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Difficulty: Very hardVertebrates: Poikilothermic Classes (Pisces, Amphibia, Reptilia)

An investigation comparing the anatomical and physiological adaptations of three poikilothermic vertebrates—the Nile tilapia (Oreochromis niloticus), the adult African toad (Sclerophrys regularis), and the rainbow lizard (Agama agama)—evaluated their cardiac chamber arrangement and primary nitrogenous excretory product. Which of the following combinations correctly identifies both features for each organism in sequence?

  1. Nile tilapia: 2 chambers and ammonia; Adult African toad: 3 chambers and urea; Rainbow lizard: 3 chambers (incomplete ventricular septum) and uric acidAnswer
  2. B
    Nile tilapia: 3 chambers and ammonia; Adult African toad: 2 chambers and urea; Rainbow lizard: 3 chambers (incomplete ventricular septum) and uric acid
  3. C
    Nile tilapia: 2 chambers and urea; Adult African toad: 3 chambers and uric acid; Rainbow lizard: 4 fully separated chambers and ammonia
  4. D
    Nile tilapia: 2 chambers and ammonia; Adult African toad: 3 chambers and uric acid; Rainbow lizard: 3 chambers (incomplete ventricular septum) and urea

Answer

The correct combination is Nile tilapia: 2 chambers and ammonia; Adult African toad: 3 chambers and urea; Rainbow lizard: 3 chambers (incomplete ventricular septum) and uric acid.
The correct response accurately synthesizes the cardiac structural evolution and excretory physiological adaptations across the three poikilothermic classes. Bony fishes such as the Nile tilapia possess a 2-chambered heart and practice ammonotelism (excreting ammonia). Adult amphibians such as the African toad have evolved a 3-chambered heart (2 atria, 1 ventricle) and practice ureotelism (excreting urea). Non-crocodilian reptiles like the rainbow lizard feature a 3-chambered heart with an incomplete inter-ventricular septum and practice uricotelism (excreting insoluble uric acid to conserve body water).

Step-by-Step Solution

1
Analyze cardiac chamber architecture across the three poikilothermic vertebrate classes.
Pisces (Nile tilapia) possess a 2-chambered heart (1 atrium, 1 ventricle) with single circulation. Adult Amphibia (African toad) possess a 3-chambered heart (2 atria, 1 ventricle) with double circulation. Non-crocodilian Reptilia (rainbow lizard) possess a 3-chambered heart with a partially divided ventricle.
Evolutionary trends in poikilothermic vertebrates display a transition from single systemic-branchial circulation to incomplete double circulation.
2
Evaluate the primary nitrogenous excretory product for each vertebrate class based on habitat and water conservation needs.
Aquatic fishes (ammonotelic) excrete highly soluble and toxic ammonia directly into surrounding water. Terrestrial adult amphibians (ureotelic) excrete less toxic urea. Terrestrial reptiles (uricotelic) excrete insoluble uric acid paste to minimize water loss.
Nitrogenous waste elimination adaptations directly correlate with water availability in each organism's ecological niche.
3
Synthesize the combined heart chamber count and excretory product for all three representative species in sequence.
Nile tilapia = 2 chambers, ammonia; Adult African toad = 3 chambers, urea; Rainbow lizard = 3 chambers (partially divided ventricle), uric acid.
Matching all criteria simultaneously identifies the single accurate response.

Key Concept

Comparative cardiac anatomy and nitrogenous waste excretion across poikilothermic vertebrate classes (Pisces, Amphibia, Reptilia)
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Topics

Vertebrates: Poikilothermic Classes (Pisces, Amphibia, Reptilia)

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