Final answer:
The chicken egg yolk's large size is due to its role as a nutrient reservoir for the developing embryo, negating the need for external nutrient uptake. This allows it to bypass the size constraints of other cells related to nutrient exchange and waste removal. The substantial yolk volume houses the nutrients and energy necessary for early embryonic development.
Step-by-step explanation:
The yolk of a chicken egg is indeed a very large cell, and its size can be attributed to its role in embryonic development. Unlike most cells, which need to take in nutrients through processes like diffusion and active transport, the egg yolk has a pre-stocked supply of nutrients to support the developing embryo. This is because the egg yolk serves as a food source, containing all the necessary materials like proteins, nucleic acids, and other organelles required for the early stages of embryonic growth.
In this sense, the yolk's large size is advantageous; it has enough volume to store ample nutrients and energy sources. Also, because the yolk does not need to take in nutrients from the external environment, it is not constrained by the limitations that affect other cells, such as the surface area-to-volume ratio, which typically restricts cell size to ensure efficient nutrient uptake and waste removal.
Additionally, in eggs with large amounts of yolk, such as those of birds and reptiles, only a portion of the cell undergoes division (partial cleavage) due to the presence of this nutrient-rich material. Thus, the egg yolk's size can be maintained without compromising the needs of the developing embryo, allowing it to be much larger than most other cells.