Which of the following is a defining feature of all chordates at some stage of their life?
A. Vertebral column
B. Gills
C. Notochord
D. Scales
Answer: Option C
Solution (By JKExamLibrary)
All chordates possess a notochord, a dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail at some stage of development. The notochord may be replaced by the vertebral column in vertebrates. Gills and scales are not universal (e.g., mammals lack both). The notochord provides skeletal support and is the defining feature of the phylum Chordata.
Explanation:
The juxtaglomerular apparatus (JGA) is a specialized structure where the distal convoluted tubule (DCT) comes into contact with the afferent arteriole. It consists of juxtaglomerular cells (modified smooth muscle cells in the afferent arteriole that secrete renin), macula densa cells (modified DCT cells that sense NaCl concentration), and extraglomerular mesangial cells. It plays a crucial role in regulating blood pressure and glomerular filtration rate via the renin-angiotensin-aldosterone system.
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