Final answer:
The idea that an organism or organ arises through the sequential appearance and development of new structures is true.
Step-by-step explanation:
The idea that an organism or organ arises through the sequential appearance and development of new structures is true. Development involves changes in the size, form, and structure of an organism throughout its lifetime. This process includes the organization of cells into tissues, which then form organs, and further organize into organ systems to create the whole organism.