In Animals,a Sphere of Embryonic Cells Surrounding a Fluid-Filled Cavity

Question

In animals,a sphere of embryonic cells surrounding a fluid-filled cavity is called a
A) coelom.
B) gastrovascular cavity.
C) hydrostatic skeleton.
D) blastula.
E) gastrula.

Accepted Answer

A sphere of embryonic cells surrounding a fluid-filled cavity is called a blastula. This is an early stage of development in animals, following cleavage of a fertilized egg.

Option A, coelom, refers to a body cavity that forms later in development and is lined with mesoderm-derived tissues. 
Option B, gastrovascular cavity, refers to a simple digestive cavity seen in some animals, such as cnidarians. 
Option C, hydrostatic skeleton, refers to a type of support system seen in some invertebrates, such as worms, where the body cavity is filled with fluid and the surrounding muscles can create pressure that allows for movement and support.  
Option E, gastrula, refers to a later stage in development where the blastula undergoes further differentiation, forms layers of embryonic tissues (such as the endoderm, mesoderm, and ectoderm), and begins to shape the body plan.