Step 1: The notochord is a flexible, rod-shaped structure that provides support to the body in early development in chordates. In many chordates, the notochord is replaced by the vertebral column (backbone) during development.
Step 2: In the case of Petromyzon (the lamprey, a type of jawless fish), the notochord persists throughout the organism's life. Lampreys are a part of the group called agnathans, and unlike most vertebrates, they retain the notochord as the primary structure for support throughout their life. |
Step 3: In most fish (Option 2), the notochord is replaced by the vertebral column as the animal matures, so it does not persist throughout life.
Step 4: In frogs (Option 3), the notochord is replaced by the vertebral column during early development, so it does not persist throughout life.
Step 5: In Latimeria (Option 4), also known as the coelacanth, the notochord is replaced by the vertebral column as development progresses, so it does not persist throughout life.
Conclusion: The notochord persists throughout life only in Petromyzon.
Match the following:
List - I | List - II | ||
---|---|---|---|
A) | Thyroid gland | I) | Calcitonin |
B) | Adrenal medulla | II) | Nor epinephrine |
C) | Pineal gland | III) | Melatonin |
D) | Pancreas | IV) | Glucagon |
Study the following and pick up the correct combinations:
S.No. | Spinal nerves | No. of pairs in man | Location |
---|---|---|---|
I | Cervical nerves | 7 pairs | Neck region |
II | Thoracic nerves | 12 pairs | Thorax |
III | Sacral nerves | 5 pairs | Lumbar region |
IV | Coccygeal nerves | 1 pair | Caudal region |
Match the following:
List - I | List - II | ||
---|---|---|---|
A) | Radius, ulna | I) | Fore limb |
B) | Tibia, fibula | II) | Hind limb |
C) | Scapula, clavicle | III) | Pectoral girdle |
D) | Ilium, pubis | IV) | Pelvic girdle |
The percentage error in the measurement of mass and velocity are 3% and 4% respectively. The percentage error in the measurement of kinetic energy is:
If \( L, M, N \) are the midpoints of the sides PQ, QR, and RP of triangle \( \Delta PQR \), then \( \overline{QM} + \overline{LN} + \overline{ML} + \overline{RN} - \overline{MN} - \overline{QL} = \):