Why does the sea star embryo have no need of yolk associated with chicken embryo?

Sea star embryos are marine invertebrates that develop from eggs that are fertilized externally. They have a relatively simple developmental process compared to vertebrates such as chickens. Sea star embryos do not need yolk because they obtain their nutrition from the surrounding seawater. The seawater provides them with the necessary nutrients and minerals for their growth and development. In contrast, chicken embryos develop inside the egg, and the yolk serves as a source of nutrients for the developing embryo. The yolk is rich in proteins, fats, and vitamins, which are essential for the embryo's growth and development.