Question

Sequence of the developmental events in the life cycle of a frog is :
A. Zygote formation
B. Larva formation
C. Gamete formation
D. Blastula formation
E. Gastrula formation
Choose the correct answer from the options given below :

• A. A, B, C, D, E
• B. B, C, A, D, E
• C. B, C, E, D, A
• D. C, A, D, E, B

Hint:

Embryonic development sequence is universal across most animals: Zygote $\rightarrow$ Morula $\rightarrow$ Blastula $\rightarrow$ Gastrula. (Alphabetical order B before G!).

Answer 1

The Correct Option is D

Step 1: Concept:
This question tests knowledge of the chronological stages of embryological development and the subsequent life cycle of an amphibian (a frog).

Step 2: Step-by-step Explanation:

• 1. Gamete formation (C): The life cycle begins in the adult frogs with the production of haploid sex cells (sperm in males, eggs in females) through meiosis.

• 2. Zygote formation (A): During fertilization, a sperm and an egg fuse to form a single diploid cell known as a zygote.

• 3. Blastula formation (D): The single-celled zygote undergoes rapid mitotic cell divisions (cleavage) to form a hollow sphere of cells called a blastula.

• 4. Gastrula formation (E): The blastula undergoes major cellular reorganization, folding inward to form distinct germ layers (ectoderm, mesoderm, endoderm) in a stage called the gastrula.

• 5. Larva formation (B): The embryo eventually develops organs and hatches from the egg as a free-living, aquatic larva (the tadpole), which will later undergo metamorphosis into an adult frog.

• The correct chronological sequence is: C $\rightarrow$ A $\rightarrow$ D $\rightarrow$ E $\rightarrow$ B.

Step 3: Final Answer:
The sequential order is C, A, D, E, B, which corresponds to option (D).