A(n) _______________________________ is an animal without a backbone.

Which of the following is NOT a characteristic of animals?

An animal with a backbone is a(n) __________________________.

Animals that have a body cavity between the endoderm and mesoderm are ____________________ animals.

In a process called _____________________, the unicellular zygote of a sea urchin divides to form two new cells.

What is the earliest developmental stage of an embryo?

Fishes have one fin along their backs. Because fishes are bilaterally symmetrical, this fin is called the ___________________ fin.

A _____________________________ is an example of an animal with radial symmetry.

Organisms that don't move from place to place are ____________________________ animals.

Of these, which is NOT an example of a vertebrate animal?

The _______________________ is a framework of support on the outside of the body of an animal.