Which one of the following statements is incorrect about the occurrenc...
Humans belong to the phylum Chordata. Animals belonging to the phylum Chordata possess a notochord either during early embryonic life or throughout the embryonic life. In some, it is replaced by vertebral column. In humans, notochord is present only in the embryonic stage, it is replaced by vertebral column in the adult form.
Which one of the following statements is incorrect about the occurrenc...
Explanation:
The notochord is a flexible rod-like structure present in the embryos of all chordates, which includes vertebrates and some invertebrates. It serves as a supportive structure and is located ventral to the nerve cord.
Incorrect statement:
c) It is absent throughout life in humans from the very beginning.
Explanation:
The notochord is present in humans during the early stages of embryonic development. It is one of the defining features of chordates. The notochord forms from the mesoderm during gastrulation and provides support to the developing embryo. However, in humans, the notochord is eventually replaced by the vertebral column during fetal development.
Correct statements:
a) It is present only in larval tail in ascidian.
In ascidians, which are a type of marine invertebrate chordate, the notochord is present only in the larval tail. It disappears during metamorphosis as the adult ascidian adopts a sessile lifestyle.
b) It is replaced by a vertebral column in adult frog.
In frogs and other vertebrates, the notochord is present during the early stages of development. However, it is gradually replaced by the vertebral column, which consists of individual vertebrae that provide support and protection to the spinal cord.
d) It is present throughout life in Amphioxus.
Amphioxus, also known as lancelets, are a primitive group of chordates. The notochord is a prominent feature in Amphioxus and remains present throughout their entire life. It provides support to the body and serves as a flexible axis for locomotion.
In summary, the incorrect statement is c) It is absent throughout life in humans from the very beginning. The notochord is present in humans during early embryonic development but is eventually replaced by the vertebral column.
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