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As far as I understand, two gametes fuse to create a zygote. Gametes are created via miosis, they are haploid and when they fuse they become a complete cell (diploid). And diploid cells divide via mitosis. However, I wonder why a zygote does not become two zygotes? What is different about it that makes it divide internally? In other words, why does a liver cell become two separate cells, yet the zygote becomes two cells inside the same shell?

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Final answer:

A zygote divides through mitosis to form an interconnected group of cells rather than separate entities, as it contains a diploid set of chromosomes and shares a common cytoplasm important for early development. Unlike typical cell division for tissue maintenance, such as in liver cells, embryogenic cell division is part of the organism's development.

Step-by-step explanation:

Zygote Division and Differentiation

During sexual reproduction, a haploid sperm and a haploid egg combine to form a diploid zygote. This zygote contains two sets of chromosomes, one from each parent, initiating the development of a new organism. Unlike a liver cell, which divides to create two separate cells, a zygote undergoes mitosis but does not fully separate into individual cells. Instead, it starts forming a multicellular structure through a series of mitotic divisions, creating an interconnected group of cells. This is because the zygote and its subsequent cells share a common cytoplasm and are enclosed within a membrane that keeps them together as part of the developing embryo. This division and specialization process is called embryogenesis, leading to the formation of different cell types and eventually organ systems.

The Importance of Cytoplasm in Early Development

The cytoplasmic material within the egg cell plays a crucial role in early embryonic development. It contains organelles, nutrients, and molecular signals that guide the initial cell divisions and differentiation. In contrast, typical cell division like that in liver cells results in separate, independent cells because these cells divide within the context of tissue maintenance and not organismal development.

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