The amniotic egg, which evolved in ________, was important because it allowed eggs to be laid ________.

Sexual reproduction in animals entails a fusion of ____________ and ____________ from different individuals.

Budding, fission, and parthenogenesis are all forms of _________ practiced by animals. In parthenogenesis, an ____________ develops into an adult organism.

An animal that possesses both male and female sex organs is known as a ________.

Sponges obtain nutrition and oxygen, and get rid of wastes, by ________through themselves.

The three most familiar classes of molluscs are the gastropods, one example of which is ; the bivalves, one example of which is ________; and the cephalopods, one example of which is ________.

Cnidarians tend to exhibit both a mobile ________ stage in which their mouths are on ________ of their bodies, and a sessile ________ stage, in which their mouths are

All arthropods share the features of an ________or external material that provides support and protection, and ________, ________ appendages.

Every cell in a flatworm of phylum Platyhelminthes must get its oxygen directly from the environment around it because flatworms lack a ________ system.

Which of the following traits are not shared by all chordates at some point in their lives: notochord, dorsal nerve cord, exoskeleton, pharyngeal slits, sessile living, post-anal tail?

The sponges in phylum Porifera are outliers in the animal kingdom in that, almost alone among animals, their bodies are not composed of ____________ and their body structure lacks the quality of ____________.