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

During embryonic development, all vertebrates exhibit vestigial gill slits, reflecting their evolutionary ancestry.
However, the idea that embryos pass through the adult stages of other animals (recapitulation theory) has been disproved.
Embryonic development is better explained by shared evolutionary traits rather than a progression through adult forms of other species.