Arrange the given events of embryonic development in sequence.
Organogenesis
Implantation
Blastulation
Gastrulation

Options

A. III, II, IV and I
B. II, III, IV and I
C. I, II, III and IV
D. IV, III, II and I

Answer

To arrange the events of embryonic development in sequence, we can follow these steps:

1. **Blastulation**: This is the first step where the morula (a solid ball of cells) transforms into a blastula or blastocyst. The blastula is a hollow structure that forms after several divisions of the zygote.

2. **Implantation**: After the formation of the blastula, it travels to the uterus and embeds itself into the uterine wall. This process is known as implantation.

3. **Gastrulation**: Following implantation, the blastula undergoes gastrulation, which is the process where the single-layered blastula reorganizes into a multi-layered structure called the gastrula. This stage involves the formation of three germ layers: ectoderm, mesoderm, and endoderm.

4. **Organogenesis**: Finally, after gastrulation, the process of organogenesis begins. This is where the germ layers develop into various organs and structures of the body.

Thus, the correct sequence of events is:
1. Blastulation
2. Implantation
3. Gastrulation
4. Organogenesis