Question

Read the following statements: Statement I: All vertebrates develop a row of vestigial gill slits during embryonic stage. 
Statement II: Embryos always pass through the adult stages of other animals.

• A. Statement I is correct, Statement II is incorrect.
• B. Statement I is incorrect, Statement II is correct.
• C. Both Statements I and II are correct.
• D. Both Statements I and II are incorrect.

Hint:

Embryology provides evidence for evolution by showing common developmental features among vertebrates.

Answer 1

The Correct Option is A

Analyzing the embryological statements:

Statement I: "All vertebrates develop a row of vestigial gill slits during embryonic stage" - Correct. This reflects the fundamental biogenetic law (von Baer's law) where vertebrate embryos show pharyngeal pouches (often called "gill slits"), representing an ancestral trait, though these develop into different structures in terrestrial vertebrates.

Statement II: "Embryos always pass through the adult stages of other animals" - Incorrect. This misrepresents Haeckel's recapitulation theory ("ontogeny recapitulates phylogeny"), which was disproven. Embryos show similarities to embryonic (not adult) stages of ancestors, and developmental pathways diverge.

The correct evaluation is: (A) Statement I is correct, Statement II is incorrect. While pharyngeal arches appear in all vertebrate embryos, they never fully resemble adult forms of ancestral species.

Answer 2

Statement I : "All vertebrates develop a row of vestigial gill slits during embryonic stage."
This statement is correct . During embryonic development, all vertebrates pass through a stage where they have pharyngeal slits (gill slits). These slits are vestigial in terrestrial vertebrates but are functional in aquatic forms like fish. This is evidence of common ancestry among vertebrates.

Statement II : "Embryos always pass through the adult stages of other animals."
This statement is incorrect . Embryos do not pass through the adult stages of other animals. Instead, they undergo ontogeny , which reflects their own developmental stages. While embryos may exhibit phylogenetic recapitulation (repeating ancestral features), they do not fully develop into the adult forms of other species.

Thus, Statement I is correct, and Statement II is incorrect.