Examkin

Question

Difficulty: HardVertebrates: Poikilothermic Classes (Pisces, Amphibia, Reptilia)

During a comparative laboratory investigation of preserved poikilothermic vertebrate specimens, a biology student records three distinct anatomical and physiological profiles:

Specimen X possesses dermal placoid scales, a two-chambered heart operating a single-circuit circulatory system, and retains high concentrations of urea in its body fluids for osmoregulation.
Specimen Y exhibits a moist, highly vascularized skin lacking epidermal scales, a three-chambered heart with two atria and one undivided ventricle, and relies on cutaneous respiration alongside buccopharyngeal ventilation.
Specimen Z features dry skin covered in keratinized epidermal scales, a heart with an incompletely divided ventricle (partial septum), and excretes nitrogenous waste primarily as insoluble uric acid.

Which of the following taxonomic groupings correctly identifies Specimens X, Y, and Z respectively?

  1. Class Chondrichthyes, Class Amphibia, Class ReptiliaAnswer
  2. B
    Class Osteichthyes, Class Reptilia, Class Amphibia
  3. C
    Class Chondrichthyes, Class Reptilia, Class Amphibia
  4. D
    Class Osteichthyes, Class Amphibia, Class Reptilia

Answer

Class Chondrichthyes, Class Amphibia, Class Reptilia
The combination of placoid scales and urea retention strictly defines cartilaginous fish (Class Chondrichthyes). Moist glandular skin for cutaneous respiration coupled with a three-chambered heart identifies Class Amphibia. Dry epidermal scales, an incompletely divided ventricle, and uricotelic nitrogenous excretion are hallmarks of Class Reptilia. Therefore, the sequence matching Specimens X, Y, and Z is Class Chondrichthyes, Class Amphibia, Class Reptilia.

Step-by-Step Solution

1
Analyze the characteristic features of Specimen X
Placoid scales (denticles), a 2-chambered heart (single atrium and single ventricle), and urea-based osmolyte retention are diagnostic features of cartilaginous fishes belonging to Class Chondrichthyes.
Bony fishes (Osteichthyes) have cycloid, ctenoid, or ganoid scales and primarily excrete ammonia directly across gills, distinguishing them from Chondrichthyes.
2
Analyze the characteristic features of Specimen Y
Moist, scale-less, glandular skin used for gas exchange combined with a 3-chambered heart (two atria, one ventricle) uniquely identifies Class Amphibia.
Amphibians depend on skin moisture for cutaneous respiration and lack the epidermal keratinized scales found in reptiles.
3
Analyze the characteristic features of Specimen Z
Dry skin covered in keratinized scales, an incompletely divided ventricle preventing complete mixing of blood, and uricotelic excretion (uric acid) to conserve water identify Class Reptilia.
Uric acid excretion and cornified scales are terrestrial adaptations characteristic of non-avian reptiles.
4
Synthesize the sequence of taxonomic classes
The correct ordered sequence for Specimens X, Y, and Z is Class Chondrichthyes, Class Amphibia, and Class Reptilia.
Matching all three diagnostic feature sets leads uniquely to this combination.

Key Concept

Comparative integumentary, circulatory, and excretory diagnostic features among poikilothermic vertebrate classes (Pisces, Amphibia, Reptilia)
Estimated Time:2m 0s
Rate this question

Topics

Vertebrates: Poikilothermic Classes (Pisces, Amphibia, Reptilia)

More questions from this topic