You could be a little more lenient. For example, vaccine for vaccination.
Oestrogen is spelled incorrectly.
A series of organs working together on a specific function is an organ system, not an organism.
Cell---> Tissue---> Organ ---> Organ System ---> Organism
While your description is technically correct, a zygote is, more specifically, the initial single cell that results from the fusion of a sperm cell and an egg cell.
An organism is not a series of organs that perform a specific function, that would be called an organ system. An organism is defined as a single life form.
Oestrogen is spelled incorrectly.
A series of organs working together on a specific function is an organ system, not an organism.
Cell---> Tissue---> Organ ---> Organ System ---> Organism
While your description is technically correct, a zygote is, more specifically, the initial single cell that results from the fusion of a sperm cell and an egg cell.