You are observing a developing embryo under a microscope and see that it has a space in the middle of the endoderm, but no features of a notochord are present. In which stage of development is this embryo?
A) zygote
B) blastula
C) gastrula
D) fetus

Question

Quizplus · Accepted Answer

The presence of a space in the middle of the endoderm is a characteristic of the gastrula stage, which is when the three germ layers (endoderm, ectoderm, and mesoderm) are formed. The notochord, which is a defining feature of the chordate phylum, does not develop until later in embryonic development. Therefore, this embryo is in the gastrula stage.

You Are Observing a Developing Embryo Under a Microscope and See