Discussion
Anatomically the conversion of series heart to parallel heart with separation of oxygenated and deoxygenated blood circulation observed as primary feature in the following evolutionary sequence in chordate evolution :
Answer: B
The change is seen in the step Fishes to Amphibia.
A fish has a single, series circulation: the two-chambered heart pumps deoxygenated blood to the gills, and the blood passes on from there to the body before returning to the heart. In amphibians, with the move to lungs, a pulmonary circuit appears: two atria receive oxygenated blood from the lungs and deoxygenated blood from the body, so blood passes through the heart twice per circuit, in parallel pulmonary and systemic loops.
Agnathans and fishes share the series pattern, so that step shows no such change. Reptiles, birds and mammals refine a double circulation that already exists in amphibians, separating the ventricle partly or completely, rather than introducing it.
Post your comment
Please log in or register to post a comment.
Examination Categories
- SSC Exams
- Banking Exams
- Teaching Exams
- Civil Services Exams
- Railways Exams
- Engineering Recruitment Exams
- Defence Exams
- State Government Exams
- Police Exams
- Insurance Exams
- Nursing Exams
- Other Government Exams
- NRA CET
- PG Entrance Exams
- Campus Placement
- MBA Entrance Exams
- CUET and UG Entrance
- Judiciary Exams
- Regulatory Body Exams
- Software Development