Life cycle generally includes an aquatic larval stage that breathes through gills, followed by metamorphosis into a semi-terrestrial adult capable of both lung and cutaneous respiration. However, some species are direct developers, bypassing larval stages.
Gill-Breathing Larvae:
- In typical amphibians, larvae possess either external or internal gills. In contrast, adults evolve to have lungs paired with cutaneous respiration.
Anamniotic Eggs:
- Amphibian eggs are characterized by the absence of an amnion, chorion, and allantois. They must remain moist to survive and are usually laid in water or moist environments. Certain direct developers may have exceptions to this rule.

Tetrapod:
- Defined by possessing four limbs; limbs may be reduced or absent in caecilians and certain salamander species. It is important to note that amphibians evolved from lobe-finned fish approximately 360 million years ago (mya).

Amphibians can absorb oxygen (O₂) and release carbon dioxide (CO₂) through their moist skin. Notably, some lungless salamanders depend exclusively on this method for respiration, which also makes them particularly sensitive to pollutants that come into contact with their skin.